【作者】 邹华维；

【导师】 徐僖；

【作者基本信息】 四川大学 ， 材料学， 2005， 博士

【摘要】 高分子材料制品的质量取决于材料的选择和加工性能,一些具有优异性能的聚合物由于可加工性的限制,发展缓慢。本文选择了具有一定代表性的难于加工的聚合物,采用SEM、FT-IR、GPC、XRD、转矩流变仪和高压毛细管流变仪等分析测试方法研究了mPE、UHMWPE、UHMWPE/HDPE和PVC等体系在碾磨力场作用下形态结构、加工流变行为和性能的变化及机理。研究结果表明:由于磨盘形力化学反应器的独特结构,碾磨产生的强大挤压、剪切和环向应力场作用能够有效改变聚合物的微观形貌和结构,利用应力诱导反应实现了难加工聚合物加工流变行为的改善和性能的提高,突破了传统加工改性方法的诸多限制和弊端,为聚合物的加工改性和高性能化开辟了一条操作简便、清洁、高效、无污染和易于工业化的新途径。1.碾磨可使mPE分子量下降,支化度提高,生成单斜晶系。经10次碾磨处理,mPE熔体流动指数从1.91 g/10min提高到3.28 g/10min(230℃,2.16kg)。碾磨可使mPE熔体表观粘度降低,熵弹性减小,粘流活化能增大,粘度对温度的敏感性提高,出现不稳定流动的临界剪切速率提高,熔融时间缩短,机器负荷降低,挤出物外观质量得到显著提高。碾磨处理在保持mPE优异的冲击性能同时,可提高制品的断裂强度、断裂伸长率和杨氏模量,使mPE的力学性能得到增强。经碾磨15次,UHMWPE熔体流动指数从0 g/10min提高到0.096g/10min(250℃,21.6kg),屈服强度和杨氏模量提高,断裂伸长率变化不大,断裂强度略有下降。2.HDPE的加入可使UHMWPE的加工流动性获得改善,经10次碾磨处理的UHMWPE/HDPE(70/30)共混体系熔体流动指数达到0.926g/10min,是未经碾磨样品的4倍,能够采用一般设备进行加工。碾磨可有效解决UHMWPE和HDPE共混时粘度不匹配的难题,改善共混体系的相态结构,力学性能得到全面提高,经10次碾磨处理UHMWPE/HDPE(70/30)的断裂强度、屈服强度、杨氏模量和断裂伸长率从未经碾磨处理试样的30.4MPa、24.16MPa、765.8MPa、505.8%分别提高到41.0MPa、25.4MPa、1163MPa、530.4%,亦全面高于未经碾磨处理的UHMWPE试样的36.9MPa、22.6MPa、491.9MPa、386.8%。3.碾磨处理可使PVC固有的多层次结构和微晶结构破坏,分子量下降。经过10次碾磨处理,PVC S1000粒径从160μm下降至3.3μm,塑化时间从132s降至33s,塑化速率和熔融效率提高,平衡扭矩从22.1Nm降至18.6Nm,挤出产物的表观质量提高、离模膨胀减小,加工性能得到明显改善。碾磨处理可使PVC制品塑化度提高,力学性能改善,经过10次碾磨处理PVC S1000屈服强度和杨氏模量分别从58.5 MPa、2.36 GPa提高到66.2 MPa、2.94 GPa。研究发现经碾磨处理的PVC不经过熔融塑化阶段即可获得较高的塑化度。4.PVC的冲击强度为4.6kJ/m2,PVC/SBS共碾磨可生成PVC-SBS共聚物,有效改善了PVC/SBS共混体系的相容性,经10次碾磨处理PVC/SBS(100/8)共混材料的冲击强度从22.4 kJ/m2提高到72.4 kJ/m2,增韧效果大幅提升,屈服强度、断裂伸长率和杨氏模量均得到一定程度改善。共碾磨可促进超细无机粒子在聚合物基体中均匀分散,避免粒子团聚现象发生,有利于力学性能的提高。经过10次碾磨处理的PVC/SBS/CaCO3(100/8/4)三元共混材料在大幅提高韧性的同时保持了良好的刚性,冲击强度66.3 kJ/m2、屈服强度56.7 MPa、断裂伸长率达到92.9%、杨氏模量2.39GPa,综合性能得到优化。5.利用激光瞬时高能量特点,首次实现了PVC的激光非晶化处理。经激光处理的PVC的红外光谱中与微晶有关吸收峰强度减弱或消失,粒子微观形貌和分子量及其分布变化不大,玻璃化温度降低,PVC塑化性能有一定改善。更多还原

