以CO2为发泡剂,用高压釜式法制备了发泡聚丙烯(EPP)珠粒.采用差示扫描量热仪和扫描电子显微镜探讨了发泡温度(Tf)和发泡压力(pf)对EPP结晶熔融行为和发泡特性的影响.结果表明,分别提高发泡温度或压力,EPP的熔融双峰均向高温方向移动,低温晶体与高温晶体的结晶度之比增大,而且温度对双峰的影响比压力更敏感.pf在2～4MPa内,EPP的发泡倍率和泡孔密度随pf增大而增大;Tf在133.6～ 140℃间,发泡倍率和泡孔尺寸随Tf升高而变大,泡孔密度随Tf升高而变小.在Tf为133.6℃,pf为4 MPa时,EPP的熔融双峰结构比例合适,发泡倍率较大,泡孔密度最大且尺寸分布均匀、表面光滑.
Expended polypropylene (EPP) was prepared through autoclave foaming process,using CO2 as blowing agent.The influence of foaming temperature (Tf) and foaming pressure (pf) on melting/crystallization behavior and foaming properties of EPP were investigated by DSC and SEM.The results indicate that the double melting peaks of EPP move to higher temperature and the ratio of crystallinity between high-temperature crystal and low-temperature crystal increases with increasing Tf or pf.Furthermore,the effect of Tf on double melting peaks of EPP becomes more sensitive than pf.When pf ranges from 2 MPa to 4 MPa,the expansion ratio and cell density of EPP increase with increasing pf.When Tf ranges from 133.6 ℃ to 140 ℃,the expansion ratio and cell size increase with increasing Tf,but the cell density decreases with increasing Tf.When Tf and pf are 133.6 (and 4 MPa,respectively,EPP with desired double melting peaks,uniform cell structure and smooth surface is obtained.The cell density is the largest,and the distribution of cell size becomes the narrowest.
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