【作者】 苏新清；

【导师】 华幼卿； 乔金樑；

【作者基本信息】 北京化工大学 ， 高分子化学与物理， 2004， 博士

【摘要】 通用高分子材料的高性能化、高功能化研究是近年来高分子材料理论与应用研究领域的热点,具有十分重要的意义。本论文采用喷雾干燥法制备了丁苯橡胶/纳米CaCO3复合弹性粒子(RPS)。通过双螺杆挤出熔融共混法制备了PP/RPS三元复合材料,系统研究了不同丁苯橡胶/nano-CaCO3配比、不同苯甲酸钠含量的RPS以及不同分子量的PP对复合材料的力学性能(静态和动态)、结晶性能(含等温和非等温结晶动力学)和加工流变性能的影响规律,探讨了该种新型材料的逾渗增韧机理,对PP的高性能化具有重要的理论意义和实用价值。首次采用喷雾干燥法,将丁苯胶乳和纳米碳酸钙浆液同时喷雾干燥得到了具有特殊包藏结构的复合粉末橡胶(RPS)。同时制备了含有和不含有苯甲酸钠的yRPS和nRPS。改变丁苯橡胶和纳米碳酸钙的比例,得到不同配比的yRPS和nRPS。同时,用喷雾干燥法制备了丁苯粉末橡胶(DB-50 ENP)研究了纯PP,PP/nano-CaCO3,PP/丁苯粉末胶(DB-50 ENP),PP/丁苯粉末胶/nano-CaCO3,PP/nRPS体系的形态结构与力学性能之间的关系。结果表明,DB-50 ENP和nano-CaCO3对聚丙烯具有协同增韧的作用,PP/DB-50 ENP/nano-CaCO3和PP/RPS三元复合材料的冲击强度均高于PP/nano-CaCO3、PP/DB-50 ENP体系,其中PP/nRPS的冲击韧性又高于PP/DB-50 ENP/nano-CaCO3。试样的TEM观察结果显示,PP/nRPS的微观结构为带有包藏结构分散相的海岛结构,nano-CaCO3以纳米级尺寸包藏于丁苯胶粒之中。正是这种特殊的包藏结构,增加了橡胶相的表观体积分数,减少了平均粒间距即基体层厚度,促进了材料的脆-韧转变。系统研究了RPS中丁苯胶/纳米碳酸钙配比、苯甲酸钠用量以及不同分子量PP对相同配比PP/RPS三元复合材料力学性能和耐热性的<WP=4>影响规律。表明所研究的三个RPS试样中,随着纳米碳酸钙含量增加,RPS粒径减小,以游离形式分散在PP中的碳酸钙增多,体系的拉伸强度、弯曲强度、耐热性有了一定提高,Izod缺口冲击强度也有所改善。苯甲酸钠作为PP的成核剂,可促进PP结晶,提高了材料的刚性和耐热性;同时对RPS起着隔离剂的作用,使其粒径减小,有利于材料增韧。PP的分子量大,有利于RPS在PP中的分散,体系冲击性能显著提高。比较了纯PP、PP/nano-CaCO3、PP/DB-50 ENP、PP/DB-50 ENP/nano-CaCO3、PP/nRPS体系的动态力学性能。发现上述体系中,PP均呈现三个转变,分别为α、β、γ转变。几个试样中PP的β转变及丁苯粉末胶的β转变温度基本不变。nano-CaCO3的加入使PP的储存模量E’增加,DB-50 ENP的加入使PP的E’降低,RPS的加入同样降低了体系的E’。PP/RPS的损耗模量E’’在整个温度范围内依次高于PP/DB-50 ENP/nano-CaCO3和PP/DB-50 ENP体系,尤其在低温区域,损耗模量的提高更为明显。采用DSC方法进一步研究了PP/RPS三元复合材料的结晶性能及等温结晶、非等温结晶动力学。研究表明,RPS对PP具有一定的促进结晶的作用,且含有苯甲酸钠的yRPS对PP的成核作用较之未加苯甲酸钠的nRPS更为显著,故RPS的加入提高了PP的结晶温度、熔融温度和结晶度。动力学研究表明,体系结晶速率常数K增加,t1/2下降。这些结果与体系刚性、耐热性提高密切相关。研究了PP/RPS复合材料的动态流变行为。该体系表现出假塑性流体的流动行为,RPS的加入使体系的复数粘度η*增大,且随着RPS用量增加而增大。在所研究的配比范围内,体系粘度与RPS中纳米碳酸钙的含量无关。贮能模量G’和损耗模量G’’均随ω的提高而增加,但G’对ω的敏感性大于G’’。首次对PP/RPS三元复合材料的逾渗增韧机理进行了研究,得到不同丁苯橡胶/纳米碳酸钙配比的RPS复合粉末橡胶增韧PP体系的临界基体层厚度Tc值,证明了S Wu的逾渗理论同样适用于该种新型三元复合材料的脆韧转变描述,但临界基体层厚度Tc值随RPS中纳米<WP=5>碳酸钙含量的增加而减小。更多还原

