国内外振动技术在塑料成型工艺中的应用

介绍国内外振动技术在塑料成型工艺中的应用。通过振动保压、多点动态进料保压及推—拉注塑技术在注塑成型中的应用，有效地消除了制件中的缩孔、疏松和表面沉陷，控制了制件中增强纤维和分子链的取向，消除熔合痕，从而提高了产品质量。所述振动保压技术的基本工作机理是在保压过程中，使熔体产生剪切，得到内热，从而延缓了薄壁部位的冷却时间，使厚壁部分冷却收缩时能从浇口得到足够的熔料补充；其余两种技术是振动保压技术的进一步发展，它们能使熔融塑料受到更大的剪切，从而效果更好。上述技术成功的应用实例有：３ｍｍ厚的ＰＰ玻纤增强塑料采用多点动态进料保压成型，其熔接线强度提高了５０％～８５％；ＡＢＳ采用动态保压注塑成型，制品的拉伸强度提高了１７％；玻纤增强ＬＣＰ进行推—拉注塑，拉伸强度和弯曲模量分别提高了４２０％和２７％。     

共混体系HDPE/m-LLDPE在动态保压注射成型中增强增韧的研究

在动态保压注塑成型技术提供的单方向往复剪切应力场作用下，制备了HDPE／m-LLDPE增强增韧试样，探讨了增强增韧效果与工艺条件的关系。发现加人适量m-LLDPE后的HDPE经过动态保压注射成型，可以明显提高HDPE／m-LLDPE试样的拉伸强度和冲击强度，拉伸强度提高了4倍以上，而冲击强度提高了近2倍，从而达到了增强又增韧的效果。     

注塑工艺对均聚聚丙烯拉伸性能的影响

采用正交试验研究了保压压力、注射压力、注射速度等注塑工艺参数对均聚聚丙烯S1003和K2760拉伸性能的影响。结果表明:保压压力为90 MPa,注射压力为80 MPa,注射速度为20 mm/s时,S1003的拉伸性能最佳。通过单因素实验对K2760的注塑工艺进行了进一步优化。结果表明:当保压压力为9 MPa,注射压力为40 MPa,注射速度为18 mm/s时,K2760的拉伸性能最佳。通过极差分析法分析了各因素的影响程度:注射速度对S1003的拉伸屈服应力和断裂标称应变影响最大,对K2760的拉伸性能影响不大;注射压力对S1003的拉伸断裂应力和拉伸弹性模量影响最大,对K2760的拉伸屈服应力影响最大;保压压力对K2760的拉伸断裂应力和拉伸弹性模量影响最大,对S1003的拉伸性能影响不大。     

几种动态注射成型方式的比较

在分析传统静态保压注射过程中聚合物取向特点的基础上，介绍了“推－拉”注塑、双塞移动保压和螺杆直射动态保压等几咱动态注射成型方式，并对各种动态注射成型方式的特点及适用性进行了探讨。     

模塑保压新技术的应用

在工程塑料(特别是增强塑料)的注射成型中,保压压力的合理控制对制品质量的提高,非常重要。本文介绍了一种新型模塑保压装置,采用这种保压装置成型玻璃纤维增强塑料有比较明显的效果。     

在低压动态注射过程中LDPE对HDPE自增强的增韧改性

本文研究了ＬＤＰＥ在低压动态保压注射过程中ＨＤＰＥ的自增强的增韧改性体的结构与性能，扫描电镜观察到ＨＤＰＥ与ＬＤＰＥ动态保压注射试样的拉伸断面呈多层断裂结构，剪切层与芯层的断裂面韧性成分显著增加，同纯ＨＤＰＥ自增强试样相比，拉伸强度（ＨＤＰＥ／ＬＤＰＥ，８０／２０）没有下降，韧性却显著增加，在一定程度上克服了ＨＤＰＥ自增强后呈脆断的缺点，试验表明，试样剪切层强度的提高是由于大分子沿流方向高度取向所     

注塑工艺对煤基均聚聚丙烯S1003拉伸性能的影响

采用正交试验法,研究了保压压力、冷却时间、注塑速率、注塑压力等注塑工艺条件对煤基均聚聚丙烯S1003拉伸性能的影响。结果表明:注塑S1003的保压压力为9 MPa、注射压力为7 MPa、注射速度为120 mm/s,其他工艺条件按GB/T 2546.2—2003进行时,S1003的性能最佳。通过极差分析对注塑工艺的影响程度进行排序为:注射压力对S1003的拉伸屈服应力影响最大,保压压力对S1003的拉伸断裂应力影响最大,注射速度对S1003的断裂标称应变影响最大,冷却时间对S1003的拉伸性能影响不大。     

工艺参数对微注塑制品轴向拉伸变形量的影响

采用模流与结构有限元软件联合分析,针对微拉伸试样的工艺参数变化对其轴向拉伸变形量的影响进行分析研究。结果表明:熔体温度、模具温度、注射压力与保压压力的变化对微拉伸试样的轴向拉伸变形量有明显影响,而流动速率与保压时间之间存在一个最佳对应值。     

