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Polychloroprene rubber (PCR) is a synthetic elastomer obtained by the emulsion polymerization of the monomer 2-chloro-1,3-butadiene (chloroprene), and it carries one chlorine atom in every repeat unit of the polymer chain. Identified by CAS No 9010-98-4, it is the basic member of the rubber family whose international abbreviation is CR and which is known in commercial language largely by the name “neoprene”. It is available in two main commercial forms: solid rubber in the form of white-to-cream chips coated with talc, and an aqueous dispersion (latex). The fact that most of the chain has a regular trans-1,4 structure and that the polymer contains chlorine makes this material more resistant to oil, ozone, weathering and flame than natural rubber and styrene-butadiene rubber.
Polychloroprene combines properties such as high mechanical strength, good tear and abrasion resistance, resistance to dynamic fatigue, resistance to chemicals and aging, a self-extinguishing tendency and good adhesion to metals and fabrics in a balanced way. Solid grades are generally cured (vulcanized) with metal oxides such as zinc oxide (ZnO) and magnesium oxide (MgO) and, where necessary, organic accelerators, and are converted into products such as hoses, belts, gaskets, cable sheaths, bridge bearing pads and vibration-isolation elements. Soluble grades with a high crystallization rate are the main polymer of contact adhesives in the footwear, furniture and construction sectors. Latex grades, in turn, are used in dipped products, foam, adhesive and coating systems, fabric impregnation and bitumen modification.
Polychloroprene is not a single uniform product. The type of modification (sulfur, mercaptan or xanthogen disulfide), the Mooney viscosity, the crystallization rate, the degree of pre-crosslinking and the product form (solid or latex) determine its behavior in the application.
WHAT IS POLYCHLOROPRENE RUBBER?
Polychloroprene rubber, chemically known as poly(2-chloro-1,3-butadiene), is a homopolymer formed by the free-radical polymerization of chloroprene monomer, a derivative of butadiene in which one hydrogen atom has been replaced by chlorine. In industry, polychloroprene rubber is referred to as chloroprene rubber, or CR for short; the abbreviation CR is used for this rubber type in the ISO 1043 and ASTM D1418 systems. The name “neoprene” was originally a trademark of the DuPont company and over time has become the generic name of this rubber class.
The history of the material goes back to observations made in 1930 in the DuPont laboratories by Arnold Collins, who worked in the research group of Wallace Carothers, while examining a by-product. The material was first introduced to the market in 1931–1932 under the name DuPrene and took the name Neoprene in 1936. Arising from the need to develop a synthetic alternative to natural rubber, this product is regarded as the first commercially successful synthetic elastomer. Today, commercial production of polychloroprene rubber takes place mainly in the USA, Germany, Japan and China.
Chloroprene monomer is nowadays produced mainly by the chlorination of butadiene; the older method proceeded from acetylene via vinylacetylene. The monomer is emulsified in water together with an emulsifier and molecular weight regulators and polymerized with free-radical initiators. If solid rubber is wanted, the resulting latex is coagulated by lowering the pH or by freezing, then washed, dried and formed into chips; the surface is usually coated with talc to prevent sticking. If latex is wanted, it is stabilized after polymerization and supplied as a concentrated dispersion.
The physical appearance of polychloroprene rubber is generally white, cream, beige or light brown chips, pieces or bales; it typically has a faint characteristic odor, is insoluble in water and has a density of about 1.23–1.25 g/cm³. Compared with natural rubber, its density is higher, it is more resistant to water and hydrocarbon solvents, and its permeability to many gases is low.
Because its name is similar, polychloroprene should not be confused with certain other concepts. Chloroprene monomer is a toxic and flammable liquid; the polymer, on the other hand, is a solid, stable material that is not subject to dangerous goods transport rules. Polyvinyl chloride (PVC) is a different polymer. Expressions such as neoprene fabric, neoprene foam or neoprene wetsuit describe the finished-product form of polychloroprene rubber. Acrylonitrile-butadiene rubber (NBR), chlorosulfonated polyethylene (CSM) and chlorinated polyethylene (CM) are different polymers that contain chlorine or polar groups.
COMMON PRODUCT AND CHEMICAL NAMES OF POLYCHLOROPRENE RUBBER:
Polychloroprene Rubber
Polychloroprene
Chloroprene Rubber
Neoprene
Polychloroprene
Chloroprene Rubber
CR (Chloroprene Rubber)
PCR (abbreviation used in the title; see the note below)
Poly(2-chloro-1,3-butadiene)
Poly(2-chloro-1,3-butadiene)
1,3-Butadiene, 2-chloro-, homopolymer
2-Chloro-1,3-butadiene homopolymer
Chloroprene Polymer
Neoprene
DuPrene (Duprene)
Neoprene Latex / Polychloroprene Latex
Baypren (ARLANXEO)
Neoprene (Denka)
Denka Chloroprene (Denka)
Dispercoll C (polychloroprene dispersions)
Butaclor, Sovprene, Mustone (regional trade names)
2-Chloro-1,3-butadiene / 2,3-dichlorobutadiene copolymer
Some of these names refer to chemical designation, some to trademarks, and some to the product form or quality class. Poly(2-chloro-1,3-butadiene) and 1,3-Butadiene, 2-chloro-, homopolymer are the systematic or CAS index names of the polymer. Neoprene and DuPrene were originally DuPont brands; today the Neoprene brand is used for the product family within Denka. Baypren is the polychloroprene product name of ARLANXEO, and Denka Chloroprene is the polychloroprene product name of Denka. Dispercoll C is a trade name used for the series of aqueous polychloroprene dispersions.
The international standard abbreviation is CR. Because the abbreviation PCR used in this title may have different meanings in other fields, stating the grade name, the abbreviation CR and the CAS number together in purchase correspondence avoids confusion. Grade components such as the 2-chloro-1,3-butadiene / 2,3-dichlorobutadiene copolymer (CAS 25067-95-2) and the copolymer with sulfur (CAS 37450-42-3) may also be listed separately in product SDS documents as copolymers. Chloroprene, the monomer, is a separate substance (CAS 126-99-8); the subject of this page is the polymer, not the monomer.
CAS NO, EC / EINECS NO AND CHEMICAL IDENTIFICATION OF POLYCHLOROPRENE RUBBER
Product name: Polychloroprene Rubber / Polychloroprene / Chloroprene Rubber
Common abbreviation: CR (ISO 1043, ASTM D1418); the trade name “neoprene” is also widely used
Chemical name: Poly(2-chloro-1,3-butadiene); CAS index name: 1,3-Butadiene, 2-chloro-, homopolymer
CAS No: 9010-98-4
EC / EINECS No: There is no classical EINECS registration for the polymer; some manufacturer SDS documents give the list number 618-463-8 for the homopolymer, while others state the EC number as “not applicable”. The current status should be verified from the SDS document of the relevant product.
