PET注拉吹制品壁厚分布的研究

通过注射拉伸吹塑实验分析了二次吹胀压力、拉伸杆速度以及吹胀延迟时间对瓶子轴向壁厚分布的影响。实验结果表明：吹胀压力的改变对瓶子轴向壁厚分布影响不大，拉伸杆速度与吹胀延迟时间的变化对瓶子轴向壁厚分布有显著影响。吹胀延迟时间的改变会形成不同的型坯轮廓发展模式，在注拉吹可视化实验结果的基础上，结合应力和温度场两方面的因素解释了型坯轮廓发展模式的成因。     

注射拉伸吹塑模拟及相关技术的研究方法

简介注射拉伸吹塑模拟的一般思路，对国外拉伸吹胀阶段数值模拟的研究进展进行了全面的阐述。认为在注射拉伸吹塑模拟时不宜将某种材料模型绝对化，有必要建立一个合理的型坯吹胀破裂判断标准；结晶取向和应变硬化现象的微观模拟与宏观成型过程的数值模拟相结合是今后研究的方向和难点。     

基于响应面法PE吹塑用汽油瓶工艺参数优化分析

为改善塑料制件壁厚不均造成的产品成型质量问题,以PE汽油瓶为研究对象,通过Polyflow软件模拟了其吹塑过程,研究了吹胀压力、型坯初始温度以及型坯初始壁厚对汽油瓶制件壁厚均匀性的影响,并且以最终制件壁厚均匀性为评判标准,建立二次多项式响应面模型,将响应面模型与有限元法相结合来优化汽油瓶吹塑成型工艺参数。实验表明:优化后的工艺参数吹胀压力为0.29 MPa,型坯初始温度为189℃,型坯初始壁厚为0.004 m时,该条件下制品壁厚均匀性较好,通过该法可以为后续吹塑制品成型提供一定的理论指导。     

吨包装内胆挤出吹塑成型型坯吹胀的数值模拟

针对吨包装内胆挤出吹塑型坯吹胀阶段的成型工艺,采用Workbench-Polyflow分析软件实现型坯吹胀模拟。建立型坯及模具的几何模型和网格模型;利用Polyflow中的参数渐进方法建立型坯吹胀阶段中的模具闭合运动模型。获得型坯在吹胀过程中的型坯轮廓曲线分布以及吹胀完毕后的型坯壁厚分布;分析了模具运动速度和吹胀压力对型坯与模具的接触时间、吹胀时间及壁厚的影响。     

瓶坯尺寸对拉伸吹塑成型PET瓶壁厚分布的影响

通过对多个瓶坯的拉吹成型过程进行模拟分析,预测出不同尺寸的瓶坯所成型的PET瓶壁厚分布,并分析比较瓶坯尺寸对制品壁厚分布的影响。结果表明,瓶坯尺寸对于拉吹成型PET瓶的壁厚均匀性有较大影响,其中瓶坯局部厚度及瓶坯高度是主要影响因素。瓶坯整体壁厚对PET瓶轴向壁厚分布影响较小。PET瓶(不考虑体积时)最优瓶坯高度受瓶坯壁厚影响不大,采用有限元建模(FEM)仿真试验进行模拟分析可得到瓶坯最优高度取值范围。通过模拟计算和对瓶坯进行优化设计,可显著提高吹塑成型PET瓶的壁厚均匀性,且有助于PET瓶轻量化设计。     

型坯温度对HDPE油桶成型的影响

为了研究高密度聚乙烯(HDPE)熔体温度对油桶吹胀成型工艺的影响,使用K-BKZ本构模型拟合了实验测试的HDPE流变数据,得到了HDPE的本构模型参数,通过热分析(DSC)实验研究了HDPE冷却速率和结晶度的关系。用POLYFLOW数值模拟了HDPE油桶的非等温吹胀过程,并研究了初始型坯温度对制品温度、制品厚度、制品与模具接触时间的影响。结果表明,温度的最小值出现在油桶的拐角处,而温度的最大值出现在桶口处;随着初始型坯温度的升高,吹塑制品熔接线处的厚度增加,吹塑制品与模具接触时间增大。     

PET瓶吹塑应注意技术细节

PET瓶吹瓶流程是一个双向拉伸的过程，在此过程中，PET分子链呈双向延伸、取向和排列，从而增加了瓶壁的力学性能，提高了拉伸、抗冲击强度，并有很好的气密性。虽然拉伸有助于提高强度，但也不能过分拉伸，要控制好拉伸吹胀比：径向不要超过3．5～4．2，轴向不要超过2．8～3．1。瓶坯的壁厚不要超过4．5mm。     

能用PET设备吹塑成型的PP牌号

BP Amoco化工公司新推出Acclear HP I系列PP树脂牌号，特点为可以在用于PET瓶成型的标准重新加热(reheat)吹塑(中空成型)机上进行注坯拉伸吹塑(注拉吹)成型。     

医用床头板挤出吹塑成型工艺参数优化

为改善复杂非轴对称挤出吹塑制品的壁厚均匀性,以医用床头板为例,基于Polyflow软件模拟了医用床头板的非等温吹胀过程,并用目标函数评估最终制品的壁厚均匀性。根据正交实验分析了吹胀压力、吹胀时间、型坯初始温度及型坯初始壁厚4个成型工艺参数对制品壁厚均匀性的影响,得到最佳工艺参数组合为A3B3C1D1,即吹胀压力0. 7 MPa、吹胀时间5 s、型坯初始温度180℃、型坯初始壁厚3 mm,最后对最佳工艺参数组合进行了模拟验证。结果表明,优化后的工艺参数可使最终医用床头板的壁厚更加均匀,为在实际生产过程中复杂非轴对称挤吹制品的成型工艺参数改进提供有效指导,提高生产效率。     

