Polychloroprene rubber properties

Both side groups and carbon-carbon double bonds can be incorporated into the polymer structure to produce highly resilient rubbers. Two typical examples are polyisoprene and polychloroprene rubbers. On the other hand, the incorporation of polar side groups into the rubber structure imparts a dipolar nature which provides oil resistance to these rubbers. Oil resistance is not found in rubber containing only carbon and hydrogen atoms (e.g. natural rubber). Increasing the number of polar substituents in the rubber usually increases density, reduces gas permeability, increases oil resistance and gives poorer low-temperature properties. 

The elastomers considered in this section have been selected considering the most commonly used in rubber base adhesives natural rubber butyl nibber and polyisobutylenes styrene-butadiene rubber nitrile rubber polychloroprene rubber (neoprene). Typical properties of these rubbers are shown in Table 2. 

Lee [242] studied the dependence of the physico-mechanical properties of Wollastonite-filled polychloroprene rubber on the type of agent used to pre-treat the filler. The composition contained 26.9 part (weight) of the filler per 100 parts (weight) of the rubber (compositions CR-1100, CR-174, CR-151). The finishing agents were y-aminopropyl triethoxysilane (CR-1100 and CR-174) and vinyl triethoxysilane (CR-151). The mechanical properties of the compositions are listed in Table 7 below. The author proposed an empirical equation to relate the modulus with the equilibrium work of adhesion in the following form ... 

DuPont was looking for a synthetic rubber (SR). Carothers assigned Arnold Collins to carry out this research. Collin s initial task was to produce pure divinylacetylene. While performing the distillation of an acetylene reaction, in 1930, he obtained a small amount of an unknown liquid, which he set aside in a test tube. After several days the liquid turned to a solid. The solid bounced and eventually was shown to be a SR polychloroprene, whose properties were similar to those of vulcanized rubber but was superior in its resistance to ozone, ordinary oxidation, and most organic liquids. It was sold under its generic name neoprene and the trade name Duprene. ... 

Neoprene is the generic name for polychloroprene rubber. It has been produced commercially since 1931 and had rapid and wide acceptance because it is much superior to natural rubber for heat and oil resistance. Heat resistance is far better than NR, BR or SBR. but less than EPDM. When heated in the absence of air, neoprene withstands degradation better than other elastomers which are normally considered more heat resistant, and retains its properties fifteen times longer than in the presence of air. Compression set at higher temperature is better than natural rubber and 100°C is typically the test temperature rather than 70°C. Abrasion resistance is not as good as natural rubber but generally better than most heat resistant and oil resistant rubbers. This is also true for tear strength and flex resistance. 

Neoprene, or polychloroprene rubber (CR) was one of the very first synthetic rubbers produced. It was a material of choice for exterior applications such as profiles used in vehicles, building seals, and cables. Many more marketable products have benefited from this plastic. Except for SBR and IR, neoprene (CR) elastomers are perhaps the most rubberlike of all materials, particularly with regard to its dynamic response (Table 2.6). CRs are a family of elastomers with a property profile that approaches that of NRs (natural rubbers) but has better resistance to oils, ozone, oxidation, and flame. CRs age better and do not soften up on exposure to heat, although their high-temperature tensile strength may be lower than that of NRs. They are suitable for service at 250C (480F). 

Two distinctive properties of polychloroprene rubbers call for brief comment The first is chemical resistance. This is considerably greater than that of hydrocarbon diene-based rubbers. The principal weak points at which diene-based mbbers are attadted chemically are the olefinic double bonds and the a-caibon atoms adjacent to the double bonds. The superior chemical resistance of poly-chloropiene rubbers is primarily a consequence of deactivation of these sites by the vinylic chlorine atoms. Thus the origin of the superior chemical resistance is essentially the same as that of the reduced susceptibility to conventional... 

Uses Bonding agent for bonding rubber doughs, sol n. coatings, and solv.-based dips to a variety of syn. textiles, rec. for adhesives, esp. those based on polychloroprene and on chlorinated rubbers Properties Dk. bm. low vise, liq. dens. 1070 kg/m (20 C) 54% act. Toxicoiogy Harmful by inh. irritating to skin, eyes, and respiratory tract may cause sensitization by inh. 

Chem. Descrip. Triphenyl phosphate CAS 115-86-6 EINECS/ELINCS 204-112-2 Uses Rame retardant platinizing agent, plastidzer tor collodion cotton plastidzer w/o gelatinizing properties for acetyl cellulose reduces tiamm. ot NC and acetyl cellulose-based plastic compds. and lacquer films flame retardant plasticizer tor photographic film materials, surf, coatings, phenolic laminates, cellulose acetate film/compds., rubber articles made from acrylonitrile-butadiene, polychloroprene rubber Features Not compat. with PVC... 

Further information on rubber-based adhesives is to be found in specialized articles Natural Rubber-Based Adhesives, Nitrile Rubber Adhesives, Polychloroprene Rubber Adhesives Applications and Properties and Polychloroprene Rubber Adhesives Modifiers and Additives. 

