18. Wildcard week#

Composite: Resin & Hardener - Polyester Resin#

Explanation of the difference between Epoxy, Vinylester and Polyester Resin here. In summary…

Epoxy: - Most expensive - 3x stronger than next strongest resin type - Adheres to Carbon Fiber, Fiberglass, Aramid (Kevlar) - Forms a leak proof barrier - Adheres to older expoxy well - Most will Yellows over time with UV exposure - All weather expoxy harder (ex: West System 207, Adtech 820) type should be selected for extreme temperature or water exposure use - Amber color initially, become clear when enough applied to wet out the composite…yellowing will occur to yellow Kevlar and White Fiberglass - West System 207 and Adtech 824 are perfectly clear expoxy resin with UV protection - Different expoxy soften at different temperatures (135F for West System, 210F for Adtech)


  • less strength than epoxy Resin
  • adheres poorly to Carbon Fiber and Aramid


  • cheapest
  • poor bonding capability…never used for structural carbon or aramid work
  • good on fiberglass

Nittoku FRP Polyester Resin

Safety & Technical Datasheet: - dont contiminate with water or oil…wont cure - 5deg+ to cure - curing agent must be 1% of resin - 30-40min cure time - disposable as normal garbage as burnable trash when infused on newspaper - skin irritation…wear protection…clean with acetone wash with water and soap if contact - eye…wash with water - fumes…use in well ventilated - melts styrine plastic

Mix Ratio: 99:1 Resin to Hardener

Test Coupons#

Observations - Fabric Types Tested: Polyester, Jute, Polyester

  • Length of Time: 10mins already hardening…a warm 28deg day in Kamakura
  • Compression: Dries slower as the moisture has no where to escape…smoother finish (the coupons were compressed together between two pieces of wood tightened by clamps)
  • Layers: double layer stiffer than single Layer…the material fusing together with the resin

Compressed Coupons:

Double Layer, Compressed Spandex…very stiff. But Spandex curls when saturated with liquid.

Single Layer Compressed Jute…relatively stiff. Even the aluminum foil used protect the wood compress fused to the surface (…can be removed with some effort)

Double Layer Compressed Polyester…very flexible. Like a plastic sheet.

Non-Compressed Coupons:

Single Layer Non-Compressed Spandex…super flexible. Seems very strong against bending but virtually no structural stiffness. Feels like lamination of paper.

Double Layer Non-Compressed Spandex…rather flexible. Like a plastic sheet. Some reasonable stiffness at the overlap of the material…acting like a structural seam.

Single Layer Non-Compressed Polyester…very flexible. Like a plastic sheet. Would not seem to break with bending force and maybe rather resistant to impact force.

Single Layer Non-Compressed Jute…reasonably stiff, but would likely break with impact or bending force.

  • Heat Generation: The chemical reaction between the resin and hardener generates a significant amount of Heat…must be mindful of this in future resin work
  • Fumes: Polyester resin smells…terrible. Without ventilation, a headache is guaranteed…and internet research suggests that these fumes are VERY bad for my health. I worked outside from this point forward. (I really don’t like this resin…will see if Expoxy is any better in future composite work)

Soft Robotics#