低密度BMC复合材料性能的研究

研究了四种不同种类的空心玻璃微珠的加入对团状模塑料(BMC)密度及性能的影响,观察空心玻璃微珠在BMC中的分散及破损情况以及空心玻璃微珠S38含量的变化对BMC密度及性能的影响。结果表明,随着微珠含量的增加密度及拉伸强度逐渐下降;微珠含量为5%时弯曲及冲击强度达到最大值。研究微珠的表面处理对BMC性能的影响,结果表明,微珠的表面处理能有效提高BMC的力学性能。     

长玻璃纤维增强聚丙烯复合材料的力学性能研究

采用熔体浸渍技术制备了长玻璃纤维母料(LGF/PP-g-MAH/PP)增强聚丙烯(PP)复合材料(LGF/PP)。通过双螺杆挤出机制备了同等配比的短玻纤增强聚丙烯(SGF/PP)复合材料。研究了LGF含量、环氧树脂(EP)和固化剂(2E4MZ)对LGF/PP复合材料的力学性能影响。结果表明:当LGF质量分数为35%～40%时,LGF/PP的综合力学性能最好,且明显优于同样组成的SGF/PP复合材料。EP和含固化剂(2E4MZ)的EP对LGF/PP复合材料的力学性能提高有一定的作用。SEM照片分析表明:EP的加入能改善玻纤与聚丙烯基体的界面粘接。     

加工工艺对聚乙烯热收缩膜性能的影响

以低密度聚乙烯(LDPE)、线型低密度聚乙烯(LLDPE)和高密度聚乙烯(HDPE)为原料,采用吹塑成型法制备了热收缩膜。研究了原料配方、模具吹胀比、吹膜机牵伸比、挤出温度和膜泡冷却时间等因素对聚乙烯热收缩膜力学性能和透明度的影响。结果表明:与加入HDPE相比,配方中加入LLDPE的原料所生产的热收缩膜的综合性能较好;随着机组运行牵伸比的增大,PE热收缩膜的拉伸性能、收缩率和透光率均呈上升趋势;随着模具吹胀比的增大,PE热收缩膜的纵向收缩率下降,横向收缩率和透光率均上升;随着挤出机工艺温度的升高,PE热收缩膜的纵、横向收缩率同时上升;随着膜泡冷却时间的延长,PE热收缩膜的纵、横向收缩率和透光率均下降。     

PBA/OMMT制备及其对PA6力学性能的影响

用十二烷基磺酸钠(SDS)将Na基蒙脱土(MMT)改性成有机蒙脱土(OMMT),采用原位聚合法制备了聚丙烯酸丁酯(PBA)/OMMT,并将其按适当比例添加到尼龙6(PA6)中。通过红外光谱仪、差示扫描量热仪等表征了OMMT、PBA/OMMT的结构,并检测了PA6/PBA/OMMT复合材料的力学性能。结果表明:添加5%的PBA/OMMT后,PA6/PBA/OMMT复合材料的拉伸强度提高了23.1%,缺口冲击强度的降低幅度有所减缓。     

Mechanical properties of SiCp/Al2O3 ceramic matrix composites prepared by directed oxidation of an aluminum alloy

Silicon carbide particulate reinforced alumina matrix composites were fabricated using DIrected Metal OXidation (DIMOX) process. Continuous oxidation of an Al-Si-Mg-Zn alloy with appropriate dopants along with a preform of silicon carbide has led to the formation of alumina matrix surrounding silicon carbide particulates. SiC_p/Al₂O₃ ceramic matrix composites fabricated by the DIMOX process, possess enhanced mechanical properties such as flexural strength, fracture toughness and wear resistance, all at an affordable cost of fabrication. SiC_p/Al₂O₃ matrix composites were investigated for mechanical properties such as flexural strength, fracture toughness and hardness; the composite specimens were evaluated using standard procedures recommended by the ASTM. The SiC_p/Al₂O₃ ceramic matrix composites with SiC volume fractions from 0.35 to 0.43 were found to possess average bend strength in range 158-230 MPa and fracture toughness was found to be in range of 5.61-4.01 MPa√m. The specimen fractured under three-point loading as observed under scanning electron microscope was found to fail in brittle manner being the dominant mode. Further the composites were found to possess lower levels of porosity, among those prepared by DIMOX process.     

