Nitrile rubber grafted polymers

At one time butadiene-acrylonitrile copolymers (nitrile rubbers) were the most important impact modifiers. Today they have been largely replaced by acrylonitrile-butadiene-styrene (ABS) graft terpolymers, methacrylate-buta-diene-styrene (MBS) terpolymers, chlorinated polyethylene, EVA-PVC graft polymers and some poly acrylates. 

The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile. The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73-77 parts acrylonitrile and 23-27 parts by weight of methyl acrylate in the presence of a 8-10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber). The Du Pont product NR-16 was prepared by graft polymerisation of styrene and acrylonitrile in the presence of styrene-butadiene copolymer. The Monsanto polymer Lopac was a copolymer of 28-34 parts styrene and 66-72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile. This polymer contained no rubbery component. 

The mechanical degradation and production of macroradicals can also be performed by mastication of polymers brought into a rubbery state by admixture with monomer several monomer-polymer systems were examined (10, 11). This technique was for instance studied for the cold mastication of natural rubber or butadiene copolymers in the presence of a vinyl monomer (13, 31, 52). The polymerization of methyl methacrylate or styrene during the mastication of natural rubber has yielded copolymers which remain soluble up to complete polymerization vinyl acetate, which could not produce graft copolymers by the chain transfer technique, failed also in this mastication procedure. Block and graft copolymers were also prepared by cross-addition of the macroradicals generated by the cold milling and mastication of mixtures of various elastomers and polymers, such as natural rubber/polymethyl methacrylate (74), natural rubber/butadiene-styrene rubbers (76) and even phenol-formaldehyde resin/nitrile rubber (125). 

Bis(2,3-dibromopropyl) fumarate has been used as a fourth monomer in nitrile rubber- and graft-type ABS materials giving flame-resistant polymers. At least 10% bromine incorporation is required to pass the Underwriters Laboratories Subject 94 test. The graft-type materials fail at 7-10% bromine only because of dripping. Both types pass the ASTM D-635 test with 7% or more bromine. For the impact strength to be equivalent to that of conventional ABS, the fourth monomer must be present in both the rubber and resin phases. Thermal stability is marginal but can be improved with typical PVC stabilizers. 

Graft Blends. The properties of ABS-type polymers involving mixtures of terpolymer resins and graft rubbers are shown in Table IV. As with the nitrile rubber types, there is a pronounced gain in impact strength at a given rubber level when DBPF is present in both phases (Blends 1 vs. 3 and 2 vs. 4). 

Use of bis(2,3-dibromopropyl) fumarate as a fourth monomer in either nitrile rubber- or graft-type ABS materials gives flame-resistant polymers. With either type, better impact strength is obtained when the fourth monomer is present in both the rubber and resin phases. The compositions are more thermally stable than poly (vinyl chloride) and can be stabilized by typical PVC stabilizers. 

The catalyzed graft copolymerization of styrene-methyl methacry-late-EASC and a-methylstyrene-methacrylonitrile-EASC onto nitrile rubber in solution is shown in Table XII. In addition, grafting has been done on ethylene-propylene copolymers, polybutadiene, acrylic ester copolymers, and other polymers containing labile hydrogen atoms. 

Table XVII shows the grafting of poly (styrene-alt-acrylonitrile) on nitrile rubber precomplexed with EASC. This system is heterogeneous since addition of EASC to the polymer solution causes the polymer to agglomerate or precipitate.

Another potentially important development in the free-radical polymerization area is the nitrile barrier resins. These products generally are graft polymers containing a glassy phase comprised of 80% acrylonitrile and 20% styrene or other vinyl monomer grafted onto a rubber substrate. The commercialization of these materials has been interrupted by an adverse ruling by the Food and Drug Administration (FDA) in connection with extraction of traces of acrylonitrile in food-related applications. The amounts involved are very small. A new attitude under development in the FDA may lead to the eventual clearance of these materials. 

