PVC微孔塑料加工工艺与泡孔结构及耐热性关系研究

以超临界CO2为发泡剂,用动态发泡实验装置在不同的发泡温度、气体饱和压力及振动频率和振幅等加工工艺条件下制备了聚氯乙烯(PVC)微孔塑料。研究发现,发泡温度存在着一个最佳温度范围,使得泡孔密度最大、泡孔尺寸最小;气体饱和压力越大,泡孔结构越好;当剪切速率较低时,在发泡过程中施加强振动作用能显著提高泡孔密度,减小泡孔尺寸,当剪切速率较高时,施加较弱的振动作用即可改善泡孔形态,而施加较强的振动作用可能会产生较大的剪切热和脉动剪切应力,从而破坏泡孔结构;PVC微孔塑料的维卡软化温度与泡孔结构有着密切的关系,泡孔密度越大、泡孔尺寸越小,维卡软化温度就越高。

STUDY ON RELATIONS OF PROCESSING CONDITIONS AND CELL STRUCTURE AND HEAT RESISTANT PROPERTY FOR PVC FOAMS

PVC foams are prepared at different processing conditions of foam temperature,gas saturation pressure,vibration frequency and amplitude by a dynamic foaming experimental setup with supercritical CO_(2) as a foaming agent.The results of cell structures by SEM show that there is an optimal foaming temperature to make cell density maximal and cell size minimal.The higher the gas saturation pressure,the better the cell structure is.When the shear rate is low,the cell density is increased and the cell size is decreased by imposing the strong vibration effect in the foaming process;when the shear rate is high,the cell structure is improved by only imposing weak vibration,and the high shear heat and high oscillatory shear stress can be generated by strong vibration effects and the microstructure of foams might be destroyed thereby.The heat resistant property testing shows that Vitca softening temperature of PVC foams is related with the cell structures.The higher the cell density and the smaller the cell size,the higher the Vitca softening temperature is.