Effect of filler content on mechanical strength in bis-GMA-based resins with urethane linkages

Bis-GMA-based visible-light-cured resins containing urethane linkages exhibited improved hardness and strength by addition of filler to the unfilled resins. The urethane monomers in the resins strengthened the resin matrix, exhibiting an increased Shore hardness value. Urethane monomer derived from 2HEMA and N3500 was more effective than that from 2HEMA and HT. The increased strength in the resin matrix occurred after storage in water at 37°C. Addition of filler to bis-GMA-based resins increased compressive strength (110 MPa as the maximum), while diametral strength values of 20 MPa were obtained.     

稻壳纤维粒径和掺量分数对水泥复合材料性能的影响

以稻壳纤维（Rice husk fiber,RHF）为增强材料,以水泥为基体,制备了RHF/水泥基复合材料。研究了粒径对RHF在水泥基体中分散性能的影响;并以RHF粒径和掺入质量比为考察因素,采用响应曲面法,以RHF/水泥基复合材料的密度、抗折强度、含水率、吸水率和导热系数为响应值,建立数学模型,对RHF/水泥基复合材料的成型工艺进行优化设计。结果表明：RHF的粒径越小,在水泥基体中分散性能越好,粒径为150 μm的RHF分散系数达到最大值,为0.981;响应曲面模型分析表明RHF的粒径为150 μm、掺入质量为水泥质量的3%时,RHF/水泥基复合材料的性能达到最优,此时RHF/水泥基复合材料的密度为1 559.26 kg/m³,抗折强度为9.38 MPa,含水率为7.05%,吸水率为16.71%,导热系数为0.50 W/（m·K）,达到了建筑行业标准JC/T 411-2007的要求。     

Influence of ZnO filler size on the nonlinear electrical properties of ZnO ceramic-epoxy composite material

The ZnO ceramic-epoxy composite material is an excellent candidate for field grading material. The influence of ZnO filler size on the electrical properties of the ceramic-epoxy composite material was studied in this work. ZnO filler with different sizes was prepared and dispersed uniformly in the epoxy matrix. The curves of leakage current density versus electric field were measured and showed remarkable nonlinearity. With increasing filler size, the switching electric field and the resistivity both decreased significantly, while the nonlinear coefficient increased slightly. The observed results are explained physically.     

Effects of filler shape and size on the properties of silver filled epoxy composite for electronic applications

Epoxy composites filled with nano- and micro-sized silver (Ag) particulate fillers were prepared and characterized based on flexural properties, coefficient of thermal expansion, dynamic mechanical analysis, electrical conductivity, and morphological properties. The influences of these two types of Ag fillers, especially in terms of their sizes and shapes, were investigated. Silver nanoparticles were nano-sized and spherical, while silver flakes were micron-sized and flaky. It was found that the flexural strength of the epoxy composite filled with silver flakes decreased, while the flexural strength of the epoxy composite filled with silver nanoparticles showed an optimum value at 4 vol.% before it subsequently dropped. Both silver composites showed improvement in flexural modulus with increasing filler loads. CTE value indicated significant decrements in filled samples compared to neat epoxy. Results on the electrical conductivity of both systems showed a transition from insulation to conduction at 6 vol.%.     

聚苯乙烯-磁性吸收剂复合材料微波吸收特性研究

采用铁氧体和铁合金纳米晶材料组成的磁性吸收剂对回收的聚苯乙烯泡沫塑料进行复合电磁改性处理,得到聚苯乙烯-磁性吸收剂复合材料;使用微波矢量网络分析仪系统测量复合材料试样的复磁导率、复介电常数频谱特性及材料标样的电磁波吸收性能。结果表明,随磁性吸收剂含量增加,复合材料磁性和介电性增强,当磁性吸收剂质量含量达15%(质量分数)时,复合材料具有明显的吸波材料特性,在2～18GHz频段呈现多个共振型电磁能吸收峰,2GHz附近的损耗吸收峰值达-12dB;电磁改性的聚苯乙烯复合材料在原有的隔热、隔音特性基础上可兼具吸波性能,成为一种颇具应用价值的多功能材料。     

