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Intrinsically Foamed SMA in Interior Trim Applications
ISSN: 0148-7191, e-ISSN: 2688-3627
Published March 01, 1994 by SAE International in United States
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Co-Polymers of styrene and maleic anhydride have been around since the '40's. The addition of maleic anhydride to the polymer backbone has a two fold effect; firstly, it increases chain stiffness and secondly chain-chain interactions are increased. Both of these effects increase the glass transition temperature of the co-polymer.
A production technology has been developed which enables to generate co-polymers containing a relatively high maleic anhydride content (typically up to 35 wt %) resulting in materials with glass transition temperatures up to 170 °C.
A technology has been discovered and patented whereby these high maleic anhydride containing co-polymers can, under the influence of the right chemistry and temperatures (between 230 - 260 °C), release carbon dioxide which is then used as the blowing agent to generate low density (intrinsically blown) foams.
In general these foams are produced on tandem foaming lines and typically have the following property profile:
The advantages of SMA-foam produced by the intrinsic foaming technology are obvious:
High temperature resistance.
Environmental friendly (no CFC or hydrocarbon emission).
Based on this intrinsically blown SMA foam, a new generation of headliners has been developed. The thermomechanical properties of these headliners are comparable to those of structures based on thermosetting polyurethane. The SMA used in the headliners can be recycled using a “solvent recycling” process.
Due to the large segmental repulsion between the polar/a-polar monomer units SMA forms miscible or compatible blends with a large range of polymers or co-polymers, which effectively reduces this internal repulsion. Examples of polymers which are compatible with SMA are PMMA, SAN, PVC, PCL, ABS, PA and PET. This broad miscibility/compatibility range enhances options for recycling.