Molecular formula: (C₄H₅Cl)ₙ; linear formula: [–CH₂–CH=C(Cl)–CH₂–]ₙ
Molecular weight: Repeat unit (chloroprene) 88.54 g/mol; the average molecular weight of the polymer varies with the grade and the type of modification, so commercial grades are defined by Mooney viscosity rather than by molecular weight
Chemical class: Synthetic elastomer; chlorinated diene polymer (polychloroprene)
Main functions: Base polymer of rubber products, binder of contact adhesives and sealants, raw material for latex coating and dipped products, flame-retardant and oil- and ozone-resistant elastomer
Polychloroprene is a polymer whose composition cannot be reduced to a single low-molecular-weight molecule. For this reason, commercial products that share the same CAS number differ significantly in terms of modification type, viscosity, crystallization rate, auxiliary additives (stabilizer, talc, resin salt) and product form. In other words, the CAS number confirms that the product is polychloroprene but does not define its performance.
The absence of an INCI name does not mean that a product can be used in cosmetics; likewise, the presence or absence of a single registration number does not show that every use complies with the legislation. In the European Union, polymers are generally exempt from the registration obligation under REACH; however, REACH registration numbers exist for the monomers used in the production of the polymer, 2-chloro-1,3-butadiene and 2,3-dichlorobutadiene, and they are stated in manufacturer SDS documents. Some polychloroprene grades currently on the market are also supplied with a REACH declaration of conformity.
CHEMICAL STRUCTURE AND MOLECULAR PROPERTIES OF POLYCHLOROPRENE RUBBER
Polychloroprene is a linear chain formed by the linking of chloroprene monomer (CH₂=CCl–CH=CH₂) through a 1,4-addition reaction. The main repeat unit of the chain is –CH₂–CH=C(Cl)–CH₂–; the double bond remains in the polymer backbone, while the chlorine atom is attached to the double-bonded carbon. Because this chlorine is “vinylic chlorine”, it is quite inert toward nucleophilic reactions. This explains both the protection of the double bond against oxygen and ozone attack and the relatively good aging resistance of the polymer.
When emulsion polymerization is carried out at around 40 °C, approximately 85–87% of the repeat units have the trans-1,4 structure, 10–13% the cis-1,4 structure, and 1–3% the 1,2- and 3,4-addition structures. As the polymerization temperature is lowered, the trans-1,4 proportion increases. The regularity of the chain structure makes polychloroprene prone to crystallization. As the trans-1,4 proportion rises, the tendency to crystallize increases; while this property is deliberately exploited for the rapid development of initial bond strength in adhesives, it can turn into an undesirable effect such as hardening at low temperature in rubber products. For this reason, manufacturers copolymerize chloroprene with small amounts of 2,3-dichlorobutadiene, acrylonitrile and similar comonomers in order to reduce crystallization.
Molecular weight and chain structure are adjusted by the chain transfer agent used during polymerization. Sulfur, mercaptan or xanthogen disulfide is used for this purpose, giving rise to different grade groups. Sulfur-modified grades (G type) carry sulfur bridges in the chain; these break easily during mastication, allowing the polymer to drop to a workable viscosity, and the grades often cure without needing an organic accelerator.
Mercaptan- or xanthogen-modified grades (W and related types), on the other hand, offer a more stable raw polymer but generally require an organic accelerator such as ethylene thiourea (ETU) or alternative systems to achieve good mechanical properties. In addition, some grades are produced with a pre-crosslinked (gel-containing) structure; these provide dimensional stability, particularly in processes such as extrusion and calendering.
The polar character at the molecular level (the C–Cl bond) makes polychloroprene more polar than natural rubber. For this reason, it shows lower swelling resistance than NBR, but better swelling resistance than natural rubber and EPDM, against mineral oils and aliphatic hydrocarbons. Aromatic and chlorinated solvents, ketones and esters, in turn, can swell or dissolve polychloroprene; this is why solvent-based adhesives are prepared with these solvent groups.
During heat, light and long-term aging, hydrogen chloride can be released from the polychloroprene chain (dehydrochlorination). The released HCl both accelerates the degradation of the polymer and can cause corrosion on metal surfaces. For this reason, acid acceptors such as MgO are included in the recipes. Laboratory studies have shown that on aging in the 70–90 °C range, the elastic modulus of polychloroprene compounds increases and the elongation at break decreases; that is, the material hardens over time.
Vulcanized polychloroprene, unlike natural rubber, is crosslinked not with sulfur but mainly with metal oxides. The reactive allylic chlorine carried by the small number of 1,2-addition units in the polymer chain is considered to play a role in crosslinking. Zinc oxide acts as the crosslinker, while magnesium oxide serves predominantly as the chlorine (HCl) acceptor; when the two are used together, a balanced result is obtained in terms of both cure time and degree of cure.
PHYSICAL AND CHEMICAL PROPERTIES OF POLYCHLOROPRENE RUBBER
General technical specifications: The values below are for general introductory purposes and are typical values for the polychloroprene rubber family; they are not a binding specification. Exact grade-specific values should be taken from the manufacturer’s current TDS and COA documents.
Physical appearance: White, cream, beige or light brown chips, pieces or bales; solid grades are generally coated with talc. Latex grades are milky white aqueous dispersions.
Chemical character: Chlorinated diene polymer; polar, synthetic elastomer with an unsaturated backbone; insoluble in water
Molecular formula: (C₄H₅Cl)ₙ
Molecular weight: Repeat unit 88.54 g/mol; the average polymer molecular weight varies with the grade
CAS No: 9010-98-4
EC / EINECS No: No classical EINECS registration; the list number 618-463-8 may appear in manufacturer SDS documents
Purity (assay): Polychloroprene content; depends on the grade according to the proportion of talc, resin salt, stabilizer and auxiliary additives.
Density: Approximately 1.23–1.25 g/cm³ (solid rubber, according to the manufacturer’s SDS document); some reference sources give 1.23 g/mL at 25 °C
Water solubility: Insoluble. Soluble in toluene, xylene, chloroform and ethylene dichloride; of limited solubility or swollen in acetone, butanone, ethyl acetate and cyclohexane; insoluble in n-hexane and mineral spirits.
Decomposition: Manufacturer SDS documents state a decomposition temperature above 200 °C; some commercial sources give a range of 230–260 °C. HCl may be present in the decomposition products. The flash point is above 260 °C in one manufacturer’s SDS document.
Chloride content: The covalently bonded chlorine in the chain is theoretically about 40% by mass (35.45/88.54).
Reactivity: Stable under normal conditions. It should be kept away from heat, direct sunlight and strong oxidizing agents. Prolonged exposure to high temperature can lead to dehydrochlorination and release of HCl. The manufacturer’s SDS document notes that nitrosamines can form with secondary amines under certain conditions.
Polychloroprene rubber is a polar, dense, water-insoluble elastomer that contains covalently bonded chlorine in its structure. The glass transition temperature is reported as approximately –48 °C for a reference grade. In the same source, the Mooney viscosity is given as approximately 40; this value is only for that sample grade. In cured products, tensile strength can reach 25–28 MPa with suitable reinforcing systems; in general-purpose compounds, the hardness range is approximately 40–90 Shore A.
