Polyurethane is a modern and versatile material that is used in various forms. In fact, we use this plastic day in and day out without even being aware of it. Polyurethanes can be found in car parts, in furniture and even in shoe soles. It is used as an adhesive and sealer and also for insulation.
The uses of polyurethane are not restricted to industrial applications alone as it also functions as a good mold making material. In fact, there’s a lot going in favor of this aliphatic material as it displays superior physical and performance properties and can actually outperform all other rubber type materials in mechanically abusive environments. It can also withstand high temperatures and is resistant to UV rays, ozone, water, oil, grease and chemicals.
What’s more, polyurethanes are formulated with varying Shore Hardness to yield soft, medium and hard compounds. Therefore, you can easily make both flexible and rigid molds. A unique formulation actually expands in size when submerged in water, thus allowing for easy enlarging of molds.Excellent chemical/physical resistance is essential, Polyurethane coatings are particularly recommended for application to surfaces that are subject to high levels of wear-and-tear.
Coming at a reasonable price, polyurethane rubbers prove to be quite economical on the pocket too.
And if this is not enough, polyurethanes are extremely easy to work with as well. It is a two-part formula and has to be mixed with a curative in the prescribed ratio prior to use. The pot time is about half an hour which gives a sufficient window for working with the rubber.
The tough polyurethane rubber compound yields negligible shrinkage and does not form air bubbles easily either. Therefore degassing on a vibrating table or vacuum chamber is also not necessary. It will cure at room temperature overnight or within approximately 24 hours. The shelf life is generally 6 months provided it is sealed and stored properly after use.
However, proper care is required when handling polyurethane rubber. It can irritate the eyes and skin and is harmful when swallowed. It is better to wear gloves and protective overalls when working with the compound. Appropriate ventilation is also advisable to avoid repetitive inhalation.
It is important to pay attention to the humidity level in the studio as well. Use a dehumidifier if required, as excess moisture is known to cause foaming in polyurethane rubbers!
You will find that polyurethane rubber captures details well and reproduces an excellent mold of the specimen. But using a suitable release agent is essential. The resultant molds prove to be highly durable as well.
Polyurethane mold can be used to cast various materials such as wax, epoxy, plaster of Paris, gypsum, polyurethane resin and certain types of foams. As they can withstand the abrasive action, polyurethanes work extremely well with concrete mixes.