【Abstract】 Recently, many researches have focused on the studies of common polymer materials with high performance and multiple functions. In this thesis, a new kind of rubber powder with “salami” structure (RPS) was prepared by spray drying method. The PP/RPS ternary composites were prepared by melt blending method. The influences of the viscosity ratio, of the RPS with a series of styrene-butadiene rubber/nano-CaCO3 ratio and the RPS with different sodium benzoate content on the mechanical properties, crystallization properties and rheological properties of the composites were systematically investigated. The toughening mechanism of PP/RPS ternary composites was also studied. The RPS complex powdered rubber was prepared by spray drying the mixture of styrene-butadiene rubber latex and nano-CaCO3 slurry. yRPS (RPS with benzoate) and nRPS(RPS without benzoate) were also prepared. By adding different ratio of styrene-butadiene rubber latex and nano-CaCO3 slurry, a series of yRPS and nRPS were prepared. The <WP=7>Elastomeric Nano-Particle (DB-50 ENP) was also prepared by spray drying the styrene-butadiene rubber latex (DB-50 rubber latex).The relationship between the microstructure and the mechanical properties in PP/nano-CaCO3, PP/DB-50 ENP, PP/DB-50 ENP/nano-CaCO3 and PP/RPS systems was investigated. From the results it can be seen that the DB-50 ENP and nano-CaCO3 have a synergistic toughening effect on PP. The Izod impact strength of PP/RPS composites is not only higher than that of PP/ DB-50 ENP and PP/nano-CaCO3, but also higher than that of PP/DB-50 ENP/nano-CaCO3. TEM photograph shows that microstructure of PP/RPS composites is an “sea-island” structure with “salami” like structure in RPS, in which nano-CaCO3 particles are embedded in styrene-butadiene rubber particles at nano-size. The effect of preparing method on morphology is apparent, the microstructure of the PP/DB-50 ENP/nano-CaCO3 composites is different from PP/RPS, in which small amount of the CaCO3 particles are occluded by the DB-50 ENP, the most are dispersed in PP matrix. The impact resistance is affected by the volume fraction of rubber incorporated and the average surface-to-surface interparticle distance or the matrix ligament thickness of PP. The occlusion of nano-CaCO3 in elastomer is expected to increase the apparent volume fraction of the rubbery phase and decrease the average surface-to-surface distance between the elastomer particles, and thus the impact resistance of the matrix is improved. <WP=8>The effect of the DB-50 ENP/nano-CaCO3 ratio, of the sodium benzoate content in RPS and the viscosity ratio on the mechanical and the heat resistance properties of PP/RPS ternary composites with the same mass ratio was investigated. It can be seen that, with the increase of nano-CaCO3 content in the three RPS samples, RPS particle size decreases and the free nano-CaCO3 in PP increases. As a result, the tensile strength, the flexural strength and the heat resistance of the ternary system are enhanced, and the Izod impact strength is slightly improved. The crystallization temperature and the crystallinity of PP increase due to the nucleation effect of sodium benzoate, which contributed to the improvement of the rigidity and heat resistance of the composites. The sodium benzonate in RPS, also acting as a partitioning agent, can help decrease the particle size of the rubbery phase, and thus facilitate the toughening of PP. Low viscosity ratios are found to produce fine and uniform dispersion of RPS in PP, therefore the impact resistance of the composites is improved.The dynamic mechanical properties of PP, PP/nano-CaCO3, PP/ DB-50 ENP, PP/DB-50 ENP/nano-CaCO3 and PP/RPS were studied. The results show that the glass transition temperature of PP and DB-50 ENP changes little in all the samples. The storage modulus E’ increases with the addition of nano-CaCO3, but decreases with the addition of DB-50 ENP or RPS. The loss modulus E’’ of PP/RPS was higher than the PP/DB-50 ENP <WP=9>and the PP/DB-50 ENP/nano-CaCO3 in the whole temperature更多还原