Water Crosslinked Millable Vulkollan for Compression Moulding

WATER CROSSLINKED MILLABLE VULKOLLAN FOR COMPRESSION MOULDING 

As described in Chapter 1 water reacts with isocyanates with the evolution of carbon dioxide gas. This is the basis of water-crosslinked Vulkollans in which water is substituted for the glycols normally employed for chain extension. 

As has been seen for the water-crosslinked Vulkollan material, the NDI/polyester urethane can be obtained in a cellular form by the use of 

Prepolymer is prepared as already described and cooled to a temperature between 70 and lOO C. This is then used as one stream in the continuous mixing machine. The other stream consists of water, emulsifying agent (e.g. sulphonated castor oil), and a foam stabilizer (silicone oil). Different hardnesses can be achieved by varying the NDI content together with the water content. Density control is obtained by the metering of precise quantities of reaction mixture into the mould which is then closed to enable the material to expand to fill the mould without overspill. After removal from the mould the product requires an oven cure of 24h at 110 C. 

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