Cellulose man-made fibre reinforced polypropylene—correlations between fibre and composite properties

A series of viscose fibres from the tyre cord type varying in mechanical parameters and titre were compounded with polypropylene to produce fibre reinforced composites. Single fibre strength is analysed in detail and conclusions are drawn with respect to effective strength values in composite applications. Composites were analysed in terms of tensile and impact properties. Correlations between single fibre and composite properties are studied. High fibre elongation leads to favourable composite impact properties via high composite elongations at break. Using water as a plastisizing agent increasing fibre elongation, notched Charpy impact strength can be improved by more than 50%. Using a modified rule of mixtures and a shear lag model for the composite modulus it was shown how a titre reduction improves the composite stiffness by an increased interfacial area. A direct fibre-composite strength correlation was not found.     

Melt flow behavior of polypropylene composites filled with multi-walled carbon nanotubes during extrusion

Polypropylene (PP) composites filled with multi-walled carbon nanotubes (MWCNTs) were prepared using a twin-screw extruder. The melt flow properties of the composites were measured with a capillary rheometer in a temperature range from 180 to 230 °C and at various apparent shear rates varying from 100 to 4000 s⁻¹. The results showed that the melt shear stress increased almost linearly while the melt shear viscosity decreased almost linearly with increasing shear rates in a bi-logarithmic coordinate system. The melt shear flow followed the power law relationship and the dependence of the melt shear viscosity on temperature obeyed the Arrhenius equation. The relationship between the melt shear viscosity and the MWCNT weight fraction was roughly linear under the investigated range of temperature or shear rate.     

Tracking lubricants during single screw extrusion of uPVC

Lubrication is one of the most important parameters in unplasticized polyvinyl chloride (uPVC) processing apart from the PVC resin and processing equipment. Lubricants are used in specific ratios to ensure effective fusion of PVC particles. The exact mechanism on how these lubricants interact is not yet fully understood. A widely accepted theory is the interaction mechanism proposed by Rabinovic et al. where lubricants are said to act as surfactants and slip agents. In this study a method for tracking lubricants, by simulating the extrusion process within a single screw extruder, was proposed. A three stage fusion simulation consisted of the feeding zone (stage 1), the compression zone (stage 2) and the metering zone (stage 3). The association interactions between the individual components of a typical uPVC formulation were followed throughout the three stages. External polar and nonpolar lubricants in combination with an internal lubricant was studied. Lubricants were successfully tracked using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). In conclusion it was found that the use of an internal lubricant promotes dispersion of external lubrication towards PVC. It was also found that there is a competition between the internal lubricant and polar external lubricant.     

Enhanced directional thermal conductivity of polylactic acid/polybutylene adipate terephthalate ternary composite filled with oriented and surface treated boron nitride

A combination of solution casting and melt extrusion technique was used to fabricate Boron nitride (BN)-filled Polylactic acid (PLA)/polybutylene adipate terephthalate (PBAT) blend composites. The BN particles were surface treated with a silane coupling agent and functionalization was confirmed via spectroscopic analysis. Field emission scanning electron microscopy confirmed that the BN surface treatment improved the particle adhesion with the polymer matrices and acted as a compatibilizer for the polymers. Moreover, changes in the particle orientation in the blend composite yielded improved thermal conductivity in different directions. The inclusion of the treated BN particles enhanced the in-plane (~1.1 W m⁻¹K⁻¹) and through-plane (~0.8 W m⁻¹K⁻¹) thermal conductivity of the composites as compared to the neat PLA. In addition, the storage modulus of the composite become more than 3 GPa that is twice that of the PLA/PBAT blend with a reasonable tensile property. In general, compared with the PLA/PBAT blend, the blend composites exhibited superior thermal and mechanical properties.     

