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Chapter 33

Chapter 33. Processes Used to Condition Composite Materials. Objectives. Processes to make composite surface conducive to resin adhesion Changing thermal conductivity and specific gravity by introducing additives to the resin. Irradiation.

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Chapter 33

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  1. Chapter 33 Processes Used to Condition Composite Materials

  2. Objectives • Processes to make composite surface conducive to resin adhesion • Changing thermal conductivity and specific gravity by introducing additives to the resin

  3. Irradiation • Irradiation is exposure of a material to energy from a radioactive source. • Controlled radiation can be used to improve the ability of the plastic work pieces to withstand exposure to extreme temperatures. • This process can also be used to enhance the electrical resistance characteristics of wire insulation.

  4. Improving Bonding of Composites • Wetting a substrate with liquid or adhesive paint is also influenced by the cleanliness of the substrate. • Air bubbles, oil, dust, or moisture buildup will interfere with the ability of the coating to wet the surface. • Electrical surface treating: Since most plastic films and sheets have a smooth slippery surface (low surface tension) the electrical surface treating or corona discharge treating essentially roughens the surface (raising the surface tension) which improves the adhesion of inks, paints, and adhesives. • Coupling agents: Coupling agents (adhesion promoters) improve the internal bond between matrices (resin), reinforcement materials, fillers and laminates.

  5. Protection from weathering • Ultraviolet stabilizers and carbon black are sometimes used with polyesters, polystyrenes, and other plastics to reduce damage from ultraviolet rays. • Other additives call anti-ozonanats are used to help prevent the composite from being damaged by the ozone in the atmosphere.

  6. Changing Composite Characteristics • Cellular foams are sometimes desired in applications where improved thermal insulation, light weight, and impact resistance are necessary. A foaming agent causes the resin to expand into a foam. • Blowing agents are useful when forming a composite structure in a closed mold and are frequently used to ensure that the mold is completely filled.

  7. Temperature Degradation of Composites • Graphite, ceramic, and boron fibers are typically resistant to high temperatures. • Most polymeric composite ,materials exposed to intense heat will char and decompose.

  8. Summary • Controlled radiation can be used to improve the ability of the plastic work pieces to withstand exposure to extreme temperatures. • This process can also be used to enhance the electrical resistance characteristics of wire insulation. • Air bubbles, oil, dust, or moisture buildup will interfere with the ability of the coating to wet the surface. • Electrical surface treating: Since most plastic films and sheets have a smooth slippery surface (low surface tension) the electrical surface treating or corona discharge treating essentially roughens the surface (raising the surface tension) which improves the adhesion of inks, paints, and adhesives. • Ultraviolet stabilizers and carbon black are sometimes used with polyesters, polystyrenes, and other plastics to reduce damage from ultraviolet rays. • Graphite, ceramic, and boron fibers are typically resistant to high temperatures. • Most polymeric composite ,materials exposed to intense heat will char and decompose.

  9. Home Work • 1. What are the advantages of irradiation of composites? • 2. How does electrical surface treating or corona discharge treating improve adhesion?

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