Polybutadiene grafting

To produce the Type 2 polymers, styrene and acrylonitrile are added to polybutadiene latex and the mixture warmed to about 50°C to allow absorption of the monomers. A water-soluble initiator such as potassium persulphate is then added to polymerise the styrene and acrylonitrile. The resultant materials will be a mixture of polybutadiene, polybutadiene grafted with acrylonitrile and styrene, and styrene-acrylonitrile copolymer. The presence of graft polymer is essential since straightforwsird mixtures of polybutadiene and styrene-acrylonitrile copolymers are weak. In addition to emulsion processes such as those described above, mass and mass/suspension processes are also of importance. 

ABS copolymers obtained by this method consists of a mixture of polybutadiene, polybutadiene grafted with acrylonitrile and styrene and styrene-acrylonitrilecopolymer. The graft copolymer gets cross-linked. 

To improve the thermal stability of PVC, it is common to add stabilizers, generally metalloorganic compounds, in concentrations of 1-5 parts per 100 parts of PVC. Although the cis-1,4-polybutadiene grafted PVC, in the absence of an added stabilizer, yielded essentially colorless or only faintly discolored films, completely colorless films were obtained when the conventional stabilizers were added in concentrations of 0.1-0.3 parts per 100 parts of modified PVC. Organotin stabilizers were not necessary and, in some cases, actually resulted in greater color development than when they were absent. 

The addition of small amounts of various stabilizers to untreated or polybutadiene-grafted PVC decreased the rate of hydrogen chloride evolution. Thus, as shown in Figure 1, 0.15 phr which is less than 10% of the recommended amounts of a mixture of non-toxic calcium-zinc stabilizers, increased the time for 0.1 mole % dehydrochlorination of suspension polymerized PVC from 28 to 36 minutes and of Type M PVC prepared from the suspension polymer from 41 to 47 minutes. Type P PVC prepared from the same polymer required 49 minutes for the same extent of dehydrochlorination. 

Mechanism of Stabilization. The improved thermal stability of the cis-1,4-polybutadiene-grafted PVC may arise as a result of the treatment to which the polymer is subjected and/or to the structural changes generated thereby. 

Figure 16. Effect of monomer conversion on critical surface tension of polybutadiene grafted with styrene, doubly precipitated...

Grafting is achieved by chain transfer of the growing polymer chains to the rubber molecules. For unsaturated rubbers such as polybutadiene grafting probably occurs at allylic carbons or at pendant double bonds. 

Polybutadiene-graft-poly(methacrylic acid) Ethanol Polystyrene... 

Interpolymers are produced by copolymerizing styrene and acrylonitrile in the presence of polybutadiene rubber (latex) by using batch or continuous emulsion polymerization. The resultant materials are a mixture of polybutadiene, SAN copolymer, and polybutadiene grafted with styrene and acrylonitrile. The mixture is made up of three phases a continuous matrix of SAN, a dispersed phase of polybutadiene, and a boundary layer of SAN graft. 

Cyrolite Rohm Styrene-polybutadiene graft copolymers... 

High-impact polystyrene (HIPS) is a graft copolymer. It is a PS backbone with chains of polybutadiene grafted onto the backbone. PS gives the material strength, but the rubbery polybutadiene chains give resilience to make it less brittle. 

The most important example of graft eopolymers having polystyrene sidearms is high-impaet polystyrene (HIPS), in whieh polystyrene is the continuous phase and polybutadiene grafted with polystyrene forms the separated phase. Grafting occurs when some of the radicals react with the double bonds in polybutadiene [182-186], Grafting is also possible onto poly(ethene-co-propene-co-butadiene) [187] and polyacrylic ester [188], High-impact polystyrene is reviewed in detail in Ref. [189]. 

If unsaturation occurs in the branched arm of the polymer that is to be blocked (e.g., 1,2-polybutadiene), graft copolymers (7) and (8) will arise by vinylic and metathesis pathways, respectively ... 

Poly(butadiene-co-styrene) Polybutadiene grafted with poly(styrene-co- 1788, 2341... 

ABS polymers prepared in this way consist of a continuous matrix of styrene-acrylonitrile copolymer, dispersed particles of polybutadiene and a boundary layer of polybutadiene grafted with acrylonitrile and styrene. 

A similar expression can be deduced for monomer . Figure 3.4 represents the partitioning of styrene and methyl methacrylate between monomer droplets and latex particles consisting of poly(styrene-co-methyl methacrylate) and polybutadiene-graft-poly(styrene-co-methyl methacrylate), respectively (Aerdts et al, 1993). As is shown in Figures 3.4 and 3.5, the experimental data can be described by this model, that is, by Equation 3.13. Figure 3.5 shows the mole fraction of methyl methacrylate in the latex particles as a function of the mole fraction of methyl methacrylate in the monomer droplets. Here again, the model can describe the experimental results extremely well. 

Figure 3.5 Experimentally determined fractions of methyl methacrylate in the droplet phase as a function of the fraction of methyl methacrylate in different latex particles. Methyl methacrylate and styrene in polybutadiene (open circles), SMMA-free (open squares), SMMA-graft (open triangles) from polybutadiene-graft-poly(styrene-co-methyl methacrylate) latex particles, while the closed squares represent a poly(styrene-co-methyl methacrylate) latex swollen with styrene and methyl methacrylate. The solid line gives the theoretical prediction according to Equation 3.13.

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