在单方向往复低剪切力场中生成双向自增强HDPE试样的研究——(Ⅰ)试样制备及工艺条件对力学性能的影响

介绍在动态保压注塑成型技术提供的单方向往复低剪切应力场作用下来制备双向自增强试样。作者设计并制造了成型装置，初步研究了其成型原理、成型工艺、探讨了自增强效果与各工艺条件之间的关系。结果表明，采用本文所述的动态保压注塑成型技术显著提高了ＨＤＰＥ试样的力学性能——流动方向和垂直流动方向的拉伸强度均从２５ＭＰａ提高到３６ＭＰａ以上，达到了双向自增强的效果。自增强ＨＤＰＥ试样的拉伸强度强烈依赖于熔体的流动条件：流动方向的拉伸强度随液压站输出压力的提高而提高，垂直流动方向的拉伸强度则有一个对应最大拉伸强度的液压站输出压力；模具温度对拉伸强度的影响与压力对拉伸强度的影响相类似；熔体温度的提高有利于两个方向拉伸强度的提高；保压周期太长或太短均会使拉伸强度下降。     

长玻纤增强聚甲醛注塑成型工艺的研究

制备了长玻璃纤维(LGF)增强聚甲醛(POM)复合材料。通过6因素2水平的正交试验,探讨了注射压力、注射速度、模具温度、保压压力、保压时间、冷却时间等工艺条件对LGF增强POM复合材料的制品表观和拉伸强度的影响。结果表明:注射压力、注射速度、保压时间和模具温度等4个工艺条件对LGF增强POM制品表观和拉伸强度的影响最大,当注塑成型条件分别为料筒温度180¹90℃、注射压力60 MPa、注射速度60 mm/s、模具温度80℃、保压时间15 s时,制品具有最佳的表观和力学性能。     

Structure and properties of self-reinforced polyethylene prepared by oscillating packing injection molding under low pressure

This article reports the influence of oscillating pressure on the mechanical performance of general-grade high-density polyethylene (HDPE). The tensile strength of 93 MPa and the Young's modulus of 5 GPa were obtained by an oscillating packing technique. The great improvement of the mechanical properties of HDPE specimens is due to the existence of the shish-kebab crystalline structure, the orientation of the molecular chains along the flow direction, and the more perfect crystallites. © 1995 John Wiley & Sons, Inc.     

Analysis of crack phenomenon for injection‐molded screw using moldflow simulation

The screw for ice water filter machine was injection molded with acrylonitrile–butadiene–styrene (ABS)/polycarbonate (PC) [ABS/PC] alloy resin and its crack phenomenon after mechanical stress was analyzed by commercial Moldflow software. The cracked morphology and tensile properties of ABS/PC have been studied by scanning electron microscopy (SEM) and universal test machine (UTM). The injection pressure and the residual stress has been compared with two injection molding conditions as actual manufacturing and reduced injection flow rate. This analysis has found that residual stress is higher at actual manufacturing condition. SEM study reveals that in the micrographs taken on the surface of cracked sample ABS rubber domains tend to extremely align in the direction of mold flow. The combined data suggest that the majority of the crack comes from residual stress in final part originated from higher injection pressure during injection‐molding process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of processing parameters on the mechanical properties of in situ compatibilized polybutylene terephthalate/acrylonitrile–butadiene–styrene blends

To evaluate mechanical properties of blends prepared by intermeshing corotating twin‐screw extrusion (ICTSE), it is usually necessary to injection mold specimens after the extrusion mixing process. At this study an alternative method is used to obtain testing specimens from ribbons extruded polybutylene terephthalate/acrylonitrile–butadiene–styrene blends, (PBT/ABS), compatibilized with methyl methacrylate–glycidyl methacrylate‐ethyl acrylate (MGE) by ICTSE, and then to correlate their mechanical properties with the processing parameters. Regarding to the extrusion process parameters, it has been noted that higher feed rates, lower screw speeds and narrower kneading blocks have reduced the ductile‐brittle transition temperature (DBTT) of the compatibilized PBT/ABS blends, thereby suggesting that the molecule integrity of blend polymeric components has been preserved and that a good dispersion of the ABS domains in the PBT matrix has been achieved. Injection molded PBT/ABS blends were obtained to compare to the extruded ribbons. The mechanical tests for both specimens have shown the same trends. The injection molded samples have presented poorer impact strength, tensile strain at break and tensile strength, when compared to the respective extruded samples. That behavior has been attributed to the high level of molecular orientation resulting from the injection molding process and mainly to PBT degradation during process. The PBT degradation could have increased its degree of crystallinity, which has been confirmed by DSC measurements. As result, the blend became more brittle, decreasing its Izod impact strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bi‐axial self‐reinforcement of high‐density polyethylene induced by high‐molecular weight polyethylene through dynamic packing injection molding

