兼具优异低温韧性与强韧平衡的热塑性树脂合金制备及性能研究

Poor low-temperature toughness is a main bottleneck of thermoplastic resins such as polypropylene (PP) and polyvinyl chloride (PVC), especially for the application in northern and alpine regions of China. It is necessary and important to improve the low-temperature toughness of them. It has been found that interfacial tensile stress can decrease glass transition temperature of rubber component in polymer alloy and in turn influence the brittle-ductile transition temperature of the alloy. Furthermore, either low-temperature toughening or balanced strength-toughness can be achieved by molecular design and phase structure modification. Consequently, based on correlation between interfacial tensile stress and brittle-ductile transition temperature, a ternary blends consisting of copolymer elastomer, rubber and thermoplastic resin were prepared by molecular design and phase structure modification in this proposal. The influences of microphase interface in copolymers and phase interface in alloys on interfacial tensile stress were investigated. In addition, the balanced strength-toughness mechanism in the ternary blend was also studied. Subsequently, PP alloy and PVC alloy with good low-temperature toughness and balanced strength-toughness were obtained. A new method to fabricate thermoplastic alloys with excellent low-temperature toughness and balanced strength-toughness was established.

低温冲击性能差是制约许多热塑性树脂在我国北方地区和高寒地区使用的瓶颈。实现其低温韧性，不仅是高分子材料产业面临的技术难题，同时也是通用高分子材料高性能化的必然要求。已有研究结果表明，在一定界面强度下，适当的组分热膨胀系数差能有效降低高分子合金中橡胶相的玻璃化转变温度，进而影响材料脆韧转变温度。通过弹性体共聚物（橡胶）分子设计和宏观相结构调控不但可以有效改善材料低温韧性，而且能够实现材料的强韧平衡。因此，本申请项目拟以组分热膨胀系数差与界面强度对橡胶相玻璃化温度的降低作用出发，通过弹性体分子设计和宏观相结构设计制备共聚物弹性体/橡胶/热塑性树脂合金，探明合金脆韧转变温度的热膨胀系数差、界面强度影响机制及强韧平衡机制。制备兼具优异低温韧性和强韧平衡的聚丙烯合金和硬质聚氯乙烯合金，建立一种基于组分热膨胀系数差、界面强度和凝聚态结构调控的兼具优异低温韧性和强韧平衡的热塑性树脂合金高性能化新技术。

聚丙烯（PP）和聚氯乙烯（PVC）作为通用树脂的代表，均存在脆性较大，低温不耐冲击的问题，严重影响其在汽车、管道、电池电缆等领域的应用。通过多尺度相界面构筑与调控以及纳米复合技术，我们建立了：①基于组分间膨胀系数不匹配和界面强度调控的热塑性树脂低温增韧理论。探明了组分间热膨胀系数差与界面强度对聚合物合金玻璃化转变温度的影响规律，初步揭示了基于热膨胀系数差的PP合金和PVC合金的低温增韧机制，制备了具有优异低温韧性的强韧平衡的聚丙烯合金和硬质聚氯乙烯合金。PP和PVC合金的脆-韧转变温度均低达-30oC，PP材料-20oC下缺口冲击强度大于50kJ/m2，PVC材料-20oC下缺口冲击强度大于30kJ/m2，明显优于市场同类改性材料；②基于纳米填料选择性分布的橡胶-纳米填料协同低温增韧理论，制备了兼具优异低温韧性与刚韧平衡的PP和无规共聚聚丙烯（PPR）复合材料。通过调控纳米填料表面性质、复合材料组成、加工工艺条件，制得的PP复合材料的脆-韧转变温度低达-45oC，其-30oC缺口冲击强度大于50kJ/m2。阐明了纳米填料与弹性体对低温增韧的协同机制来源于填料在橡胶-基体界面的选择性分布。这种选择性分布抑制了橡胶分散相的粗化和并显著增大了橡胶分散相的分子损耗是，使得材料脆-韧转变温度与分散相面积、损耗呈现线性依赖性。此外，通过动态硫化、黏弹性调控可以显著强化纳米粒子在相界面的定向分布，从而进一步提高材料的低温抗冲击性能。本项目的理论研究成果对于制备低温高抗冲热塑性树脂，实现聚丙烯等通用树脂的高性能化具有重要意义。目前，本项目的部分理论成果已经进入技术应用开发研究阶段。