Molecular weight studies of the γ‐irradiation degradation of poly(methyl methacrylate) doped with poly(p‐sulfanilamide)

The protection of some poly(methyl methacrylate) (PMMA) samples against γ rays was investigated in the absence and presence of poly(p‐sulfanilamide). Pure PMMA (without additives) and PMMA–poly(p‐sulfanilamide) blend samples were irradiated with γ rays for different exposure doses (5, 15, 25, 35, 50, 75, and 100 kGy). The viscosity‐average molecular weights were determined and thin‐layer chromatography measurements were carried out after each irradiation dose. The maximum protection against γ rays was found when 1% poly(p‐sulfanilamide) was used. The radiation chemical yield for main scission (G_s) was calculated and had lower values in the case of 1% poly(p‐sulfanilamide). The energy absorption per scission was maximum for 1% poly(p‐sulfanilamide), and this confirmed the obtained G_s data. From thin‐layer chromatography studies, it was observed that both the retention factor (R_f) values and polydispersity of the PMMA samples increased with an increasing exposure dose. The effect of γ irradiation on PMMA films doped with 1% poly(p‐sulfanilamide) was investigated with UV spectroscopy after the extraction of the additives. A change in the intensity of the absorption bands with an increasing irradiation dose was recorded. It is suggested that PMMA films doped with this type of polymer can be used as dosimeters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

羟丙基纤维素/水/甘油体系三元相图的计算机模拟

通过凝固点降低法和平衡溶胀法分别测定了甘油与水、羟丙基纤维素与甘油的相互作用参数,结合羟丙基纤维素与水的相互作用参数,利用Flory-Huggins聚合物溶液理论,以及Matlab计算机程序,首次计算出羟丙基纤维素/水/甘油三元体系的双节线和旋节线,并绘制出羟丙基纤维素/水/甘油体系的三元相图。     

“链接”化学在高分子合成中的应用

简介了"链接"化学的基本特点,综述了近几年来叠氮-炔"链接"化学在合成不同结构聚合物中的应用。     

Role of block copolymer on the coarsening of morphology in polymer blend: Effect of micelles

The reactive compatibilization of polystyrene/ethylene‐α‐octene copolymer (PS/POE) blend via Friedel–Crafts alkylation reaction was investigated by rheology and electron microscope. It was found that the graft copolymer formed from interfacial reaction reduced the domain size and decreased the coarsening rate of morphology. The reduction of the interfacial tension is very limited according to the mean field theory even assuming that all block copolymer stays on the interface. With the help of self‐consistent field theory and rheological constitutive models, the distribution of graft copolymer was successfully estimated. It was found that large amount of copolymer had detached from the interfaces and formed micelles in the matrix. Both the block copolymer micelles in matrix and the block copolymers at the interface contribute to the suppression of coarsening in polymer blend, but play their roles at different stages of droplet coalescence. In droplet morphology, the micelles mainly hinder the approaching of droplets. © 2014 American Institute of Chemical Engineers AIChE J, 61: 285–295, 2015     

Comparative study on electrical properties of copper nanowire/polypropylene and carbon nanotube/polypropylene composites

Nanocomposites using copper nanowires (CuNWs) or carbon nanotubes (CNTs) as fillers with polypropylene (PP) as matrix were prepared by miscible solution mixing and precipitation method. Comparative studies on electrical conductivity and electromagnetic interference shielding properties were reported. On the conductivity curve, a plateau was found for both CuNW/PP composite and CNT/PP composite. The plateaus are located at a different concentration range for each composite type: for CuNW/PP composite, it is between 0.8 and 1.7 vol %, while for CNT/PP composite the plateau occurs in a narrower range between 0.4 and 0.6 vol %. The shielding effectiveness (SE) increases with increased concentration of fillers. CNT/PP composite has higher SE at concentrations less than 2 vol %; the two curves cross near 10 dB at this point and at concentrations higher than 2 vol %, CuNW/PP composite has higher SE. © 2014 American Institute of Chemical Engineers AIChE J, 61: 296–303, 2015     

Morphology of polystyrene/poly(methyl methacrylate) blends: Effects of carbon nanotubes aspect ratio and surface modification

