Variety type
(a) Isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene
Polypropylene contains a methyl group and is classified into isotatic polypropopylene, atactic PolyPropylene and syndiotatic Polypropylene according to the position of the methyl group . The methyl group is arranged on the same side of the molecular backbone as isotactic polypropylene; if the methyl groups are disorderly distributed on both sides of the molecular backbone, atactic polypropylene; when the methyl groups are alternately arranged on both sides of the main chain, the syndiotactic Polypropylene. In general production of polypropylene resin, the isotactic structure content (called isotacticity) is about 95%, and the rest is random or syndiotactic polypropylene. Polypropylene resins currently produced in China are classified according to the melt index and the additives added. Table 22-16 lists the main types of polypropylene resins.
Table 22-16 Main models of polypropylene
type     number
Melt Index (MI) g/10min
Wait    Regulation
%
Pull  Strength
MPa (kgf/cm2)
blow    Plastic
1200
1230
0.4 to 0.7
0.4 to 0.7
96 to 98
96 to 98
25.5
25.5
(260)
(260)
Note    Plastic
1700
1400
1300
1730
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