【Abstract】 The effect of stress-induced reactions on rheological behavior and properties of some typically difficult processing polymers, mPE, UHMWPE, UHMWPE/HDPE blend and PVC, is studied in this paper through SEM, FT-IR, GPC, XRD, torque rheometer and high-pressure capillary rheometer analysis. The results show that during pan-milling, under the influence of the strong squeezing, shear and three-dimensional stress exerted by the pan-mill, the structure and morphology of these polymers are altered, the rheological behavior and properties of these difficult processing polymers get improved. The method is proved to be a viable, easy in operation, clean and efficient routes in polymer processing.1. After 10 cycles of pan-milling, the melt flow index of mPE is increased from 1.91g/10min to 3.28g/10min (230℃, 2.16kg), the critical shear rate from 1152s-1 to 2880s-1. Pan-milling can shorten melting time, lighten the load of processing machine and improve the surface quality of extrudate, the excellent impact property of mPE are remained after pan-milling, elongation at break, Young’s modulus and strength at break of mPE are improved. After 15 cycles of pan-milling, the melt flow index of UHMWPE is increased from 0g/10min to 0.096g/10min (250℃, 21.6kg). Strength at yield and Young’s modulus of UHMWPE are increased and elongation at break is unchanged, strength at break is slightly decreased.2. Addition of HDPE may improve the processing flowability of UHMWPE. The melt flow index of 10 cycles co-milled UHMWPE/HDPE (70/30) blend reaches 0.926g/10min, as much as 4 times of un-milled samples. This result makes it possible for UHMWPE to process in ordinary processing equipment. The solid-state stress induced by pan-mill is able to overcome the difficulty of viscosity un-matching between UHMWPE and HDPE melt. The mechanical properties get increased evidently. Compared with un-milled UHMWPE, strength at break, yield strength, Young’s modulus and elongation at break of UHMWPE/HDPE (70/30) blend pan-milled 10 cycles increases from 30.4MPa, 24.16MPa, 765.8MPa, 505.8% to 41.0MPa, 25.4MPa, 1163MPa, 530.4% respectively, better than UHMWPE alone also.3. Through pan-milling, PVC’s multilayers structure and microcrystal structure are destroyed, the molecular weight of PVC is decreased after pan-milling. The experimental results show the grain size of PVC S1000 reduces from 160μm to 3.3μm after 10 cycles of pan-milling, the plasticizing time and torque at balance drop down from 132s to 33s and from 22.1Nm to 18.6Nm respectively, both plasticizing rate and melting efficiency are improved, the surface quality of PVC extrudate gets advanced, die swell is decreased, both processabilities and mechanical properties of pan-milled PVC are improved. Strength at yield and Young’s modulus of PVC S1000 increase from 58.5M and 2.36GPa to 66.2MPa and 2.94GPa respectively after 10 cycles of pan-milling.4. The Izod impact strength of PVC is 4.6kJ/m2. PVC-SBS copolymer is obtained through co-milling of PVC and SBS. After 10 cycles of pan-milling, the Izod impact strength of PVC/SBS (100/8) is enhanced from 22.4kJ/m2 to 72.4kJ/m2, strength at yield, elongation at break and Young’s modulus are also improved in a certain extent. Co-milling may promote the dispersing ability of ultra-fine CaCO3 in the PVC matrix, reduce the agglomeration, the interfacial adhesion gets improved. The PVC/SBS/CaCO3 ternary blends are prepared through pan-milling. The impact strength of PVC/SBS/CaCO3 (100/8/4) blend pan-milled 10 cycles is 66.3 KJ/m2, strength at yield is 56.7 MPa, elongation at break is 92.9%, and Young’s modulus is 2.39GPa, the toughness and stiffness of PVC blend are both improved.5. Through instantaneous high energy of laser, amorphous PVC is prepared. The absorbance spectrum of FTIR shows that the microcrystal of the laser-treated PVC is weakened and even disappeared. Changes in morphology of PVC particle, molecular weight and its distribution are indistinct, glass transition temperature of PVC is decreased. The plasticizing property is enhanced slightly.更多还原