SiC_W含量对SiC_W/Si_3N_4复合陶瓷力学及高温微波性能影响

以α-Si_3N_4粉、β-SiC_W为原料,Al_2O_3、Y_2O_3为烧结助剂,采用凝胶注模工艺制备了SiC_W/Si_3N_4复合陶瓷材料,烧结温度为1 650℃,保温1.5h。研究了SiC_W加入含量对SiC_W/Si_3N_4复合陶瓷的微观结构、力学及常温/高温微波吸收性能的影响。结果表明:随着SiC_W含量的增加,SiC_W/Si_3N_4复合陶瓷的抗弯强度和断裂韧性都有先増后减的趋势,当含量为10wt%时,抗弯强度达到最大值505MPa,断裂韧性达9.515MPa·m1/2。常温介电常数在SiC_W含量为10wt%时,实部达最大值12,在12GHz最大吸收值为-21dB。高温介电常数随着SiC_W含量的增加有先增后减的趋势,在含量为10wt%时,实部达到最大值12.5。相比于纯Si_3N_4陶瓷,当SiC_W含量为10wt%时,SiC_W/Si_3N_4复合陶瓷在11.7GHz左右最大吸收可达-27dB,有效吸收频带(小于-5dB)为11.2~12.3GHz。     

Mechanical and wear behaviours of nano and microfilled polymeric composite: Effect of filler fraction and size

The addition of ceramic reinforced material, SiC particles, to resin matrices, results in the improvement of the overall performance of the composite, allowing the application of these materials as tribo-materials in industries such as: automotive, aeronautical and medical. Particle-reinforced polymeric composites are widely used as biomaterials, for example as dental filler materials and bone cements. These reinforced composites have improved mechanical and tribological performance and have higher values of elastic modulus and hardness, and also reduce the shrinkage during the polymerisation compared with resin matrices. However, the effect of the filler level in mechanical and tribological behaviour is not quite understood.The aim of this work is to determine the influence of the particle volume fraction and particle size in the wear loss of the composites and their antagonists. Reciprocating wear tests were conducted using a glass sphere against resin polyester silica reinforced composite in a controlled medium, with an abrasive slurry or distilled water. For 6 μm average particle dimension, seven particles contents were studied ranging from 0% to 46% of filler volume fraction (FVF). Afterwards, filler volume fractions of 10% and 30% were selected; and, for these percentages, 7 and 4 average particle dimensions were tested and were evaluated regarding their wear behaviour, respectively. The reinforcement particle dimensions used ranged from 0.1 μm to 22 μm with the 10% filler fraction, and for 30% of filler content the range extended from 3 μm to 22 μm. The results allow us to conclude that in an abrasive slurry medium the composite abrasion resistance decreases with the increase of the particle volume fraction, in spite of the accompanying rise in hardness and elastic modulus. With constant FVF, and abrasive slurry, the composite wear resistance increases with increasing average particle dimension. In a distilled water medium and with several FVF values, the minimum wear was registered for a median particle content of 24%. In this medium and with constant FVF the highest wear resistance occurred for average reinforcement particles of 6 μm. The removal mechanisms involved in the wear process are discussed, taking into account the systematic SEM observations to evaluate the wear mechanisms.     

Structure and properties of PP/CaSO4 composite Part III: Effect of the filler grade on properties

The mechanical properties viz.impact strength and tensile modulus of polypropylene (PP) containing two different types of calcium sulphate (prepared by in situ method under controlled conditions in a polymer matrix i.e. polyethylene oxide in the composition range 0–25 wt% of filler were studied. Increase of impact strength together with high crystallinity and improved tensile modulus was observed in one of the grades of CaSO₄ filled composite as compared to pure PP. This could be associated with the long needle shaped CaSO₄ crystals and the change in the structure and morphology induced by the same in the PP matrix.     

Optical and thermal properties in experimental Bis-GMA-based resins influenced by filler characteristics

The optical and thermal properties were examined in experimental 2,2-Bis-[4-(3-methacryloxy-2-hydroxypropoxy)phenel]propane (Bis-GMA)-based composite resin systems, each of which contained silica, silica-alumina and alumina filler particles. The filler particles were surface-treated by 1% -methacryloxypropyl trimethoxy silane and directly dispersed into the visible-light-cured Bis-GMA-based resin matrix. The average particle size was from 0.012 to 70 µm (silica filler), 2.4 to 8.4 µm (silica-alumina) and 0.02 µm (alumina). The analyses indicated that the filler-containing resin had a larger value of light transmittance when the difference in refractive index between comonomer and filler was smaller. In selected properties such as light transmittance, refractive index and depth of cure, the transmittance and the refractive index difference were important in the increased depth of cure in the Bis-GMA-based resins.     

