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
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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
单选Which of the following property would thermoplastic elastomer have over natural rubber and synthetic rubber（）
A High elasticity
B Good resilience
C Recyclability
D Oil resistance
In comparison with PE,__ is or are correct（）
A. Nylon has a higher degree of crystallinity, and a higher melting point
B. Nylon has a higher degree of crystallinity, and a lower melting point
C. PVC and PAN have higher degrees of crystallinity, and higher melting points
D. PVC and PAN have lower degrees of crystallinity, and lower melting points
Most polymers are flammable in their pure form, except___（）
A. Polystyrene
B. Poly（vinyl chloride）
C. Polytetrafluoroethylene
D. Polyimide
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