Factors affecting the performance of polyurethane elastomers mainly include raw materials, formulas and process conditions.
Effect of oligomer polyol on elastomer properties: When the diisocyanate raw materials are the same and the ratio is similar, the polyurethane elastomer using polyester diol as the oligomer polyol raw material will generally have a strength ratio based on ordinary
Polyether polyols have higher polyurethane properties, but the hydrolysis resistance of ordinary polyester polyurethanes is not as good as polyether polyurethanes. Among polyester polyurethanes, polyurethanes based on crystalline polycarbonate diol and polycaprolactone diol have high strength and higher hydrolysis resistance than ordinary polyester polyurethanes. Among polyether polyurethanes, polyurethanes based on crystalline polytetrahydrofuran diol with regularity in polymer structure have higher mechanical properties than polyurethanes based on ordinary polyether raw materials.
Impact of diisocyanate on elastomer properties: When the oligomer diol raw materials are the same and the formula is similar, the strength of polyurethane based on aromatic diisocyanate is generally higher than that of aliphatic diisocyanate, but its yellowing resistance is poor. When other raw materials are the same, compared with TDI, which contains one benzene ring in the molecule, MDI contains two benzene rings in the molecule and has a symmetrical structure. The physical properties of polyurethane made from MDI, such as strength, are higher than TDI-type polyurethane.
Effect of chain extender on elastomer properties: As the third important raw material of polyurethane elastomer, chain extender also has a greater impact on elastomer properties. First, increasing the amount of chain extender will increase the hardness and strength of the product; secondly, It is the influence of different types of chain extenders. Aromatic chain extenders can increase the hardness, strength and heat resistance of materials better than aliphatic chain extenders. Aromatic chain extenders with symmetrical molecular structures such as MOCA, HQEE, and MCDEA are more effective on parts. The improvement in performance is greater than that of chain extenders with asymmetric molecular structures.
In addition to raw material factors, the preparation process (one-step method, prepolymer method) and post-curing conditions (temperature, time) have an impact on the properties of polyurethane elastomers.