Thermoset polymer matrix

Polymer matrix composites, where polymers act as binder or matrix to secure in place incorporated particulates, fibres or other reinforcements, can be formulated with a diversity of properties for a wide variety of structural end uses.Thermoset polymer matrix composites were the first developed for structural applications, including glass–reinforced polyester radar domes on aircraft and graphite-epoxy payload bay doors on the space shuttle. They have been used since World War II. Continuing research has led to an increased range of thermoset resins, polymers or plastics, as well as engineering grade thermoplastics, all developed for use in the manufacture of polymer composites with enhanced and longer-term service capabilities. Thermoset polymer matrix technologies also find use in a wide diversity of non-structural industrial applications.

This article characterises the thermoset polymers and resins which are the most widely used matrix material in structural composites by their individual composition, properties and applications. The foremost types of thermosetting polymers used in structural composites are:

These are made by the reaction of phenols, formaldehyde and primary amines which at elevated temperatures (400 °F (200 °C)) undergo ring–opening polymerisation forming polybenzoxazine thermoset networks; when hybridised with epoxy and phenolic resins the resulting ternary systems have glass transition temperatures in excess of 490 °F (250 °C).

Cure is characterised by expansion rather than shrinkage and uses include structural prepregs, liquid molding and film adhesives for composite construction, bonding and repair. The high aromatic content of the high molecular weight polymers provides enhanced mechanical and flammability performance compared to epoxy and phenolic resins.

Formed by the condensation reaction of a diamine with maleic anhydride, and processed basically like epoxy resins (350 °F (177 °C) cure). After an elevated post-cure (450 °F (232 °C)), they will exhibit superior properties. These properties are influenced by a 400-450 °F (204-232 °C) continuous use temperature and a glass transition of 500 °F (260 °C).

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