The typical continuous service temperature is given as –20 to +100 °C depending on the compound, and the upper limit can rise to about 120 °C for short-term use; above these temperatures, the loss of elasticity becomes pronounced. Polychloroprene can slowly crystallize and harden in the cold, particularly below about 10 °C; it also crystallizes under strain. This crystallization is reversible and can be reversed by heating.
These values are for general technical introduction; they should not be used as the binding specification of the product to be purchased. Parameters such as Mooney viscosity, crystallization rate, volatile matter, ash/talc content, stabilizer type and the shelf life of the raw polymer should be checked through the supplier’s current TDS and COA documents.
HOW DOES POLYCHLOROPRENE RUBBER WORK AT THE MOLECULAR LEVEL?
The function of polychloroprene rubber does not arise from a single chemical reaction but from the combined action of three separate molecular features: the electronic effect of the chlorine atom in the chain, crystallization due to chain regularity, and crosslinking with metal oxides.
Effect of chlorine: The chlorine atom bonded directly to the double bond reduces the electron density of the double bond. In natural rubber the double bond is open to attack by oxygen, ozone and radicals; in polychloroprene this reactivity is markedly lower. As a result, resistance to ozone cracking, weathering and aging increases. The polarity of the C–Cl bond provides less swelling in mineral oils. The release of chlorine as HCl during combustion suppresses burning in the flame zone; polychloroprene is therefore known as one of the few self-extinguishing rubbers.
Effect of crystallization: Chains with a high trans-1,4 proportion can line up parallel to one another and form regular crystalline regions. These regions behave like physical crosslinks. In contact adhesives prepared with soluble grades, when two surfaces are joined, the polymer chains diffuse and crystallization begins rapidly; bond strength increases without waiting for chemical crosslinking.
Grades with a high crystallization rate give fast initial strength, while medium-rate grades provide a longer open time. Heating melts the crystals and cooling re-forms them; heat-activated adhesive systems are therefore possible. Crystallization that occurs under strain, in turn, contributes to the high tensile strength and tear resistance of the rubber.
Crosslinking (vulcanization): Zinc oxide interacts with the reactive allylic chlorine sites in the polymer chain and forms bridges between chains. Magnesium oxide captures HCl and improves scorch safety. Organic accelerators (historically the most effective being ethylene thiourea, ETU) increase the rate and degree of cure; however, the classification of ETU for reproductive toxicity has accelerated the search for alternative accelerators. Curing with peroxide is also possible. In sulfur-modified grades, the sulfur bridges in the chain assist curing.
At the polymerization stage, the mechanism is free-radical emulsion polymerization: the monomer propagates in micelles and polymer particles; the chain transfer agent (sulfur, mercaptan, xanthogen disulfide) controls the chain length. The temperature, conversion and type of transfer agent at this stage determine the viscosity, crystallization tendency and storage stability of the product.
Aging: Under heat, oxygen and light, polychloroprene degrades both oxidatively and through dehydrochlorination. For this reason, antioxidants and acid acceptors are added to compounds. Additives such as calcium resinate are used to improve heat resistance.
IN WHICH SECTORS IS POLYCHLOROPRENE RUBBER USED?
Polychloroprene rubber is used as a “property-driven” elastomer in many sectors thanks to its oil and weather resistance, tear and abrasion resistance, flame-retardant tendency and good adhesion. Because its price is higher than that of natural rubber and SBR, it is generally preferred in applications where these properties are required.
Main areas of use:
• Automotive and transportation: air springs, axle boots, wiper blades, belts, hoses, molded parts, vibration-isolation elements
• Cable and wire industry: cable and wire sheaths, coating and insulation compounds
• Industrial rubber products: conveyor belts, V-belts, gaskets and sealing elements, cooling-system seals, coated fabrics
• Building and construction: bridge bearing pads, window and door profiles, roof coverings, sealants, floor and roof adhesives, bitumen modification
• Footwear, furniture and wood-finishing industry: solvent-based and water-based contact adhesives
• Sports and textiles: neoprene foam, diving and surfing suits, orthopedic supports, coated fabrics
• Protective gloves and dipped products: household, industrial and (with special grades and approval) medical gloves
• Marine and inflatable boats: adhesives for joining coated fabrics
• Protective coating and lining applications: linings for chemical storage tanks and reaction equipment
• Special defense and aerospace applications: some sources mention specific uses such as a rocket propellant binder
IS POLYCHLOROPRENE RUBBER USED IN COSMETIC, FOOD AND PHARMACEUTICAL APPLICATIONS?
Polychloroprene rubber is essentially an industrial elastomer. Its use as a raw material in the cosmetic, food and pharmaceutical fields is limited and must be evaluated separately for each field. That it can be used in one sector does not mean that it is suitable for other sectors.
Food: Polychloroprene is neither a food additive nor a component of food. In the context of equipment that comes into contact with food, indirect contact is involved. In the USA, the provision of 21 CFR 177.2600 lists chloroprene polymers among the polymers that may be used in repeated-use rubber articles (for example conveyor belts, gaskets and sealing elements). This use depends on the type and amount of auxiliary substances in the formulation and on the limits for extractable substances that pass from the finished article into aqueous or fatty food.
The legislation requires that the additives used are not intended to have an effect on the food, that the total of accelerators does not exceed a certain weight proportion of the rubber article, and that cleaning is carried out before first use. The use of polychloroprene in single-use food packaging is not a common practice.
Because there is no common specific measure for rubber that applies in all member states in Europe, and the general framework regulation and national rules are considered together, the current food contact legislation of the target market must be checked. For food contact uses, a declaration of conformity and a test report should be requested for the finished article.
Pharmaceutical and medical applications: Polychloroprene latex is mentioned in the literature and in patents as a raw material for household, industrial and surgical gloves produced by dipping. However, manufacturers may require that their products not be used, without a written agreement and explicit permission, in medical devices implanted in the body or in applications that come into contact with internal body fluids and tissues. For medical uses, the compliance of the finished article with the relevant medical device legislation must be evaluated separately.
As a general approach, industrial-grade polychloroprene rubber should not be used as a cosmetic ingredient, food additive or pharmaceutical raw material. In every application in which the finished article comes into contact with people, regulatory compliance documents should be requested at the level of the raw material, the additives and the finished article.
INDUSTRIAL APPLICATIONS OF POLYCHLOROPRENE RUBBER
The industrial use of polychloroprene rubber divides into different branches according to product form (solid, soluble, latex) and grade group. The applications below summarize the most important groups of use for polychloroprene.
Technical rubber products: hose, belt, gasket and molded part
Purpose: Producing parts that must withstand oil, ozone, weathering and dynamic loading at the same time.
Function of the chemical: As the main elastomer it forms the load-bearing mechanical network; it is cured with metal oxide.
Process and product type: Calendering, extrusion, injection or compression molding; air spring, axle boot, wiper blade, V-belt, conveyor belt, cooling-system seal.
