Blends NBR/PVC

Flgure 4 tanS versus temperature for NBR-PVC blends curve 1-BMI/MBTS curve 2-S/PNDA curve 3 = DHBP/ PETA. Source Ref. 21. 

Wang and Chen [41] studied the compatibility problems of incompatible NBR-PVC blends. Poly(vinyl-idene chloride-covinyl chloride) is reported to act as an efficient interfacial agent. Blends of PVC, NBR, and the copolymer were prepared by the solution casting technique using THE as a solvent. Improvement in mechanical properties can be achieved in NBR-PVC blend by the addition of different types of rubbers [42]. Different rubbers include NR, styrene butadiene (SBR) and butadiene (BR). Replacement of a few percent of NBR by other rubbers will improve the mechanical properties and at the same time reduce the cost of the blend. 

It is Interesting that unimodal distributions are observed for the other filled systems. The distribution of tg for pure NBR is shown in Figure 9 by dotted line, and the NBR PVC blend by solid line. The blend system shows clearly unimodal distribution. The type of the distribution of pure NBR, however, is biased from the exponential type as will be discussed later. It is seen that the distribution of tg in the filled system shifts towards the unimodal. 

The analysis of the difference in those P(tg) of NBR and NBR-PVC blended system shows that the effect of creep strain on P(tg) is also negligible and the difference between the distributions of tg for those materials is considered to be the difference coming from the difference in their failure mechanisms. 

Bur-A-Loy . [Mach-1 Compounding] NBR/PVC blends can be viilcanized, used as a thermoplastic or as a hardness enhancer used for extruded or molded prods. 

Humes. [Hules Mexicanos] Nitrile elastomer or NBR/PVC blends used for molded parts, mech. goods subjected to oils and fuels, wire and cable jackets, soles, hoses. 

Nipol . [Zeon] Butadiene-acrylonitrile copolymer or NBR/PVC blends used for hose, sheet packing, molded and extruded goods, oil seals, sundries, adhesives, plastic modification, o-rings, coated materials. 

Rhenoblend. [Rhdn Chemie] Chloro-prene, fiuoro rubber, or NBR/PVC blends for tech, mold goods. 

The different formulations of NBR/PVC blends marketed by Zeon under the trade name NipoP show either a co-continuous or dispersed structure. The NBR/PVC formulations vary from 50 50 to 70 30 wt%. The blends are processed mostly by extrusion into products such as cable jackets and hose covers. Injection molding is also being carried out. The blends show good ozone and abrasion resistance. Grades with higher AN content in the NBR display better ozone and fuel resistance while lower AN content results in improved low temperature flexibility. 

NBR/PVC blends marketed by Uniroyal Parac-riP OZO) cover the concentration range NBR/PVC = 70 30 to 60 40 and show a dispersed morphology. They are typically formed by injection molding, extrusion and calendering and show the good fuel and oil resistance and low compression set. 

Blends of butadiene-acrylonitrile copolymer rubber (nitrile rubber or NBR) and PVC are among the oldest known examples of commercial elastomer/ thermoplastic blends. The shortage of natural rubber during World War II stimulated research in the USA on the compounding and modification of synthetic polymers to produce rubber-like materials. An outcome of this research was the commercial introduction of NBR/PVC blends by B.F. Goodrich in 1947 under the trade name of Geon Polyblends [Pittenger and Cohan, 1947]. The blend showed improved ozone resistance and melt processability compared to the nitrile rubber (Table 15.12). 

K. J. Kim (Kim, 2012) has studied the effect of addition of organo bifitnctional silane (TESPD) into siliea eontained NBR/PVC blend. The addition of the TESPD irrto sihea filled NBR/PVC eompoimd leads to an increase in the degree of cross-linking by formation of a strong three-dimerrsional network stmcture between silica sitrface and mbber matrix via conpling reaction, which results in improved me-ehanieal properties and proeessabihty. 

FIGURE 14.14 Comparison of tensile strength of sulfur and electron beam cured NBR-PVC blend (Mark and Bdaes, 1986)... 

Two routes are offered by producer on which articles based on NBR/PVC blends can be manufactured processing of ready to use blends described below and application of developed powdered nitrile elastomers which can be easily dispersed in continuous mixing operation which enables them to be used directly in extrusion and injection molding. If second option is used it is important to remember that plasticizers and stabilizers should be predispersed in PVC because otherwise they may swell the elastomer and cause formation of lumps. PRODUCER... 

NBR is very compatible with PVC because of similar solubility parameters (i.e., cohesive energy density). If properly fluxed, an NBR/PVC blend will possess very good ozone resistance. 

The use of this NBR/PVC blended product has been decreasing in the United States and Europe. Other thermoplastic polyolefins are replacing it. 

NBR to which PVC resin is added results in a compound with much improved ozone and abrasion resistance as well as green strength during processing. A minimum of 25% PVC resin provides ozone resistance, hence most simple NBR/PVC blends are 70/30 blends. The presence of PVC resin detracts from both the low- and high-temperature resistance. 

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