Difference Between Polyamide and Polyimide

关键差异 - 聚酰胺与聚酰亚胺

Polyamide and polyimide are high-temperature-resistantthermoplastic弹性体with a wide range of applications. The major difference between polyamide and polyimide is in their chemical structures;polyamide has the amide (-CONH-) linkages in their polymer backbone, while polyimide has imide group (-CO-N-OC-) in their polymer backbone.

These two polymers are also known for their excellent electrical and physical properties in addition to high thermal stability.

内容

1.Overview and Key Difference
2.What is Polyamide
3.What is Polyimide
4.并排比较 - 表格形式的聚酰胺与聚酰亚胺
5.概括

What is Polyamide?

聚酰胺是高性能的热塑性弹性体，其特征在于其高服务温度，良好的热老化和溶剂耐药性。另外，聚酰胺具有较高的模量和撞击特性，低摩擦系数和高耐磨性。尽管多酰胺的发展具有广泛的特性，但它们都由聚合物主链中的酰胺（-conh-）链接组成。尼龙是最常见和广泛使用的聚酰胺类型。这是Carothers开发的最早的聚合物之一。如今，尼龙已成为美国最重要，最广泛的聚合物之一。

酰胺基是一个极性组，它允许聚酰胺在链之间建立氢键，从而改善链吸引力。这增强了聚酰胺的机械性能。在尼龙中，链中的柔性脂肪族碳基团通过降低熔体粘度来改善材料的加工性。通过增加酰胺键之间的碳原子数量，可以降低强度和刚度。因此，烃骨架的长度是决定聚酰胺材料性能的关键特性。由于酰胺基的极性，极性溶剂（主要是水）会影响聚酰胺。

There are two types of polyamides:aliphatic and aromatic polyamides.Nylon can be either an aliphatic or semi-aromatic polyamide. The main applications of polyamides include radiator header tanks in cooling systems, switches, connectors, ignition components, sensors and motor parts in auto electrical systems, wheel trims, throttle valves, engine covers, heat resistant under-bonnet components, airbrake tubing, etc.

What is Polyimide?

聚酰亚胺s are high performance polymers, containing imide group (-CO-N-OC-) in their repeating units. The polymer chains are either open chain or closed chain. Polyimides are known for their excellent thermal stability, along with decent electrical and mechanical properties. Usually, polyimide has short exposure temperature stability. Moreover, polyimide shows excellent wear and solvent resistance, and also high abrasion resistance. These properties have led polyimide to be used as a specialty material in certain applications including insulating films, laminates, coatings, molded parts, structural adhesives, high-modulus fibres, permseletive membranes and high-temperature composites.

可溶性共酰亚胺用于制造粘合剂，密封剂和成型树脂。良好的氧化稳定性和高玻璃过渡温度(t_g) can be achieved with polyimide with aromatic structures. Based on the synthesis method, polyimides are classified into three categories, namely; condensation polymers-non melting and thermoplastic, addition polymers and hybrid polymers.

What is the Difference Between Polyamide and Polyimide?

Polyamide vs Polyimide
Polyamides are made of amide linkages (-CONH-).	聚酰亚胺s are made of imide linkages (-CO-N-OC-).
Synthesis
聚酰胺是通过二氨基和二羧酸之间的聚合合成的。	聚酰亚胺s are synthesized by the polymerization between dianhydride and diisocyanate or diamine.
Chemical Formula
Common trade names are Nylon andKelvar.	The common trade name is卡普顿.
申请
Polyamides are used as radiator header tanks in cooling systems; switches, connectors, ignition components, sensors and motor parts in auto electrical systems; wheel trims, throttle valves, engine covers, heat resistant under-bonnet components, airbrake tubing, etc	聚酰亚胺s are used as insulating films, laminates, coatings, molded parts, structural adhesives, high-modulus fibres, permselective membranes and high-temperature composites

摘要 - 聚酰胺与聚酰亚胺

聚酰胺和聚酰亚胺都是具有高热和氧化稳定性的热塑性弹性体。聚酰胺由其主链中的酰胺连接组成，并通过二氨基和双羧酸之间的聚合合成。聚酰亚胺在其主链中含有酰亚胺链接，并通过苯二氢化酯和二异氰酸酯或二氨酸之间的聚合合成。这是聚酰胺和聚酰亚胺之间的差异。

Reference:

1. Kricheldorf, Hans R. Handbook of Polymer Synthesis. Dekker, 1992.
2. Chanda, Manas, and Salil K. Roy. Industrial Polymers, Specialty Polymers, and Their Applications. CRC Press, 2009.
3. Ghosh, Malay K., and K. L. Mittal. Polyimides: Fundamentals and Applications. Dekker, 1996.
4. Mckeen, Laurence W. Fatigue and Tribological Properties of Plastics and Elastomers. Elsevier, 2016.

Image Courtesy:

1.Jü的“聚酰胺酰胺组V.1” - 自己的作品（CC0）通过Commons Wikimedia
2. “Polyimide” By Ed (Edgar181) – Own work (Public Domain) viaCommons Wikimedia