Performance effect: Good tear and abrasion resistance, low compression set, resistance to fatigue and crack growth, retention of elasticity during aging. Manufacturer data indicate that polychloroprene-based products can retain their elasticity for many years in ozone-containing environments and are more resistant to oil swelling than SBR, natural rubber and EPDM.
Reason for preference: Balanced ozone, weather, moderate oil and flame resistance offered by a single polymer.
Limitations: Fuel and mineral oil resistance is not as high as that of NBR; low-temperature performance is moderate; elasticity is lost above 120 °C; the unit price is higher than that of SBR and natural rubber.
Alternatives: NBR, EPDM, CSM, SBR/NR blends, FKM and AEM.
Cable and wire sheaths
Purpose: Cable sheathing and insulation that must limit flame spread and resist abrasion and chemicals.
Function of the chemical: Main polymer of the sheathing compound; the chlorine content contributes to the flame-retardant property.
Performance effect: Self-extinguishing tendency, abrasion and tear resistance, weather and ozone resistance. Polychloroprene is not as good as natural rubber in terms of electrical insulation properties; it is therefore used predominantly as a sheathing material.
Limitations: In high-frequency electrical insulation, the polar structure is a disadvantage.
Contact adhesives (solvent-based and water-based)
Purpose: Bonding a wide variety of materials (rubber, leather, wood, metal, plastic) with fast initial strength and a long open time.
Function of the chemical: It is the binder polymer of the adhesive. Soluble, linear grades are used in solvent-based systems; latex dispersions are used in water-based systems. Besides the rubber, the adhesive contains a resin (for example alkylphenolic), magnesium oxide, zinc oxide, an antiaging agent and a solvent blend.
Performance effect: When the surfaces are joined after the adhesive has been applied and the solvent has evaporated, crystallization produces rapid bond strength. The complex of phenolic resin with MgO increases heat resistance and adhesion.
Important note: About one third of polychloroprene production is used as adhesive raw material. The footwear sector was the first major market for polychloroprene contact adhesives; the furniture, construction and automotive sectors are also important areas of use.
Limitations: VOC emissions and flammability in solvent-based systems; an application time that must be adjusted to the crystallization rate; settling of MgO and ZnO in the solution over time; the need to compare drying time and initial tack of water-based systems with those of solvent-based systems.
Alternatives: Polyurethane dispersions, SBS-based and acrylic-based adhesives, EVA-modified systems.
Latex applications: dipping, foam, impregnation, bitumen and coating
Purpose: Using the polymer dispersed in water as a film, foam or binder.
Function of the chemical: The latex forms a film that is cured with a suitable vulcanization system. In the dipping process, the former is wetted with coagulant and immersed in the latex bath, and the resulting film is dried and cured.
Product type: Household, industrial and surgical gloves; fabric and fiber impregnation, paper coating, textile finishing, modified asphalt (bitumen), highly elastic cementitious systems, foam.
Performance effect: Mechanical strength, weather and chemical resistance, low odor in an aqueous system. Special emulsifier systems are used for dispersion stability under freezing conditions.
Limitations: The shelf life and temperature range of the latex are shorter (one manufacturer’s SDS document states a shelf life of 6 months for the liquid dispersion); risk of freezing and coagulation.
Alternatives: Natural rubber latex, nitrile latex, synthetic polyisoprene latex.
Foam and textile-related products
Purpose: Sportswear, diving suits and supports that require thermal insulation and flexibility.
Function of the chemical: Foamed polychloroprene offers a cellular structure containing a large number of small gas voids and is insulating. It is usually laminated on both sides with a fabric such as nylon or Lycra; joining is done with adhesive.
Limitations: Reduced thermal resistance under diving pressure; performance closely related to thickness, density and cell structure.
Construction and infrastructure: bearings, profiles, coverings
Purpose: Vibration damping, load bearing, and air and water tightness.
Function of the chemical: It forms the elastomeric base structure in bridge bearings, vibration-isolation pads, window profiles and roof coverings.
Performance effect: Long-term ozone and weather resistance, resistance to soil bacteria and fungi, low compression set.
Limitations: Hardening due to crystallization at low temperature; hardening with long-term aging.
POINTS TO CONSIDER WHEN USING POLYCHLOROPRENE RUBBER
The most common mistake in using polychloroprene rubber is to select the product only by the name “neoprene” or “CR” and to overlook the differences between grades. The following points are particularly important:
• Grade selection: Sulfur-modified (G type), mercaptan- or xanthogen-modified (W type), pre-crosslinked, fast- or slow-crystallizing grades and grades with different Mooney viscosities are intended for different applications. Fast-crystallizing soluble grades are preferred in contact adhesives, and crystallization-resistant grades in seals that operate in the cold.
• Storage stability of the raw polymer: In sulfur-modified grades, the Mooney viscosity of the raw polymer can decrease during storage; for this reason, stabilizers are used in the products and the storage period is limited.
• Crystallization and cold storage: Raw polymer kept in the cold can harden. The product must be brought to a suitable temperature before processing.
• Cure system: When zinc oxide and magnesium oxide are used together, a balanced result is obtained. With zinc oxide alone the cure starts quickly but crosslinking may remain inadequate; with magnesium oxide alone the cure is slow and of a low degree. Ethylene thiourea (ETU), used as an accelerator, is classified for reproductive toxicity; ETU-free systems or systems with alternative accelerators are therefore gaining increasing importance.
• Heat and aging: Keeping the material at high temperature for a long time leads to HCl release, hardening and loss of elasticity. The use of antioxidants and acid acceptors is necessary.
• Avoid contact with strong oxidizing agents: Manufacturer SDS documents list strong oxidizing agents as incompatible materials.
• Nitrosamine risk: Manufacturer documents state that nitrosamines can form with secondary amines under certain conditions. This risk should be evaluated when selecting an accelerator or additive that contains a secondary amine.
• Solvent-based systems: The choice of solvent determines both solubility and VOC emissions. Aromatic and chlorinated solvents dissolve polychloroprene; some ketones and esters are weak solvents on their own. Solvents are flammable; ventilation, control of ignition sources and fire safety are mandatory.
• In latex systems: Storage temperature, freezing, coagulation, pH and emulsifier compatibility should be monitored.
• End use of the article: For food, drinking water, medical device or skin-contact articles, the compliance of the raw materials and additives with the relevant legislation must be verified separately.
• Emissions during processing: Small amounts of irritating gas or particulates may be released during drying, cleaning and molding; adequate ventilation is required.
• Dust control: Talc-coated chips and rubber dust can generate dust during processing.
• Waste management: If waste polychloroprene is to be incinerated, it should be burned in facilities with systems that capture the acidic combustion products (HCl).
• Manufacturer documents: TDS, SDS and COA should be reviewed separately for each batch and grade.
STARTING FORMULATION APPROACHES FOR POLYCHLOROPRENE RUBBER
The examples below are conceptual starting approaches prepared to show how polychloroprene rubber can be evaluated in formulation and process development.
