Structure development in PP/CaSO2 composites: Part II Effect of filler on crystallization and morphology

The structure development in melt crystallized polypropylene (PP) containing different types and concentration of calcium sulphate has been studied by X-ray diffraction and optical polarizing microscopy. The commercial CaSO4 containing mostly the anhydrite form gives the form of PP while the CaSO4 prepared by in situ method yields the form of PP. This takes place first by conversion of the dihydrate form of CaSO4 to the form which preferentially nucleates the form of PP. The crystallization behaviour in the latter case clearly reveals two processes. The presence of PEO which is used for the in situ preparation of CaSO4, however, is found to hinder the rate of crystallization and nucleation of the form of PP but it gives a high degree of orientation of the CaSO4 needle-like crystals during extrusion of the PP–CaSO4 composites. © 1998 Chapman & Hall     

Structure development in PP/CaSO4 composites: Part I Preparation of the filler by an in situ technique

The structure, growth and morphology of calcium sulphate prepared in situ of a polymer has been investigated using polyethylene oxide as the growth medium. The structure was predominantly the dihydrate type with monoclinic configuration for these samples as compared to the anhydrite type with orthorhombic structure obtained in commercial samples. The crystal morphology consisted of sharp needle shape, having aspect ratio of more than 10. The concentration of the polymer used had a profound effect on the crystal size and its distribution. The size distribution became narrow and the average crystal size reduced with the increase of polymer concentration. Highly oriented crystals could be obtained with application of, small shearing force on the samples. These results have been explained on the basis of polymer mediated crystallization and large interaction between the filler and the matrix. © 1998 Chapman & Hall     

Stitched glass/PP composite. Part I: Tensile and impact properties

Stitching has proven to be an effective way to increase the through-the-thickness mechanical properties of fibre-reinforced polymer composites. However, there are rare investigations which concentrate on the stitching effect on fibre-reinforced thermoplastic polymer composite, particularly under different temperature environments. Here, we investigate the tensile and impact behaviours of stitched glass/polypropylene woven composites. The effect of various sewing threads, stitch row orientations, and spacing are evaluated. Our data indicate that the stitching in through-the-thickness direction considerably increases the impact damage tolerance especially at low temperature. In addition, glass sewing threads does not deteriorate the tensile performance of the stitched composite. The study of ductile ratio (D.R.) shows that suitable sewing thread can reduce the sensitivity of ductile behaviour of composite to the variation of temperature. A strong correlation of energy absorption with respect to sewing thread fracture work in relation to its fibre volume fraction was found.     

Micromechanical deformations in PP/lignocellulosic filler composites: Effect of matrix properties

Polypropylene composites were prepared from three different PP matrices, a homopolymer, a random and a heterophase copolymer, and corn cob to study the effect of matrix characteristics on deformation and failure. The components were homogenized in an internal mixer and compression molded to 1 mm thick plates. Mechanical properties were characterized by tensile testing, while micromechanical deformations by acoustic emission measurements and fractography. The results proved that the dominating micromechanical deformation process may change with matrix properties. Yield stress determined from the stress vs. strain traces may cover widely differing processes. Debonding is the dominating process when the adhesion of the components is poor, while matrix yielding and/or filler fracture dominate when adhesion is improved by the introduction of a functionalized polymer. The dominating deformation mechanism is determined by component properties and adhesion. Interfacial adhesion, matrix yield stress and the inherent strength of the reinforcement can be limiting factors in the improvement of composite strength. The properties of polymer composites reinforced with lignocellulosic fillers are determined by micromechanical deformation processes, but they are independent of the mechanism of these processes.     

