Polychloroprene rubber, surface

To meet this specification a special cover compound was designed at BTR. It is a carbon-black filled polychloroprene rubber, which forms a smooth, carbonized, glazed surface during the drum friction test, and usually gives a maximum temperature of 200-250 C. 

Other polymers used in the PSA industry include synthetic polyisoprenes and polybutadienes, styrene-butadiene rubbers, butadiene-acrylonitrile rubbers, polychloroprenes, and some polyisobutylenes. With the exception of pure polyisobutylenes, these polymer backbones retain some unsaturation, which makes them susceptible to oxidation and UV degradation. The rubbers require compounding with tackifiers and, if desired, plasticizers or oils to make them tacky. To improve performance and to make them more processible, diene-based polymers are typically compounded with additional stabilizers, chemical crosslinkers, and solvents for coating. Emulsion polymerized styrene butadiene rubbers (SBRs) are a common basis for PSA formulation [121]. The tackified SBR PSAs show improved cohesive strength as the Mooney viscosity and percent bound styrene in the rubber increases. The peel performance typically is best with 24—40% bound styrene in the rubber. To increase adhesion to polar surfaces, carboxylated SBRs have been used for PSA formulation. Blends of SBR and natural rubber are commonly used to improve long-term stability of the adhesives. 

Chlorinated rubber is also used to promote the adhesion of solvent-borne CR adhesives to metals and plasticized PVC. Addition of a low molecular weight chlorinated rubber (containing about 65 wt% chlorine) improves the shear strength and creep resistance of polychloroprene adhesives [75] but a reduction in open time is also produced. A heat reactivation (process in which the surface of the adhesive film is raised to 90-100°C to destroy the crystallinity of the film and allowing diffusion to produce polymer chain interlocking more rapidly) restores tack to the polychloroprene adhesives. 

Fluoroelastomers Novikova et al. [32] reported unproved physico-mechanical properties of fluoro mbbers by reinforcement with chopped polyamide fibers. Other fiber reinforcements are covered by Grinblat et al. [33]. Watson and Francis [34] described the use of aramid (Kevlar) as short fiber reinforcement for vulcanized fluoroelastomer along with polychloroprene mbber and a co-polyester TPE in terms of improvement in the wear properties of the composites. Rubber diaphragms, made up of fluorosilicone mbbers, can be reinforced using aramid fiber in order to impart better mechanical properties to the composite, though surface modification of the fiber is needed to improve the adhesion between fluorosUicone mbber and the fiber [35]. Bhattacharya et al. [36] studied the crack growth resistance of fluoroelastomer vulcanizates filled with Kevlar fiber. 

Polychloroprene (neoprene) Toluene, methanol, isopropanol 1. Abrasion followed by brushing. Grit or vapor blast or 100-grit emery cloth followed by solvent wipe. 2. Etch surface for 5-10 min at RT following procedure 2 for natural rubber. Adhesion improved by abrasion with 280-grit emery cloth followed by solvent wipe... 

Calendering and Extrusion. Friction compounds are used to build up composite structures of fabric and rubber. The surface of the calendered fabric mnst have good green strength or building tack. Thus calendered stocks are nsnally made from slow-crystallizing polychloroprene types. Polychloroprene... 

Polychloroprene (CR) has much more chlorine than the chlorobutyl rubber examined by Lawson and good adhesion to untreated CR wonld be expected provided there was no weak layer was on the surface. If such layers exist a suitable solvent treatment or abrasion should result in good adhesion. Cyclisation has been recommended as a pre-treatment [50, 51]. Lawson noted a large uptake of chlorine, nitrogen and oxygen on treatment of polychloroprene with TCICA, indicating addition across the carbon-carbon donble bond. 

It is possible to determine the effect on polymers of different substances or media and to differentiate them [3]. When a medium causes a chemical reaction with a polymer, it is called a chemically active medium [2]. These effects are irreversible and the deterioration caused to the polymeric material is very important. Such media are acids, bases, oxidants, and all other substances that can cause chemical reactions such as substitution, addition, and hydrolysis. In some cases the chemical reaction is limited to the polymer surface and produces a protective layer against a deeper deterioration by the corrosive chemical. Such surface reactions are those produced by nitric acid on vulcanized PI and SB rubbers or by sulfuric acid on vulcanized polychloroprene and NR [4-7]. 

Bonding Soles to the Lasted Uppers. Polychloroprene and polyurethane solvent adhesives, occasionally also dispersions of the same polymers, are used for this purpose. Various pretreatments are used to improve the bond application of a thin first coat of adhesive, especially for absorbent surfaces priming, in particular the halogenation of vulcanized rubber and thermoplastic rubber soling the use of base-coat primers for nylon and other synthetics, as well as UV-curing primers for EVA and other substrates in athletic footwear. 

A study was made of the effects of chloramine disinfectants and free chlorine in water on rubber mechanical parts used in water distribution systems. Tests were undertaken to investigate swelling, surface cracking and loss of elasticity and tensile strength of specimens based on NR, SBR, polychloroprene, nitrile mbber, EPDM, butyl mbber, fluoroelastomers and silicone mbbers. 9 refs. 

DOP and other phthalate plasticizers are commonly used in rubber compounds based on polar elastomers such as nitrile rubber or polychloroprene, for example. DOP is used in these specialty elastomer-based compounds because like dissolves like. In the language of thermodynamics, these elastomers have a solubility parameter similar to that of DOP. A polar plasticizer is used with a polar elastomer because they are compatible with each other, and the plasticizer has sufficient affinity for the elastomer that It does not bleed (or bloom) to the surface of the rubber product. 

The cure reaction for many silicone sealants is initiated by acid added at low levels to the sealant formulation. Acids are chemically incompatible with concrete, marble, and limestone. When acid-containing silicone sealants are used in joints with these substrate materials, the acid reacts with the substrate bond surfaces, creating salts at the bond interface. These salts destroy the sealant/substrate adhesion and cause debonding and loss of the seal. In order to use a silicone sealant with these substrates, a silicone formulated without acid is required. Other known chemical incompatibilities are silicone and polychloroprene. Use of these two materials together in a sealant joint is to be avoided. Solvated sealant use in joints containing plastic or rubber materials should be undertaken only after chemical compatibility studies of the sealant with these materials is performed. Typical incompatibility will manifest itself over time by causing the sealant or substrate to soften, harden, crack, and/or craze. A standard test method for determining chemical compatibility is ASTM D-471. 

Abstract This chapter constitutes one of the very few reviews in the existing literature on shoe bonding, and it gives an updated overview of the upper to sole bonding by means of adhesives. The surface preparation of rubber soles and both the formulations of polyurethane and polychloroprene adhesives are described in more detail. The preparation of adhesive joints and adhesion tests are also revised. Finally, the most recent development and technology in shoe bonding is described. 

In the past, polychloroprene adhesives were more extensively used in upper to sole bonding, but nowadays polyurethane adhesives are preferred. Polychloroprene adhesives have better tack and improved wettability than polyurethane adhesives, but the polychloroprene adhesives are not compatible with surface chlorinated rubber soles and cannot be used to joint PVC soles. Therefore, polyurethane adhesives show better versatility on higher number of substrates and also have lower oxidative degradation in time. However, they require always the surface preparation of the materials to be bonded. 

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