浅谈在公共图书馆建设中导入VI——兼论深圳图书馆形象塑造

探讨了VI及其对于图书馆之定义和意义所在，介绍了公共图书馆VI所包含的内容，并结合深圳图书馆新馆建设中的实际情况，论述了在公共图书馆建设中导入VI的重要性和紧迫性。     

聚丙交脂-乙交酯纤维的温压成形

通过溶液沉析纺丝法制备聚丙交酯-乙交酯(PLGA)纤维,观察纤维的形貌并对其进行XRD和SEM表征.采用纤维温压成形法控制压力和温度得到条形的PLGA材料结合试样断口分析,研究成型压力与温度对PLGA材料的力学性能的影响.研究结果表明:非晶多孔结构的PLGA纤维可通过溶液沉析纺丝的方法获得,其孔径为0.1～ 1.0 μm;压制压力和压制温度对材料的力学性能影响较大,材料的抗弯强度、剪切强度和抗弯模量均随着温度和压力的增大而先增大后降低;在压制压力为105 MPa,压制温度为160 ℃时,试样的力学性能比较理想,此时,其抗弯强度可达到187.3 MPa,剪切强度达到100.1 MPa,抗弯模量达到2.5 GPa,可望作为非承重部位骨折愈合内固定材料.     

先进陶瓷的精密注射成型

讨论了陶瓷粉末注射成型制备精密陶瓷部件这一新技术及其国内外发展状况.先进陶瓷精密注射成型的科学基础是现代高分子精密注塑理论和现代陶瓷制造技术,它将高分子流变学、陶瓷粉体技术、陶瓷工艺学和金属模具精密制造技术结合在一起.该技术突出的优点有:①可净近成型各种复杂形状的陶瓷零部件,使烧结后的陶瓷产品无需进行机加工或少加工,从而减少昂贵的陶瓷成本;②成型制品具有极高的尺寸精度和表面光洁度;③可实现微成型(M icro In jection Mold ing),制备μm~mm范围内的微型陶瓷零件;④成型过程机械化和自动化程度高,重复性好,便于规模化低成本生产.该技术已用于陶瓷发动机、通讯产业中光纤连接器陶瓷插芯(Ferru le)、计算机工业中光盘和磁盘驱动用陶瓷轴承和生物医学用陶瓷制品等精密陶瓷件的制造.随着微注射成型新技术的发展,微型陶瓷部件将应用于环境要求苛刻、结构复杂的MEMS系统.     

New rheological developments for reactive processing of poly(ε-caprolactone)

This short review aims to show how an integrated activity on reactive processing have been developed these last years in our laboratory. We can say that the originality of this approach is based on combining developments in chemistry, in line instrumentation, and rheology aspects. Our rheological works can be divided into four important contributions: rheo-physics, rheo-chemistry, rheo-mixing and rheo-processing. These different parts are illustrated from the ε-caprolactone polymerisation in bulk and dispersed media. Rheo-physics studies allowed us to calculate the molecular weight distribution and chain structures of in situ polymerised poly(ε-caprolactone) samples. From rheo-chemistry works, we are now able to predict the variation of the complex shear modulus versus the extent of the polymerisation. The developments of new rheological tools such as rheo-mixer enable us to investigate complex mixing situations encountered in reactive polymer blends and formulations. Lastly, a rheo-processing approach based on the in-line measurement of the viscosity in a slit rheometer at the die exit of the extruder allows us to envisage its application to the experimental control of the reactive processing in extruder. To cite this article: P. Cassagnau et al., C. R. Chimie 9 (2006).     

在湿型铸造中造型材料对改善铸件表面质量的作用

提高铸件表面质量是当今工业发展的迫切需要。笔者通过生产实践，就湿型铸造中如何发挥造型材料对改善铸件表面质量的作用这一问题，提出了一些具体的看法。     

酚醛树脂复合泡沫塑料的研制

简述了酚醛泡沫的发展概况，研究了甲阶酚醛树脂的合成工艺及其泡沫的成型工艺。通过添加空心玻璃球、实心玻璃微珠、短切玻璃纤维及外覆玻璃钢，试制了具有优良力学性能的复合泡沫塑料。并分析了其应用前景。