Effects of physical crosslinking on properties of plasticized high molecular weight PVC

A series of high molecular weight PVC (HMW-PVC) resin was synthesized by suspenion process at various temperatures and compounded to prepare plasticized HMW-PVC. Plasticized HMW-PVC is physically crosslinked by microcrystallites and chain entanglements. The molecular weight and degree of crystallinity of PVC resin increase with decrease of polymeri-zation temperature. More dense physical crosslinking networks are formed in plasticized PVC with the decrease of polymerization temperature of PVC resin. Plasticized HMW-PVC exhibits thermal reversible processability, but the gelation temperature and melt viscosity increase with increasing physical crosslinking density. Physical crosslinking also has great effects on the mechanical properties of plasticized HMW-PVC. The compression set and deformation decrease as molecular weight and crystallinity of PVC resin increase, but the softening temperature and tensile strength increase. The crosslinking network of plasticized HMW-PVC is more similar to the dissociable network of gels than to the permanent network of crosslinked rubber and is not stable under stretching at high stress.     

稀土PVC热稳定剂作用模式的研究

探索了一种研究PVC热稳定剂作用模式的数学方法,所建立的曲线回归方程有效地反映了热稳定剂类型的差异;采用红外光谱研究表明稀土热稳定剂的作用可以改变PVC分子的构象,增加PVC的稳定性。     

三元能量对于PVC热稳定剂性能改进的研究

在封闭体系中，用三元能量对合成ＰＶＣ热稳定剂系统进行处理，动态热稳定性有所提高，压析性得以改善，气味得以减弱，耐光性得以增强。     

某硬质PVC绝缘套管的配方设计

结合生产实际 ,通过配方设计和性能测试 ,给出了一种新型改性硬质PVC绝缘套管的典型配方 ,该配方应用于低温注射成型 ,取得了满意的效果     

真空输送管静电危害的消除或利用

针对一些冶炼厂在使用橡胶吸水管或者PVC塑料钢丝管做真空氧粉输送管中,所产生的静电对真空输送工会造成电击伤害现象,文章从静电产生的原因进行深入分析,并对如何消除它以及作为一种生产过程中伴生出来的二次能源,如何进行合理的利用它,从而即达到消除危害,又可再生利用,变废为宝的目的。     

The case study of an Italian contemporary art object: Materials and state of conservation of the painting “Ragazzo seduto” by Remo Brindisi

This paper deals with the scientific survey of Remo Brindisi's painting “Ragazzo seduto” (Seated boy), made at the end of the 1950s, that is a symbolic figure of both his personal artistic solitude and the crisis of values determined by the economic boom in the post-war period. In a period of great changes and economic regrowth, the need to find a new style that could be the most authentic and personal as possible pressed the artist to experiment innovative products, including non-conventional support. Photographic and analytical techniques demonstrated the use of innovative products as an experimentation tendency, that pressed the artist to use non-conventional support, industrially treated with plasticized PVC and primed with acrylate polymers and to paint with traditional and industrial pigments mixed with an oil-modified alkyd resin. In the span of a few years, an unexpected and extended degradation on the whole surface of the painting took place, with the consequent formation of lifting and detachment of the paint film. The detected alteration is mainly due to the fast ageing of the employed polymeric materials, actually responsible of the impermanence of many contemporary works of arts. Clarifying the unknown aspects of the Remo Brindisi's stylistic choices together with the deterioration processes of the employed painting materials, this paper highlights the general problems related to the conservation of contemporary art, a neglected area of research in Italy, where more efforts are committed to the enormous and more ancient cultural heritage.     

英语词汇的构词力及其局限性

英语词汇具有极强的构词力 ,缀合和合成是两种最常见、最有生命力的构词方法。从理论上讲 ,任何一个base +affix或两个自由词素都可以按照一定规则构成一个无限长的word。但新词的产生和创造过程中必须遵循一定顺序 ,往往受到语音、语义、语法和语用很多方面的限制