Influence of Hydroxyl-Terminated Hyperbranched Polymer and Coupling Agent on the Performance of SF/PLA Composites

Abstract

Herein, a hydroxyl-terminated hyperbranched polymer (HPN) with abundant terminal hydroxyl groups was employed to modify straw-plastic composites and studied the effect of HPN concentration on straw fiber reinforced polylactic acid (SF/PLA). Silane coupling agent (CA) was used to improve the interfacial compatibility between SF, HPN and PLA matrix. The mechanical strength, thermal properties and water resistance of different SF/PLA composites were tested and analyzed. When the concentration of HPN is 6%, the HPN-SF/PLA has the best mechanical strength index. HPN modification, CA modification and the combination of both have positive effect on improving mechanical performance. Compared with the UN-SF/PLA, the tensile, flexural and impact strength of HPN+CA-SF/PLA composites were increased by 24.7%,16.6% and 10.8%, respectively. The crystallinity of SF/PLA treated with HPN, CA, and their combination increased from 28% to 29.4%, 36.9%, and 42.3%, respectively. However, low melting point of HPN caused a decrease in the Tg, Tm, Tc, Td5% and Tdmax of SF/PLA. These characteristic temperatures can be enhanced by adding CA for co-modification. In addition, the three modified approach were able to enhance the water resistance of SF/PLA composites due to the reduction of the number of hydroxyl groups on the SF surface and the enhancement of the interfacial bonding properties.

Keywords

• hyperbranched polymer
• coupling agent
• straw fiber/polylactic acid composite
• mechanical properties
• thermal properties
• water resistance