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What is heat-resistant adhesive? How to choose heat-resistant adhesives in lamination packaging?

Heat-resistant adhesive, also known as anti-high-temperature adhesive, refers to an adhesive suitable for use under high-temperature conditions.

In actual applications, it is often expressed by the bond strength-temperature-time relationship. There is no strict definition and standard for heat-resistant adhesives internationally. But generally speaking, those that meet the following conditions can be considered as heat-resistant adhesives, that is, long-term use (1~5 years) at 121-176 ℃, or use 20000 ~40000 hours at 204-232 ℃; use 24~200 hours at 260- 371 ℃; use 24~200 hours at 371-427 ℃; use 2-10 minutes at 538~ 816 ℃. It has also been called a heat-resistant adhesive that can be used for more than 1000 hours at 204 ℃.

The commonly used organic heat-resistant adhesives mainly include epoxy, phenolic, silicone and heterocyclic adhesives. Heat-resistant adhesives such as aminobenzoate-cured epoxy resin adhesive, aromatic diol-cured cycloaliphatic epoxy resin adhesive, epoxy-phenolic adhesive, phenolic-butyl rubber adhesive, etc., can be used for a long time at -60-232 ℃, and the highest use temperature can reach 260-316 ℃

Here we mainly discuss how to choose heat-resistant adhesives with corresponding heat resistance when designing/producing water-boiling resistant and retort laminated bags. From the perspective of application time, these adhesives cannot be called heat-resistant glue, they can only be said to have heat resistance.

In the flexible packaging industry, it refers to the peel strength of the laminated film processed with a specific adhesive will not decrease significantly after undergoing boiling and retorting treatment.

The boiling-resistant laminated bags can be divided into two categories: plastic/plastic lamination and aluminum/plastic lamination, the heat treatment temperature is 60~100℃.  Retort-resistant laminated bags can also be divided into plastic/plastic lamination and aluminum/plastic lamination two categories, the heat treatment temperature is below 121℃, 121~125℃, 135℃, 150℃ and so on.

Different lamination structures and heat treatment temperatures of laminated bags require different adhesives. At the same time, corresponding heat treatment tests should be carried out before mass production to verify whether the selected adhesive and substrate are suitable for the processing and application conditions of this enterprise and downstream customers.

Choosing a suitable adhesive is only one of the basic conditions, and the heat resistance of the substrate for lamination is another issue that must be considered. For substrates for lamination, their heat resistance is not only reflected in the melting point of the substrate itself but more importantly, in the longitudinal and transverse thermal shrinkage rate indicators of the substrate under corresponding heat treatment conditions. Generally speaking, the thermal shrinkage rate of the substrate under corresponding heat treatment conditions should not be greater than 1.5%, and the thermal shrinkage rate difference between substrates should not be greater than 0.5%.

Welcome to contact for details of laminating adhesives that have heat resistance.

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耐热胶粘剂,又称耐高温胶粘剂,系指适合于在高温条件下使用的胶粘剂。实际应用中多用胶接强度-温度-时间来表示。

关于耐热胶粘剂的严格定义及标准,国内外尚无定论。但一般认为属于下列情况者均可算作耐热胶粘剂,即在121-176摄氏度下长期使用(1~5年),或在204-232 摄氏度下使用20000 ~40000小时;在260- 371摄氏度下使用24~200小时;在371-427 摄氏度下使用24~200小时;在538~ 816 摄氏度使用2-10分钟。也曾有把204摄氏度下可使用1000小时以上者称为耐热胶粘剂。

常用的有机耐热胶粘剂主要有环氧类、酚醛类、有机硅类和杂环类胶粘剂。环氧类和酚醛类耐热胶粘剂如氨苯矾固化环氧树脂胶、芳香族二醇固化脂环族环氧树脂胶、环氧-酚醛胶、酚醛-丁睛胶等,可在-60-232摄氏度长期使用,最高使用温度可达260-316摄氏度.

在这里我们主要讨论在设计/生产耐水煮、耐蒸煮复合膜袋时,选用的具有相应的耐热性的胶黏剂。从应用时间来说,这些胶黏剂不能称之为耐热型胶水,只能说它们具有耐热性。

在软包装行业,胶粘剂的耐热性是指使用特定的胶黏剂所加工的复合薄膜的剥离力在经受了水煮、蒸煮处理后,其剥离力不会有明显下降的特征。

耐水煮复合膜袋可分为塑/塑复合、铝/塑复合两大类,热处理的温度为60~100℃。耐蒸煮复合膜袋也可分为塑/塑复合、铝/塑复合两大类,热处理的温度为121℃以下、121~125℃、135℃、150℃等几种。

不同的复合结构及热处理温度的复合膜袋需要选择不同的胶黏剂。同时要在大批量投产前进行相应条件的热处理试验,以验证所选择的胶黏剂及基材是否适用于本企业及下游客户的加工、应用条件。

选择合适的胶黏剂只是基础条件之一,复合用基材的耐热性也是必须考虑的另一个问题。对于复合用基材而言,其耐热性不只是表现在基材本身的熔点上,更重要的一点是基材在相应的热处理条件下的纵、横向的热收缩率指标。一般情况下,基材在相应的热处理条件下的热收缩率应当不大于 1.5%,基材间的热收缩率差异应不大于 0.5%。

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