Thermosets

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Thermosets

  1. 1. THERMOSETS<br />05.03.2010<br />
  2. 2. Thermosets<br />Cross-linked in a 3d network. Strength of bond. Hardness & strength in material not affected by temperature.<br />Polymerization will require heat & pressure so that the shape of the part is permanently set.(curing)<br />Irreversible. Decomposes. Chars.<br />
  3. 3. Thermosets<br />Tg not sharply defined. Become rubbery over a narrow range.<br />Polymerization in 2 steps. At chemical plant & at parts-producing plant.<br />Phenolics. Pots & pans.<br />Possess better insulating, mechanical & chemical properties. Also better dimensional stability.<br />
  4. 4. Mechanical Properties<br />
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  6. 6. Melamine/Aminos<br />Formica is a brand of composite materials which are heat-resistant, wipe-clean, plastic laminate with melamine resin.<br />If exposed to enough heat, melamine will decompose. For this reason, melamine dishware should not be exposed to high temperatures like those in the oven and microwave.<br />
  7. 7. Advantages of Melamine<br />Toxicity, None- Extinguishing, Self- Halogen Content, None- Electrically Insulating- Hardness, High- Gloss, High- Scratch Resistant- Copolymer- Strength, High<br />
  8. 8. Melamine<br />Uses for melamine include floor tiles, kitchenware, fire retardant fabrics, and commercial filters.<br />Melamine is an organic compound that is often combined with formaldehyde to produce melamine, a synthetic polymer which is fire resistant and heat tolerant.<br />melamine releases water.<br />
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  10. 10. Copolymer<br />A heteropolymer or copolymer is a polymer derived from two (or more) monomeric species, as opposed to a homopolymer where only one monomer is used<br />
  11. 11. Epoxies <br />Excellent mechanical & electrical properties. <br />Good dimensional stability & excellent adhesive properties.<br />Application requiring mechanical strength & thermal insulation. Used as coatings & adhesives.<br />
  12. 12. Epoxies <br />have low shrinkage, good chemical resistance, excellent adhesive properties.<br />Downsides are the higher cost, a need for an accurate resin/hardener ratio (epoxies use a hardener not a catalyst, and the ratio will vary) when mixing and the need for skin protection.<br />
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  14. 14. Disadvantages<br />Strongly exothermic, this can lead to cracking. <br />Contracts on curing (up to 8%).<br />Protective measures must be taken before mixing and using any of the thermosetting resins.<br />High temperature & pressure required <br />UV-sensitive<br />
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  16. 16. Designing With Thermosets<br />there are potential pitfalls which can lead to designs difficult to produce, or costly failures in the field.<br />The first important consideration is stiffness. <br />far more rigid and dimensionally stable than thermoplastic.<br />
  17. 17. Designing With Thermosets<br />For applications requiring precise dimensional tolerances and low deformation under load, thermosets are an excellent choice. <br />another important design criterion is associated with cross section thickness.<br />Impact strength is another area requiring special attention.<br />Applications which require flat surfaces may best be molded from a thermoset.<br />
  18. 18. Thermosets As A Replacement For Metal<br />Because of their dimensional stability, high strength, and thermal resistance, thermosets are often chosen as an alternative to metals. <br />Potential benefits include cost saving, weight reduction, and improved chemical and corrosion resistance. <br />

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