They are not verified commercial recipes, production instructions or final formulas that comply with the legislation. Polychloroprene is a solid polymer and is of low hazard; on the other hand, the solvents, accelerators and metal oxides used together with it in formulations may carry their own risks. For this reason, laboratory trials, performance testing, occupational safety assessment and regulatory checks must be carried out for every application.
The proportions given are example starting levels for preliminary laboratory trials. The percentages are approximate weight percentages of the formula, and each formula adds up to 100; in Example 3, the proportions are on a dry solids basis. The grade of polychloroprene used, the viscosity, the crystallization rate and the other raw materials can change the result significantly.
EXAMPLE 1: EVALUATION OF POLYCHLOROPRENE GRADE AND RESIN/METAL OXIDE IN A SOLVENT-BASED CONTACT ADHESIVE
Purpose: To examine the effect of the polychloroprene grade and of the resin and metal oxide proportions in a contact adhesive on initial bond strength, open time and heat resistance.
Starting approach:
Polychloroprene (fast-crystallizing soluble grade): about 16.7%
Alkylphenolic resin or terpene/rosin ester: about 6.7%
Magnesium oxide: about 0.7%
Zinc oxide: about 0.7%
Antiaging agent (e.g. hindered phenol type): about 0.3%
Solvent blend: about 74.9%
The resin is about 40% of the weight of the polychloroprene; magnesium oxide and zinc oxide are each about 4% of it. The solvent blend is chosen so that the solids content is about 25%; since acetone and methyl acetate are weak solvents for polychloroprene on their own, a blend must be used.
Application approach:
The polychloroprene is dissolved in the solvent blend with stirring.
A premix of the resin and metal oxides is prepared and added to the solution.
The antiaging agent is added and the solution is homogenized.
The adhesive is applied to both standard surfaces, the solvent is allowed to evaporate, and the surfaces are joined after defined open times.
Peel strength, initial tack, open time and heat resistance are measured; the results are compared with different polychloroprene grades.
Settling of the metal oxide and changes in viscosity are monitored during storage.
Because of the flammability of the solvents and respiratory and skin exposure, ventilation and control of ignition sources must be ensured, and the compliance of the final adhesive with labeling and VOC legislation must be checked separately.
EXAMPLE 2: EVALUATION OF THE METAL OXIDE CURE SYSTEM IN A SOLID POLYCHLOROPRENE COMPOUND
Purpose: To examine the cure characteristics, mechanical properties and heat aging performance of a general-purpose polychloroprene rubber compound according to the metal oxide proportions.
Starting approach:
Polychloroprene: about 71.50%
Carbon black (e.g. N762): about 21.45%
Zinc oxide: about 3.58%
Magnesium oxide: about 2.86%
Stearic acid: about 0.36%
Ethylene thiourea (ETU, reference accelerator): about 0.25%
This composition is a reference compound close to the ISO 2475 test mix. Zinc oxide serves as the crosslinker and magnesium oxide as the HCl acceptor; during the trial, the ratio of these two components is varied and the total is made up to 100%.
Application approach:
The polychloroprene rubber is masticated in an internal mixer or on a two-roll mill.
The metal oxides, carbon black and stearic acid are added; the accelerator is added last and at a low temperature.
The compound is allowed to rest and its cure characteristics are measured with a rheometer.
The cure conditions are determined and test plaques are prepared.
Mooney scorch time, rheometer curve, tensile strength, elongation at break, hardness, compression set and the change after hot-air aging are measured; the results are compared with different metal oxide ratios.
Because ETU is an accelerator classified for reproductive toxicity, the SDS and workplace exposure limits must be observed, alternative systems should be evaluated where possible, and adequate ventilation must be provided for emissions and dust during curing.
EXAMPLE 3: EVALUATION OF A DIPPED FILM FROM AQUEOUS POLYCHLOROPRENE LATEX AND OF A WATER-BASED CONTACT ADHESIVE
Purpose: To examine the effect of the polychloroprene latex grade and the cure system on film flexibility, mechanical strength and adhesive performance.
Starting approach, dipped film (on a dry solids basis):
Polychloroprene latex (anionic or nonionic, crystallization-resistant grade): about 93.46%
Zinc oxide dispersion: about 4.67%
Antiaging agent dispersion: about 1.87%
Starting approach, water-based contact adhesive (on a dry solids basis):
Polychloroprene latex: about 68.03%
Resin dispersion: about 27.21%
Zinc oxide dispersion: about 3.40%
Antiaging agent dispersion: about 1.36%
Application approach:
The latex compound is prepared at a suitable temperature and the required maturation time is allowed.
For the dipped film, the former is prepared with a coagulant solution, dipped into the latex compound and withdrawn.
The resulting film is dried and cured under controlled conditions.
Film thickness, tensile strength, elongation at break, flexibility, hardening in the cold and freeze-thaw stability are measured.
In the water-based adhesive trial, the compound is applied to the surfaces, dried and joined; initial tack, open time, bond strength and heat resistance are measured.
The results are compared with different latex grades and cure systems.
Since the chemicals used in the latex compound may cause skin sensitization, suitable protective equipment must be used; for articles that come into contact with people, such as gloves, the safety and regulatory assessment of the final product must be carried out separately.
SIMILAR PRODUCTS AND ALTERNATIVES TO POLYCHLOROPRENE RUBBER
The alternative to polychloroprene rubber is not simply a matter of choosing another elastomer. When determining an alternative, oil and fuel resistance, ozone and weather resistance, temperature range, flame behavior, mechanical strength, adhesion, cost and regulatory requirements must be evaluated together. The comparisons below describe general tendencies; they may vary with the compound and the grade.
Polychloroprene and nitrile rubber (NBR)
Depending on its acrylonitrile content, NBR is markedly more resistant than polychloroprene to mineral oil and fuel; as the acrylonitrile proportion increases, oil resistance increases and low-temperature flexibility decreases. Polychloroprene, on the other hand, is superior in weather, ozone and flame behavior. Both materials can be used in a similar general temperature range (approximately –40 to +120 °C). In seals in continuous contact with fuel and oil, NBR stands out; in applications where outdoor exposure and flame-retardant properties are required, polychloroprene stands out.
Polychloroprene and EPDM
EPDM performs better than polychloroprene against ozone, UV and weathering and can be used over a wider temperature range (approximately –55 to +150 °C). However, EPDM swells severely in mineral oils. Polychloroprene is superior to EPDM in terms of oil and flame resistance. EPDM is common in outdoor sealing profiles; in environments with oil vapor or splashes, polychloroprene may be more suitable.
Polychloroprene and chlorosulfonated polyethylene (CSM)
CSM rivals polychloroprene in weather, ozone and chemical resistance and shows superiority particularly in acidic and oxidizing environments. Flame resistance is good in both materials. Polychloroprene offers better dynamic mechanical properties and rubber-to-metal adhesion; CSM, on the other hand, is used in chemical and outdoor coatings.