塑料挤出吹塑的机理问题

采用不同的方法对挤出吹塑过程的型坯成型、型坯吹胀与制品冷却三阶段的机理问题进行了研究.采用人工神经网络方法预测了受模口温度和挤出流率影响的型坯成型阶段的膨胀.利用建立起来的神经网络模型预示的膨胀与实验结果很吻合,且可在一定范围内,预示不同工艺条件下型坯的直径膨胀和壁厚膨胀,为型坯的直径和壁厚的在线控制提供了理论依据.基于薄膜近似和neo-Hookean本构关系,建立了描述型坯自由吹胀的数学模型,并通过实验方法获得了型坯吹胀的瞬态图象.     

Visualization study and analysis on preform growth in polyethylene terephthalate stretch blow molding

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     

双轴向拉伸吹塑成型技术原理和实验研究

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。     

Validating injection stretch‐blow molding simulation through free blow trials

A 2D isothermal finite element simulation of the injection stretch‐blow molding (ISBM) process for polyethylene terephthalate (PET) containers has been developed through the commercial finite element package ABAQUS/standard. In this work, the blowing air to inflate the PET preform was modeled through two different approaches: a direct pressure input (as measured in the blowing machine) and a constant mass flow rate input (based on a pressure–volume–time relationship). The results from these two approaches were validated against free blow and free stretch‐blow experiments, which were instrumented and monitored through high‐speed video. Results show that simulation using a constant mass flow rate approach gave a better prediction of volume vs. time curve and preform shape evolution when compared with the direct pressure approach and hence is more appropriate in modeling the preblowing stage in the injection stretch‐blow molding process. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

基于正交试验的PET瓶拉伸吹塑优化设计

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 %。     

Experimental study and numerical simulation of the injection stretch/blow molding process

The injection stretch/blow molding process of PET bottles is a complex process, in which the performance of the bottles depends on various processing parameters. Experimental work has been conducted on a properly instrumented stretch/blow molding machine in order to characterize these processing parameters. The objective being a better understanding of the pressure evolution, preform free inflation has been processed and compared with a simple thermodynamic model. In addition, a numerical model for the thermomechanical simulation of the stretch/blow molding process has been developed. At each time step, mechanical and temperature balance equations are solved separately on the current deformed configuration. Then, the geometry is updated. The dynamic equilibrium and the Oldroyd B constitutive equations are solved separately using an iterative procedure based on a fixed-point method. The heat transfer equation is discretized using the Galerkin method and approximated by a Crank-Nicholson's scheme over the time increment. Successful free blowing simulations as well as stretch/blow molding simulations have been performed and compared with experiments.     

塑料拉伸吹塑中型坯再加热阶段的研究进展

介绍了拉伸吹塑的相关理论。从型坯的取向和结构、红外辐射在拉伸吹塑再加热阶段的应用、型坯的温度分布对再加热拉伸吹塑制品性能的影响等方面对塑料拉伸吹塑中型坯再加热阶段进行了综述;并对今后的研究提出了展望。     

Experimental study of preform reheat temperature in two‐stage injection stretch blow molding

Plastic bottles used for carbonated soft drink (CSD) packages are most commonly made from poly(ethylene terephthalate) (PET) by injection stretch blow molding (ISBM). The required bottle performance criteria vary with its application but typically include top‐load strength, burst strength, optical clarity, thermal stability, and barrier properties. An experimental study of the preform reheat temperature was carried out for a 1.5‐l PET bottle produced by a two‐stage ISBM machine. The overall temperature of the preform was changed by controlling the reheat temperature of the preform; all the other process variables and preform dimensions were kept constant. Performance of the PET bottles for differing preform reheat temperatures was measured experimentally in terms of top‐load strength, burst pressure resistance, environmental stress cracking resistance (ESCR), and thermal stability. It was observed that the ESCR values and the burst strength decreased with the increasing reheat temperature, whereas the top‐load strength increased. Thermal stability tests confirmed that high‐preform reheat temperatures had a detrimental effect on the self‐standing feature of the bottles. Decreasing the reheat temperature as low as possible, while maintaining a certain preform temperature profile, ensured high ESCR and burst strength values and prevented the concaveness at the bottom of the bottle. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

饮料PET瓶坯的数值模拟及优化设计

根据相应的吹塑成型工艺要求限定瓶坯各参数的范围,设计8个瓶坯,在Moldflow环境中模拟各个瓶坯的注塑成型过程,得到相应的充填和保压时间,通过BP算法建立模型,并以充填和保压的总时间为目标值,得到在参数范围内的最优设计方案。结果表明,该方法能够指导瓶坯设计,具有一定的实际意义。     

Experimental study and finite element analysis of the injection blow molding process

A finite element numerical analysis of preform inflation associated with the injection blow molding process has been developed using a neo-Hookean constitutive model. The analysis is capable of predicting final wall thickness distributions for axisymmetric mold geometries. Experimental studies were conducted on a Uniloy injection blow molding machine (Model 189-3 and Model 122). A twelve ounce (355 mL) cylindrical bottle mold was instrumented with contact sensors, thermocouples, and pressure transducers. Visualization studies of the inflation process were performed using specialized tooling and high-speed video cameras. The experimental studies provide justification for analyzing the deformation by means of a static elastic approach. The predicted wall thickness distribution is in reasonable agreement with the experimental data. Nonuniformities in the temperature distribution in the preform were found to have the most significant impact on the inflation behavior and the resulting wall thickness.