陶瓷-尼龙复合纤维含量对石膏铸型性能和微观形貌的影响

向石膏粉料中添加不同含量陶瓷-尼龙复合纤维制备石膏铸型试样，测试分析陶瓷-尼龙复合纤维交织强化石膏试样的性能并观察其断口，研究陶瓷-尼龙复合纤维含量对石膏铸型性能和微观形貌的影响。结果表明，陶瓷-尼龙复合纤维含量对石膏铸型性能影响显著，随着陶瓷-尼龙复合纤维含量增加，石膏试样生胚抗弯强度呈倒V字形变化趋势，焙烧后的抗弯强度变化不大；石膏试样透气率随陶瓷-尼龙复合纤维含量的增加而增大，当石膏混合料中陶瓷-尼龙复合纤维质量分数为1.25wt%时达到最大值32.3，与传统石膏铸型相比，增大近21倍，尼龙纤维焙烧后形成的孔洞提高了石膏铸型透气率，陶瓷纤维保留在基体中提高强度，当陶瓷-尼龙复合纤维质量分数大于0.75wt%时，纤维会团聚并割裂基体；导热性和抗热震性随陶瓷-尼龙复合纤维含量的增加而先增大后减小，当陶瓷-尼龙复合纤维含量为0.75wt%~1wt%时，导热性和抗热震性相对最佳。      

铝基材料TIG焊填充材料对接头组织性能的影响

采用TIG焊方法焊接铝基复合材料,讨论了填充材料钛对焊缝综合性能的影响及填充材料的厚度与焊缝中生成物之间的关系.研究表明:填充材料的加入,提高了熔池的流动性,使得焊缝中的孔洞、未熔合明显减少;在高温下钛优先与增强颗粒SiC发生原位反应,从而抑制了有害相Al4C3,的生成,而且生成的TiC颗粒在焊缝中起增强作用;接头的机械性能与填充材料的厚度有着密切关系,填充材料的厚度过小,抑制有害反应的作用减弱,填充材料的厚度过大,则焊缝的脆性增大,本实验条件下填充材料厚度为0.45mm时获得最佳接头.     

Electron-beam curing of epoxy resins: Effect of alcohols on cationic polymerization

Electron-beam (e-beam) induced polymerization of epoxy resins proceeds via cationic mechanism in presence of suitable photoinitiator. Despite good thermal properties and significant processing advantages, epoxy-based composites manufactured using e-beam curing suffer from low compressive strength, poor interlaminar shear strength, and low fracture toughness. A detailed understanding of the reaction mechanism involving e-beam induced polymerization is required to properly address the shortcomings associated with e-beam curable resin systems. This work investigated the effect of hydroxyl containing materials on the reaction mechanism of e-beam induced cationic polymerization of phenyl glycidyl ether (PGE). The alcohols were found to play important roles in polymerization. Compared to hydroxyl group of aliphatic alcohol, phenolic hydroxyl group is significantly less reactive with the oxonium active centre, generated during e-beam induced polymerization of epoxy resin system.     

Effect of grain size on mechanical,surface and biological properties of microwave sintered hydroxyapatite

Hydroxyapatite (HA) compacts having average grain sizes of 168 ± 0.086 nm, 1.48 ± 0.627 μm and 5.01 ± 1.02 μm are processed from synthesized HA powder by microwave sintering at varying sintering temperature for different times. Superior mechanical and biological properties are shown by nano-grain HA compacts as compared to their micron grained counterparts. Compressive strength, indentation hardness, and indentation fracture toughness are increased with the decrease in HA grain size. The highest surface energy and maximum wettability are exhibited by nano-grain HA. HA compacts are assessed for cell–material interaction by SEM, MTT and immunochemistry assays using human osteoblast cell line for 1, 5 and 11 days. MTT assays showed higher number of living cells and faster proliferation on nano-grain HA surface. Osteoblast cells on nano-grain HA surface expressed significantly higher amount of vinculin and alkaline phosphatase (ALP) protein markers for cell adhesion and differentiation respectively. This study shows the effect of grain size on physical, mechanical and in vitro biological properties of microwave sintered HA compacts.     

