单选Polyethylene pipes can be processed by（）
A Injection
B Extrusion
C Compression
D Blow molding
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多选Which one （s） of the following is or are correct（）
A Isotactic and syndiotactic polymers possess stereo-regular structures
B Atactic and isotactic polymers possess stereo-regular structures
C Isotactic and syndiotactic polymers are rigid, crystallizable, high melting, and relatively insoluble
D Atactic polymers are rigid, crystallizable, high melting, and relatively insoluble
单选 which polymer has excellent elastic hysteresis（）
A SBR Styrene-butadiene rubber
B NBR Nitrile butadiene rubber
C PIP Polyisoprene
D IIR Butyl rubber
多选Which ones of the following are correct（）
A Trans-polyisoprene is more readily packed and crystallizable, and has properties of crystalline polymers
B Cis-polyisoprene is more readily packed and crystallizable, and thus has properties of crystalline polymers
C Trans-polyisoprene is tougher and harder than cis-polyisoprene
D Cis-polyisoprene is tougher and harder than trans-polyisoprene
单选Upon heating, normally amorphous polymers will suffer the following process（）
A Liqiud-Viscous liquid-Rubbery-Glass transition-Glassy state
B Liqiud-Viscous liquid-Crystallites in a rubbery matrix- Crystallites in glassy matrix
C Glassy state-Glass transition- Rubbery-Viscous liquid-Rubbery- Liqiud
D Liqiud-Crystallites in glassy matrix -Crystallites in a rubbery matrix- -Viscous liquid
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