Effect of nucleation,filler anisotropy and orientation on the properties of PP composites

Polypropylene (pp) composites containing CaCO₃ and talc were prepared and investigated as a function of composition. The effect of nucleation was studied by thermoanalytical methods, structure and particle orientation were investigated by electron spin resonance spectroscopy, light and electron microscopies, while tensile and fracture tests were carried out to characterize mechanical properties. For both types of composite, particle anisotropy and orientation have a more pronounced effect on properties than nucleation. Orientation of the anisotropic filler particles occurs even under mild shearing conditions and its degree depends on the composition. In tension, the composition dependences of the yield stress and tensile strength are determined by the decrease of effective load-bearing cross-section and interaction. In impact, crack initiation plays an increased role, as does the reinforcing effect of the filler. In failure of particulate-filled composites the main energy-consuming process is plastic deformation of the matrix, which is modified by the presence of the filler. Dewetting increases, while interfacial interaction and formation of an interphase decrease, plastic deformation and energy consumption.     

ATO/CaSO4复合导电粉的制备及表征

复合导电粉具有良好的导电性、稳定性和分散性,广泛用于防静电、电磁屏蔽等领域。以硫酸钙晶须为载体,采用共沉淀法在其表面包覆一层锑掺杂氧化锡(ATO)制备了ATO/CaSO4复合导电粉,研究了焙烧温度对导电粉电阻率的影响。运用热重-差热分析(TG-DSC)和X-射线衍射(XRD)对产物进行了表征,并通过扫描电镜(SEM)观察了粉体的形貌。结果表明,最佳的焙烧温度为650℃,与TG-DSC得到的结论相一致。     

ATO/CaSO4复合导电粉制备的研究

复合导电粉具有良好的导电性、稳定性和分散性,广泛用于防静电、电磁屏蔽等诸多领域.采用共沉淀法在硫酸钙晶须表面包覆一层ATO来制备ATO/CaSO4复合导电粉,并研究制备条件对导电粉电阻率的影响.结果表明,最佳制备条件为:Sb/Sn摩尔比1∶10,硫酸钙晶须浓度7.5％,水解温度35℃,水解pH6,煅烧温度650℃,煅烧时间2h.     

On the luminescence properties of CaSO4:Ce

In conformal moving beam therapy with fast neutrons, the contributions to dose from the direct beam, scattered radiation and the gamma component vary with the position in the phantom. To determine this variation in radiation quality, microdosimetric measurements of energy deposition spectra were performed at different position in a therapy phantom. Fixed beam irradiation at different incidence angles showed strong changes in the lineal energy spectrum. An increase of slow protons (20 < y < 110 keV.micron-1) and a decrease of fast protons (2 < y < 20 keV.micron-1) was seen for irradiation outside the direct beam. During moving beam irradiation, different positions on the same isodose curves (55% or 35%) showed differences in YD of up to 5%. Variations in the quality parameter, R, determined by applying an empirical biological weighting function, were of similar magnitude. Thus, spatial variations in radiation quality should be taken into account in biological dose planning for moving beam neutron therapy.     

沉淀法制备CaSO4:Eu和CaSO4:Dy荧光体及发光性能的研究

采用传统的液相沉淀法制备了CaSO4:Eu和CaSO4:Dy粉体,研究并对比了产品的光致发光性能.光谱测试表明,CaSO4:Eu呈近紫外窄带发射.Dy3 掺杂碱土金属硫酸盐因基质不同,发射带有所不同,以CaSO4为基质,Dy3 占据高对称的格位,具有反演对称中心,发射光谱以蓝光发射为主.     