Contact wear mechanisms of a dental composite with high filler content

The contact wear behavior of a dental ceramic composite containing 92 wt% silica glass and alumina filler particles in a polymeric resin matrix was examined. Because this composite is used for dental restorations, the tests were conducted under contact conditions that were relevant to those that exist in the mouth. Wear tests were conducted on a pin-on-disk tribometer with water as a lubricant. Results on wear volume as a function of load indicated two distinct regimes of wear. The wear volume increased slightly as the load was increased from 1 to 5 N. As the load was further increased to 10 N, the wear volume increased by one order of magnitude. At loads above 10 N (up to a maximum of 20 N), the wear volume was found to be independent of load. Examination of the wear tracks by SEM revealed that a surface film had formed on the wear tracks at all loads. Examination of these films by TEM showed that the films contained a mixture of small gamma-Al₂O₃ crystallites and glass particles. FTIR analysis of the adhered films indicated the presence of hydrated forms of silica and alumina, suggesting reaction of filler particles with water. Chemical analysis by ICP-MS of water samples collected after the wear tests confirmed the presence of Al and other elemental constituents of the filler particles. It is proposed that three simultaneous processes occur at the sliding contact: tribochemical reactions and film formation, dissolution of the reacted products, and mechanical removal of the film by microfracture. At low loads, wear occurs primarily by a tribochemical mechanism, i.e., formation and dissolution of the reaction products. At higher loads, wear occurs by a combination of tribochemical processes and mechanical detachment of the surface film.     

混合型固化剂对环氧树脂室温和低温力学性能的影响

研究了一种刚性和柔性胺混合型固化剂（芳香胺DETD和聚醚胺D-400）固化环氧树脂浇铸体的力学性能、材料断裂表面的微观形貌和玻璃化转变温度等性能。结果表明:当D-400加入量占固化剂总量的40%时,其室温拉伸强度呈现最大值,为82.52 MPa,弹性模量为2.30 GPa,与未加D-400的体系相比分别提高了6.3%和14.4%,其低温冲击强度提高了14%。对冲击断面形貌进行扫描电子显微分析表明:D-400的加入致使断口形貌变得粗糙,抗开裂能力得到提高。热分析实验结果显示,体系的玻璃化转变温度随着D-400含量的增加而降低。此外,还探讨了环氧树脂体系低温增韧机制。      

Effect of filler size and shape on local nanoindentation modulus of resin-composites

The aim of this study was to determine the Young’s moduli (E) of a series of model dental resin-composites using nanoindentation, and to examine how E was influenced by differences in filler-size and shape. Materials with different filler-sizes and shapes but constant filler volume-fraction were investigated. Disc specimens, mounted in polystyrene resin were mechanically polished and tested with a nanoindenter. One-way ANOVA and Bonferroni test were used for the statistical analysis. Regression analysis was used to investigate the correlation between E and filler-size. E ranged from 9.31 to 12.54 GPa for spherical fillers and from 14.09 to 17.03 GPa for irregular fillers. Statistically significant differences were found among the groups. Strong quadratic correlations were observed between E and filler-size for unimodal materials with spherical and irregular fillers, but were not statistically significant. Filler-size and shape seemed to be fine-tuning factors for E.     

Ag颗粒含量对SnCu基复合钎料性能的影响

利用颗粒增强原理研制了新型Ag颗粒增强SnCu基复合钎料,研究了Ag颗粒不同含量对复合钎料性能影响.结果表明:当Ag含量(体积分数)为5%时,复合钎料铺展面积最大,润湿角最小,钎焊接头蠕变寿命最长,比基体钎料提高23倍.     

稀释剂对环氧树脂电子束辐射固化性能的影响

对分别加入4 种稀释剂的双酚A 环氧树脂和酚醛环氧树脂的电子束辐射固化性能进行了研究。分析了稀释剂种类及含量对环氧树脂体系辐射产物的固化度、固化均匀性、固化区域大小及其动态力学性能的影响规律。结果表明: 电子束固化环氧树脂体系中加入稀释剂后, 辐射产物的固化度、玻璃化转变温度及储能模量有所下降, 但固化均匀性得到提高; 加入稀释剂的环氧树脂电子束固化区域的厚度均小于未加稀释剂树脂, 而底面直径却大于未加稀释剂树脂; 随着树脂中实际稀释剂含量的增加, 电子束固化环氧树脂固化度逐渐降低, 固化层厚度减小, 固化区域的底面直径先增加后减小。