布管扩胀法生产PVC双向拉伸自增强管材设备与实验

对比国内外拉伸增强管材的生产工艺,借鉴热缩管生产中的布管扩张法,研究开发一整套布管式PVC管材双向拉伸自增强的设备.设备解决了现有扩胀技术存在的缺点,并把非连续扩胀变为连续扩胀.通过实验表明:采用布管内压扩胀法可以得到外观均匀、管径稳定的扩胀管.由于高分子材料的取向作用,管材的环向拉伸强度和拉伸弹性模量都有大幅提高.     

振动力场下PP增强管材的制备及性能研究

采用电磁动态塑化挤出机挤出聚丙烯（PP）管材,通过爆破压力测试、拉伸性能测试、差示扫描量热（DSC）分析和X射线衍射（XRD）分析研究了振动频率和振幅对PP管材结构与力学性能的影响。力学性能测试结果表明,振动挤出PP管材的周向强度有了显著提高,实现了管材的双向自增强。与稳态挤出的PP管材相比,振动挤出PP管材的爆破压力最大提高了27．03％,轴向拉伸屈服强度最大提高了7．3％。DSC分析和XRD分析表明,振动挤出的PP管材结晶度提高,熔点升高,结晶完善,晶粒变小,有利于管材力学性能的提高。     

Synergistic effect of self‐assembling nucleating agent and crystallization promoter on polypropylene random copolymer pipes via rotation extrusion

In this study, high hoop tensile strength and toughness polypropylene random copolymer (PPR) pipes were successfully prepared through rotation extrusion and synergistic effect of self‐assembling nucleating agent (TMB‐5) and crystallization promoter (isotactic polypropylene, iPP). The result indicated low temperature toughness of PPR pipes could be improved by incorporating TMB‐5 and iPP, as the result of highly improved PPR crystallization capability and abundant β‐form crystal production. Both molecular chains and anisotropic crystallites deviated off the axial direction due to the hoop stress generated by rotation extrusion, leading to increased hoop orientation and pronouncing enhancement in hoop strength. Accordingly, the hoop tensile strength and impact strength of the modified PPR pipe reached 28.9MPa and 5.7kJ/m², increased by 126% and 43% compared to the convention‐extruded PPR pipe. POLYM. ENG. SCI., 56:866–873, 2016. © 2016 Society of Plastics Engineers     

PVC/锯末塑木材料的研制

以锯末和PVC胶粘剂为主要原料，用高速混合机制备了PVC／锯末塑木材料，并通过平板硫化机热压成型，制备出了新型的PVC／锯末塑木板材；测试了塑木板材的拉伸强度，弯曲强度，冲击强度，拉伸弹性模具，弯曲弹性模量等力学性能，讨论了增塑剂和胶粘剂用量对塑木板材性能的影响，实验结果表明：随增塑剂用量的增大，PVC／锯末塑木板材的刚性下降，韧性升高；随胶粘剂用量的增大，PVC／锯末塑木板材的力学性能和耐水性均有提高。     

PVC塑料供水管的配方研究

研究了CaCO3和ABS对硬聚氯乙烯（UPVC）复合体系的力学性能的影响。结果表明,在实验数据范围内,复合体系中加入ABS可以提高其冲击强度和弹性模量（少于5份）,但材料的拉伸强度下降;在体系中加入适量的经表面处理的CaCO3能明显提高材料的冲击强度和断裂伸长率,当CaC03用量为12份时,其冲击强度和断裂伸长率分别提高了2．5倍和2.8倍左右,复合体系的弹性模量随CaCO3用量增加而提高。最优配方为：PVC100份（质量份,下同）、CaCO3 12份、ABS5份、钙锌复合稳定剂3．5份、其他助剂适量。以该配方生产的UPVC供水管各性能完全符合GB／T1000 2．1标准规定。     

Biaxial orientation of linear polyethylenes using the compressive deformation process

