PET容器应力开裂的科学探讨

自1978年位于美国马萨诸塞州福尔河的制罐公司研发生产2升整体PET瓶以来,应力开裂一直是PET容器的致命点。随之,出现了很多有关影响应力开裂的原因分析和补救措施。这些分析既不完全正确也不完全错误,需要时间来验证。只有通过科学的探讨才能找到有用的信息,从中得到的经验和教训既适用于PET瓶,也适用于一般的塑料瓶成型。[第一段]     

聚酯(碳酸饮料)瓶应力开裂解决方法

通过对应力开裂机理进行研究和讨论,找出了影响碳酸饮料瓶应力开裂的因素．提出了解决思路和方法,并在生产实践中对制瓶工艺进行优化,最终解决了碳酸饮料瓶的应力开裂技术难题。     

PET瓶的等离子处理技术--ACTIS

一、　等离子（ＡＣＴＩＳ）技术原理ＡＣＴＩＳ技术是法国西得乐公司开发的、利用等离子技术在ＰＥＴ瓶内壁上,涂布一层碳氢阻隔层制备高阻隔性塑料瓶的一种新方法。等离子法（ＡＣＴＩＳ）是将气态的乙炔导入ＰＥＴ瓶中,通过微波处理器将乙炔激化,使之呈等离子状态,等离子态的颗粒撞击在瓶壁上能量骤然消失,在壁上形成一层极薄而致密的固态涂层（高度氢化的无定型碳涂层）,涂层的厚度不到２００Ａ,一只容量为５００ｍｌ的ＰＥＴ瓶的涂层,仅８～９毫克,但却具有极佳的阻透性能。二、　等离子（ＡＣＴＩＳ）技术的工业化装置ＡＣＴ…     

曲臂应力腐蚀开裂分析

曲臂是车体中的重要零件。制造中采用模锻件调质热处理,然后对加工的销钉孔局部进行高频淬火加中低温回火,要求销钉与销钉孔静配合,整体进行磷化处理。该批零件组装前进行检验时发现28％的零件在位于销钉孔周边薄壁处发生开裂或断裂。经过三件裂纹曲臂进行材质、硬度、显微组织结构、裂纹特征分析以及断裂面扫描电子显微镜（SEM）二次电子像和X射线能谱仪（EDS）元素定性分析认为,由于销钉孔高频热处理后硬度偏高并产生变形,销钉装配过盈量较大,造成销钉孔周边存在较大的内应力;高频淬火工艺控制不当,使销钉孔表面发生脱碳现象,降低了材料低御裂纹形成和扩展的能力;在磷化处理过程中因氢腐蚀导致零件开裂。     

硫化物应力腐蚀开裂试验应力环载荷的测量及标定

硫化物应力腐蚀开裂试验的常用载荷测量方法是通过测量应力环的变形量计算载荷。指出了该方法在标定和测量过程中容易产生较大误差的原因。通过测量对比,证明了采用载荷传感器直接测量载荷的方法可减小误差,更适合作为试验过程中的载荷标定方法。     

LDPE环境应力开裂性研究

研究了低密度聚乙烯接枝聚硅氧烷后的环境应力开裂性。用红外光谱分析了低密度聚乙烯与聚硅氧烷接枝反应的过程,并用电子扫描显微镜分析了接枝后聚乙烯环境应力开裂的断面形态。实验结果表明,接枝聚硅氧烷后,增加了聚乙烯分子间链缠结．晶粒间连接分子数增多,因而提高了它的耐环境应力开裂性。     

残余应力对包装机械腐蚀开裂的影响及对策研究

包装机械零，部件在制造过程，内部都会产生残余应力，通过实验阐述了残余应力对包装机械腐蚀开裂性能的影响，以及防止腐蚀开裂的措施。     

面向残余应力检测的聚碳酸酯在溶剂环境下的初始应力-开裂时间关系

本研究利用四点弯曲应力松弛实验装置,获得了聚碳酸酯(PC)材料在不同比例甲苯/正丁醇混合溶剂中的初始应力-开裂时间实验数据;依据离散数据的几何相似性,建立了一个指数关系模型,拟合得到了初始应力-开裂时间的连续分布,并基于对拟合曲线的抽样误差分析,建立了残余应力与初始应力之间的关系式,可用于提高PC制品残余应力的检测精度。     

Effect of hydrogen on stress corrosion cracking of copper

The effects of hydrogen on electrochemical behavior and susceptibility of stress corrosion cracking (SCC) of pure copper were studied. SCC susceptibility of pure copper in a 1 M NaNO₂ solution was increased by pre-charged hydrogen. The effect of hydrogen on the susceptibility is more obvious in the low stress region due to the longer fracture time, which resulted in a longer time for more hydrogen to diffuse toward the crack tip. Synergistic effects of hydrogen and stress on corrosion and SCC processes were discussed. The results showed that an interaction between stress and hydrogen at the crack tip could increase the anodic dissolution rate remarkably.     

TEM investigations of intergranular stress corrosion cracking in austenitic alloys in PWR environmental conditions

Abstract

Analytical transmission microscopy has been used to investigate the initiation of stress corrosion cracking in Inconel 600 subjected to constant load testing under simulated pressured water reactor primary water conditions. The observations revealed that intergranular attack proceeded by the development of a zone of polycrystalline chromia along the boundary plane intersecting either the free surface or a blunted, open crack in contact with the free surface. Ni-rich metal particles were interspersed within the chromia. Conversely, open cracks were filled with nanocrystalline NiO and large compound particles of spinel and NiO, indicating a difference in potential between closed, attacked boundaries and open cracks. Open cracks appeared to have initiated by fracture of the chromia zones, such fracture being strongly dependent on boundary geometry with respect to loading direction. The observations suggest that stress corrosion crack initiation and propagation is dependent on diffusion of oxygen through the porous oxides. Dislocations and stress could enhance diffusion as chromia was observed along slip planes at the arrested tips of blunt cracks.     