It is interesting to compare the properties of NBR adhesives with those of another polar rubber Polychloroprene rubber adhesives applications and properties. 

Most Rubber-based adhesives may be cured by a sulphur-based vulcanizing system (see Rubber-based adhesives compounding), however, as mentioned in Polychloroprene rubber adhesives applications and properties, CR adhesives are cross-linked by various reactions involving the labile chlorine atoms in the repeat unit. This is reflected in the additives used, as discussed below. ... 

During the World War II, several new synthetic elastomers were prodnced, and new types of adhesives (mainly styrene-butadiene and acrylonitrile copolymers (see Nitrile rubber adhesives)) were manufactured to produce adequate performance in joints produced with new difficult-to-bond substrates. Furthermore, formulations to work under extreme enviromnental conditions (high temperature, resistance to chemicals, improved resistance to ageing) were obtained using polychloroprene (Neoprene) adhesives (see Polychloroprene rubber adhesives applications and properties and Polychloroprene rubber adhesives modifiers and additives). Most of those adhesives need vnlcanization in order to perform properly. 

Several elastomers can be used in rubber-based adhesives. The elastomer provides the backbone of the adhesive, so the main performance of the adhesive is provided by the rubber properties. However, several specific properties for application are imparted by adding other ingredients in the formulations. The most common elastomers used in rubber-based adhesives are natural rubber (NR), butyl rubber (BR) and polyisobutylenes, styrene-butadiene rubber (SBR), nitrile rubber (NBR) and polychloroprene rubber Neoprene) (CR). 

Polychloroprene rubber (CR) is the most popular and versatile of the elastomers used in adhesives see Polychloroprene rubber adhesives applications and properties and Polychloroprene rubber adhesives modifiers and additives. 

Sanchez studied the functionalization of oxidized SWCNTs and MWCNTs dispersed in thermoplastic elastomers based on poly(butylene terephthalate) (PBT)/ poly(tetramethylene oxide) (PTMO). These nanocomposites showed good dispersion and enhancement in thermo-oxidative stability [27]. 1 % of pristine multi-walled carbon nanotube (MWCNTs) were dispersed in silicon rubber. The SR nanocomposites showed 28 % better thermal stability and 100 % improvement in the ultimate tensile strength is achieved as compared with the pristine polymer matrix counterpart [28]. Also ionic liquids have been tested to improve the dispersion and thermal stability of MWCNTs in polychloroprene rubber (CR) showing improvement in these properties [29]. On the other hand the effect of carbon nanofiber on nitrile rubber was studied. It has been found that the nanofiber increase the thermal stability and decrease the flammability [4]. 

OTHER POLYMERS SHOWING THESE SPEQAL PROPERTIES Solvent resistance polysulfide rubbers second order transition temperature styrene-butadiene rubbers weather and ozone resistance polychloroprene rubbers. 

The polychloroprene rubber preferred is the Neoprene W type. Neoprene G would perhaps give slightly superior properties, but W-type gives the best compromise between properties and processability, (ref. 3). A special low-viscosity grade, similar to W-Ml is used. The compound contains approximately 40 phr high abrasion furnace (HAF) black to reinforce it. 

This second type of blend ratio was initially developed as a means of improving the ozone resistance of nitrile rubber, " where it was used mainly as a competitor for polychloroprene rubber. The amount of PVC present in the blend can vary up to 50 parts, but to have any measurable improvement in weathering properties, at least 25 parts of PVC must be present in the blend. Most commercial producers of... 

The early commercial synthetic rubbers created were the polysulphide rubbers now known as Thiokols these rubbers had good oil resistance, unlike natural rubber, but with a very serious drawback which prevented their widespread acceptance, namely their smell. Processing of these materials in factory-size batches proved to be very obnoxious. Acrylonitrile-butadiene copol3nners (nitrile rubbers) were developed by Bayer and were to find eventually worldwide acceptance in many applications requiring oil resistance. In the mid 1930s polychloroprene rubbers became a commercial proposition after early experimental work at Du Pont. These rubbers, intermediate in properties between nitrile and natural rubber, soon found wide acceptance. 

Kim and Hamed [10] prepared a vulcanizate based on a 50/50 natural mbber/c -butadiene rubber (NR/c s-BR).This blend has been found to retain the rupture resistance property of NR vulcanizate and resistance to slow fatigue crack growth property of c s-BR vulcanizate. Botros et al. [11] studied the properties of acrylonitrile butadiene mbber/polychloroprene rubber blend (NBR/CR). The blend was found to possess the thermal resistance of CR and the oil resistance of NBR. 

Exxon elastomers display good resistance to attack by animal or vegetable oils. However, they are like other petroleum derived synthetic polymers in that their resistance to the attack of hydrocarbons, oils, and other petroleum based chemicals is low. Only VISTALON 6505 blends with nitrile and polychloroprene rubbers maintain good physical properties after prolonged exposure to these materials. 

---