Polyester polyols, which are organic substances, are usually formed by condensation (or transesterification) of an organic dicarboxylic acid (anhydride or ester) with a polyol (including a diol) or by polymerization of a lactone with a polyol. The dibasic acid is phthalic acid or phthalic anhydride or an ester thereof, adipic acid, halogenated phthalic acid or the like. The polyhydric alcohol is ethylene glycol, propylene glycol,
diethylene glycol, trimethylolpropane, pentaerythritol or the like. Different types of polyester polyols have different properties due to different types or different preparation processes. Several indicators that are important for polyester polyols are hydroxyl number, acid value, moisture, viscosity, molecular weight, density, and color. Characteristics and uses of polyester polyols: Polyester-based polyurethane contains a large number of polar groups such as ester groups and amino groups in the molecule, and has strong cohesive strength and adhesion, and has high strength and wear resistance.
Polyether polyol (referred to as polyether) is composed of an initiator (active hydrogen group-containing compound) and ethylene oxide (EO), propylene oxide (PO), butylene oxide (BO), etc. in the presence of a catalyst. It is obtained by polyaddition reaction. The largest yield of polyether is glycerol (glycerol) as the initiator and epoxide (usually PO and EO). Various general-purpose polyether polyols are produced by changing the feeding mode of PO and EO (mixing plus or separately adding), the ratio of addition, the order of addition, and the like.
