共查询到19条相似文献,搜索用时 78 毫秒
1.
动态保压注射成型技术研究 总被引:1,自引:0,他引:1
本文阐述了动态保压注射成型技术原理及设备,并用该技术成功地制备了表面无凹陷,内部无缩孔、尺寸偏差小的高密度聚乙烯厚壁塑件。详细研究了加工工艺参数对生产精密厚壁塑件的影响。研究表明动态保压注射成型技术能克服传统注射成型技术的一些缺点并能改善塑件的力学性能,是生产高精度尺寸塑件的一种崭新方法。 相似文献
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研究加有β晶型成核剂的聚丙烯.在动态保压注塑成型时获得的既增强又增韧的聚丙烯制件,其拉伸强度、冲击强度和断裂伸长率得到大幅度提高;通过形态表征对增强增韧的机理进行了探讨. 相似文献
3.
注塑双向自增强聚丙烯的力学性能与形态 总被引:9,自引:0,他引:9
采用动态保压注塑技术,在单方向剪切应力场中制得了双方同自增强的聚丙烯试样。研究了其沿流动方向和垂直于流动方向的拉伸强度和冲击强度,结果显示,双向自增强试样增强效果明显,在流动方向的拉伸强度提高了66%,冲击强度提高4.7倍; 相似文献
4.
采用少量高分子量聚乙烯(HMWPE)在动态保压剪切应力场中诱导中等分子量聚乙烯(MMWPE),在这种双重诱导的作用下得到了性能良好的聚乙烯材料,其平行于流动方向的拉伸强度和冲击强度达到了71.17 MPa和75.79 kJ/m<'2>,分别提高了209.4%和252.8%;通过差示扫描量热(DSC),X射线衍射(WAX... 相似文献
5.
自增强高密度聚乙烯/超高分子量聚乙烯复合材料制备与表征 总被引:1,自引:0,他引:1
用自制模具制备出自增强高密度聚乙烯(HDPE)/超高分子量聚乙烯(UHMWPE)棒材.通过SEM观察、X射线分析、DSC分析以及力学性能测试,研究了挤出自增强HDPE/UHMWPE棒材微观结构和力学性能.研究结果表明,在HDPE和UHMWPE最佳配比为8:2的情况下,自增强试样的拉伸强度、抗弯强度和弹性模量分别为168.5、164.8MPa和4.9GPa,比未增强试样分别提高了534.9%、261.2%和408.3%.与普通模压试样相比,自增强试样内部有大量的微纤结构和串晶互锁结构,结晶度获得提高,(110)面和(200)面的峰值均获得提高,并且熔点向高温区发生漂移. 相似文献
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利用自行研制的低频振动注射实验装置,研究振动注射成型工艺对HDPE哑铃试样的力学性能的影响。与常规注射相比,低频振动注射能明显改善试样的拉伸强度,实现注射试样的自增强。在0 Hz~0.93 Hz之间增加振动频率能明显提高试样的强度,断裂伸长率下降;当大于0.93 Hz,频率增加对拉伸强度的改变不大,断裂伸长率有明显的回升。压力振幅的增加可以明显地改善注射试样的屈服强度,HDPE 6100M试样屈服强度由39.8 MPa增加到60.6 MPa,增加的百分数为52.3%,断裂伸长率同时有所下降。SEM显示振动注射有利于片晶顺着流动方向行式排列,并具有明显的串晶结构。 相似文献
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在动态保压剪切力场及高分子量聚乙烯线形成核的诱导下制备了性能良好的聚乙烯复合物,本次实验证实了HMW PE的诱导作用,考察了拉伸试样的应力应变行为,发现了断裂方式的转变,而SEM照片中网状串晶这一特殊结构也得到了合理的解释。 相似文献
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为了给超高分子量聚乙烯(UHMWPE)的挤出成型加工技术及设备开发提供理论基础,对UHMWPE单螺杆挤出机挤出成型过程进行了分析,建立了挤出压力的数学模型以及原料的熔融过程理论,提出了能够正常挤出的两个基本条件:即P3max>PN和熔融过程必须充分,建立、丰富和完善了高黏度材料挤出成型理论. 相似文献
9.
通过扫描电镜(SEM)观察了气体辅助注射成型(GAIM)和常规注射成型(CIM)高密度聚乙烯(HDPE)的结晶形态,发现CIM试样为区分不明显的皮芯结构,而GAIM试样形成了包括球晶、串晶和取向片晶的多层结构.且GAIM试样球晶尺寸显著小于CIM制品.在结晶形态分析的基础上,初步探讨了气体辅助注射成型制品结晶形态的形成机理. 相似文献
10.
