Plastic films appear in:
-electronic circuitry as insulation, dielectrics and bases for printed
wiring;
-multi-layer insulations (MLI)usedfor thermal-control purposes: basic components;
-inflatable and erectile devices: e.g. "structural" applications;
-flexible second-surface mirrors (solar reflectors).
Thermoplastics, either plain or reinforced, find multiple uses in spacecraft, including:
-electrical insulators,
-gaskets,
-small mechanical parts,
-lacing and tie devices,
-sleeves and tubing.
The main film-forming polymers used are: polyolefins,
polyester, fluorinated plastics, polyimides, polycarbonates and acetals. Composite laminated films are commercially available. Uncoloured films are transparent or translucent white to yellow, but dyed and pigmented grades exist in any shade. Classical plastic additives are used in films: plasticisers, antioxidants, antistatic agents. Film surfaces can be modified by chemical treatment and by metallization. The latter use mainly vacuum-deposited aluminium, silver, gold or copper. Films are
sold in rolls or sheets. Thickness varies from a few micrometres upwards. Thicknesses of less than 5 µm to7浵m are generally difficult to procure in large quantities.
Commercial thermoplastics are extremely numerous. Most of them can find some space use, for example, polyamides, acetal, polyolefins, polycarbonate, acrylics, polystyrene, fluorinated resins and polyphenylene oxide. Some are hard and brittle, others are tough; some are flexible and soft. Pure products vary from
transparently clear to translucent white or light yellow, but most of them can be dyed or pigmented. Fillers are sometimes used as well as other additives such as antioxidants, plasticizers, UVstabilizers and processing aids. Reinforced thermo-plastics based on glass fibres or chopped carbon fibres are commercially available.
Many types of thermoplastics appear as textile items. Shrinkable plastics exist on the market, as well as foamed plastics. High-performance thermoplastics, with
continuous fibre-reinforcement, were promoted for structural applications, |
