长链支化聚乳酸的多重松弛行为

Multiple Relaxation Behavior of Long Chain Branched Polylactic Acid

在辐照法制备长链支化聚乳酸(LCB-PLA)的基础上,采用凝胶渗透色谱-多角度激光光散射联用(SEC-MALLS)表征了LCB-PLA的支化结构,利用动态流变学方法考察了PLA的黏弹松弛行为,计算得到了线型及支化PLA在较宽时间范围内完整的加权松弛时间谱.结果表明,由于长支链的引入及支链长度的增加,导致LCB-PLA松弛时间谱加宽,松弛时间增长,并呈现多重松弛行为.提出了一种计算长链支化聚合物支链长度的方法,可以定量表征LCB-PLA的支链长度以及长支链的分子量.

The long chain branched polylactic acid（PLA） samples were successfully fabricated by high energy irradiation in the presence of a small amount of poly-functional monomer.The branched structures of PLA were convinced by size exclusion chromatography（SEC） coupled with a multi-angle laser light scattering（MALLS）.By the means of oscillatory shear and creep measurements,the shear rheological behavior of branched PLA was investigated.Meanwhile,the weighted relaxation spectra of PLA were calculated in light of the combined dynamic modulus data.The multiple relaxation behavior of PLA,which was attributed to the existence of different lengths of long chain branches,was actually observed.In addition,a novel procedure for quantificatio-nal determination of the lengths of branches and the arm molecular weight of PLA was put forward.It was found that the lengths of branches of PLA were extended and the arm molecular weight was enhanced with increasing amount of poly-functional monomer.The above results could facilitate the fabrication of long chain branched PLA with well-controlled branched structures and improved rheological properties that may dominate the future bio-plastics industry.