Synthesis of MoSi2-TiC nanocomposite powder via mechanical alloying and subsequent annealing

MoSi₂-30 wt.% TiC nanocomposite powder was successfully synthesized by ball milling and following heat treatment. Effect of milling time and annealing temperature were investigated. The products synthesis and reactions progress were characterized by XRD. Morphology and microstructure of milled powders were monitored by SEM and TEM, respectively. Results showed that the synthesis of this composite begins after 10 h of milling and progresses gradually up to 30 h of milling. MoSi₂-TiC composite was completely synthesized after annealing of 30 h milled powder at 900 °C. On the basis of Reitveld refinement method, the mean grain size and microstrain of 13.2 nm and 0.44% were obtained, respectively for 30 h milled powder that is in consistent with TEM image. In the spite of grain growth and strain release, this nanocomposite powder maintained its nanostructure after annealing.     

高密度聚乙烯/石墨/碳纤维导热复合材料性能的研究

采用高密度聚乙烯(HDPE)、石墨、碳纤维制备高导热、高强度的复合材料。通过SEM照片考察高密度聚乙烯/石墨/碳纤维复合体系的微观结构;研究石墨及碳纤维的加入是否可以形成导热通道以及随着石墨的添加量的提高,复合材料的导热性能及其力学性能的变化。结果表明:当石墨的质量分数为60%,碳纤维的质量分数为5%时,复合材料的导热系数达到7.938 W/(m.K),是纯HDPE的20倍。     

Investigation of synergistic effect of nano sized Ag/TiO2 particles on antibacterial,physical and mechanical properties of UV-curable clear coatings by experimental design

The synergistic effect of nano titanium dioxide (10 and 30 nm) and nano silver (10 nm) as antibacterial agents were investigated on UV curable clear coating. Antibacterial and physical–mechanical properties of coating were optimized using experimental design in response surface method. Twenty different samples of nano Ag and nano TiO₂ were prepared in this method. Antibacterial properties on Gram-negative bacteria (Escherichia coli) were investigated. The results revealed that using equal amounts of two sizes of nano TiO₂ promote the antibacterial activity of nano Ag. So, the coating shows strong activity against E. coli. Physical–mechanical properties such as surface hardness, abrasion resistance, scratch resistance and gloss of the coating were evaluated. The results depicted appropriate physical–mechanical properties. Also, scanning electron microscope (SEM), atomic force microscope (AFM) and Fourier transform infrared (FT-IR) spectroscopy were used to study the effect of nano particles on coating properties.     

Optimized synthesis and properties of surfactant-free water-reducible acrylate-alkyd resin emulsion

In this work, a modified alkyd resin (basic alkyd resin) was synthesized using maleic anhydride (MAH) to replace part of phthalic anhydride (PA) to achieve the target product acrylate-grafted-alkyd hybrid resin. The resin was then dispersed in water to form water-reducible emulsion. The properties were examined, including the extent of neutralization of final emulsion, ratio of MAH/PA in basic alkyd resin, mole ratio of basic alkyd resin to modified vinyl monomers, mole ratio of vinyl monomers (MMA/St/AA) on water dispersion stability of emulsion, particle size, drying time and mechanical properties. The optimal synthesis conditions produced a final emulsion particle size of 81.1 nm with good storage stability, hydrolytic stability and shorter drying time. The optimized synthesis conditions were identified as 80% neutralization, 1:0.8 mole ratio of basic alkyd resin to modified monomers, 4:3:2 modified monomers MMA/St/AA and 0.18 mole ratio of MAH/PA.     

Effect of starch addition on microstructure and properties of highly porous alumina ceramics

Porous alumina ceramics with ultra-high porosity were prepared through combining the gel-casting process with the pore-forming agent technique. Porosity and pore size distribution of the sintered bulks were evaluated with and without adding starch, respectively. In particular, the influences of starch addition on the properties, including thermal conductivity and compressive strength were studied. It was found that the incorporation of starch increased the nominal solid loading in the suspension and subsequently promoted the particle packing efficiency. The porosity is raised with increasing starch content from 0 to 30 vol%, which brings the decrease in thermal conductivity, whereas the compressive strength isn't seriously degraded. The further higher starch addition (40 vol%), however, would deteriorate the performance of the alumina porous ceramics. It is believed that the appropriate starch amount (lower than 30 vol%), working as a pore-forming agent, suppresses the driving force of densification without affecting the connections of neighboring grains while excessive starch amount would lead to the collapse of the porous structure.