Multiwalled carbon nanotubes (MWCNTs) with aspect ratios (ARs) ranging from 94 to 474 were incorporated into polystyrene (PS)/poly(methyl methacrylate) blends using solution mixing and melt mixing. Also, two functionalized MWCNTs were prepared from the nanotubes having AR 94: one was oxidized by nitric acid while the other was further modified with amine‐terminated PS attached to carboxyl groups to form amides. The two functionalized MWCNTs (1 wt %) were used to show that which phase the carbon nanotubes (CNTs) were located in could be controlled with nanotube surface chemistry. When nanotubes were confined to the minor phase, the size of the minor domain first decreased with adding low AR CNT as expected due to the increased viscosity of the minor phase. However, at higher ARs, the size increased beyond the size for the minor domain with no nanotubes, and at high enough AR, the shape of the minor domain changed from spherical to an elongated irregular shape. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3500–3510, 2015     

高分子基导电复合材料研究进展

高分子基导电复合材料凭借其导电性、稳定性、加工性等方面的明显优势,成为导电材料研究的热点。系统地介绍了复合型导电高分子材料的导电机理、制备方法并对导电复合材料的应用进行了总结,并展望了导电高分子复合材料的发展趋势。     

汽车内饰注塑工艺优化、数值模拟及缺陷分析

主要介绍了聚丙烯、丙烯腈-丁二烯-苯乙烯塑料以及其它高分子材料的汽车内饰件的生产工艺对制件质量的影响,通过工艺优化、数值模拟和缺陷分析,设计出合理的浇注系统和冷却系统,得到最佳的加工工艺,从而提高制件的美观度、降低制件的尺寸收缩、翘曲变形、熔接痕等缺陷的产生,还对数值模拟在汽车内饰件生产工艺优化方面的发展进行了展望.     

钴基自修复聚酰胺导电高分子材料的制备与性能

以二聚脂肪酸、二乙烯三胺、尿素等为原料制备室温自修复型聚酰胺。通过溶液水热法制备导电单质钴颗粒,并采用纳米复合工艺将导电单质钴颗粒掺杂入自修复聚酰胺体系中,经高温模压制得一种新型钴基自修复聚酰胺导电高分子材料。采用傅里叶变换红外光谱仪、X射线衍射仪、扫描电子显微镜等仪器对单质钴和自修复聚酰胺进行结构表征。系统研究了自修复聚酰胺的自修复能力及抗溶胀性能,以及自修复导电高分子材料的导电和自修复性能。结果表明,所制备的单质钴平均粒径为3.43μm,且表面粗糙易于与聚酰胺基体复合;自修复聚酰胺基体在室温下的自修复次数可达20余次;当交联剂尿素用量为6.6 g/20 g二聚脂肪酸或交联温度为145℃时,自修复聚酰胺对水、碱溶液和油具有较好的综合抗溶胀性能。当单质钴质量分数达到50%后,自修复导电高分子材料的导电率发生突变,导电能力大幅提升;单质钴的加入降低了材料的自修复能力,但单质钴质量分数为50%的材料在室温下的自修复次数仍可达10余次。由于这种材料同时具有较好的导电性能和自修复性能,有望应用于可穿戴装备、电子器件等领域。     

Cold sintering process: A new era for ceramic packaging and microwave device development

Cold sintering process (CSP) is an extremely low‐temperature sintering process (room temperature to ~200°C) that uses aqueous‐based solutions as transient solvents to aid densification by a nonequilibrium dissolution‐precipitation process. In this work, CSP is introduced to fabricate microwave and packaging dielectric substrates, including ceramics (bulk monolithic substrates and multilayers) and ceramic‐polymer composites. Some dielectric materials, namely Li₂MoO₄, Na₂Mo₂O₇, K₂Mo₂O₇, and (LiBi)_0.5MoO₄ ceramics, and also (1?x)Li₂MoO₄?xPTFE and (1?x)(LiBi)_0.5MoO₄?xPTFE composites, are selected to demonstrate the feasibility of CSP in microwave and packaging substrate applications. Selected dielectric ceramics and composites with high densities (88%‐95%) and good microwave dielectric properties (permittivity, 5.6‐37.1; Q × f, 1700‐30 500 GHz) were obtained by CSP at 120°C. CSP can be also used to potentially develop a new co‐fired ceramic technology, namely CSCC. Li₂MoO₄?Ag multilayer co‐fired ceramic structures were successfully fabricated without obvious delamination, warping, or interdiffusion. Numerous materials with different dielectric properties can be densified by CSP, indicating that CSP provides a simple, effective, and energy‐saving strategy for the ceramic packaging and microwave device development.