Graft copolymer compositions

Table VI shows that crosslinking ability of the VC/PE (50-50) graft copolymers is good (little flow at 200°C). To work with products of similar hardness, the PVC compound mentioned in that table for comparison was plasticized with 30 phr of dioctylphthalate. Another outstanding property of the graft copolymer compositions is their very low brittle point. Crosslinking of these compositions is rapid.

Table VII. Crosslinking of Plasticized VC/PE Graft Copolymer Compositions...

Table VII shows that incorporation of a plasticizer in the graft copolymer compositions gives vulcanizates of lower hardness. Their flow resistance remains good. Elongation of the plasticized vulcanizates is improved.

The graft copolymer compositions are easily extrudable at temperatures low enough to avoid scorching. 

From the data generated so far, an attempt was made to determine the epoxy-acrylic graft copolymer composition. 

Still another starch-polyester graft copolymer and a chemically modified starch-polyester graft copolymer composition has been described. The starch-polyester graft copol5mers are synthesized by the reaction of starch with biodegradable polyester polymers in the presence of maleic acid and glycerol as plasticizer. Examples of biodegradable polyesters are summarized in Table 7.6. 

The calculation methods described above may be used for multiphase polymers such as blends, block or graft copolymers, composites, and semicrystalline polymers. 

Monomer compositional drifts may also occur due to preferential solution of the styrene in the mbber phase or solution of the acrylonitrile in the aqueous phase (72). In emulsion systems, mbber particle size may also influence graft stmcture so that the number of graft chains per unit of mbber particle surface area tends to remain constant (73). Factors affecting the distribution (eg, core-sheU vs "wart-like" morphologies) of the grafted copolymer on the mbber particle surface have been studied in emulsion systems (74). Effects due to preferential solvation of the initiator by the polybutadiene have been described (75,76). 

Porous membranes with selective permeabiUty to organic solvents have been prepared by the extraction of latex films prepared with moderate ratios of PVA—PVAc graft copolymer fractions. The extracted films are made up of a composite of spherical cells of PVA, PVAc microgel, and PVA—PVAc graft copolymers (113). 

Two commercially significant graft copolymers are acrylonitrile—butadiene—styrene (ABS) resins and impact polystyrene (IPS) plastics. Both of these families of materials were once simple mechanical polymer blends, but today such compositions are generally graft copolymers or blends of graft copolymers and homopolymers. 

There has been a conventional sense that the PVAc latexes prepared in the presence of PVA as a protective colloid contain the graft copolymer of PVA and PVAc, so that PVAc particles in the dried latex film are not extracted at a high ratio with solvents. In this Chapter, it has been defined without an influence by the usual sense that the porous PVA-PVAc composite can be prepared from the PVAc latex film with acetone extraction. The porous film consists of the spherical cells of PVA... 

Grafting provides a convenient means for modifying the properties of numerous polymers. It is often required that a polymer possess a number of properties. Such diverse properties may not be easily achieved by the synthesis of homopolymers alone but can be achieved through the formation of copolymers or even terpoly-mers. The formation of graft copolymer with sufficiently long polymeric sequences of diverse chemical composition opens the way to afford speciality polymeric materials. 

As mentioned earlier, the graft molecular weight and copolymer compositions dictate the properties of the system. 

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