Matrices for composites have so far been mainly thermoset matrices used in established processes that draw on many years of experience. Used with the same reinforcing fibers, thermoplastic matrices allow significantly shorter cycle times in component production, can be stored indefinitely at room temperature, absorb less water (depending on the matrix), and are particularly suitable for medium- and large-scale production. Also particularly noteworthy are the simpler bonding technique (fusion) and the significantly higher continuous working temperatures (up to 200 °C, depending on the polymer) and impact tolerance of components with a
In Polyetheretherketone (PEEK) and Polyamide 12 (PA12), Evonik offers thermoplastic polymers that have proven their worth as matrices and can be selected for different requirements in regard to continuous working temperature and mechanical properties.
VESTAKEEP® PEEK compounds and powders are particularly suitable for applications where extreme mechanical, thermal, and chemical requirements must be satisfied.
VESTAKEEP® is suitable as a matrix for unidirectional fiber layouts or woven fabrics of glass or carbon fibers, and thus makes it possible to produce fiber composite materials with a thermoplastic matrix. The thermoplastic fiber composite materials are produced by a powder-coating or dispersion-coating process.
Evonik has developed optimized powders suited specifically to these processes, thus confirming
its eligibility for production of composites. Its VESTAKEEP® 2000 powder line with different
particle sizes is established as the ideal polymer for this application. The semi-crystalline polymer features superior thermal and chemical resistance.
- High Tg
- Self-extinguishing parts
- Very high heat deflection temperature
- High stiffness
- Low water absorption and therefore high dimensional stability
- Excellent chemical resistance
- Excellent hydrolytic stability
- Good processability
- No tendency to stress cracks
VESTAMID® PA12 or the powder form VESTOSINT® has been used as a matrix in composites for many years. A superior grade is now used for manufacturing tapes based on carbon fibers.
Composites with polyamide 12 as the matrix are processable at a lower temperature. Compared to high temperature-resistant matrices such as PEEK, PPA, and PPS, this presents an advantage, thus significantly shortening cycle times for mass-production.
Moisture absorption behavior
PA12 is distinguished by low water absorption compared with, e.g., PA6 and PA66. In the conditioned state, therefore, the decrease in tensile strength is only very small. This is an
additional benefit for the long-term behavior of the resulting composites. the general properties are
- Low weight
- High impact resistance
- High elongation and high abrasion resistance, even at low temperatures
- Low water absorption
- Good electrical isolation and dielectric strength