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This article was updated on 4th Feb 2020 by Gaea Marelle Miranda
While structural polymer composites have many beneficial properties such as low density, good insulation, environmental resistance, and good mechanical properties, they can be chemically unstable. For example, an impregnated intermediate or prepreg that has a limited shelf life.
Thermoplastic composites (TMCs) evolved from structural polymer composites. These materials do not experience chemical instability because they utilize a thermoplastic matrix. When heated, TMCs soften and can be remolded without degradation. When they cool, they solidify into the finished shape. This heating-cooling cycle can be repeated multiple times, giving the product an almost indefinite shelf life.
Thermoplastic composites could also be shaped using techniques derived from wood and metalworking. They have increased recycling and damage tolerances due to the tough nature of the matrix material.
Types of Thermoplastic Composites
Thermoplastic composites could be categorized into either Glass Mat Thermoplastics (GMT) or Advanced Thermoplastic Composites (ATC).
Glass Mat Thermoplastics (GMTs)
GMTs can use nearly any thermoplastic for the matrix; however, choices have been limited to polyvinyl chloride, polypropylene, polyamide, polyesters, polycarbonate, and polyphenylene sulfide, with polypropylene accounting for about 95% of commercial use.
It is also a suitable material when service temperatures remain below 110 °C. When higher temperatures are encountered and service conditions are harsher, more expensive polyphenylene sulfide can be used. E-glass fiber in the form of chopped fibers, random chopped fibers, or continuous mats is the most common reinforcing phase.
Advanced Thermoplastic Composites (ATCs)
Originally, ATCs used amorphous resins such as polyethersulphone and polyetherimide for the matrix. However, in applications where increased solvent resistance was required, semi-crystalline polymers such as polyether ether ketone and polyphenylene sulfide may be employed.
A limited number of pseudothermoplastics, including polyamide-imide and polyimides, could also be used. The continuous reinforcement phase may be in strand, woven, knitted or braided fabric forms and be made from carbon, aramid and/or S-, R- and E-glass. Carbon is the most popular material for higher temperature applications, while E-glass dominates lower temperature applications.
Key Properties of Advanced Thermoplastic Composites
- Low density, hence lightweight
- Good strength
- Good toughness
- Good environmental resistance
- Ability to be remolded
- Compositions can be customized to suit a range of temperature and environmental conditions
Applications of Thermoplastic Composites
Thermoplastic composites could be applied to a variety of industries, including the automotive industry, aerospace industry, construction industry, and materials handling.
Due to their lightweight and high toughness, GMTs have been adopted by automotive industries for a variety of uses. Applications include seat frames, battery trays, bumper beams, load floors, front ends, valve covers, rocker panels, and under-engine covers.
ATCs have found limited use in the aerospace industry, but they emerged from the need for tougher composites. They are analogous to the first thermoset composites with fiber contents above 50% and utilize a highly aligned continuous fiber structure. Actual applications include missile and aircraft stabilizer fins, wing ribs and panels, fuselage wall linings, and overhead storage compartments.
Thermoplastic composites could be used in the construction industry for structural profiles, pipes, concrete rebars, and lightweight structural and insulating panels.
The materials handling industry benefits from these thermoplastic composites in the form of pallets and cargo containers.