共查询到19条相似文献,搜索用时 125 毫秒
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在型坯再加热条件不变的情况下,通过全透明模具和数码摄像机研究了两步法拉伸吹塑中拉伸与吹气的时序(即预吹气延迟时间t0)对型坯拉伸吹胀模式的影响。研究表明,t0是影响拉伸吹胀模式的一个关键因素,随着t0的增加,型坯预先被拉伸的轴向长度也增加,这时瓶肩的厚度减小,瓶底的厚度增大。实验观察到型坯的拉伸吹胀存在海豚型、积沙型和截圈型3种模式。以海豚型模式成型时,型坯在轴向和径向同时得到充分地拉伸,成型瓶壁厚分布最合要求,积沙型次之,而以截圈型得到的瓶子不合要求。 相似文献
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利用Moldflow软件模拟分析了一模两腔PET/PEN瓶坯的注射成型过程,预测塑件成型过程中可能出现的缺陷,优化冷却水道直径、布局和浇注系统尺寸,提出优化的注射成型方案,然后利用注塑机和PET/PEN瓶坯模具注射成型高质量的瓶坯,再利用吹瓶机等设备拉伸-吹塑成型PET/PEN瓶,这样可确保成型瓶子的厚度均匀分布,以生产合格的PET/PEN瓶. 相似文献
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采用聚丙烯(PP)薄膜对鼠标外壳进行模外装饰贴膜,采用有限元方法对该成型过程进行模拟仿真,获得了薄膜厚度的分布、应力分布及其在x、y方向变形分布,并对其工艺参数的选择作了分析。采用不同的工艺参数模拟该成型过程,重点研究了不同的应变速率对最终成型的影响。结果表明,当应变速率增大时,薄膜的厚度和应力值也随之增大,对在x、y方向上变形影响较小,并且不同的加载方式对成型效果影响比较大。 相似文献
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针对传统拉伸吹塑工艺生产出的聚对苯二甲酸乙二酯(PET)瓶具有底部积料严重、材料拉伸不充分等缺点,提出双轴向拉伸吹塑方法。在双轴向拉伸吹塑中,模具的底模中心设置一根下杆,下杆在吹塑过程中上升到一定高度并停留一段时间,使底部材料能够充分拉伸,然后下杆卸载,上杆继续下降至底模位置,瓶坯在高气压下进一步成型为瓶子。通过实验和运用仿真软件Polyflow,对质量85 g体积4 500 mL的PET瓶分别在双轴向拉伸吹塑工艺和现有拉伸吹塑工艺下成型进行对比,发现双轴向拉伸吹塑能明显降低瓶底的厚度和质量。通过对比两种工艺在底部开始发生大幅度变形时刻的温度分布,数据表明在双轴向拉伸吹塑工艺中瓶底部分在接触模具之前保持高温状态的时间更长。分别对下杆停留时间、下杆上升延迟时间和下杆上升高度三项重要影响参数进行实验研究,三个参数均能显著降低瓶底质量,而且下杆上升高度会影响瓶整体材料分布。 相似文献
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针对部分聚对苯二甲酸乙二醇酯(PET)成型瓶靠近底端壁厚较小的缺陷,采用Polyflow仿真软件对PET瓶拉伸吹塑成型过程进行数值模拟。重点采用交互作用的正交试验方法,对瓶坯的加热温度、拉伸杆拉伸速度、预吹压力、延迟时间和高吹压力等工艺参数进行优化组合,使瓶子的最小厚度增大,瓶体更加均匀。结果表明,较优组合工艺参数分别为:延迟时间0.06 s、拉伸速度为1.6 m/s、预吹压力0.7 MPa、瓶坯温度110 ℃;优化后最小壁厚增大了28 %,瓶体壁厚均匀度提高了63 %。 相似文献
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A study was carried out of the development of orientation during processing of conventional blow molded bottles made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The level of molecular orientation was found to be relatively low in all of the polyethylene bottles examined; it increased with increasing inflation pressure and decreasing extrusion temperature. Pole figures for the HDPE bottles indicated a slight a-axis orientation toward the circumferential direction of the bottle. The b-axes, which correspond to the lamellar growth direction, tend to be parallel to the bottle thickness direction. A comparison was made of the structure developed in blow molded bottles and blown films. The results for both films and bottles indicate that crystallization during processing involves both an increase in level of molecular orientation and an increased tendency toward biaxiality. Based on pole figures and small angle X-ray scattering patterns, a morphological model for HDPE blow molded bottles is proposed. 相似文献
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运用三维有限元对啤酒瓶进行轻量化研究 总被引:1,自引:1,他引:0
运用三维和前限单元法建立了啤酒瓶的应力分布数学模型,在此基础上模拟了厚度分布和造型对啤酒瓶应力分布的影响,通过优化造型设计、厚度分布,在保证强度的前提下,实现了啤酒瓶的轻量化。 相似文献
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由乙烯-丙烯酸酯-马来酸酐共聚物(CP)与共聚尼龙(COPA)在双螺杆挤出机中进行反应共混制备改性共聚尼龙(MCOPA)。采用MCOPA/高密度聚乙烯(HDPE)材料制备高阻隔性中空吹塑瓶。对制品的加工工艺、阻隔性能、形态结构等进行了研究。结果表明,加工工艺对制品阻隔性能会有很大的影响。同时形态分析表明.吹塑瓶瓶口、瓶身、瓶底各个部位的横断面和纵断面都具有清晰、连续的层状结构。 相似文献
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Different modified polyamide (MPA) and modified polyethylene (MPE) resins were prepared by reactive extrusion of different contents of a compatibilizer precursor (CP) with either polyamide (PA) or polyethylene (PE). The MPE and MPA resins were then blow‐molded with designed amounts of PA or PE resins to prepare four different sets of MPE/PA and PE/MPA bottles with the same CP, PA, and PE compositions. Somewhat surprisingly, the xylene permeation resistance of the MPE bottles is worse than that of the base PE bottle and decreases consistently as MPE contains more CP. In contrast, the MPE/PA and PE/MPA bottles exhibit much better xylene permeation resistance than that of the base PE bottle, wherein the PE/MPA bottles show significantly better permeation resistance than that of the corresponding MPE/PA bottles prepared at the same blow‐molding conditions. On the other hand, it is worth noting that the xylene permeation rate of each of the MPE/PA and PE/MPA bottles prepared at a fixed extrusion temperature reaches a minimum when prepared with an optimum screw