Cast elastomers
Liquid components poured into a mould and cured into solid parts such as rollers, wheels, pads and liners.
Cast elastomersReference / polyurethane-components.com
Two liquids. Endless parts.
Isocyanates, polyols, extenders, catalysts and additives. A plain reference to what goes into polyurethane, what each part does and how the mix becomes wheels, foams, coatings and glue.
The component table
Every topic on the site, laid out like a periodic table. Large tiles are components, forms, guides and tools. Small tiles are reading and reference.
A side. B side. One network.
Polyurethane is chemistry you can hold. Get the components, the ratio and the conditions right and the same two liquids can become almost any part you need.
Drum to part
Five steps from drum to part
Whether the part is cast, sprayed or rolled on, the same habits keep each batch consistent.
Read the casting guide- 01
Condition
Bring both sides and the mould or surface to the temperature on the data sheet.
- 02
Weigh
Measure each side by the ratio on the data sheet. Use the calculator to split a batch.
- 03
Mix
Blend fully, scraping the sides and bottom, without whipping in air.
- 04
Degas and place
Pull out trapped air where needed, then pour, spray or spread within the pot life.
- 05
Cure
Leave it undisturbed, demould on time and post cure when the system calls for it.
Interactive
Pick a component, see its job
Select a tile to see what each family of ingredients does and what it changes in the finished material.
A side
Isocyanate
The reactive side that links everything together.
- Crosslink density and hardness
- Colour stability outdoors
- Reaction speed with the B side
B side
Polyol
The backbone that sets softness, toughness and resistance.
- Flexibility and elongation
- Water and oil resistance
- Viscosity of the blend
B side
Chain extender
Short molecules that build the hard segments.
- Hardness and modulus
- Tear strength
- Heat resistance
B side
Catalyst
Small doses that set the clock.
- Pot life and gel time
- Demould time
- Balance of blowing and gelling in foam
Either side
Additives
Pigments, fillers and helpers that tune the finish.
- Colour and appearance
- Cell structure in foam
- Weathering and fire behaviour
A side
Prepolymer
Isocyanate that has already met some polyol.
- Processing control
- Viscosity and handling
- Final hardness range
Six forms
One chemistry, many forms
Change the components or the process and polyurethane becomes something new.
Foams
Gas bubbles trapped as the polymer forms. Flexible foams go into seating and padding. Rigid and spray foams insulate buildings and tanks.
FoamsCoatings
Thin films brushed, rolled or sprayed onto floors, steel, wood and concrete to protect and finish them.
Coatings
Spray elastomers
Fast reacting two part systems sprayed through heated plural component equipment to build thick linings.
Spray elastomers
Adhesives and sealants
Polyurethane glues and joint sealants bond metal, wood, glass and plastics while staying flexible.
Adhesives and sealants
Thermoplastic polyurethane
Pellets that melt and reshape like other thermoplastics, used for hose, film, cable jackets and moulded parts.
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FAQ
Quick answers
What are the A side and B side?
In most systems the A side is the isocyanate or prepolymer and the B side is the polyol blend with extenders, catalysts and additives. See the components.
Can I change the mix ratio to make a part softer?
Not safely. The ratio balances the reactive groups on each side. Use a system made for the hardness you need.
Weight or volume?
Use whichever the data sheet gives. Weight is usually more accurate. The calculator splits a batch either way.
What does Shore hardness mean?
It is a reading from a durometer on the Shore A or Shore D scale. Read hardness and Shore scales.
Why does my casting have bubbles?
Moisture, fast stirring and skipping degassing are the usual causes. See casting polyurethane parts.