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Formation of PLA stereocomplex crystals during melt-blending of asymmetric PLLA/PDLA/PMMA blends of varying miscibility
Polymer Journal ( IF 2.8 ) Pub Date : 2019-08-22 , DOI: 10.1038/s41428-019-0256-6
Yuri Iguchi , Shuichi Akasaka , Shigeo Asai

Polylactide (PLA) enantiomers of poly( l -lactide) (PLLA) and poly( d -lactide) (PDLA) were melt-blended with poly(methyl methacrylate) (PMMA) and compression-molded at a temperature between the melting points of PLA homocrystals ( T m,HC ) and stereocomplex (SC) crystals ( T m,SC ), causing the selective formation of SC crystallites. The degree of crystallinity of the SC crystals ( χ c,SC ) did not change with the PMMA weight fraction but did vary with changes in the weight ratio of PLLA to PDLA. From differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) measurements, the miscibility of PLA and PMMA was confirmed, but the formation of SC crystals during melt-blending induced phase separation into PLA-rich and PMMA-rich phases. The formation of homocrystals was hindered by increases in the weight fraction of PMMA and χ c,SC . The thermal and viscoelastic properties of the PLLA/PDLA/PMMA blends were also affected by the PMMA weight fraction and χ c,SC . According to the DMA results, the storage modulus of the ternary blends with higher χ c,SC values showed a gentler decrease at the glass transition temperature; the ternary blends also exhibited a higher storage modulus than the PLLA/PMMA blends at high temperatures near T m,HC . PDLA weight fraction dependence of stereocomplex crystallinity χ c,SC for PLLA/PDLA/PMMA blends with PDLA weight fractions of 5, 10, and 20 wt%.

中文翻译:

不同混溶性的不对称 PLLA/PDLA/PMMA 共混物在熔融共混过程中形成 PLA 立体络合物晶体

聚(l-丙交酯)(PLLA)和聚(d-丙交酯)(PDLA)的聚丙交酯(PLA)对映体与聚(甲基丙烯酸甲酯)(PMMA)熔融共混,并在熔点介于PLA 均晶 (T m,HC) 和立体络合物 (SC) 晶体 (T m,SC),导致 SC 微晶的选择性形成。SC 晶体的结晶度 (χ c,SC ) 不随 PMMA 重量分数而变化,但确实随 PLLA 与 PDLA 重量比的变化而变化。从差示扫描量热法 (DSC) 和动态力学分析 (DMA) 测量中,PLA 和 PMMA 的混溶性得到证实,但在熔体共混过程中 SC 晶体的形成导致相分离成富含 PLA 和富含 PMMA 的相。PMMA 和 χ c 的重量分数增加阻碍了均晶的形成,SC . PLLA/PDLA/PMMA 共混物的热和粘弹性性能也受 PMMA 重量分数和 χ c,SC 的影响。根据 DMA 结果,具有较高 χ c,SC 值的三元共混物的储能模量在玻璃化转变温度下表现出较温和的下降;在接近 T m,HC 的高温下,三元共混物还表现出比 PLLA/PMMA 共混物更高的储能模量。PLLA/PDLA/PMMA 共混物的立体络合物结晶度 χ c,SC 的 PDLA 重量分数依赖性,PDLA 重量分数为 5、10 和 20 重量%。在接近 T m,HC 的高温下,三元共混物还表现出比 PLLA/PMMA 共混物更高的储能模量。对于 PLLA/PDLA/PMMA 共混物,PDLA 重量分数为 5、10 和 20 wt% 时,立体络合物结晶度 χ c,SC 的 PDLA 重量分数依赖性。在接近 T m,HC 的高温下,三元共混物还表现出比 PLLA/PMMA 共混物更高的储能模量。PLLA/PDLA/PMMA 共混物的立体络合物结晶度 χ c,SC 的 PDLA 重量分数依赖性,PDLA 重量分数为 5、10 和 20 重量%。
更新日期:2019-08-22
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