渔用纳米蒙脱土改性聚乳酸单丝降解性能

Degradation properties of fishery polylactic acid monofilament modified by nano-montmorillonite

为研究纳米蒙脱土(nano-MMT)改性聚乳酸(PLA)单丝在海水环境中的降解特性,试验测试了纯PLA单丝、0.5wt%、1.0wt%nano-MMT/PLA单丝在浙江舟山海域海水中15个月的降解特性。结果显示,纳米蒙脱土改性聚乳酸单丝在海水环境中自然降解9个月时间内,其力学性能和数均分子量下降较为缓慢;当降解时间超过9个月后,改性聚乳酸单丝的断裂强度和数均分子量呈加速下降趋势。表明改性聚乳酸单丝在海水中降解9个月后进入加速降解阶段,推断改性聚乳酸单丝在海水环境中的最佳使用寿命为9个月。加入nano-MMT后,改性聚乳酸单丝力学性能和数均分子量下降较纯聚乳酸单丝要快。在海水中降解15个月后,加入0.5wt%nano-MMT的改性聚乳酸单丝断裂强度和数均分子量分别下降了25.0%和50.0%,而纯的聚乳酸单丝则仅下降了20.4%和30.6%。由于nano-MMT的加入,会使PLA与nano-MMT的界面结合产生缺陷,nano-MMT与聚乳酸大分子链之间的界面结合缺陷会成为水分子进入聚乳酸大分子内部的通道,从而加速改性PLA单丝在海水环境中的降解。同时nano-MMT的加入会加快改性PLA单丝耐磨性的下降趋势,纯PLA单丝在海水中降解15个月后,耐磨度由2.20 F/tex下降为1.32 F/tex,耐磨度下降40%;而0.5wt%nanoMMT/PLA的耐磨度由2.34 F/tex下降为0.70 F/tex,耐磨度下降70.1%。

Degradation properties of fishery polylactic acid monofilament modified by nano-montmorillonite （nano-MMT/PLA） were studied in the seawater near the Zhoushan sea area. The breaking strength of the PLA monofilament was 2.4 cN/dtex, and the breaking strength of the 0.5wt% nano-MMT/PLA and 1.0wt% nano-MMT/PLA monofilament were 3.2 cN/dtex and 2.5 cN/dtex, respectively. It was shown that when the amount of the additional nano-MMT was fixed at 0.5%, the nano-MMT/PLA monofilament had the best strength. In the first 6 months of the degradation process, the mechanical properties of the PLA and nano-MMT/ PLA monofilaments remained stable. When the degradation increased to 9 months, the mechanical properties and number-average molecular weight of nano-MMT/PLA fishery monofilament decreased slowly. The breaking strength of the PLA monofilament was 2.15 cN/dtex, and the breaking strength of the 0.5wt% nano- MMT/PLA and 1. Owt% nano-MMT/PLA monofilament were 3.0 cN/dtex and 2.25 cN/dtex, respectively. The breaking strength loss rate of pure PLA monofilament was 10.4%, and the breaking strength loss rate of 0. 5wt% nano-MMT/PLA and 1. Owt% nano-MMT/PLA monofilament were 6.3% and 10.0%, respectively. However, when the degradation time was more than 9 months, the mechanical properties of nano-MMT/PLA fishery monofilament decreased rapidly. When the degradation time increased to 15 months, the breaking strength loss rate of pure PLA monofilament was 20.4%, and the breaking strength loss rate of 0.5wt% nano- MMT/PLA and 1. 0wt% nano-MMT/PLA monofilament were 25. 0% and 36. 8%, respectively. This indicated that the addition of nano-MMT would increase the degradation of the PLA. To summarize, it was shown that after 9 months, the degradation of nano-MMT/PLA fishery monofilament was in an accelerated process, and it was concluded that the optimum lifetime of modified PLA monofilament in seawater environment was 9 months. Furthermore, after 15 months of degradation, the number-average molecular weight of pure PLA monofilament decreased by 30.5%. However, the number-average molecular weight of 0.5 wt% nano-MMT/PLA monofilament decreased by 50.0%. After degradation in the seawater for 15 months, the wear resistance of pure PLA monofilament decreased from 2.20 F/tex tol. 32 F/tex by 40.0%. Nevertheless, the wear resistance of 0.5wt% nano-MMT/PLA monofilament decreased from 2.34 F/tex to 0.70 F/rex by 70.1%. The addition of nano-MMT in PLA monofilament can increase the crystallization of the PLA, which can improve the wear resistance of the modified PLA monofilament, with the increased degradation of the nano- MMT/PLA monofilament, the interface defects generated between PLA and nano-MMT could become channels for water molecules entering the interior of polylactic acid molecules, which would increase the degradation and decrease the wear resistance property of the modified PLA monofilaments.