纳米铜粉/PP复合材料的流变性能及动态力学性能研究

将纳米铜粉经硅烷偶联剂KH550处理后,按不同的配比与聚丙烯(PP)混合,经螺杆挤压制得纳米铜粉/PP复合材料,研究了纳米铜粉在PP复合材料中的分散性以及PP复合材料的流变性能和动态力学性能。结果表明:经改性后的纳米铜粉均匀分散在PP中;纳米铜粉/PP复合材料为非牛顿假塑性流体;在低剪切速率下,复合材料熔体的黏度高于纯PP的,随着纳米铜粉的含量增加,复合材料体系的表观黏度增大,高剪切速率时,纳米铜粉的添加量对复合材料的流动性能影响较小;当复合材料体系中纳米铜粉的质量分数小于或等于0.5%时,其熔体流动性能提高,储能模量小于纯PP的,当纳米铜粉质量分数大于0.5%时,其储能模量提高并高于纯PP的。     

PMMA/SMA共混体系流变行为与温度依赖性的研究

研究了甲基丙烯酸甲酯/苯乙烯马来酸酐共聚物(PMMA/SMA)体系的流变行为,探讨了SMA中马来酸酐(MA)含量对于共混体系时温叠加和温度依赖性的影响。结果表明,MA含量为12%(质量分数,下同)的PMMA/SMA12体系符合时温叠加原理,在低温下松弛时间与组分的关系存在正偏差,随温度上升浓度涨落加剧而有负偏差的情况出现;MA含量为28%的PMMA/SMA28体系时温叠加原理由于动力学不对称性而失效,在低温区域松弛时间与组分符合对数线性关系,高温区域则出现正偏差;与PMMA/SMA12相比,PMMA/SMA28具有更强的温度依赖性。     

Fabrication of zirconia all-ceramic crown via DLP-based stereolithography

Zirconia ceramics have shown a wide applicable prospect in dental prosthetics because it possesses excellent mechanical performance and biocompatibility. The rheological behavior and curing properties of zirconia stereolithography slurry were studied, as well as the microstructure of the green, pyrolyzed, and sintered body. Variquat CC-42 NS was proved to be effective for zirconia powder dispersing in photocurable resin (SP-RC700). The curing characteristic of slurry showed that the depth of penetration tended to increase with the solid loading. Finally, the zirconia all-ceramic crowns were fabricated via DLP-based stereolithography printer. Results showed that the particles were evenly distributed in the cured resin matrix without obvious agglomeration, and the interlayered structure disappeared after binder burnout. The sample with a major crystalline phase of tetragonal zirconia and a porosity of 10(1)% were obtained after sintering at 1550°C.     

Evaluation of polyphosphoric acid on the performance of polymer modified asphalt binders

The aim of this research is to evaluate the effect of polyphosphoric acid (PPA) on the mechanical performance of styrene–butadiene–styrene (SBS) and styrene–butadiene–rubber (SBR) modified asphalt. Conventional properties, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS) tests were conducted to evaluate the performance characteristics of asphalt at different PPA inclusions. Gel-permeation chromatography (GPC), saturates, aromatics, resins, and asphaltenes (SARA), and Fourier transform infrared (FTIR) were carried to reveal the molecular weight, component and infrared spectra of asphalt. Results showed that PPA hardened the asphalt, improved the rutting and fatigue performances of polymer modified asphalt (PMA) binder, but weakened the anti-cracking performances. Besides, storage stability had a significant improvement as the addition of PPA. The addition of PPA brought more macromolecules into asphalt and led to more high-average molecular weight compounds. Furthermore, PPA changed four component ratios of asphalt. Both PMA with or without PPA have similar absorption peaks. This may be due to absorption peak of PMA covered the changes in PPA modification process as the low content of PPA. 0.8% dosage of PPA may be considered optimum for composite modified binder combining the above experimental results for this binder source.     

PP/PB共混材料的力学及流变性能研究

采用哈克双螺杆挤出机制备了聚丙烯/聚丁烯-1(PP/PB)共混材料,考察了PB的熔体流动速率(MFR)和用量对PP流变性能和力学性能的影响。结果表明:PP与PB二者相容性良好,当PB质量分数为30%时,PP/PB200(MFR为200 g/10 min)共混材料的MFR最大为37.90 g/10 min,约是纯PP的4.15倍,PP/PB0.5(MFR为0.5 g/10 min)共混材料的MFR最小为7.59 g/10 min,与纯PB相比降低了16.87%;随着PB MFR的增加,PP/PB共混材料的熔体强度降低;当PB MFR为0.5 g/10 min时,对PP有明显的增强和增韧效果,PP/PB共混材料的拉伸强度为31.11 MPa,冲击强度为48.52 kJ/m²,与纯PP相比分别提高了28.82%和185.24%。     

Flow instability in capillary extrusion of plasticized poly(vinyl chloride)

Flow instability in a capillary extrusion is studied for a high molecular weight, plasticized poly(vinyl chloride) (PVC). The onset of melt fracture correlates with the long time relaxation ascribed to the generation and/or growth of PVC crystallites. An increase in the residence time in the cylinder leads to this long time relaxation and results in the melt fracture, although the apparent shear stress remains constant, irrespective of the residence time. The extrudate temperature and the species of the plasticizer also have a significant influence on the apparatus of the extruded products. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1277–1283, 2001     

塑料材料的流变实验与流变参数拟合

阐述了塑料材料流变参数在注射成型模拟中的重要意义,简要介绍了流变数据的测试方法,采用基因遗传算法实现流变参数的拟合,并通过实例验证了所开发的拟合算法的正确性及流变参数对CAE分析结果的影响。     

超微细ZnO表面改性及PP/ZnO共混体系流变性能

研究了超微细ZnO的表面改性条件 ,并采用正交实验确定粉体改性中最重要的影响因素为偶联剂的用量。由于粉体的团聚 ,导致粉体表面活性点的封闭 ,因此实际偶联剂用量小于理论计算值。研究发现 ,粉体表面改性中的偶联剂用量对PP ZnO共混体系流变行为有较大的影响 ,当偶联剂用量适当时 ,共混体系的表观粘度趋于最小 ,过多或过少的偶联剂用量均导致共混体系表观粘度的增加     

HDPE／NBR共混物流变性能研究

通过熔融共混法制备了HDPE／NBR共混物,用毛细管流变仪研究了其流变特性,此共混物属于假塑性流体,表观粘度随剪切速率和温度的升高而降低,随NBR和增容剂含量的降低而降低。     

水焦浆添加剂最佳用量的实验研究

为了优化石油焦的成浆效果并确定水焦浆添加剂的最佳用量,实验研究了某石油焦在分别加入3种不同类型添加剂后的成浆特性,考察了添加剂用量对水焦浆成浆性、流变性和稳定性的影响。结果表明:当添加剂用量为石油焦干基质量的0.8%时,3种添加剂下石油焦均能获得较好的成浆性;NSM(亚甲基萘磺酸钠-苯乙烯磺酸钠-马来酸钠)和NC(亚甲基萘磺酸盐甲醛缩合物)添加剂使水焦浆呈胀流性,而LS(木质素磺酸盐)添加剂使水焦浆呈假塑性,添加剂用量的多少对水焦浆流变性的影响不大;当添加剂用量为石油焦干基质量的0.6%—0.8%之间时,水焦浆具有相对较好的稳定性。因此,添加剂用量为石油焦干基质量的0.8%时,水焦浆的综合成浆品质最优。