speed near 400 rpm. Similarly, at a fixed screw speed, the highest permeation resistance of each PE/MPA bottle is always obtained when prepared at an optimum extrusion temperature of about 230oC. However, the xylene permeation resistance of each MPE/PA bottle improves consistently when prepared at the higher extrusion temperatures used in this study. These interesting phenomena were investigated in terms of the morphology, thermal analysis of the PE/MPA and MPE/PA blends, the compatibility between PE (or MPE) and MPA (or PA), and the viscosity ratios of MPA (or PA) to PE (or MPE) during the blow‐molding process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1997–2008, 2000 相似文献
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Polarised attenuated total reflection (ATR) infrared spectroscopy has been used to quantify biaxial orientation in commercially manufactured poly(ethylene terephthalate) (PET) films and stretch-blow moulded bottles. Using a single-bounce accessory with a high refractive index element, and applying appropriate data normalisation prior to measuring band intensities, measurement of the average square direction cosines that describe the orientation is simple. Using this technique it was shown that uniaxially drawn PET films were actually biaxially oriented, and there were significant gradients in orientation through the film thickness. Bulk measurements, or methods that assume uniaxial orientation, would give incorrect results from these materials. The bottles exhibited complex orientation patterns that depended on preform and mould design, and again there were strong orientation gradients through the bottle walls. Kratky's model (pseudo-affine) was used in an attempt to predict the biaxial orientation gradients as a function of preform and bottle dimensions. 相似文献
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In stretch blow molding (SBM) process, the preform growth during the stretching and blowing is critical to the thickness distribution and properties of the final bottle. Whereas the thickness distribution is one of the most important criteria in the production of bottles. So this work focused on the polyethylene terephthalate (PET) preform growth using a transparent mold, through which the instantaneous images of the preform in the stretching and blowing stage were captured. By changing the delay time of the preblow, the three preform growth types, referred to as dolphin, sandpile, and two‐bubble, were observed. The longitudinal and hoop stresses acting on the preform segment during the stretching and blowing were analyzed. Two parameters, on which the longitudinal and hoop stresses depend, respectively, were defined. Then combining the geometry and sizes of the preform, the stresses and temperature distribution on it, and the stress–strain curves of the PET material used, the cause for different preform growth types was systematically analyzed. On the basis of preform growth types, the thickness distributions of the bottles obtained under different delay times of the preblow were explained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 564–573, 2007 相似文献
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A commercial blow-molding grade, high-density polyethylene resin was employed to produce cylindrical bottles in a commercial reciprocating screw-extrusion blow-molding machine. The distributions of thickness, crystallinity, birefringence, and impact strength were obtained at various positions. The thickness is greatest near the parting lines, while minimum thickness occurs at the top and bottom of the bottle. The thickness tends to be uniform in the middle section, in agreement with earlier studies of the parison during processing. Density and crystallinity distributions are closely associated with the distribution of thickness and its effect on the cooling rates prevailing during molding. Frozen stresses and birefringence are largest at the outer surface, where cooling rates are highest. The impact strength is lowest near the parting line. Photomicrographs suggest that this is associated with internal flow and crystallization phenomena. 相似文献