Polychloroprene and natural rubber / SBR
Natural rubber and SBR are generally cheaper, and natural rubber gives high elasticity in dynamic applications. However, they fall behind polychloroprene in ozone, oil, heat and flame resistance. In these applications, polychloroprene shifts the cost–performance balance toward the property-driven side.
Polychloroprene and other specialty rubbers (CM, FKM, AEM, polyurethane)
Chlorinated polyethylene (CM), fluoroelastomer (FKM) and ethylene acrylic rubber (AEM) are considered when higher temperatures or more aggressive environments are required; these are generally more expensive. Polyurethane rubber, on the other hand, is selected for high abrasion and oil/solvent resistance.
Alternatives in adhesives
Polyurethane dispersions, acrylic-based water-based systems, SBS-based adhesives and EVA-modified systems can be used as alternatives to polychloroprene contact adhesives. The initial bond strength, open time, and heat and oil resistance of these systems may not be the same as those of polychloroprene; moreover, the transition to solvent-free or water-based systems is encouraged for environmental reasons.
Alternatives in latex gloves
In dipped products, natural rubber latex, nitrile latex and synthetic polyisoprene latex are the main alternatives to polychloroprene latex. The choice is made according to allergy risk, mechanical strength, chemical resistance and cost.
The choice of alternative must always be verified through laboratory and field tests according to the requirements of the final product.
QUALITY CONTROL AND PURCHASING CRITERIA FOR POLYCHLOROPRENE RUBBER
When purchasing polychloroprene rubber, it is not sufficient to decide on the basis of the product name and price alone. Solid rubber and latex grades, and the products of different manufacturers, have different properties.
Information recommended for review before purchase:
• Product name, manufacturer and grade code (for example W, G, AD type or the manufacturer’s series name)
• Product form (solid chips, bales or latex) and type of packaging
• CAS number (9010-98-4) and whether it is a homopolymer / copolymer
• Type of modification: sulfur, mercaptan, xanthogen disulfide or other
• Mooney viscosity (ISO 289-1 or equivalent) and test temperature
• Crystallization rate (very slow, slow, medium, fast)
• Pre-crosslinking (gel) status
• Volatile matter and ash/talc content
• Auxiliary substances: stabilizer, resin salt, type of antioxidant, talc or other parting agent
• Color, contamination and appearance
• Quality class and whether it is general-purpose or adhesive-grade
• For latex: solids content, pH, viscosity, particle size, emulsifier type (anionic / nonionic), stability
• Residual monomer level (chloroprene) and measurement method
• Cure and mechanical properties in a standard test mix (ISO 2475 or the relevant standard)
• Technical data sheet (TDS)
• Safety data sheet (SDS)
• Certificate of analysis (COA)
• Production and batch information, origin
• Storage conditions and shelf life
• REACH and related regulatory compliance information
• Additional documents for food-contact or special applications
The ISO 2475 standard defines the evaluation procedure for general-purpose polychloroprene rubber types (sulfur-modified, mercaptan-modified and others); it includes measuring the Mooney viscosity of the raw rubber according to ISO 289-1 and curing and comparing it in a standard test mix. It refers to the ISO 247 standard for ash determination, ISO 37 for tensile properties and ISO 6502 for the use of rheometers. It is known that residual monomer can be determined by gas chromatography.
The COA shows the analysis results of a specific batch; the TDS contains the general technical properties of the product and its recommended uses, and the SDS contains safe handling, storage and transport information. These documents are not substitutes for one another; they should be evaluated together. The manufacturer’s typical values should be distinguished from the binding product specification.
STORAGE AND TRANSPORT OF POLYCHLOROPRENE RUBBER
Polychloroprene rubber should be stored in a cool, dry and well-ventilated area, in its closed original packaging, under the conditions recommended by the manufacturer. It is recommended that packages be kept tightly closed to prevent moisture and contamination. Direct sunlight and heat sources should be avoided.
Storage temperature and shelf life vary with the grade. In one manufacturer’s SDS document, the typical storage temperature for solid grades is given as 7–27 °C; the shelf life is stated as 24 months for some grades (for example the AD type) and 18 months for others (for example the W, WB, WHV and TW groups). For more sensitive grades (for example some sulfur-modified G types), a range of 7–18 °C and a shelf life of 12 months are specified. For aqueous dispersion (latex) grades, the same manufacturer’s SDS document gives a range of 7–27 °C and, for some grades, a shelf life of 6 months. These values are given as examples; the exact conditions for your product should be taken from the supplier’s TDS and SDS documents.
Other points to consider during storage are as follows:
• Cold storage: Below about 10 °C, polychloroprene can slowly crystallize and harden. The crystallization is reversible; however, the product must be brought to a suitable temperature before processing.
• Heat and light: High temperature and direct sunlight can accelerate degradation and the release of HCl; these factors should be avoided in storage conditions.
• Incompatible materials: It must not be stored together with strong oxidizing agents. Flammable solvents (for example those used in adhesive production) should be stored in separate areas.
• Moisture and contamination: Opened packages should be protected from moisture and from contaminants such as dust and oil.
• Packaging: Solid rubber chips are commonly supplied in paper or similar bags of 20–25 kg; other product forms and large-volume packaging may also be available. When stacking bags, the risk of the product sticking and deforming should be taken into account.
• Stock rotation: Because shelf life is limited, the first-in, first-out (FIFO) principle should be applied. In sulfur-modified grades that have been stored for a long time, the Mooney viscosity may change, so it should be checked before use.
Transport: According to manufacturer SDS documents, solid polychloroprene chips are not classified under dangerous goods transport. Because the classification may change depending on the form of the product (solid, latex or solvent-containing mixture) and the auxiliary substances it contains, the current transport classification should be checked in the supplier’s SDS document. Polychloroprene adhesives can be classified as flammable liquids when they contain solvents. On the other hand, the monomer chloroprene is transported as a flammable and toxic liquid (Class 3) under UN 1991; it must not be confused with the polymer.
In the event of a spill, the product should be swept up without generating dust and collected in a suitable container, and large quantities must be prevented from reaching drains or surface waters. Talc-coated chips can be slippery on the floor; care should be taken during cleanup.
SAFETY INFORMATION ON POLYCHLOROPRENE RUBBER
This section is intended as informational material for the general reader. It does not replace product-specific official safety requirements; for safe use, the current SDS document of the product supplied should be taken as the basis.
Hazard class: In one manufacturer’s SDS document, solid polychloroprene chips are not classified as a hazardous substance under CLP (EC 1272/2008); there is no pictogram, signal word or hazard statement. The product is a non-flammable solid; the flash point is stated as above 260 °C. However, some grades may contain auxiliary substances (for example resin, dithiocarbamate or disulfiram-like components), and these may cause skin sensitization. The classification should therefore be verified from the SDS document on a grade-by-grade basis.
Skin, eyes and respiratory tract: No serious acute effect is expected under normal conditions. However, small amounts of irritating gas and particulates may be released during drying, cleaning and molding; this may cause irritation of the eyes, nose and throat. The resin (rosin) present in some grades may cause skin sensitization. The manufacturer’s SDS document states that no skin sensitization was found in animal tests on the product itself. For the resin, workplace exposure limits linked to occupational asthma and sensitization exist in some countries.