EVA-g-MAH对CaSO_4晶须/尼龙6复合材料性能的影响

采用马来酸酐接枝乙烯-醋酸乙烯酯共聚物(EVA-g-MAH)对CaSO_4晶须/尼龙6(CaSO_(4W)/PA6)增韧改性。通过双螺杆挤出机制备了CaSO_(4W)/PA6二元、CaSO_(4W)-(EVA-g-MAH)/PA6三元复合材料,用SEM、DSC、XRD等观察和表征了形貌、结构和结晶参数,并测试了力学性能。研究表明:添加少量CaSO_(4W)可提高PA6的结晶速率,而高含量CaSO_(4W)导致PA6结晶速率降低,促进γ晶型形成。添加10%(质量分数)CaSO_(4W)可同时提高PA6的刚性和韧性;添加30%CaSO_(4W)可进一步提高PA6的刚性,但PA6的韧性明显降低。添加2.5%和5%(质量分数)EVA-g-MAH,能使30%CaSO_(4W)-(EVA-g-MAH)/PA6的抗冲击强度分别提高25.0%和76.7%,并使其具有较高韧性。冲击强度的提高主要源于EVA-g-MAH所产生的能量耗散、改善应力的有效传递、增强CaSO_(4W)与PA6的界面以及EVA-g-MAH/PA6共混体系较好的相容性。     

CaCO3/PP复合材料的制备及力学性能研究

采用钛酸酯偶联剂对CaCO3粒子进行表面处理,通过双辊熔融共混和硫化压机压片技术制备了CaCO3/PP复合材料;测试了其拉伸强度、冲击强度和硬度,探讨了偶联剂用量和CaCO3添加量对复合材料力学性能的影响.研究表明,添加CaCO3粒子能有效提高PP材料的力学性能,且经偶联剂表面处理后的CaCO3粒子对改善PP的力学性能效果更佳,当采用2%钛酸酯偶联剂表面处理后的CaCO3粒子添加量为4%时,CaCO3/PP复合材料综合力学性能最好.     

Effect of filler content and size to properties of composite resins on microwave curing

The effect of filler content and size to property of composite resin using high purity spherical silica particles on microwave curing was examined by mechanical means and electron microscope observation to develop microwave-curing composite resin inlay. Increasing filler content in three kinds of filler particles (0.45, 0.96 and 1.46 m) resulted in increasing compressive strength, diametral tensile strength and knoop hardness and indicated the highest values at the operative mixing limit. The effect of particle size was that the mechanical property of the 0.96 m filled resin was highest, followed by 1.46 m and 0.45 m on the same filler content. The 0.96 m filled resin had about the same knoop hardness on both surfaces of the cured sample, which means that uniform polymerization occurred in the cured sample.With electron microscope observation, the bubbles of about 1.0 m and the cracks between the fillers and the matrix were observed in each cured resin. This is caused by the excessive absorption of microwave energy in fillers and surface treatment materials of fillers. Therefore, improvement of the composition of filler and surface treatment material of filler are needed, which makes it harder to absorb the microwave energy. ©©1999©Kluwer Academic Publishers     

再生PET纤维/PP复合材料的结构及力学性能

为满足环境保护和可持续发展的需要,废弃无纺布的回收再利用已经成为材料领域的又一研究热点。本文以废弃无纺布为研究对象制得再生聚对苯二甲酸乙二醇酯(PET)纤维,通过热压成型技术制备不同纤维含量的PET/聚丙烯(PP)复合材料。综合利用SEM、DSC、XRD、拉伸性能测试等手段对PET/PP复合材料的结构和性能进行了研究。结果表明:低含量的PET纤维均匀分散在PP基体中,与基体间界面结合紧密;PET纤维的异相成核作用促进了PP分子链的结晶,提高了结晶度,使晶粒细化;这些微结构的变化有利于PET/PP复合膜力学性能的提高,当PET纤维含量仅为0.1%时,PET/PP复合膜的拉伸强度提高了25.99%,断裂韧性提高了61.96%。     

空心玻璃微珠/PP复合材料的制备及性能研究

采用共混与注塑工艺制备出空心玻璃微珠/PP复合材料.通过高倍偏光显微镜、傅里叶红外光谱仪(FTIR)、扫描电镜(SEM)等对材料的结构进行了表征,重点研究了未改性与改性的空心玻璃微珠对PP复合材料力学性能影响.结果表明:改性后的空心玻璃微珠在PP复合材料中分散均匀而且具有致密的内部结构,并明显的改善复合材料的拉伸、弯曲强度,最佳填充量为15%.     

