Thermal conductivity of carbon fiber/liquid crystal polymer composites

Thermally conductive resins are needed for bipolar plates in fuel cells. Currently, the materials used for these bipolar plates often contain a single type of graphite in a thermosetting resin. In this study, varying amounts of two different types of polyacrylonitrile based carbon fibers, Fortafil 243 and Panex 30, were added to a thermoplastic matrix (Vectra A950RX Liquid Crystal Polymer). The resulting single filler composites were tested for thermal conductivity and a simple exponential thermal conductivity model was developed for the square root of the product of the in‐plane and through‐plane thermal conductivity . The experiments showed that the through‐plane thermal conductivity was similar for composites up to 40 vol % fiber. However, at higher loadings, the Panex 30 samples exhibited higher thermal conductivity. The experiments also showed that the in‐plane thermal conductivity of composites containing Panex 30 was higher than those containing Fortafil 243 for all volume fractions studied. Finally, the model agreed very well with experimental data covering a large range of filler volume fraction (from 0 to 55 vol % for both single filler systems). The model can be used with existing through‐plane thermal conductivity models to predict in‐plane thermal conductivity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5456–5462, 2006     

Influence of grafted polypropylene on the mechanical properties of mineral‐filled polypropylene composites

The purpose of this work was to study how mineral fillers would behave in a polypropylene (PP) matrix when PP modified with maleic anhydride (MA) and/or itaconic acid (IA) was used as a coupling agent in the preparation of mineral‐filled PP composites. The composites were characterized with tensile mechanical measurements and morphological analysis. The optimum amount of the coupling agent to be used to obtain composites with improved mechanical properties was established. The results indicated that these coupling agents enhanced the tensile strength of the composites significantly, and the extent of the coupling effect depended on the nature of the interface that formed. The incorporation of coupling agents enhanced the resistance to deformation of the composite. The behavior of IA‐modified PP as a coupling agent was similar to that of a commercial MA‐modified PP for the filled PP composites. Evidence of improved interfacial bonding was revealed by scanning electron microscopy studies, which examined the surfaces of fractured tensile test specimens; their microstructures confirmed the mechanical results with respect to the observed homogeneous or optimized dispersion of the mineral‐filler phase in these composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2343–2350, 2007     

In-situ growth of layered double hydroxide on montmorillonite nanosheets to improve the flame retardant performance of ABS resin

Layered double hydroxide (LDH) is a widely used flame retardant in polymer materials; however, the poor dispersion due to its high hydrophilic nature results in disappointing thermal stability and fire safety. In this work, LDH was in-situ grown on the disordered montmorillonite (MMT) nanosheets to obtain the hybrid of LDH and MMT nanosheets (LDH@MMT, simplified as LM). Various techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscope were used to characterize the microstructure of LM. In addition, the acrylonitrile-butadiene-styrene (ABS) composite containing LM and intumescent flame retardant (IFR) was prepared, and its mechanical and flame-retardant properties were also measured. The characterization results demonstrate that the LM exhibits a periodically alternating layered structure. The Limiting Oxygen Index (LOI) of the ABS composite reaches 27.2% with a V-0 rating in the UL-94 vertical burning test, while its flexural strength and tensile strength decrease by only 17.82% and 13.45%, respectively. Furthermore, the heat release rate, total heat release, smoke production rate, and carbon monoxide production rate of the ABS composite present a significant decline in cone calorimeter tests compared with those of pure ABS. The results further indicate that the hybridization could effectively improve the flame-retardant performance of ABS composites and perform lesser impacts on their mechanical properties.     