聚丙烯在单向拉伸力场中形成双向自增强片材及其结构与性能的研究 总被引:13,自引:0,他引:13
采用普通挤出设备,在机头内,于单向拉伸应力场中实现了聚丙烯片材的双向自增强,纵向拉伸强度提高了6.33倍,横向拉伸强度提高了近1倍,同时纵横向拉伸强度表现出同步增长的趋势,其值随机头收敛角的不同而变化。运用SEM、DSC等测试手段对微观结构进行表征,揭示出试样内形成了串晶啮合结构,阐述了该结构与性能之间的关系。 相似文献
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Micropowder injection molding (μPIM) is a new technology that has potential in the mass production of microcomponents. A bulk material of nanoparticles possesses completely different properties from those of large-sized particles. The main objective of this study is to study the effects of nano-sized powder addition on the μPIM process of powder-polymer mixtures for the fabrication of miniature parts. The binder systems consist of polyethylene glycol (PEG), polymethyl methacrylate (PMMA), and stearic acid (SA) with different powder loading blended with powders. The results indicate that increasing the nanopowder content to 30 wt.% increased the powder loading and decreased the injection and sintering temperatures. The sintered parts had densities of 96% of the theoretical value. High physical and mechanical properties of the sintered specimen were achieved with the 30 wt.% nano-sized powder sintered at 1200 °C at a heating rate of 5 °C/min under vacuum atmosphere. A significant reduction of the surface roughness of the sintered parts using the nano–microhybrid powder (Sa = 0.365 μm) was observed compared with the sintered parts with only micropowder (Sa = 1.002 μm). Using nanopowders, the hardness also increased from 182 HV to 221 HV with a linear shrinkage of approximately 9%, which is less than that of the micropowders (18%). 相似文献
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Ryan P. Koseski Pavan Suri Nicholas B. Earhardt Randall M. German Young-Sam Kwon 《Materials Science and Engineering: A》2005,390(1-2):171-177
The present study investigates the microstructural evolution and densification behavior of water- and gas-atomized 316L stainless steel powder. Dilatometry and quenching studies were conducted to determine the extent of densification and corresponding microstructural changes. Results indicate that water-atomized powder could be sintered to 97% of theoretical density, while gas-atomized powders could be sintered to near-full density. The difference in the densification behavior is examined in terms of the particle morphology, initial green density and the particle chemistry. 相似文献
15.
The structure of a packing of narrowly sized wet spheres with packing density 0.435 is analysed against the well-established
random close packing with packing density 0.64 by means of the Voronoi and Delaunay tessellation. The topological and metric
properties of Voronoi polyhedra, such as the number of faces, perimeter, area and volume of a polyhedron, the number of edges,
perimeter and area of a polyhedron face, have been quantified. Compared to the well established random close packing, the
distributions become wider and more asymmetric with a long tail at the higher values. The volume and sphericity of each Delaunay
cell have also been quantified. Their distributions are shown to be wider and more asymmetric than those for the random close
packing, but the peaks are almost the same. For the wet particle packing, the correlations between Voronoi polyhedron size
and shape and between Delaunay cell size and shape are more scattered. The topological and metric results are also shown to
be consistent with those obtained for the packing of fine particles, although the dominant forces in forming a packing differ.
The results should be useful to the quantitative understanding of the structure of loosely packed particles. 相似文献
16.
V. Demers F. Fareh S. Turenne N.R. Demarquette O. Scalzo 《Advanced Powder Technology》2018,29(1):180-190
Moldability and segregation of feedstock are linked to the rheological behavior of the powder-binder mixture. In this study, the impact of binders on viscosity and segregation of feedstocks was investigated. The experiments were conducted on several feedstocks obtained by mixing Inconel 718 powder with paraffin wax-based binder systems. The viscosity of feedstocks was measured by a rotational rheometer while the segregation within green parts was evaluated using a thermogravimetric analyzer. It was demonstrated that the variation in solid loading within a molded part can be measured with a sensitivity of at least ±0.25?vol% of powder. The results indicated that the predominant powder-binder separation appears clearly at the top and the bottom of the molded part. It was also shown that the viscosity profiles of feedstocks and the intensity of segregation depends significantly on the binder constituents used in feedstock formulation. The mixture containing only paraffin wax produced the best trade-off between high moldability and low segregation for an injection process requiring an extended time range between injection and solidification of the part (e.g. up to 10?min). For a short processing time (e.g. <1?min spent in molten state), the feedstocks containing paraffin wax with stearic acid or small amount of ethylene vinyl acetate can be also considered as good candidates for LPIM process because their viscosity and segregation potential are relatively low. 相似文献
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Zai-feng Li Jin-yan Li Wei Yuan Bao-qun Sun Fu-tao Zhang Zeng-lin Wang 《Frontiers of Materials Science in China》2008,2(1):99-104
The bulk catalyst effect of dibutyltin dilaurate (DBTDL) on the reaction of NCO respectively with OH and NH2 was investigated in detail. The results showed that DBTDL had specific catalyst effect on the reaction of NCO with OH and
no measurable effect on the reaction of NCO with NH2. In situ Fourier transform infrared spectroscopy (FTIR) used in the reaction injection molding (RIM) process showed that with increasing
the concentration of DBTDL, the formation rate of the soft segment became fast, and the order degree of urea carbonyls became
worse. Meanwhile, more arrange manners of urea carbonyl were present. The bands at 1653, 1647 and 1637 cm−1 were able to be detected at the low conversion. No hydrogen-bonded urea carbonyl available in the spectra at the beginning.
The tensile-stress behavior showed that, with the increase of the DBTDL content, the interaction between polar groups became
weak, while the virtual crosslinks also became weak. Although the break stress (d), 300‰δ and the hardness of elastomers decreased
obviously, however, the tear strength, associated with the morphology of polyurethane-urea (PUU), showed the maximum when
the DBTDL content was 2.63‰. 相似文献
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对气辅注射成型一维充填过程的初始注射量进行了研究,并推导出了熔体最小注射量的计算公式。为气辅注射成型工艺的实际应用起到了指导作用。 相似文献