A series of microcellular thermoplastic polyurethane foams with different apparent densities were prepared by temperature-increasing foaming method with high-pressure CO2 as blowing agent, and the relationship between the apparent density and mechanical properties was investigated. The structure of microcellular thermoplastic foam was characterized by scanning electron microscopy. The mechanical properties of the materials with different apparent densities were characterized by universal material testing machine and rotational rheometer. The results show that the apparent density of the microcellular thermoplastic polyurethane foam is mainly determined by the thickness ratio of the skin layer and the area occupation of cell. The smaller the ratio of the thickness of the skin layer and the higher the area occupation of cell, the smaller the foam density; the relationship between compression modulus E and apparent density rho of the samples in the linear strain region is as follows: E proportional to rho(1.7), which is consistent with the basic conclusion that the relationship between modulus and density of foam materials is exponential; in the cyclic compression experiment, as the density of the foam material decreases, the residual strain decreases, and the hysteresis increase; in the rheological experiment, the modulus of the foamed material does not change significantly with the density, and the damping factor tan delta does not vary monotonically with the foam density. At the same time, the dependence of compression modulus E and hysteresis with foam density was also explained.

In this work, the effect of water on the structure and mechanical properties of thermoplastic polyurethane (TPU) blends with different ratios of a high and low hardness TPU composition was explored by experiment and simulation. The decrease of modulus of the TPU blends after immersion in water (softening of TPU), and the interesting increase of modulus of wet samples after losing some free water (hardening of TPU) compared to the dry samples, were observed in this work. By analyzing the change of glass transition temperature, the degree of phase separation of samples after immersion in water, and the types of water and hydrogen bond in samples, the possible mechanism behind the above softening and hardening of wet TPU samples was proposed. The softening and hardening of wet TPU samples were attributed to the change of structure in the interface between hard and soft domains in TPU, which is a combined effect including the plasticization of free water, breakage and/or decreasing the strength of original hydrogen bond by water, and formation of new hydrogen bond (elastic active cross-linking point) by free carbonyl groups in TPU and water etc.

通过不同的发泡工艺和成型工艺制备了密度相近的热塑性聚氨酯发泡片材(TPU-FS)和发泡珠粒成形体(ETPU)材料,研究了2种泡沫材料的形貌与力学性能的关系.通过扫描电镜表征了2种聚氨酯泡沫的结构;利用万能试验机研究了二者的单向压缩性能和循环压缩性能;用旋转流变仪表征了材料在不同压力下的流变性能.研究发现,相近密度下,T PU-FS和ET PU泡沫具有相近的泡孔面积占有率,但是ET PU发泡区域泡孔的平均孔径远大于T PU-FS泡沫;在循环压缩试验中,T PU-FS泡沫具有较高的损耗能和损耗百分比;流变实验中,在不同压力时,ET PU泡沫的储能模量和损耗模量均低于T PU-FS泡沫,且阻尼因子(tanδ)较小,T PU-FS泡沫的tanδ有一定的频率依赖性,而ET PU泡沫的tanδ随频率的变化不明显.同时,对密度相近的T PU-FS泡沫和ET PU泡沫的形貌与损耗百分比的关系进行了初步探讨.

采用流变学方法研究了双组分加成型硅橡胶在不同聚氯乙烯(PVC)表皮上的固化动力学,并利用红外光谱、核磁共振波谱、电感耦合等离子体质谱仪等手段分析了PVC表皮成分,以确定导致双组分加成型硅橡胶不固化的具体原因.结果表明,PVC表皮中导致硅橡胶不固化的主要元素为P元素.在固定硅橡胶厚度为1 mm的情况下,当PVC表皮中的P元素质量分数低于3×10-3％时,浇注在其上的双组分加成型硅橡胶依然能固化;而当PVC表皮中的P元素质量分数超过约2.4×10-2％时,虽然浇注在其上的双组分加成型硅橡胶的中间层依然能固化,但与PVC表皮接触部分的硅橡胶不固化,且不固化层厚度随P元素质量分数增加而增加.本文还研究了在P元素质量分数低于3×10-3％的PVC表皮上,降低硅橡胶厚度至微米级时的固化行为,在P元素质量分数低于3×10-3％的PVC表皮上,当硅橡胶厚度低于2μm时,硅橡胶出现不完全固化现象.双组分加成型硅橡胶在含有P元素的PVC表皮表面的固化行为主要是由硅橡胶样品中铂催化剂总含量及PVC表皮中的P元素含量确定的,同时也会受到双组分加成型硅橡胶反应速率以及铂催化剂、P元素在硅橡胶中的扩散速率的影响.

本文制备了一系列不同色浆质量分数的水性聚氨酯涂料,并将其喷涂在汽车仪表板聚氯乙烯(PVC)表皮的背面形成复合材料.用旋转流变仪表征了涂料的粘度以评价其喷涂性能;用差示扫描量热仪表征了材料的玻璃化转变温度(Tg);利用万能材料试验机表征了材料在-30℃条件下的拉伸性能及抗撕裂性能;用动态热机械分析仪表征了材料的损耗比随温度的变化.结果表明:不同色浆质量分数的涂料都能喷涂,含有涂层材料PVC表皮在-30℃低温爆破性能与涂层材料的Tg、低温拉伸性能、抗撕裂性能的关系并不大,而与涂层材料的阻尼性能直接相关.材料的阻尼性能越好,其低温爆破性能越好.