金红石型纳米TiO2对CaSO4晶须/PP-R树脂复合材料性能的影响

以金红石型纳米TiO2为添加剂改善了CaSO4晶须/PP-R树脂复合材料的各项性能,并研究了金红石型纳米TiO2对PP-R树脂的力学性能、耐热性能和紫外老化性能的影响.研究结果表明:由于纳米TiO2和CaSO4晶须的协同作用,添加纳米TiO2后可进一步提高CaSO4晶须/PP-R树脂复合材料的力学性能和耐热性能;金红石纳米TiO2的加入可以大幅度提高PP-R树脂的耐紫外老化性能,添加5%纳米TiO2后的CaSO4晶须/PP-R树脂复合材料经紫外辐射72 d后,其拉伸强度仅下降了0.36MPa,冲击强度仅下降了0.36kJ·m-2,熔融温度仅下降了5.4℃;而未添加纳米TiO2的CaSO4晶须/PP-R树脂复合材料的拉伸强度下降了1.96MPa,冲击强度下降了1.47kJ·m-2,熔融温度下降了18.6℃.     

Effect of interfacial interaction on morphology and mechanical properties of PP/POE/BaSO4 ternary composites

Ternary composites of Polypropylene (PP)/ethylene-octene copolymer (POE)/Barium Sulfate (BaSO₄)(PP/POE/BaSO₄) were prepared through a two-step process: BaSO₄ master-batches were first prepared through blending of BaSO₄ and POE, then blending with PP. Two families of phase structure were confirmed through SEM and DSC, depending on their interfacial interaction. Separation of POE and BaSO₄ filler was found when untreated or titanate coupling agent treated BaSO₄ filler were used. Encapsulation of BaSO₄ particles by POE elastomer was achieved by using BaSO₄ master-batch prepared through reactive blending of BaSO₄ with POE in the presence of maleic anhydride (MAH) and dicumyl peroxide (DCP). The mechanical properties of the composites greatly rely on the morphology. The yield strength and the impact toughness of a composite with core-shell morphology are higher than those of composites with separated morphologies, but the former has lower flexural modulus and elongation at break than the latter. The interfacial interaction was evaluated by semi-empirical equations developed previously. The deformation and toughening mechanisms of the composites were also investigated.     

偶联剂用量对玻璃纤维增强聚丙烯性能的影响及表征

研究了偶联剂用量对玻璃纤维增强聚丙烯复合材料力学性能的影响,并通过扫面电镜对玻璃纤维增强聚丙烯的界面及冲击断面进行研究.结果表明,玻璃纤维含量固定在35％时,偶联剂用量约为1％时,冲击强度最高.经偶联剂处理,可以明显增强玻璃纤维与聚丙烯基体的界面结合,改善复合材料的力学性能.     

Crystal growth and electrical properties of CaSO4:Dy single crystals

Single crystals of CaSO₄:Dy, with and without charge compensator were grown by the solution growth technique. Electrical conductivity was studied at room temperature for diverse concentrations of Dysprosium and showed that it increases upto 0.2 wt % of Dy, beyond which saturation sets in. Electrical conductivity was studied in the region 400 to 700°K and the migration energies estimated for various dopant concentrations. The variation of electrical conductivity and migration energy with diverse dopent concentration is explained on the basis of the theory of defects. The thermoelectric power measurements reveal that the crystals grown are ofP type.     

超分散剂对SF/PP木塑复合材料结构与性能的影响

以丁二酸酐、聚乙二醇、多乙烯多胺为原料,合成含柔性链段且具有两亲结构的水溶性超分散剂,研究了超分散剂对SF/PP木塑复合材料力学性能、热性能及微观结构的影响,探讨了复合材料的界面增客机理。实验结果表明,当超分散剂的用量为SF的5%(质量分数)时,复合材料的冲击强度达27.4kJ/m~2,弯曲强度达40.1MPa,比未经超分散剂处理的复合材料分别提高了64%和34%,复合材料的结晶度也有所提高。