何谓结晶性树脂Heat resistance.doc

何谓结晶性树脂Heat resistance树脂大致分为热塑性树脂和热固性树脂。热塑性树脂是一种热熔冷固性树脂。热固性树脂则是一种树脂其原材料在被加热后会发生化学反应，并在固化后不再熔化的树脂。热塑性树脂可进一步分为结晶性树脂和非结晶性树脂。那么结晶性树脂是一种什么东西呢？下面是其三种结构模式：(A)熔融时的分子链(B)结晶状态(C)结晶性树脂的内部分子链随机混杂并运动分子链排列整齐结晶部分与非结晶部分混杂在一起熔融时，树脂的分子链像(A)图那样随机混杂并运动。树脂冷却后，分子链开始像(B)图那样整齐排列，最终像(C)图那样结晶部分与非结晶部分混杂在一起并固化。即便是结晶性树脂有时也不会100结晶，其中必然混杂有非结晶部分。另一方面，非结晶性树脂则在(A)图那样的随机状态下固化。根据其物理结构上的差异，结晶性树脂和非结晶性树脂的特点如下：结晶性树脂非结晶性树脂 存在分子链排列整齐的“结晶” 有玻璃转化温度和熔点 分子链是随机的 仅有玻璃转化温度 优点 良好的刚性和弹性 良好的耐疲劳性 机械强度高 良好的耐药品性 缺点 难以透明 成型收缩率大 优点 易于透明 良好的耐冲击性 成型收缩率小 吸水性小 缺点 耐药品性差 耐疲劳性差 滑动性差 上面的表中提到“玻璃转化温度”一词。玻璃转化温度也是树脂的一个重要特性，但可能有人并不理解其含义，因此在下一次的工程小塑料讲座里将予以详细介绍。Heat resistanceThe heat resistance of resins (plastics) is broadly divided into (1) one in cases where the temperature is instantaneously attained (softening, deformation, melting, ignition) and (2) one in cases where the product-life cycle is estimated when the product is always used at that temperature (material decomposition, breakage associated with degradation, etc.). For the case of the above question, accordingly, it is required to consider (1) whether the product is not softened or deformed in an environment of 100 and (2) whether the product is not broken due to material degradation when it is used for its life cycle (e.g. 10 years) in an environment of 100. As a well-known heat-resistance evaluation index, for example, there is deflection temperature under load (DTUL), which is an index to evaluate heat resistance for a short period of time. This is evaluated using the following test method:Evaluation method using deflection temperature under load/en/support/Tecin/methods/netu_TAWA.htmlAccording to the Data Sheets, the DTUL value for DURACON M90-44 is 95. However, this does not indicate that it can always be used in any environment provided that the temperature is less than 95 or that it can never be used in any product that will rise to 95 or more even instantaneously. It may be used even if the temperature is 95 or more provided that the applied load is small, or a lower temperature may be the upper limit working temperature in a reverse case. The upper limit working temperature will also be lower when the allowable deformation volume is small.On the other hand, it is also required to consider the environmental temperature limit (especially upper limit temperature) and product-life cycle for resin parts. Such long-term heat resistance evaluation indexes include the UL temperature index, as an example. This is a temperature index adopted in cases where the physical properties of the material are reduced to 50% of the initial value after 100,000 hours (approx. 11.4 years). The physical properties are broken down into electrical, shock and mechanical properties (tensile strength), and the temperature index for each is indicated. The higher the temperature is, the faster the degradation behavior of a resin becomes, thus shortening the allowable working period (product-life cycle).Now, is the UL temperature index always better for a material having a higher DTUL?Fig. 1 Relationship between deflection temperature under load (DTUL) and temperature index As is evident from above, the matter is not so simple and both temperature indexes are completely different.Generally, the long-term heat resistance of resins maintains a roughly constant value depending on the resin type. On the other hand, even for the same resin, the glass fiber-reinforced grade has a higher DTUL value than the unreinforced grade. This is due to a higher elastic modulus.Now, you must understand that it is required to consider various conditions to evaluate the heat resistance of res