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关于吸热发泡剂对金属模具的影响分析

Aluminum molds are widely used for the production of injection molded plastics, and are most often used in low-pressure structural foam molding (SFM)。

铝合金模具在塑料注塑模具中广泛使用,并且在低压结构性发泡成型(SFM)中经常被使用。


There are many steel components in aluminum molds, for example steel ejector (knock-out) pins. These are usually made of hardened H-series tool steel, and may be specially treated to improve wear properties. Because of the intimate contact between the aluminum and steel, there is great potential for corrosion and pitting of the steel components because of a phenomenon called:

在铝合金模具中有很低钢成分,例如钢喷射(敲)针。这些是硬化H系列工具钢造的,或者特别针对磨损性能的。因为在铝和钢之前紧密接触,钢部件有潜在很大的腐蚀和点蚀的可能性,因为这个现象称作:


BI–METALLIC CORROSION

双金属腐蚀


Bi-metallic corrosion is also known by other names, forexample:

双金属腐蚀也被称作其他名字,例如:


GALVANIC, CONTACT,OR TWO-METAL CORROSION

电偶腐蚀,接触,或者两金属腐蚀


ELECTROLYTIC AND ELECTRO-CHEMICAL DEGRADATION

电解和电化学降解


广西快3官网Bi-metallic corrosion may be defined as the corrosion associated with the current flow caused by an electrical coupling of dissimilar metals in an electrolyte。

广西快3官网双金属腐蚀或许可以定义为电解质中不同金属电耦合引起的与电流流动有关的腐蚀。


An electrolyte is a substance, such as sodium or calcium chloride, or sulfuric acid, which can conduct an electric current。 The current flow results in the preferential attack of the more active (less noble, or anodic) steel metal, while the corrosion of the other metal, aluminum, the less active (more noble, or cathodic) metal, slows down or stops completely。

一个电解质是一种物质,例如钠或者氯化钙,或者硫酸,可以传导电流。电流在优先损害更活跃的(更少正极)钢金属,同时另外的金属的腐蚀,铝,更不活跃的(更多负极)金属,慢下来或者全部停止。


When two dissimilar metals or alloys are exposed to a corrosive or electrically conductive solution, and when these metals are either in direct contact, or are electrically connected by a conductor or a conductive medium, then a galvanic cell or battery is formed. In such a galvanic cell the more active, less noble part – e.g. the steel - will act as the anode and will corrode away as a result of the current flow.

当两个不同的金属或者合金裸露在一个腐蚀性或者导电性的溶液中,并且这些金属不是直接接触,就是被导体,或者导电介质用电相连,电偶分子或者电池就形成了。在这个电偶分子更活跃,更少负极的部分-例如钢-将会成分正极以及电流侵蚀的结果。


Corrosion of steel components can occur even when only new polymer is used and no additives or chemical foaming agents are present. The electrolyte may be provided by the presence of water in the polymer, condensation on the mold, or residues generated by catalyst scavengers. For example, calcium stearate is widely used in polyolefins to scavenge the chloride ions left from co-catalyst residues. The calcium ions bind with the chloride ions, forming an electrolyte - calcium chloride salt residue. In one study, examination of corroded steel ejector pins from aluminum molds used to make large SFM nitrogen-foamed HDPE parts revealed high levels of calcium chloride on the pins. The only likely source of the calcium chloride was from the polymer itself.

当仅有新聚合物被使用并没有添加剂或者发泡剂的时候,也会引起钢成分腐蚀。聚合物中的水存在或许也可以提供电解质,模具的冷凝液,或者催化清洁剂产生的余渣。例如,硬脂酸钙是在聚烯烃清洁复合催化余渣中的氯化铁。钙铁与氯化铁结合,形成电解质-氯化钙盐余渣。在一项研究中,铝合金的腐蚀钢喷神针的检测,过去曾经使大型低压结构性发泡成型的发泡氮高密度聚乙烯零件针上的高层的氯化钙显示出来。氯化钙的可能仅有来源是来自聚合物本身。


Corrosion may also result from thermal and shear degradation of the base polymer, or from thermal. degradation of processing aids or additives in the polymer. In polypropylene, for example, the C – C bonds become unstable at temperatures approaching 315°C (600°F) and chain scission (breaking) occurs, liberating low molecular weight fragments which can oxidize to acidic species which will corrode metal.

腐蚀也可以由基本聚合物的热能和降解切力产生,或从聚合物中的加工助剂或添加剂的热降解。聚丙烯,例如,碳 – 碳键在接近315°C(600°F)的温度下变得不稳定,断链发生,释放低分子量碎片,氧化成酸性物质,腐蚀金属。


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