Previously, bi‐axial self‐reinforcement of high‐density polyethylene (HDPE) was achieved through a uni‐axial shear stress field introduced by dynamic packing injection molding technology. Here, further improvement of tensile strength along the flow direction (MD) was achieved by blending a small amount of high‐molecular‐weight polyethylene (HMWPE) with HDPE, while the tensile strength along the transverse direction (TD) still substantially exceeded that of conventional moldings. Tensile strengths in both flow and transverse directions were considerably enhanced, with improvements from 23 MPa to 76 MPa in MD and from 23 MPa to 31 MPa in TD. The effect of HMWPE content and molding parameters on tensile properties was also investigated. The tensile strength along MD was highly dependent on HMWPE content, oscillating cycle, mold temperature, melt temperature and packing pressure, while that along TD was insensitive to composition and processing parameters within the selected design space. According to the stress–strain curves, samples with HMWPE produced by dynamic packing injection molding had a special tensile failure mode in MD, different from both typical plastic and brittle failure modes. There were no yielding and necking phenomena, which are characteristic during tensile testing of plastic materials, but there was still a considerably higher elongation compared to those of brittle materials. However, in TD, all dynamic injection molding samples exhibited plastic failure as did typical conventional injection molding samples. Copyright © 2006 Society of Chemical Industry     

增容改性对ABS/亚克力人造石废粉复合材料力学性能的影响

以亚克力人造石废粉对ABS进行填充改性,采用熔融共混法制备了ABS基复合材料。通过力学性能测试研究了苯乙烯-马来酸酐共聚物(SMA)、ABS接枝马来酸酐(ABS-g-MAH)和钛酸酯偶联剂三种改性剂的引入对ABS/亚克力人造石废粉复合材料力学性能的影响。结果表明:改性剂SMA、ABS-g-MAH和钛酸酯偶联剂均能在一定程度上改善ABS/亚克力人造石废粉复合体系的界面相容性,其最佳用量分别为4%、4%和3%,其中SMA对复合材料的改性效果优于ABS-g-MAH和钛酸酯偶联剂。当SMA用量为4%,亚克力人造石废粉用量为20%,复合材料的拉伸强度和弯曲强度达到最高值,分别为42.17 MPa和83.43 MPa。     

发泡母粒对ABS发泡材料泡孔结构及力学性能的影响

采用化学注塑发泡制备了丙烯腈–丁二烯–苯乙烯(ABS)发泡材料,研究发泡剂母粒载体分别为高抗冲聚苯乙烯(PS–HI),PS–HI+苯乙烯–丁二烯–苯乙烯塑料(SBS),SBS,ABS及聚烯烃弹性体(POE)时发泡剂母粒对ABS泡孔结构及力学性能的影响。结果表明,发泡母粒载体对ABS发泡试样的泡孔结构及力学性能具有较大的影响,以POE为发泡母粒载体所制得的ABS发泡样品的泡孔结构、力学性能较好。其泡孔平均直径为18.5μm,泡孔密度为4.183×107个／cm3,冲击强度为11.7 kJ／m2,拉伸强度为30.8 MPa。     

HDPE/m-LLDPE共混体系的双向自增强研究

茂金属聚乙烯是20世纪90年代才开发出来的新一代聚乙烯,它以独特的立构规整性及良好的物理力学性能引起材料界和产业界的极大关注,迅速掀起了世界范围内的研究热潮[1]。本实验通过动态保压注塑成型方法,在单方向往复低剪切应力场作用下制得了双向自增强的HDPE/m-LLDPE平板试样,研究了双向自增强效果与液压站输出压力的大小以及不同配方等工艺条件之间的关系。实验结果表明,在低剪切应力场的作用下,该共混体系的动态保压注射成型试样的拉伸强度与模量在平行于物料流动方向和垂直于物料流动方向上都得到了明显增强。通过扫描电镜发现了串晶互锁结构的生成。     

相容剂及其在PC/ABS合金中的应用

采用水相悬浮聚合法合成了SAN-g-MAH、SAN-g-MMA、SAN-g-GMA3种相容剂,比较了3种相容剂对PC/ABS合金的增容效果,着重研究了工艺条件对接枝率的影响及相容剂用量对合金力学性能的影响。结果表明,相容剂的最大接枝率可达5.76%,添加相容剂后,PC/ABS合金的力学性能有明显提高,拉伸强度和缺口冲击强度分别可达61.91MPa和10.12kJ/m2。     

制备工艺对PVC/ABS合金力学性能和维卡软化温度的影响

通过正交试验研究了制备工艺（开炼温度、开炼时间、平板硫化机压力和冷却温度）对PVC／ABS合金力学性能和维卡软化温度的影响。结果表明：影响PVC／ABS合金力学性能和维卡软化温度的主要因素是冷却温度。PVC／ABS合金的最佳制备工艺为：开炼温度180℃、开炼时间7min、平板硫化机压力15MPa、冷却温度100℃。