研究了高吸水树脂的质量分数对其在木板上附着性能的影响.通过流变学方法和倒置实验确定样品形成凝胶的浓度区间,同时测定了该吸水树脂的最大吸水倍率,求得其吸水饱和浓度.通过模拟消防车中喷枪喷向火灾现场进行灭火的场景,对样品进行了喷涂实验,以在固定面积范围的木板上凝胶的附着厚度来判断其附着性能的大小.结果表明:高吸水树脂的附着性能与其质量分数相关,随着质量分数的升高,样品的附着性能提高,当高吸水树脂样品的质量分数达到其凝胶浓度时,附着性能有着大幅度的提高,在质量分数继续增加时,附着性能提高的幅度较小,此时由于重力影响,附着层会整块掉落.

将不同形貌的碳粒子加至双组分室温加成型硅橡胶中制备了填充型液体硅橡胶,研究了多壁碳纳米管(MWCNTs)、炭黑(CB)和石墨烯(GR)3种填料对填充型液体硅橡胶制备工艺和使用性能差异性的影响,探究了填料用量对硅橡胶固化反应程度、体积电阻率和力学性能的影响.结果表明,MWCNTs和GR对硅橡胶固化具有阻滞延迟效果,CB则无明显的阻滞延迟效果;固化动力学上的显著差异与碳粒子表面官能团的差异性无关,而与碳粒子在体系中的分散状态直接相关,碳粒子分散状态越好,对硅橡胶的阻滞作用越弱.MWCNTs和GR的最大可用量小于CB,CB作为填料时,液体硅橡胶具有优异的加工性能和使用性能.当CB的质量分数为3.0％时,硅橡胶的体积电阻率小于107Ω·cm,拉伸强度则大于4 MPa,这表明CB在明显提升导电性能的同时,不影响力学性能.

In this study, the crosslinked ethylene-propylene-diene monomer (EPDM) foams were prepared by batch foaming using compressed CO2 as the blowing agent. The various crosslinking structures, i.e., the local primary crosslinking structure, the micro-crosslinking structure, and the full crosslinking structure, were generated by adjusting the loading of the crosslinking agent. The models were established to illustrate the fundamental influences of crosslinking structures on the evolution of cell morphology. EPDM-0.2B with 0.2 parts per hundred of rubber (phr) loading of the crosslinking agent had the micro-crosslinking structure, which improved the foamability of EPDM significantly. The foaming temperature window was broadened from 40-80 to 100-200 degrees C, and the expansion ratio was increased from 5.6 to 7.1 compared with pure EPDM. Meanwhile, the structure endows the EPDM-0.2B foam with improved creep resistance, increased thermal stability, and a melt-recycling ability. The EPDM foam with the full crosslinking structure exhibited better creep resistance and thermal stability, but the structure spoiled its melt-recycling ability significantly.

研究了6种商用聚丙烯酸类高吸水树脂(SAP)粒子尺寸大小及分布对其形成凝胶的临界浓度的影响,通过傅里叶变换红外光谱、X射线光电子能谱对样品的成分进行了分析,使用光学显微镜和ImageJ软件统计了样品未吸水时粒子的尺寸及分布,通过测定样品吸水后的膨胀比,估算得到了样品吸水后的粒子的尺寸及分布,用流变学方法和倒置实验法测定了高吸水树脂形成凝胶的临界浓度(凝胶点).结果表明,这6种商用聚丙烯酸类高吸水树脂吸水后的粒子的尺寸大小对其形成凝胶的临界浓度的影响不符合理论预测,这是由于粒子尺寸分布宽度不均一造成的.在选择粒子大小分布占优的均一范围内,样品的凝胶浓度随着粒子尺寸的增大而降低.

针对汽车内饰用模具硅橡胶出现的硫化不充分问题,通过向双组分室温硫化(RTV-2)加成型液体硅橡胶中加入一定量的三(2,4-二叔丁基苯基)亚磷酸酯与磷酸三苯酯,研究了不同价态磷(P)元素对硅橡胶硫化行为的影响以及引起铂催化剂中毒的临界P元素含量.结果表明,聚氯乙烯(PVC)表皮中引起硅橡胶不完全硫化的主要因素为不饱和态的P元素.不饱和态P元素轨道上的共享电子对会与铂结合,发生不可逆反应,引起铂催化剂中毒,从而导致RTV-2硅橡胶无法完全硫化.在实际生产中,需保证PVC表皮中不饱和P元素含量小于导致铂催化剂中铂元素中毒的临界值,RTV-2硅橡胶方可完全硫化,复制出清晰的PVC表皮花纹.

采用流变学方法研究了铂催化剂用量对加成型双组分室温硫化(RTV-2)液体硅橡胶在聚氯乙烯(PVC)表皮上硫化行为的影响,并通过调整硅橡胶中铂催化剂的用量,解决了搪塑模具制备过程中因RTV-2硅橡胶与PVC表皮中P元素反应所导致的硅橡胶硫化不完全及花纹复制率低的问题.结果表明,额外添加0.5％ ～1.0％的铂催化剂后,硅橡胶在PVC表皮上能完全硫化并形成清晰花纹.