Sheet Moulding Compounds

Described about sheet molding compound

1. CIPET-IPT,AHMEDABAD Seminar Topic – Sheet Moulding Compounds Presented By- Shravan Kumar Pathak E.N.(180520123045) Course - B.E.- 7th S e m (Plastic Technology)

2. Definition SMC is a combination of long chopped glass strands,minerals fillers and liquid thermosetting resin in the form of a malleable sheet material. Sheet Molding Compound (SMC) is a compression molding compound often used for larger parts where higher mechanical strength is needed. SMC is a fiber reinforced thermoset material. Glass reinforcement is between 10% and 60%, and glass length is slightly longer than Bulk Molding Compound (BMC) - between 1/2-inch and 1-inch (25mm ).

3. Manufacture of SMC

4. A continuous polyethylene or Cellophane film is coated with a suitably formulated polyester resin system into which is deposited a layer of either chopped strand mat (450 g/m2) or chopped rovings . A second layer of polyethylene film,similarly coated with resin system,is placed over the reinforcement and the sandwich thus formed is passed through a series of rollers to press the glass fibres into the resin and ensure thorough wetting of the reinforcement by the resin. The sandwich is then wound into a roll and allowed to stand while the resin thickens. SMC is cut to the required shape and both layers of polyethylene film are removed and SMC p laced in the mould and pressed.

5. Formulation for SMC Materials Parts by weight Polyester resin 100 t-Butyl peroxybenzoate (95%) 2- 3 Zinc stearate ( release agent) 3-4 Magnesium oxide (thickening- agent ) 2-3 Pigment dispersion 5-8 Filler 140-180 Thermoplastic additives 5-20 CSM or chopped rovings 50-100

6. Properties of SMC High   strength to weight ratio. E xcellent   corrosion resistance. Superior electrical insulation properties. Good aesthetics and colorability . Good flame retardance and easy cleanability .

7. Advantages of SMC Very high volume production ability. Excellent part reproducibility. It is a cost- effective process. scrap is reduced substantially. It is light in weight .

8. Disadvantages of SMC Low level of stiffness and strength . High Investment cost Large cycle time

9. Application of SMC

10. Application of SMC Instrumentation bases. X-ray film container . Electrical parts. Bio hazardous trash containers. Dental equipment housing.

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