复合增塑剂改性PBAT/淀粉薄膜的性能

以玉米淀粉、聚己二酸/对苯二甲酸丁二酯(PBAT)为主要原材料,甘油为主增塑剂,山梨醇、聚乙烯醇200(PEG200)、二甲基甲酰胺等为辅增塑剂,通过挤出机造粒再吹塑方法制成淀粉填充PBAT薄膜。研究对比了不同增塑剂在淀粉填充PBAT材料中的塑化效果,同时探究了不同塑化剂对复合薄膜力学性能、表面粗糙度、吸水率、溶出率及熔体流动速率的影响。结果表明:山梨醇与甘油组成的复合增塑剂的塑化效果要优于PEG200和二甲基甲酰胺,淀粉在PBAT薄膜中的粒径最小、分散最均匀,且薄膜的拉伸强度、断裂生产率、摆锤冲击强度得到明显提高。PEG200和二甲基甲酰胺与甘油的复合增塑剂对淀粉的塑化未起到作用,但二甲基甲酰胺能与淀粉分子形成较为稳定的氢键,可以大幅度降低薄膜中淀粉的溶出率。薄膜的吸水性主要取决于淀粉的吸水性。熔体流动速率在一定程度上也能体现淀粉的塑化情况。     

Optimizing the mechanical and physical properties of thermoplastic starch via tuning the molecular microstructure through co‐plasticization by sorbitol and glycerol

Nowadays, environmental hazards caused by plastic wastes are a major concern in academia and industry. Utilization of biodegradable polymers derived from renewable sources for replacing common petroleum‐based plastics is a potential solution for reducing the problem. In this regard, starch has become one of the most promising alternatives to non‐biodegradable polymers for depleting plastic waste thanks to its low expense, abundance, renewability and biodegradability. However, the main drawbacks of starch are its poor processability, weak mechanical properties and severe hydrophilicity. In this work, thermoplastic starch (TPS) samples have been prepared using glycerol and sorbitol as co‐plasticizers in a laboratory co‐rotating twin screw extruder. Based on the mechanical test results, glycerol caused higher elongation to break but had lower tensile strength and elastic modulus compared to sorbitol plasticized starch. Fourier transform infrared spectroscopy and DSC results indicated that the hydrogen bond interaction between starch chains and plasticizers could be improved by replacing glycerol by sorbitol, which resulted in higher resistance against retrogradation proved by XRD results. TGA illustrated that the higher the sorbitol to glycerol ratio was, the more stable was the TPS. Using a proper amount of plasticizers (42 wt% total plasticizer, sorbitol to glycerol ratio 2:1) led to the preparation of a TPS sample with optimized properties including enhanced mechanical properties, high thermal stability, strong hydrogen bond formation and high resistance against retrogradation. © 2017 Society of Chemical Industry     

新一代聚丙烯成核剂的合成及应用

介绍了二(3,4-二甲基二苄叉)山梨糖醇(DMDBS)的合成路线和作用机理,并以山梨糖醇和3,4-甲基苯甲醛为原料,在固体酸的作用下,不用分离水就能直接合成出新一代聚丙烯透明成核剂DMDBS.结果表明,在醇醛物质的量比2.1、催化剂加量4.5％(质量分数,以醇醛质量总和为基准,下同)、反应温度25℃、反应时间5h、溶剂...     

Mathematical modelling and its use for design of feeding strategies for L‐Sorbose fermentation

Batch sorbitol to sorbose bioconversion by Acetobacter suboxydans using initial sorbitol concentration (S₀ = 100 g/L) yielded a productivity of 10.11 g/L‐h and 98.6% conversion in 10 h time. The batch kinetics was then used to develop an unstructured mathematical model. Model parameters were identified using a nonlinear regression technique assisted by a computer program which minimized the deviation between the model predictions and actual batch experimental data. F test indicated 99% confidence on the prediction of model using optimized parameters. The batch model was eventually extrapolated to identify nutrient feeding strategies to maintain constant noninhibitory sorbitol supply and eliminate substrate limitation for fed‐batch fermentation in order to improve the sorbose productivity. The adequacy of the fed‐batch model was established by excellent agreement between experimental data and model simulation (except towards the end of fermentation).     

对氯/对甲基二苄叉山梨醇组合物对聚丙烯的成核作用

以摩尔比为1∶1∶1的对甲基苯甲醛、对氯苯甲醛和山梨醇为反应物,制备了含非对称型对氯/对甲基二苄叉山梨醇(DMCBS)的组合物;采用HPLC-MS技术表征了DMCBS组合物的组成;考察了DMCBS组合物、对称型1,3∶2,4-二(对甲基苄叉)山梨醇(DMBS)和对称型1,3∶2,4-二(对氯苄叉)山梨醇(DCBS)3种成核剂对聚丙烯(PP)的结晶温度、雾度和弯曲模量的影响。表征和实验结果表明,DMCBS组合物中含有24%(w)的DMBS、19%(w)的DCBS和57%(w)的DMCBS,在PP中DMCBS的各组分之间存在盐析效应;随PP中DMCBS组合物、DMBS和DCBS含量的增加,PP的结晶温度提高、雾度降低、弯曲模量增大。与纯PP相比,含0.40%(w)DMCBS组合物的PP的结晶温度提高了16.2℃,雾度从76.8%降低到17.9%,弯曲模量提高了43.5%。