Fire and reactivity: Solid polychloroprene does not ignite easily; if it burns, water, foam, carbon dioxide or dry chemical powder can be used. During combustion and thermal decomposition, acidic and irritating gases such as hydrogen chloride may form; firefighters must use self-contained breathing apparatus. Contact with strong oxidizing agents must be avoided.
Handling and personal protective equipment: Adequate ventilation should be provided and dust formation avoided. The use of nitrile gloves, suitable eye protection and, where dust is generated, a dust mask is recommended. Hands should be washed after handling; eating, drinking and smoking should not take place in the work area. If hot polymer contacts the skin, the area should be cooled quickly with cold water and the adhering polymer must not be peeled off.
First aid: If breathing difficulty occurs, the person should be moved to fresh air; in case of skin contact, wash with soap and water; in case of eye contact, rinse with plenty of water for at least 15 minutes; if swallowed, rinse the mouth with water. If symptoms persist or are severe, medical attention should be sought.
Spills and accidents: The product is collected by sweeping or shoveling and kept in a suitable container as waste. Large quantities are prevented from reaching drains and surface waters.
Environmental risks: According to manufacturer data, the product is not classified as PBT or vPvB. However, since some auxiliary substances may be toxic to the aquatic environment, the grade-specific SDS should be checked. Large quantities must not be released into surface waters.
Waste management: Waste and empty packaging should be disposed of in accordance with local legislation. If incineration is required, because polychloroprene forms acidic products when burned, it should be incinerated in facilities equipped with systems capable of capturing these products.
Chloroprene monomer: The chloroprene monomer used in the production of the polymer is toxic and flammable, and it is classified by IARC in Group 2B, meaning “possibly carcinogenic to humans”. Occupational exposure arises mainly in the facilities where the monomer is produced and polymerized. Keeping the residual monomer in the commercial polymer low is part of the manufacturer’s quality control; residual monomer information can therefore be requested through the TDS/COA.
Usage restrictions: Some manufacturers recommend their products only for manufacturing and research purposes and restrict their use in applications such as medical implants without a written agreement. The safety information of different manufacturers and grades should not be assumed to be the same.
WHAT SHOULD BE CONSIDERED WHEN BUYING POLYCHLOROPRENE RUBBER?
The first step in sourcing polychloroprene rubber is to clarify in which application and in which form the product will be used. The quality criteria sought for technical rubber articles, contact adhesives, latex dipping and cable sheathing are not the same.
Instead of writing only “polychloroprene”, “neoprene” or “CR” in the purchase request, specifying the following information makes it easier to select the right product:
• Correct chemical identity: the CAS number (9010-98-4), whether the polymer is a homopolymer or a copolymer, and that the product is not confused with other materials such as NBR, CSM, SBR or neoprene foam
• Grade class: sulfur-, mercaptan- or xanthogen-modified; crystallization rate; pre-crosslinking
• Mooney viscosity and acceptable range
• Product form: solid chips, bales or latex; for latex, solids content and emulsifier type
• Application: rubber article, contact adhesive (solvent- or water-based), cable, dipping, foam
• Technical specifications and test methods (for example the ISO 2475 approach)
• Packaging and logistics: bags, pallets, IBC or drum for latex; transport and storage temperature requirement
• The supplier’s technical support and application knowledge
• Batch consistency: differences in Mooney, crystallization and additives from manufacturer to manufacturer and from batch to batch
• Product documents: TDS, SDS, COA, certificate of origin
• Regulatory conditions: REACH, food contact legislation (if applicable), manufacturer restrictions in medical and skin-contact applications
• Total cost of supply: unit price, logistics, shelf life, scrap and processing yield
The price of polychloroprene varies according to the product grade and type of modification, product form, raw materials (butadiene, chlorine), energy and production costs, order quantity, packaging, logistics and market conditions. For this reason, the current price should be evaluated through a quotation together with the product specification and delivery terms. Polychloroprene is generally a more expensive specialty elastomer than natural rubber and SBR; the price difference should be considered together with the property requirement.
SUPPLY OF POLYCHLOROPRENE RUBBER FROM ATAMAN KİMYA
Polychloroprene rubber is an important specialty elastomer evaluated as a base elastomer, binder and coating raw material in rubber articles, adhesives, cables, latex, construction and textile applications. For manufacturers planning to purchase the product, it is important to clarify the grade suited to the area of use, the technical properties and the necessary documents before ordering.
Companies that wish to obtain information about the supply of Polychloroprene Rubber from Ataman Kimya can request information on product suitability, current supply status, packaging options and a price quotation by sharing their areas of use and technical needs.
The current stock status, origin, grade class, technical properties, packaging and specifications of the product should be confirmed with Ataman Kimya before ordering.
Sharing the following information in a quotation request makes it easier to evaluate the right Polychloroprene Rubber product:
• Sector of use and final application
• Requested product form (solid chips, bales or latex)
• Requested grade type and modification type
• Requested Mooney viscosity and crystallization rate
• Formulation or process information in use
• Requested quality standard
• Estimated order quantity
• Requested packaging type
• Requested technical documents
• Existing product’s TDS or COA information, if available
FREQUENTLY ASKED QUESTIONS ABOUT POLYCHLOROPRENE RUBBER
What is polychloroprene rubber?
Polychloroprene rubber (PCR) is a synthetic elastomer that contains chlorine in its structure and is obtained by the emulsion polymerization of the monomer 2-chloro-1,3-butadiene. Because it is resistant to oil, ozone, weathering and flame, it is used in technical rubber articles, adhesives, cables and latex products. In commercial language it is commonly called neoprene.
What does polychloroprene rubber mean?
Polychloroprene is the polymer of the chloroprene monomer. “Poly” means many, and “chloroprene” means a butadiene-derived monomer carrying chlorine. In Turkish it is referred to as “polikloropren kauçuk”, and in English as chloroprene rubber or polychloroprene.
What is the CAS number of polychloroprene rubber?
The CAS number for polychloroprene (homopolymer) is 9010-98-4. The CAS number for the monomer chloroprene is 126-99-8.
What is the EC / EINECS number of polychloroprene rubber?
There is no classical EINECS registration for the polymer. Some manufacturer SDS documents give the list number 618-463-8 for the homopolymer, while others state the EC number as not applicable. The EC number for the monomer chloroprene is 204-818-0.
What is the chemical formula of polychloroprene rubber?
The formula of polychloroprene rubber is (C₄H₅Cl)ₙ, and its repeat unit is –CH₂–CH=C(Cl)–CH₂–. The molecular weight of the monomer is 88.54 g/mol.
What is the difference between polychloroprene and NBR?
Both are polar synthetic elastomers, but NBR contains acrylonitrile and is markedly more resistant than polychloroprene to mineral oil and fuel. Polychloroprene, on the other hand, is superior in ozone, weather and flame behavior. The choice is made according to oil and fuel contact, outdoor use, flame-retardant property, temperature and cost.
