过氧化二异丙苯硫化制备增强耐热聚乳酸

Diisopropyl Peroxide Sulfurized Poly(lactic acid): A Route Toward Reinforced and Heat-Resistant Materials

聚乳酸的链段结构对其热力学性能有重要影响。过氧化二异丙苯(DCP)作为自由基引发剂,通过反应性共混可以诱导聚合物分子链支化、交联,进行功能化改性。文中制备了一系列不同DCP添加量的PLA/DCP共混物,重点研究了DCP含量对聚乳酸(PLA)熔融结晶行为、流变行为、耐热性能和力学性能的影响。结果表明,DCP可以诱导PLA的分子链支化和交联。当DCP质量分数大于0.5%时,交联反应占据主导作用,共混扭矩显著升高、复数黏度增大。DCP引发PLA分子链自交联,不熔的PLA链段可以作为成核中心,大幅提高了PLA成核密度,进而提高其结晶速率和结晶度。DCP的添加可以有效地提高聚乳酸的拉伸强度,但对断裂伸长率和冲击强度的影响较小。经过退火,共混物的力学性能保持不变,共混物的耐热性能大幅提高。当DCP质量分数大于0.5%时,共混物的维卡软化温度可以提高到155℃。

As a free radical initiator,diisopropyl peroxide(DCP)has been wildly used to prepare toughened poly(lactic acid)via in-situ compatibilization.However,the effect of DCP on PLA has not been investigated.In this work,a series of PLA/DCP blends with different DCP amounts were prepared.Moreover,the effect of DCP on the crystallization behavior,rheological properties,heat resistance and mechanical properties of PLA were investigated in detail.The results show that incorporating DCP causes branching and cross-linking of PLA chains.When the DCP mass fraction is greater than 0.5%,the cross-linking reaction is dominant.Therefore,the blending torque is significantly increased as well as the complex viscosity.The crosslinked PLA segments can act as nucleation centre and induce self-nucleation.Hence,the crystallization rate of PLA is dramatically improved while the content of DCP exceedes 0.5%.When adding 0.8% DCP,the crystallinity of PLA reaches 45.7%.In addition,DCP shows a positive effect on the mechanical properties of PLA due to the increased chain entanglement.The tensile strength of PLA is increased from 65.7 MPa to 72.4 MPa with 0.8% addition of DCP.After annealing,the mechanical properties of the blends remain unchanged.However,the heat resistance of the blends is greatly improved because of the increased crystallinity.Moreover,the Vicat softening temperature of PLA is increased up to~155℃,when the DCP mass fraction is greater than 0.5%.Finally,reinforced and heat-resistant PLA materials can be realized by simply blending with DCP.