Which of the following statements are correct descriptions of a glass transition in polymers?/ 以下哪一项是对聚合物的玻璃化转变的正确描述?
A.
A change in the frictional properties of the material 材料的摩擦性能发生了变化
B.
A change from stiff glass-like material to softer rubbery 从硬的玻璃态变为软的橡胶
C.
Is associated with the crystals in the fibre 只发生在天然纤维中
D.
Normally occurs at a higher temperature than melting 与纤维中的结晶区有关