What is polychloroprene rubber used for?
It is used as the base polymer or binder in products such as hoses, belts, gaskets, vibration-isolation parts, cable sheaths, contact adhesives, latex gloves, neoprene foam, coated fabrics and bridge bearings.
In which sectors is polychloroprene rubber used?
It is used in the automotive, cable, industrial rubber articles, building and construction, footwear and furniture, sports and textile, protective glove, marine and protective coating sectors.
How does polychloroprene form the bond in adhesives?
When soluble polychloroprene grades are applied to two surfaces and joined after the solvent has evaporated, they crystallize thanks to their regular chain structure. Crystallization provides high initial strength without waiting for chemical crosslinking. Adding resin and MgO increases heat resistance and adhesion. The crystallization is reversible by heating.
What is polychloroprene rubber good for?
It is used to produce elastic materials that are resistant to oil, ozone and weathering, flame-retardant, and resistant to tearing and abrasion, as well as strong adhesives.
How is polychloroprene rubber cured (vulcanized)?
It is generally cured with zinc oxide and magnesium oxide, and, where necessary, in the presence of organic accelerators (historically ethylene thiourea). Zinc oxide is the crosslinker, and magnesium oxide is the HCl acceptor. Sulfur-modified grades can also cure without an accelerator.
Is polychloroprene rubber soluble in water?
No. Polychloroprene is insoluble in water. It dissolves in solvents such as toluene, xylene, chloroform and ethylene dichloride; it does not dissolve in n-hexane and mineral spirits. The latex form is the polymer dispersed in water.
How much polychloroprene is used in a rubber compound or an adhesive?
In rubber compounds, polychloroprene is taken as the reference polymer at 100 parts (phr), and the other ingredients are calculated accordingly. In adhesives, the polymer proportion is determined by the solution viscosity, the solids target and the solvent system. The right proportions should be determined by laboratory and production trials.
Is polychloroprene rubber a hazardous substance?
Solid polychloroprene rubber is not classified as hazardous under CLP in one manufacturer’s SDS document and is non-flammable. However, irritating gas or particulates may be released during processing; the resin and auxiliary substances in some grades may cause skin sensitization. The monomer chloroprene, on the other hand, is toxic and flammable. The current SDS should be taken as the basis.
Why can polychloroprene cause an allergic reaction in some people?
No sensitization has been reported for the polymer itself. Allergic reactions are more likely to arise from the resin (rosin), accelerators and other auxiliary substances in the composition. The chemicals used in latex products should be evaluated in this respect.
Is polychloroprene rubber registered under REACH?
Polymers are generally exempt from the registration obligation under REACH. The monomers used in the production of the polymer (2-chloro-1,3-butadiene and 2,3-dichlorobutadiene), however, are registered. The current status should be checked from the SDS document of the product concerned and from official sources.
What is the physical appearance of polychloroprene rubber?
Solid grades are in the form of white, cream, beige or light brown chips, pieces or bales and are generally coated with talc. Latex grades are milky white aqueous dispersions.
What is the UN number of polychloroprene rubber?
According to the manufacturer’s SDS document, solid polychloroprene chips are not classified under dangerous goods transport; therefore they have no UN number. The monomer chloroprene, on the other hand, is transported under UN 1991.
Why are Mooney viscosity and crystallization rate important for polychloroprene?
Mooney viscosity determines the processability of the raw rubber, while the crystallization rate determines the initial bond strength in adhesives and the tendency to harden in the cold in rubber articles. These two parameters must be selected according to the application.
What does the price of polychloroprene depend on?
The price varies according to the grade and type of modification, product form, raw material and energy costs, order quantity, packaging, logistics and market conditions.
Is there an alternative to polychloroprene rubber?
Depending on the application, NBR, EPDM, CSM, SBR/natural rubber, FKM, AEM and polyurethane can be alternatives. In adhesives, polyurethane dispersions, acrylic water-based systems and SBS-based adhesives are used; in latex gloves, natural rubber, nitrile and synthetic polyisoprene latex. The choice should be made according to performance, cost and legislation.
How should polychloroprene rubber be stored?
It should be stored in a cool, dry and well-ventilated area, in its closed original packaging, away from heat, direct sunlight and strong oxidizing agents. The typical storage temperature is 7–27 °C in some manufacturer SDS documents; the shelf life may be 12–24 months depending on the grade, or shorter for latex.
Which documents should be requested when buying polychloroprene rubber?
The TDS, SDS and COA are the basic documents. In addition, information on origin, REACH and related regulatory compliance information, declarations of conformity for food-contact or special applications, and test reports may be requested.
Which technical properties are important when buying polychloroprene rubber?
The type of modification, Mooney viscosity, crystallization rate, product form, additive system (stabilizer, resin salt, talc), volatile matter, residual monomer, shelf life, and the cure and mechanical properties in a standard test mix are important.
POLYCHLOROPRENE RUBBER – TECHNICAL SUMMARY
Chemical name: Poly(2-chloro-1,3-butadiene); Polychloroprene
Common name: Polychloroprene rubber, chloroprene rubber, neoprene (PCR)
CAS number: 9010-98-4
EC / EINECS number: No classical EINECS registration; the list number 618-463-8 appears in some SDS documents
Molecular formula: (C₄H₅Cl)ₙ; repeat unit 88.54 g/mol
Chemical class: Synthetic elastomer, chlorinated diene polymer
Physical appearance: White-cream-beige chips, pieces or bales; milky dispersion in latex form
Main physical and chemical properties: Density about 1.23–1.25 g/cm³; insoluble in water; polar, chlorinated structure; chain predominantly trans-1,4; tendency to crystallize; glass transition temperature about –48 °C (reference grade); decomposition above 200 °C
Main functions: Base elastomer polymer, adhesive binder, raw material for latex coating and dipping
Important areas of application: Hoses, belts, gaskets, vibration isolation, cable sheaths, contact adhesives, latex gloves, neoprene foam, bridge bearings, coated fabrics
Parameters critical for quality control: Type of modification, Mooney viscosity, crystallization rate, volatile matter, ash/talc content, stabilizer and resin salt, residual monomer, shelf life; for latex, solids content, pH and emulsifier type
Basic storage information: Cool, dry, in closed original packaging; typically 7–27 °C; shelf life of 12–24 months depending on the grade (shorter for latex); away from strong oxidizing agents and heat; hardening through crystallization in the cold
Safety summary: The solid polymer is non-flammable and is not classified under CLP in one manufacturer’s SDS document; irritating gas and particulates may be released during processing; HCl forms on combustion; the monomer chloroprene is toxic and flammable (IARC Group 2B)
For polychloroprene rubber, the correct selection of the grade class, the type of modification, the Mooney viscosity and the crystallization rate is decisive for the performance of the final product. Before purchase, the area of use, the required product form and grade class, the viscosity and crystallization requirements, the quantity and the technical document needs should be clarified; current product, stock, origin, packaging and quotation information should be confirmed with the supplier.
