Van Belle Astrid, Demets Ruben, Mys Nicolas, Van Kets Karen, Dewulf Jo, Van Geem Kevin, De Meester Steven, Ragaert Kim
Centre for Polymer and Material Technologies (CPMT), Department of Materials, Textiles and Chemical Engineering, Faculty of Engineering and Architecture, Ghent University, Technologiepark 130, B-9052 Zwijnaarde, Belgium.
Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University-Campus Kortrijk, Graaf Karel de Goedelaan 5, 8500 Kortrijk, Belgium.
Polymers (Basel). 2020 May 20;12(5):1171. doi: 10.3390/polym12051171.
The mixing of polymers, even structurally similar polyolefins, inevitably leads to blend systems with a phase-separated morphology. Fundamentally understanding the changes in mechanical properties and occurring deformation mechanisms of these immiscible polymer blends, is important with respect to potential mechanical recycling. This work focuses on the behavior of binary blends of linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) under tensile deformation and their related changes in crystallinity and morphology. All of these polymers plastically deform by shear yielding. When unmixed, the high crystalline polyolefins HDPE and PP both exhibit a progressive necking phenomenon. LDPE initiates a local neck before material failure, while LLDPE is characterized by a uniform deformation as well as clear strain hardening. LLDPE/LDPE and LLDPE/PP combinations both exhibit a clear-cut matrix switchover. Polymer blends LLDPE/LDPE, LDPE/HDPE, and LDPE/PP show transition forms with features of composing materials. Combining PP in an HDPE matrix causes a radical switch to brittle behavior.
聚合物的混合，即使是结构相似的聚烯烃，也不可避免地会导致具有相分离形态的共混体系。从根本上理解这些不相容聚合物共混物的力学性能变化和发生的变形机制，对于潜在的机械回收利用而言至关重要。这项工作聚焦于线性低密度聚乙烯（LLDPE）、低密度聚乙烯（LDPE）、高密度聚乙烯（HDPE）和聚丙烯（PP）的二元共混物在拉伸变形下的行为及其结晶度和形态的相关变化。所有这些聚合物都通过剪切屈服发生塑性变形。未混合时，高结晶度的聚烯烃HDPE和PP都表现出渐进的颈缩现象。LDPE在材料失效前会引发局部颈缩，而LLDPE的特征是均匀变形以及明显的应变硬化。LLDPE/LDPE和LLDPE/PP组合都表现出明显的基体转换。聚合物共混物LLDPE/LDPE, LDPE/HDPE和LDPE/PP呈现出具有组成材料特征的过渡形式。在HDPE基体中加入PP会导致行为彻底转变为脆性。