Interplay of microbiological corrosion and alloy microstructure in stress corrosion cracking of weldments of advanced stainless steels

This paper presents an overview of the phenomenon of stress corrosion cracking (SCC) of duplex stainless steels and their weldments in marine environments and the potential role of microbial activity in inducing SCC susceptibility. As a precursor to the topic the paper also reviews the performance of the traditional corrosion-resistant alloys and their weldments and the necessity of using duplex stainless steels (DSS), in order to alleviate corrosion problems in marine environments. Given that the performance of weldments of such steels is often unsatisfactory, this review also assesses the research needs in this area. In this context the paper also discusses the recent reports on the role of microorganisms in inducing hydrogen embrittlements and corrosion fatigue.     

Studies on polyester packaging. Effects of basic washing on multi‐use PET and PEN bottles

Washing PET or PEN bottles intended for reuse with sodium hydroxide solutions appeared to affect the surface of the materials. The possible hydrolysis of the ester chemical function during the process was investigated. A new method for extracting and separating neutral and acidic products from the polymers was developed, and relative quantification of the isolated molecules was carried out by gas and liquid chromatography. Some adjuvants were no longer present after washing, but others were more easily extracted. A very weak hydrolysis reaction for PEN could not be excluded but it did not seem to occur for PET. Copyright © 1999 John Wiley & Sons, Ltd.     

Failures of engineering components due to environmentally assisted cracking

Examples of failures of engineering components by stress-corrosion cracking, corrosion-fatigue, hydrogen embrittlement, liquid-metal embrittlement, and solid-metal embrittlement are described. Causes of failure include inappropriate materials selection or heat treatment, poor design, and high residual stresses. The examples illustrate how fractographic characteristics, analysis of films and deposits on fracture surfaces, and other factors help in diagnosing the modes and causes of failures, thereby enabling the appropriate remedial measures to be taken.     

Assessment of stress corrosion cracking susceptibility by a small punch test

The object of this study is to establish a new test method for evaluating stress corrosion cracking (SCC) susceptibility of high-strength steel using a small punch (SP) test and acoustic emission (AE). A miniaturized specimen (10 × 10 × 0.5 mm) is adopted for SCC evaluation. The experiments are conducted at various loading rates and at various orientations of the specimen. The cumulative average amplitude of the AE signal per unit equivalent fracture strain ( ε _qf ) increases as the SCC susceptibility increases. Through the load–displacement behaviour, the fracture energy ( E _SP ), the SEM fractographs, and the correlation between the SCC susceptibility and the AE characteristics, it is proved that the small punch test method combined with AE measurements is a useful method to evaluate the SCC susceptibility of high-strength steel.     

塑料啤酒瓶的开发、应用进展与前景

近年来 ,国外采用各种现代化改性手段提高PET瓶的气体阻透性 ,使之用于一次性啤酒容器。本文综述了新型阻透材料PEN用于可重复使用 /重复灌装啤酒瓶的研究开发、测试和推广应用方面取得的突破性进展。预测塑料啤酒瓶将迅速、稳步增长 ,但不会取代玻璃和金属容器     

球罐应力腐蚀开裂研究与安全性分析

对球罐应力腐蚀开裂的原因和主要影响因素进行了分析.针对16MnR和SPV50Q球罐用钢,在分析湿硫化氢环境下应力腐蚀开裂形式的基础上,通过改进的WOL预裂纹试样的应力腐蚀开裂试验,对不同球罐用钢、不同硫化氢浓度、不同焊接状态条件下的应力腐蚀开裂进行了研究,并对设备的安全性能进行了分析,进而提出了防止应力腐蚀开裂的对策.     

Role of microstructure and testing conditions in sulphide stress cracking of X52 and X60 API steels

The resistance of X52 and X60 API steels to sulphide stress cracking (SSC) was tested by tensile tests at a constant load and also by slow strain rate tensile (SSRT) tests. Both steels were tested after hot-rolling, when they had a microstructure which consisted predominantly of ferrite and pearlite. They were then tested after laboratory quenching and tempering, when their microstructure was predominantly of tempered bainite or martensite. The results showed that the resistance of the steel to SSC depended strongly on the microstructure when it was tested under a constant load. In this case, the quenching and tempering considerably increased the resistance of the steel to SSC. The results of SSRT tests were similar regardless of the heat treatment used. Non-metallic inclusions seemed to play an important role as crack initiation sites during the SSRT tests; this may be due to the hydrogen–deformation interaction. The resistance to SSC varied as a function of the specimen's orientation during the SSRT tests. This may be related to the geometric characteristics of the non-metallic inclusions.     

On the stress corrosion cracking mechanisms of austenitic stainless steels

In this paper, experimental results on stress corrosion cracking in austenitic stainless steels are described. Crack growth data in sodium chloride solution for AISI 304 steel obtained for different metallurgical conditions, acoustic emission data recorded during crack growth and fractographic observations have been discussed with a view to identifying the operating mechanism. Some of the experimental observations such as crack propagation occurring in discontinuous jumps of the order of a few microns, lowering of the threshold stress intensity andJ-integral values on sensitization and cold working, typical transgranular fractographic features, transition in mode of fracture from transgranular to intergranular in sensitized conditions and activation energies of the order of 50 to 65 kJ/mol can all be accounted by hydrogen embrittlement mechanism. Hydrogen generated at the crack tip by corrosion reaction diffuses ahead of the crack tip under hydrostatic stress and influences the deformation process at the crack tip and also leads to the brittle component of the crack advance in jumps.