Investigations of surface degradation of high‐density polyethylene materials resulting from tracking,using physicochemical analysis

In the present work tracking phenomena were studied with high‐density polyethylene (HDPE) materials under dc voltage, with NH₄Cl and acid rain as contaminants. It was determined that the tracking time of the material depends on the conductivity and flow rate of the contaminant. Furthermore, physicochemical analysis by wide‐angle X‐ray diffraction studies, differential scanning calorimetry, and luminescence spectroscopy was carried out, whereupon it was concluded that the tracking process is a surface‐degradation process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2843–2849, 2002; DOI 10.1002/app.10260     

NIT-Ph-p-BEN氮氧自由基的制备及催化降解性

以对醛基苯甲酸为原料，通过醛酸与2,3-二甲基-2,3-二羟胺基丁烷缩合，再经NaIO4氧化最终制得4-(4,4,5,5-四甲基-1,3-二氧化物)咪唑基-1-苯甲酸（NIT-Ph-p-BEN氮氧自由基）。采用FTIR、UV、ERP（电子顺磁共振波谱仪）和元素分析等对其结构进行表征；通过催化降解废水中有机染料甲基橙、甲基蓝和罗丹明B对其催化活性进行了评估。结果表明，当甲基橙、甲基蓝和罗丹明B浓度为15 mg/L，NIT-Ph-p-BEN质量浓度为0.15 g/L，H2O2浓度为30 mmol/L时，NIT-Ph-p-BEN对甲基橙有更好的催化降解性，仅在1 h内甲基橙的降解率达到94.26%。此外，反应机理表明，H2O2有助于实现NIT-Ph-p-BEN自由基的再生和循环利用。     

聚碳酸酯的热降解

综述了聚碳酸酯的热稳定性及其影响因素,并详细论述了一些添加剂如偶联剂甲基三甲氧基硅烷、钛酸四丁酯、阻燃剂二苯砜磺酸钾(KSS)、聚氨丙基苯基倍半硅氧烷(PAPSQ)等对聚碳酸酯热稳定性的影响,阐述了Kissinger法和Ozawa法等聚合物热降解动力学的分析方法。重点介绍了近期国内外有关聚碳酸酯热降解产物和热降解机理方面的研究成果。     

Different effects of tri(acryloyloxyethyl) phosphate on the thermal degradation of photopolymerized epoxy acrylate and polyurethane acrylate films

Tri(acryloyloxyethyl) phosphate (TAEP) was blended in different ratios with epoxy acrylate EB600 and polyurethane acrylate EB270 to obtain a series of UV curable flame retardant resins. The thermal degradation mechanisms of their cured films in air were studied by thermogravimetric analysis, in situ Fourier‐transform infrared spectroscopy, and direct pyrolysis/mass spectrometry measurements. The results showed that the phosphate group in TAEP first degraded to form poly(phosphoric acid) before the degradation of EB600. Then, the formed poly(phosphoric acid) effectively promoted the conversion of EB600 to form char, which prevented the sample from further burning. However, urethane group in EB270 degraded simultaneously with phosphate group in TAEP, leading to not effectively increase the conversion of EB270 to char during the thermal degradation. It was thus found that the addition of TAEP more effectively improved the thermal stability, flame retardance, and the char yield during combustion of EB600 than those of EB270. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3130–3137, 2006     

Thermal degradation behaviors of polypropylene with novel silicon‐containing intumescent flame retardant

The N‐[3‐(dimethoxy‐methyl‐silanyl)‐propyl]‐N′‐ (9‐methyl‐3,9‐dioxo‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5.5]undec‐3‐yl)‐ethane‐1,2‐diamine/dimethoxy dimethyl silane copolymer (PSiN II), which simultaneously contains silicon, phosphorus, and nitrogen, is synthesized and incorporated into polypropylene (PP). The flame retardancy is evaluated by the limiting oxygen index value, which is enhanced to 29.5 from 17.4 with 20% total loading of PSiN II. The thermal degradation behavior of PP/PSiN II is investigated by thermogravimetric analysis under N₂ and air. The PP/PSiN II sample degrades at 400°C for different amounts of time, and the process of degradation is studied by Fourier transform IR. The morphology of the char formed at 400°C for 10 min is investigated by scanning electron microscopy. The swollen inner structure, close, and smooth outer surface provide a much better barrier for the transfer of heat and mass during fire and good flame retardancy. The thermal stability of PP is improved by incorporation of PSiN II. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2487–2492, 2005     

壳聚糖微细粉末化研究

本文研究了壳聚糖在乙酸水溶液中滴加H2O2的氧化降解条件与相对分子量的关系及结晶的影响因素，结果表明适当降低相对分子质量和添加成核剂，并在低温下干燥，才能得到高度结晶的微细粉状微晶壳聚糖。     

Study of stability of high‐temperature polyimides using TG/MS technique

The oxidative stability of the carbon fiber‐reinforced composite of polyimide was examined, in real time, using the evolved gas analysis techniques. Off‐gas degradation products suggested the onset temperature for chain scissions to be fairly low at about 190–220°C. Based on the off‐gas products present and the trend of their release, the composite degradation mechanism appeared to be similar between 190 and 371°C, thereby marking 371°C to be the highest accelerated aging temperature for its long‐term lifetime prediction. Beyond 371°C, different degradation mechanisms would apply. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1219–1227, 2002     

多孔TiO2陶瓷光催化剂降解糠醛废水

以钛酸四丁酯等为原料，采用简单工艺制得多孔TiO2陶瓷光催化剂；并研究了利用多孔TiO2陶瓷光催化降解糠醛废水。结果表明，在紫外灯下照射60min，糖醛废水的COD去除率可达59．8％，而通入空气有利于污染物的去除。     

STEAM OXIDATION OF CARBON FORMED BY THERMAL DEGRADATION OF PMMA IN ALUMINA

In the processing of multilayer ceramic multichip modules (MCM's), a ceramic substrate, such as alumina, along with a polymer, such as poly(methyl methacrylate) (PMMA), solvents, plasticizers, flocculants, is thermally degraded before sintering. The thermal degradation of PMMA from the green body of oxide ceramics leaves behind some amount of residual carbon in the ceramic. Carbon concentration above 100 ppm has a deleterious effect on the physical properties such as fkxural strength, density, breakdown voltage and dcnsification behavior of the ceramic. This paper discusses the kinetics of oxidation of carbon formed by the thermal degradation of poly(methyt methacrylate) in alumina. Pellets of 5 urn and I urn size alumina were made at 6000 psig in a single step change. Kinetic runs were made in the temperature range of 673 to 993 K with steam as the oxidant at a flow rate of 9.96E-03 g/cm² sec. The organics (polymethyl methacrylate, methyl ethyl ketone, methanol) concentration was varied from 5 to 20 by weight%. The oxidation products were analyzed using a Varian 3700 gas chromatograph coupled with CDS 111 integrator, and by volumetric analysis. Carbon analysis was carried out at the IBM Fishkill center using a Leco analyzer. Kinetic rates and activation energies are evaluated.