Owing to the intense research into PANI, one can ensure that new materials will be created in the coming months and years composites, co-polymers, (graft copolymers of PANI and nitrilic rubber [104]), PANI self-doped with organic acids, and so on. It was announced very recently that PANI electropolymerized in cam-phor.sulfonic acid (CSA) presented electrochromic properties analogous to PANI electropolymerized in common acids [105], In fact, it seems that PANl-CSA presents noteworthy stability during electrochromic cyclings [58]. 

Table 7-4. Permeability Coefficients of Gases and Water Vapor in Various Polymers at 20° C. The Gas Passage, Am, Is Measured in cmi. Barex Is a Graft Copolymer of Acrylonitrile Methyl Acrylate on Nitrile Rubber. Lopac Is a Copolymer of Methacrylonitrile and Styrene.

Tg measurements have been performed on many other polymers and copolymers including phenol bark resins [71], PS [72-74], p-nitrobenzene substituted polymethacrylates [75], PC [76], polyimines [77], polyurethanes (PU) [78], Novolac resins [71], polyisoprene, polybutadiene, polychloroprene, nitrile rubber, ethylene-propylene-diene terpolymer and butyl rubber [79], bisphenol-A epoxy diacrylate-trimethylolpropane triacrylate [80], mono and dipolyphosphazenes [81], polyethylene glycol-polylactic acid entrapment polymers [82], polyether nitrile copolymers [83], polyacrylate-polyoxyethylene grafts [84], Novolak type thermosets [71], polyester carbonates [85], polyethylene naphthalene, 2,6, dicarboxylate [86], PET-polyethylene 2,6-naphthalone carboxylate blends [87], a-phenyl substituted aromatic-aliphatic polyamides [88], sodium acrylate-methyl methacrylate multiblock copolymers [89], telechelic sulfonate polyester ionomers [90], aromatic polyamides [91], polyimides [91], 4,4"-bis(4-oxyphenoxy)benzophenone diglycidyl ether - 3,4 epoxycyclohexyl methyl 3,4 epoxy cyclohexane carboxylate blends [92], PET [93], polyhydroxybutyrate [94], polyetherimides [95], macrocyclic aromatic disulfide oligomers [96], acrylics [97], PU urea elastomers [97], glass reinforced epoxy resin composites [98], PVOH [99], polymethyl methacrylate-N-phenyl maleimide, styrene copolymers [100], chiral... 

A random co-polymer or a blend of compatible polymers will have a single glass transition temperature intermediate between those of the two homopolymers. An example is shown in Figure 14 for nitrile-butadiene-rubber (22). The specific weight percents shown are those of commercial interest for NBR. In contrast, most polymer blends, graft and block copolymers, and interpenetrating polymer networks (IPN s) are phase separated (5) and exhibit two separate glass transitions from the two separate phases. Phase separated systems will not be considered here. 

Binding the antioxidant chemically to the elastomer chain by copolymerization or grafting is a better solution to this problem. The addition of A -(4-anilinophenyl)methacrylamide [22325-96-8] (37) to a polymerization recipe for nitrile butadiene rubber (NBR) produces a polymer with a built-in antioxidant... 

Vanyorek L, Meszaros R, Barany S (2014) Surface and electrosurface characterization of surface-oxidized multi-walled N-doped carbon nanotubes. Colloids Surf A 448(1) 140-146 Verge P, Peeterbroeck S, Bonnaud L, Dubois P (2010) Investigation on the dispersion of caibon nanotubes in nitrile butadiene rubber role of polymer-to-filler grafting reaction. Compos Sci Technol 70(10) 1453-1459... 

Owing to the uncertain situation, several companies have withdrawn from this field and at the present time only one type of nitrile resin is commercially available. This product is a copolymer of acrylonitrile and methyl acrylate (70 30 parts by weight) which is formed in the presence of a butadiene-acrylonitrile rubber 00-15%). The product thus contains graft copolymer and has a structure resembling that of ABS polymers previously described (section 3.4.1(b)). 

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