Monday, 26 January 2009

Processing Silicone Prosthetics (using fiberglass) Part 1

 - Fiberglass is a strong lightweight material and is used for many products.

 - It is not as strong and stiff as carbon fiber but it's less brittle.

Health and Safety:

- Will irritate eyes, skin and respiratory system
- Potential dysphea, sore throat, hoarseness and coughing
- Safe to manufacture but have to wear protective clothing
- Mouth protection needs to filter against organic vapor (respirator)
- Hand protection (vinyl or nitrite gloves)
- Eye protection (any sort of goggles)
- Protective Clothing (baggy clothes so that it's away from skin if spills or overalls)

Materials:

- glass matting
- gel coat resin
- lay-up resin
- fine surface tissue
- catalyst (benzoyl peroxide)

Gel Coat = smooth, hard polyester surface coating of fiberglass stucture

Lay-up Resin = Synthetic Resin that undergoes polymerization during curing. Excellent adhesive, high strength, good chemical resistance.

Catalyst = methyl, ethyl, ketone peroxide

Glossary of terms:

- Core = thing sculpting onto (positive portion of a multipiece mold)
- Mould = the thing on top of the sculpt
- Cast = thing that comes out
- Flashing = excess material
- Touchdown = mould touching core
- Key = indentation to help alignment of mould
- Cutting edge = part of the mold that touches and glues thin edge
- Undercut = sculpting that creates a locking state between mould and core

Fiberglass:

- Gel coat is the first layer that goes on
- Laminating resin is a lot thinner and runnier than gel
- Chippings = little bits of fiberglass

- Vale = thin and papery fiberglass

- Catalyst is generally 2% of total volume (but can be different depending on atmosphere conditions) same for gel coat and laminating resin.


- Put mold release over plastic areas of core

- Talc the surface of the sculpt (prevents resin from building up)

- Add 2% of catalyst to gel coat layer (should change colour)

- With chip brush put an even layer of gel coat over entire sculpt and flashing and down onto core.



- Let almost cure (firm but tacky) usually takes 20-30 minutes (depends on room temperature

- Put 2% of catalyst in laminating resin

- Mix some resin with chipping and fill any deep holes that will be hard to fiberglass ( tight corners, flashing etc.)

- Wet up fiberglass chunks with resin.



- Lay over the sculpt, overlapping the pieces


- Use resin on the brush to put on top of fiberglass (knocking out airbubbles)

- Do 2 layers of fiberglass and a third round the edge for strength to pull apart.



- Lay the veil over the top and press down with resin



- Leave for a few hours to set and harden (preferably overnight)

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