拉伸冷结晶聚乳酸结构及性能研究

Study on structure and properties of tensile cold crystallized polylactide

聚乳酸(PLA)在冷结晶条件下进行不同应变的拉伸处理,通过差示扫描量热仪(DSC)、X-射线衍射(XRD)和动态力学(DMA)测试,对PLA的结晶性能和力学性能进行分析.经冷结晶拉伸处理后链段运动的松弛时间减少,结晶性能得到改善,拉伸温度对体系结晶度的影响要大于拉伸应变对结晶度的影响.冷结晶处理温度为85℃时,拉伸形变为15%的PLA结晶度最高.而在55℃和65℃冷结晶温度下,体系的结晶度随拉伸应变增大到10%出现最大值,而后随应变继续增加结晶度减小.玻璃化转变温度及以下条件下的冷结晶处理使得晶粒尺寸随应变的增加而降低,而玻璃化转变温度以上条件下的冷结晶处理晶粒尺寸基本随应变增大而增加.DMA测试不同条件下拉伸热处理的PLA的存储模量在黏弹区的大小和结晶度有直接关系;在玻璃区的存储模量则主要取决于非晶区的取向程度.玻璃化转变温度及以下条件下的冷结晶处理使得PLA的玻璃区的存储模量在较小的应变条件下降低,而玻璃化转变温度以上的冷结晶处理使得玻璃区的PLA的存储模量在较大的应变条件下降低.

Polylactide(PLA)was treated at different strains under cold crystallization condition,and the crystallization and mechanical properties of PLA were analyzed by DSC,XRD and DMA tests.After cold crystallization and stretching treatment,the relaxation time of chain segment motion was reduced and crystallinity was improved.The effect of cold crystallization temperature on crystallinity is greater than that of strain on crystallinity.When cold crystallization temperature is 85℃,the crystallinity of PLA at 15%strain is the highest.Whereas,the crystallinities of the system at cold crystallization temperature 55℃and 65℃show the maximum value when strain increased to 10%,then decrease with the continuing increase of strain.The granular size of PLA under low cold crystallization temperature decreases at the increased strain,but basically increases when cold crystallization temperature is 85℃.Storage modulus of PLA in viscoelastic region after cold crystallization and stretching treatment is directly related to crystallinity,while the value in glass region mainly depends on the degree of orientation in amorphous region.In glass region,storage modulus of PLA after cold crystallization at low temperatures decreases even at smaller strain,but when the cold crystallization temperature was increased,it shows decrease under the larger strain condition.