Polyurethane foaming is affected by the conditions, equipment, technology and ambient temperature during the construction process. Various abnormal phenomena may occur during the polyurethane reaction, such as foam shrinkage, crispiness, too soft, heartburn, cracking, smoking, shedding, and foam collapse. , large foam pores, kneaded into fine powder, slow foaming in the initial stage of reaction, slow initiation, etc., all possible situations are recorded as follows. Due to the long length, it is divided into three articles, this is the second one:
The following material A represents polyurethane white material-blend polyether polyols, material B represents polyurethane black material-polymerized MDI (polyisocyanate).
4. Rigid polyurethane foam is too soft and matures too slowly: ① The component of material B is small; ② There is too little tin catalyst in material A; ③ The temperature of the air temperature, material temperature and blanking surface is low.
5. Collapse of rigid polyurethane foam: ① The foaming gas is generated too quickly, so the amount of amine chemical agent in material A should be reduced; ② The foaming agent in material A has failed or is alkaline; ③ The catalyst has failed or has been missed, so additional A should be added. Tin catalyst in the material; ④The acid value in the raw material is large.
6. The rigid polyurethane foam has large holes: ① The foaming agent in material A fails or is missing; ② There is a lot of moisture (moisture in the foaming agent or polyether); ③ Materials A and B are not evenly mixed; ④ Material B has low purity and contains total High chlorine or acid value; ⑤ Gas generation speed is faster than gel.