The tensile properties of three grades of linear polyethylene were enhanced by a factor of as much as 15 using a melt/solid phase compressive deformation process that produced equi-biaxial planar orientation in the sheet. Ultra high molecular weight polyethylene with planar isotropy and an in-plane modulus of 10 GPa and a tensile strength of 330 MPa was produced using this method. It was found that the molecular weight had a significant influence on the optimum processing temperature, the ultimate biaxial deformation ratio and hence the ultimate tensile properties. High density polyethylene processed under ideal conditions had a tensile modulus of 2.3 GPa and a tensile strength of 250 MPa. The tensile strength increased linearly with increasing biaxial deformation ratio and the tensile modulus increased non-linearly with increasing biaxial deformation ratio. The deformation rate and the dwell time did not have a significant effect on the tensile properties. Shrinkage tests showed that biaxial deformation was less effective than uniaxial deformation in inducing orientation of the polymer chains, however differential scanning calorimetry results were consistent with the presence of extended chain crystals in very highly oriented ultra high molecular weight polyethylene sheets.     

A novel indirect tensile test method to measure the biaxial tensile strength of concretes and other quasibrittle materials

A novel indirect tensile test method, the biaxial flexure test (BFT) method, has been developed to measure the biaxial tensile strength of concretes. The classical modulus of rupture (MOR) test has been generalized to three dimensions. In this method, we use a circular plate as the new test specimen. This plate is supported by an annular ring. We apply an external load to this specimen through a circular edge. The centers of the specimen, the loading device and the support are identical. The biaxial tensile strength measured by this new method is about 19% greater than the uniaxial tensile strength obtained from the classical modulus of rupture test as reported by other researchers. However, at the same time, we also found that the stochastic deviation of the biaxial tensile strength is about 63% greater than the uniaxial strength.     

Multiaxial Loading Fracture of Al2O3 Tubes: I, Experiments

Alumina thin-walled tubes were fractured in axial tension, hoop tension, balanced biaxial tension, balanced tension-compression, and pure torsion using an electrohydraulic mechanical testing apparatus. A slight anisotropy in the axial and hoop uniaxial strengths indicated that the predominant defects were axially oriented, and probably fabrication-related as opposed to machining flaws. A 10% weakening was observed in balanced biaxial tension as compared to uniaxial tension, whereas strength was insensitive to a balanced tension-compression stress state. The strength in pure torsion was 16% higher than the axial strength. Stress state results suggest a weakening due to in-flaw plane tensile stresses and more complex fracture-initiation phenomena for stresses not oriented perpendicular to the dominant defects.     

聚醚醚酮薄膜的性能研究

采用挤出流延法制备了一系列聚醚醚酮（PEEK）薄膜，通过拉力机、差示扫描量热仪、紫外分光光度计、透光率雾度仪等对PEEK薄膜的基本性质、光学性能、力学性能进行了研究。结果表明，PEEK薄膜的透光率随结晶度的升高而降低；拉伸速率对拉伸强度、断裂伸长率的影响不大，拉伸速率快，屈服强度明显提高；拉伸强度随流延辊速度的增加而提高；双向拉伸的方法可使薄膜拉伸强度达到203 MPa；增加薄膜厚度、提高结晶度的方法可以提高薄膜的抗紫外性能。     

Novel coupling agents for PVC/wood‐flour composites *

Effective interfacial adhesion between wood fibers and plastics is crucial for both the processing and ultimate performance of wood–plastic composites. Coupling agents are added to wood–plastic composites to promote adhesion between the hydrophilic wood surface and hydrophobic polymer matrix, but to date no coupling agent has been reported for PVC/wood‐fiber composites that significantly improved their performance and was also cost‐effective. This article presents the results of a study using chitin and chitosan, two natural polymers, as novel coupling agents for PVC/wood‐flour composites. Addition of chitin and chitosan coupling agents to PVC/wood‐flour composites increased their flexural strength by ～20%, their flexural modulus by ～16%, and their storage modulus by ～33–74% compared to PVC/wood‐flour composite without the coupling agent. Significant improvement in composite performance was attained with 0.5 wt% of chitosan and when 6.67 wt% of chitin was used. J. VINYL ADDIT. TECHNOL., 11:160–165, 2005. © 2005 Society of Plastics Engineers