包装用聚酯容器

3.PET的注射拉伸吹塑工艺 PET的注射拉伸吹塑,包括型坯注射、型坯再加热以及拉伸吹塑等三个基本步序,分别简要介绍如下。 (1) 型坯的注射 注射高透明的、壁厚均匀性佳的PET型坯,是制得优良的PET拉伸吹塑瓶必不可少的条件,因此对型坯的注射成型,需要给予高度的重视。     

基于可视化的型坯拉伸吹胀模式的研究

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。     

关于挤出中空吹塑成型工艺中若干技术问题的探讨

一、概述 中空吹塑成型,是将热塑性树脂加热熔融经螺杆挤出机(或注射机)制成一定形状的型坯,置于密闭的模具内,借助压缩空气吹胀、冷却定型,而制得和模具形状一致的中空制品的一种加工方法。 中空吹塑成型,可分为挤出吹塑、拉伸吹塑和注射吹塑等多种成型工艺,这类吹塑     

两段拉伸吹塑工艺异军突起

目前,包装材料生产工艺上实现了一个新的突破,即通过两段拉伸吹塑成型工艺制备聚对苯二甲酸乙二酯(PET)饮料杯。与热成型和注射成型的PET饮料杯相比,由于拉伸吹塑工艺特有的定向作用,拉伸吹塑成型的PET饮料杯具有强度高、阻隔性好、透明度高、没有碎屑产生等优势。因此,总体上,拉伸吹塑工艺的生产成本比热成型或者注射成型低30％。并且与热成型工艺生产的饮料杯相比,拉伸吹塑的饮料杯阻隔性能提高了17％。 两段拉伸吹塑工艺的关键是在FRC-12旋转再热型拉伸吹塑机上10个加热区进行运转设计和优化加热。FRC-12有12个吹塑模槽,这些吹塑模槽的数量取决于机器运转状况以及所吹塑饮料杯的形状。可以根据实际需要增加吹     

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。     

高产量和高能效的新型吹塑设备

在K2010展会上，高产量和高能效是吹塑成型技术的两大主题。加工商们可看到最新的用于挤吹、注吹和拉伸吹塑成型的液电混合及全电动吹塑设备，用于顺序挤出两种型坯来成型多组分3D制品的设备，以及新型的二次加热拉吹小口及广口瓶生产设备。     

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。     

挤出吹塑实验研究进展

对挤出吹塑过程的三个阶段：型坯成型、型坯吹胀以及制品冷却与固化阶段的实验方法和装置的研究现状进行了详细论述。     

带把手HDPE油桶挤出吹塑型坯壁厚的数值模拟优化

使用计算流体力学软件(POLYFLOW),在温度和吹气压力相同的条件下,分别数值模拟了均一壁厚初始型坯和优化的非均一壁厚初始型坯挤出吹塑高密度聚乙烯(HDPE)带把手油桶的过程。用POLYFLOW软件中的型坯控制程序,将初始型坯分成10段,通过控制这10段型坯的厚度来控制吹塑制品的壁厚。结果表明:均一壁厚5.0 mm的初始型坯经过吹胀阶段后,油桶大部分壁厚都小于3.0 mm;使用POLYFLOW后处理程序对油桶型坯6次优化后,吹塑制品壁厚均大于3.0 mm,且在第4次优化的基础上将油桶质量从646.89 g降至642.68 g。     

吹塑成型CAE技术研究与应用现状分析

吹塑成型是成型中空塑料制品的主要成型方法,其成型过程包括型坯成型、型坯吹胀和制品的冷却固化三个阶段。中空制品的吹型成型质量受各种工艺因素的影响,包括熔融温度、吹胀压力、拉仲速率、冷却时间、聚合物材料柱能等。吹塑成型数值模拟可预测制品的壁厚均匀性,残余应力和收缩状况等,指导吹塑成型模具的优化设计,并通过优化工艺参数获得最佳性能的吹塑制品。本文对吹塑成型CAE技术的发展状况进行了详细研究,并对其应用现状作了简单分析。     

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     

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.     

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。     

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。     

A novel approach of measuring the dielectric properties of PET preforms for stretch blow moulding

Polyethylene terephthalate (PET) is the most common plastic material used in injection stretch blow molding (ISBM) process for the manufacturing of bottles. The injection‐molded PET preform has to be preheated uniformly to a pliable state before the blowing stage of the process. Microwave technology offers a potentially more economical means for preheating the preform in place of the conventional infrared oven heating. For such applications, determination of dielectric properties of PET preform of a given geometry is essential. This article describes a novel approach of measuring the dielectric properties of PET preforms at microwave frequencies instead of the common experimental procedures used for such measurements. The dielectric properties are determined by using both CST Microwave Studio electromagnetic simulation software and the automatic network analyzer together. No complex mathematical solutions are required. Validation of this new approach has been made by comparing the measured dielectric properties of some polymers with those available in the published literature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

PET瓶双向拉伸吹塑成型技术

简述了注拉吹和压拉吹成型PET瓶的生产工艺技术和PET瓶今后的发展趋势     

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     

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     

Preform shape and operating condition optimization for the stretch blow molding process

In this work, a new design approach was developed to automatically and consecutively predict optimal preform geometry and optimal operating conditions for the stretch blow molding process. The numerical approach combines a constrained gradient‐based optimization algorithm that iterates automatically over predictive finite element software. The strategy allows for targeting a specified container thickness distribution by manipulating consecutively the preform geometry (thickness and shape) and the operating parameters subject to process and design constraints. For the preform shape optimization, the preform geometry is mathematically parameterized for simplified treatment and the corresponding sensitivities are evaluated using a finite difference technique. A finite difference technique is also employed for the operating condition optimization. The constrained optimization algorithms are solved via the use of the sequential quadratic programming method that updates the design variables accordingly. Predicted optimization results obtained on an industrial case are presented and discussed to assess the validity when compared to experimental results and the robustness of the proposed approach. POLYM. ENG. SCI., 47:289–301, 2007. © 2007 Society of Plastics Engineers.