【作者】 石露；

【导师】 王依民；

【作者基本信息】 东华大学 ， 材料学， 2012， 硕士

【摘要】 涤纶是产量最大、应用最广的合成纤维品种,涤纶纱线织造所得织物质地柔软、轻薄,一般仅应用于衣着面料。如何对涤纶进行复合生产,形成用于织造的特种复合纱,拓展其应用领域,是一个值得研究的课题。聚氯乙烯(PVC)作为世界第二大通用树脂,以其价格低廉、阻燃、绝缘、耐磨损等优良的综合性能获得了广阔的市场。本论文利用共混的方法制备一系列PVC共混物,并在一定条件下将PVC共混物均匀包覆在高强涤纶长丝外围,形成PVC/PET特种复合纱。由于PVC主链上的氯原子,使PVC具有许多优异性能(如阻燃性)同时,也存在一个缺点,极性强导致分子间作用力大,尤其在低温下分子链段冻结,从而硬化、脆化,耐低温性能较差。本课题采用改变PVC配方和聚合物共混改性两种方法来改善PVC的耐寒性,进行共混改性的聚合物为聚乙烯(PE)。由于PE和PVC的不相容性,分别用有机材料乙烯-醋酸乙烯酯共聚物(EVA)和无机材料纳米碳酸钙(nano-CaCO3)作为增容剂增容两相,制备得到不同的PVC共混物作为包覆丝的包覆层材料,并对包覆层PVC共混物和包覆丝的相容性、耐寒性、耐热性和力学性能等进行表征。研究结果表明,在PVC配方中添加耐寒增塑剂和用PE进行聚合物共混改性均能够在一定程度上改善PVC的耐寒性。其中用己二酸二辛酯(DOA)作为PVC的增塑剂可以降低PVC的玻璃化转变温度(Tg)和脆化温度,但最佳效果为邻苯二甲酸二辛酯(DOP)和DOA配合使用。EVA增容PVC/PE时PVC、PE和EVA的最佳比例组成为100/10/10(质量比,下同),此时脆化温度-31.7℃。但EVA用量较大时,本身有一定的增韧效果,因此当PE用量固定时,脆化温度随着EVA含量的增加而降低。nano-CaCO3由于比表面积大、表面能高,易团聚,因此先用钛酸酯偶联剂进行表面处理,减小表面张力和表面能。用偶联剂表面处理后的nano-CaCO3增容PVC/PE共混物对PVC的耐寒改性效果最佳,当nano-CaCO3含量为5wt%时脆化温度可达到-35℃,光学显微镜观察到的相形态图也显示5wt%含量的nano-CaC03增容的PVC和PE分散相尺寸最为均匀,且两相相畴尺寸较小。对上述几种方法制备的改性PVC进行热失重分析,EVA增容的PVC/PE共混物和PVC热降解的第一阶段活化能基本相同,第二阶段活化能有较大提高,两者在平衡状态下的初始分解温度都在220℃左右。而nano-CaCO3增容的PVC/PE共混物热稳定性有较大幅度地提升,同等升温速率下初始分解温度比前两者高出20℃。而挤出包覆最适宜温度的研究表明,PVC、PVC/PE/EVA、PVC/PE/nano-CaCO3三者的最佳包覆温度依次增大。分别将PVC(不同增塑剂配方)、PVC/PE/EVA(100/10/10)、PVC/PE/nano-CaCO3(5wt%)和涤纶进行挤出包覆,制备的包覆丝强度都在3cN/dtex以上,以PVC/PE/nano-CaCO3(5wt%)/PET包覆丝强度最高,达3.6cN/dtex。更多还原

【Abstract】 Polyester is the most widely used synthetic fiber, but the fabrics from polyester yarn are usually used in clothing because they are soft and light. How to expand the application of PET fibers is of high commercial interest, such as forming a composite yarn with coated flexible resin layer. Polyvinyl chloride (PVC) is the world’s second largest general resin with extensive use because of its low price, UV resistance, flame retardance, insulation, abrasive resistance, etc. In this thesis a series of PVC blends were prepared under certain conditions, which are used as cover layer. The PVC blends were coated on the high-strength polyester multifilament, the fabrics woven from this special PVC/PET composite yarn can be used in many leisure areas, for example, bench chair and table mat in restaurant.Because of the chloride (Cl) atom in PVC chain, PVC is excellent of flame resistance. However for the strong polarity of Cl, the intermolecular force is quite strong, thus the low temperature performance is poor because the molecular chains would be frozen that leads to embrittlement and hardening in cold environment. The different PVC formulations and PVC blended with polyethylene (PE) were used to improve the cold resistance in this work. For the incompatibility of PE and PVC, the organic materials ethylene-vinyl acetate copolymer (EVA) and inorganic material nano calcium carbonate (nano-CaCO3) were used as compatibilizer, respectively. The compatibility, cold resistance, thermal stability and mechanical properties were discussed, and the proper processing conditions were also analysised in this thesis. The results indicate both different methods can improve the cold resistance of PVC to some extent. The glass transition temperature (Tg) and the brittle temperature can be reduced by adding dioctyl adipate (DOA) as the plasticizer instead of dioctyl phthalate (DOP). But DOA should be used as a secondary plasticizer with DOP for the best performance. The brittle temperature is-31.7℃of PVC/PE/EVA (100/10/10, mass ratio), and EVA is applied as the compatibilizer of PVC and PE. However with the fixed PE content, the larger amount of EVA, the lower brittle temperature of PVC/PE.Conglomeration of nano-particles has been deemed as one of the main obstacles in the preparation of polymer based nano-materials, thus the surface modification of nano-CaCO3 is necessary. Titanate coupling agent was used to decrease the surface tension and surface energy so that the nano-CaCO3 can disperse uniformly in the matrix. When the content of nano-CaCO3 is 5wt%, the brittle temperature of PVC/PE blends is lowest with the value of-35℃, as well as good thermal stability and mechanical properties. The morphology of PVC and PE phase detected via optical microscope also shows the perfect compatibility of PVC/PE.The Thermal Gravimetric Analysis (TGA) concludes that there are two stages of the thermal degradation of both PVC and PVC/PE blends. The first stage is almost the same with similar apparent activation energy (E) while the apparent activation energy of the PVC/PE blends is increased significantly for the second stage. Both the initial decomposition temperature in equilibrium state is over 220℃. The PVC/PE/nano-CaCO3 blends show the best thermal stability, under the same heating rate, the initial decomposition temperature is 20℃higher than those for PVC and PVC/PE blends. The study of optimum extruding temperature reveals that the processing temperature of PVC, PVC/PE/EVA, PVC/PE/nano-CaC03 increases in turn.Polyester multifilament was coated with PVC (different formulas with different plasticizer), PVC/PE/EVA (100/10/10, mass ratio) and PVC/PE/nano-CaCO3 (5wt%) by single screw extruder. Concentricity of the coated yarn can be well controlled. The breaking strength of all the ccoated yarns was over 3cN/dtex, and the best breaking strength was 3.6cN/dtex when the clad layer is PVC/PE/nano-CaCO3.更多还原