高密度聚乙烯共混调控烯烃嵌段共聚物拉伸性能

TAILORING THE TENSILE PROPERTIES OF OLEFIN BLOCK COPOLYMER ELASTOMER BY HIGH DENSITY POLYETHYLENE

通过熔融共混法制备了高密度聚乙烯(HDPE)与烯烃嵌段共聚物(OBC)的共混物,研究了HDPE含量对共混体系结晶和拉伸行为的影响.实验结果表明,共混物熔体存在相分离.结晶时两组分互相影响,出现共结晶现象.共混物具有优异弹性回复与高断裂伸长率,而拉伸模量与断裂强度随着HDPE含量增加而逐渐增大.借助Slip-link橡胶弹性理论对应力应变曲线进行了分析,发现拉伸曲线可以很好的用理论模型进行拟合.将共混物的微观结构变化同模型参数进行了对比,建立了共混物结构和性能的有效关联.

The effect of high density polyethylene （HDPE） on the crystallization and tensile behavior of the olefin block copolymer （OBC）-rich blends was examined. Morphological studies revealed that the two components were phase separated in the melt state. Partial miscibility between the two components came from the ＂phase mixing＂, which was attributed to the randomness of the block distribution produced by chain shuttling polymerization. Cocrystallization of HDPE and OBC was observed in slow cooling samples. Crystalline lamellae originating from the HDPE-rich phase passed through the OBC-rieh phase and organized into spherulites in a space-filling manner. With increasing HDPE fraction, the modulus and tensile strength of the blends increased gradually. Meanwhile, high fracture strain and excellent strain recovery were retained. The stress-strain curves of the elastomeric blends could be nicely described by the Slip-link model. The crystalline part in blends provided the physical basis for ＂sliplinks＂ ,while the tightened topological entanglements served as ＂crosslinks＂. The density of sliplinks and crosslinks increased with increasing HDPE content. The increased crystallinity was shown to be the reason for the increased sliplinks number. By analyzing changes of microstructure imparted by HDPE, the structure property correlation was nicely established. It was clearly demonstrated that HDPE could effectively tailor the tensile properties of OBC by simple blending approach.