聚醋酸乙烯酯对聚乳酸复合材料发泡性能的影响

采用超临界二氧化碳(SC-CO_(2))釜压发泡方法,研究了聚醋酸乙烯酯(PVAc)对聚乳酸(PLA)发泡行为的研究。首先,采用重量法研究了PVAc的重均分子量及其浓度对CO_(2)在PLA中溶解度的影响,PVAc的重均分子量为1×10^(5)、质量分数为1.5%时,CO_(2)在PLA中溶解度最高(14.0%)。然后,采用差示扫描量热仪、毛细管流变仪和扫描电子显微镜研究了PVAc含量对PLA的热学性能、流变性能及PLA泡沫泡孔结构的影响。结果表明,随着PVAc含量的增加,复合材料的结晶性能逐渐提高,其表观黏度逐渐减小,发泡倍率及泡孔密度先增大后减小,当PVAc质量分数为1.5%时,PLA复合材料的发泡性能最佳(泡孔密度为2.56×108 cm^(-3),发泡倍率为74.4倍)。

纳米柠檬酸锌对聚乳酸挤出发泡行为的影响

采用超临界二氧化碳(SC-CO_(2))连续挤出发泡方法,研究了纳米柠檬酸锌(NZnC)对聚乳酸(PLA)发泡行为的影响。首先,采用差示扫描量热仪(DSC)、扫描电子显微镜(SEM)和压缩试验机分别研究了纳米柠檬酸锌(NZnC)、食品级柠檬酸锌(FZnC)、纳米二氧化硅(N-SiO_(2))、癸二酸二苯基二酰肼(TMC-300)和滑石粉(Talc)5种成核剂对PLA等温结晶行为、成核剂/PLA复合材料的微观形貌、PLA泡沫发泡性能及压缩性能的影响。结果表明,NZnC的PLA等温结晶速率最快、在PLA中分散性及相容性最佳、PLA泡沫发泡性能及压缩性能改性效果最好。继而,研究了NZnC含量对PLA泡沫发泡性能及压缩性能的影响,其结果表明,NZnC质量分数为0.5%时,PLA泡沫的发泡性能最好(发泡倍率为31倍、泡孔密度为3.02×10^(9) cm^(-3)、平均泡孔直径为17.11μm),压缩性能也最好(压缩模量为19 MPa、压缩强度为0.35 MPa)。

Research on MLChecker Plagiarism Detection System

Plagiarism detection system plays an essential role in education quality improvement by helping teachers to detect plagiarism.Using a number of measures customized to determine occurrences of plagiarism is the most common approach for plagiarism detection tool.It is simple and effective,while it lacks flexibility when applied in more complicated situations.This paper proposes the MLChecker,a smart plagiarism detection system,to provide more flexible detection tactics.An automatic plagiarism dataset construction method was exploited in MLChecker to dynamically update the plagiarism detection algorithms according to different detection tasks.And the full-process quality management functions were also provided by MLChecker.The result shows that the detection accuracy is raised by 56%.Compared with traditional plagiarism detection tools,MLChecker is with higher accuracy and efficiency.