What is the formula or recipe for polythylene foam or polyurethane/urethane foam?
Friday, September 10th, 2010 at
12:07 am
I’d like to make my own foam for various projects such as bean bag filler, microbeads for squishy pillows or milk bottle filler, various shapes for sculpting, etc. What chemicals do I need to mix in order to achieve foam? Which should I add more or less of to achieve greater hardness or density?
Tagged with: bean bag filler • bottle filler • chemicals • density • microbeads • milk bottle • shapes • squishy pillows
Filed under: Uncategorized
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Polyurethane foams, that is, cellular polyurethanes are generally prepared by the exothermic reaction of a polyisocyanate and one or more polyols in the presence of a catalyst and a foaming or blowing agent.
As used herein, the term "polyol" refers to a compound containing a plurality of hydroxyl groups which are reactive with isocyanate groups to form urethane polymers. The polyisocyanates generally used are aromatic diisocyanates, such as toluenediisocyante (TDI) and polyaryl phenyl isocyanates. The polyols used in the reaction are generally resinous materials which have a plurality of reactive hydrogen atoms. These materials include hydroxyl-bearing resins, such as polyester and polyetherresins, and naturally occurring hydroxyl-bearing oils, such as castor oil.
Catalysts are included in the reaction mixture in order to accelerate the foaming reaction and obtain a proper cure. Stannous octoate, dibutyl tin laurate, amines and acids are commonly used as catalysts in the preparation of polyurethane foams.
The foaming or blowing agents used to expand the polyurethane into a cellular structure, may be either by-products of the reaction, such as carbon dioxide, generated by the reaction of some of the isocyanates and water; or nitrogen, generated,for example, by the decomposition of an azide; or special liquids or solids intended for the expansion, such as chlorofluoromethanes, which are vaporized by the heat of reaction of by a reduction of pressure.
Polyurethane foam is generally prepared by mixing the components of the mixture in a suitable manner and by allowing the mixture to be formed into a desired shape in a suitable space.
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