Soluble filler as a dissolution profile modulator for slightly soluble drugs in matrix tablets

The purpose of this experimental work was the development of hydrophilic–lipophilic matrix tablets for controlled release of slightly soluble drug represented here by diclofenac sodium (DS). Drug dissolution profile optimization provided by soluble filler was studied. Matrix tablets were based on cetyl alcohol as the lipophilic carrier, povidone as the gel-forming agent, and common soluble filler, that is lactose or sucrose of different particle size. Physical properties of tablets prepared by melt granulation and drug release in a phosphate buffer of pH 6.8 were evaluated. In vitro studies showed that used filler type, filler to povidone ratio and sucrose particle size influenced the drug release rate. DS dissolution profile could be changed within a wide range from about 50% per 24 hours to almost 100% in 10 hours. The release constant values confirmed that DS was released from matrices by the diffusion and anomalous transport. The influence of sucrose particle size on the drug release rate was observed. As the particle size decreased, the drug release increased significantly and its dissolution profile became more uniform. Soluble fillers participated in the pore-forming process according to their solubility and particle size. Formulations containing 100 mg of the drug, 80 mg of cetyl alcohol, 40 mg of povidone, and 80 mg of either lactose or sucrose (particle size 250–125 μm) were considered optimal for 24-hour lasting dissolution of DS.     

RCC-M中的焊接材料评定

对RCC-M中有关焊接材料评定的规定进行了介绍和讨论,认为RCC-M中的焊接材料评定是焊材厂正常产品检验和设备制造厂焊接工艺评定的简单拼凑,对标准焊材没有实际意义,对开发新焊材的控制力度又显得不够,作为法规条文并不恰当。     

纸强中填料的检测

介绍和总结了显微分析法和化学分析法检测纸张中的填料组成,为开展科研工作,优化生产原料,改善纸张性能和降低成本提供支持.     

造纸工业若干重要前沿研究课题

简要介绍近来国际造氏专家提出听若干重要前沿研究领域，包括工程纤维的研究与开发，纤维状填料的开发，单段漂白，单向压榨和新型碱回收系统。     

几种造纸填料对废纸浆过氧化氢漂白的影响

本文利用原子吸收光谱对轻质碳酸钙、高岭土、滑石粉、二氧化钛等常用造纸填料的元素组成进行分析。测定了轻质碳酸钙和高岭土两种填料悬浮液不同浓度下的ξ电位。研究填料的存在对纸浆碱性过氧化氢漂白的影响。结果表明，所用填料悬浮液的ξ电位随着填料加入量的增加而绝对值增加且均为负值，纸浆中不同的填料及其用量对过氧化氢纸浆漂白效果有不同的影响。     

Effect of model fillers on the adhesive strength of pressure-sensitive tapes

—The effect of various model fillers, namely glass beads, 'Spheriglass', and PTFE powder, on the adhesive strength of natural rubber (NR) and poly(n-butyl acrylate) (PBA) tapes has been investigated. Glass fillers treated with alkyl chlorosilane were also used. The adhesive strength was measured over a range of rates and temperatures, and corrections for the thickness of the adhesive and volume fraction of the polymer were introduced into the rate term. It was observed that the adhesive strength of PBA tapes filled with 20% PTFE is comparable to that of the control sample without filler. The strength measured over a range of strain rates increased for both untreated and treated Spheriglass-filled adhesives. Filled NR adhesives showed an enhanced strength only at very high strain rates. With 40% PTFE, this increase was quite apparent. The mechanism of improvement of the strength of adhesion due to the incorporation of a filler is explained. The addition of a filler introduces an additional mechanism of energy dissipation during deformation of the adhesive and a higher energy will be expended due to debonding of the filler and hysteresis.     

Synthesis of cobalt coated nickel powders for improving the stability of the resistivity of PPTC materials

Nickel powders coated by cobalt (Co@Ni powders) on the surface have been obtained by reduction in the ethylene glycol. The morphology and composition were characterized by scanning electron microscope and energy dispersive X‐ray spectroscopy. The valence states of cobalt in the sample were determined by X‐ray photoelectron spectroscopy. The Co@Ni powders were used as the electrically conductive fillers in the polymeric positive temperature coefficient (PPTC) materials in which polyethylene was used as the matrix. The stability of the resistivity of PPTC materials has been improved due to the protection and electrical conductivity of the cobalt layers on the surface of Ni powders. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013