Calculation of Hard and Soft Segment Contents

VIBRATHANE B 625 is a polyether prepolymer based on polytetramethylene glycol (PTMEG) and MDI raw materials. Based on the 6.5% NCO content, it can be assumed that this was prepared using 1 mole of PTMEG-1000 polyol and 2.2 moles of MDI. It can also be assumed that the HER chain extender produces crystalline hard segments 

HER Materials HQEE HER-HP HER- TG210 HER- TG225 HER- TG250 HER- TG275 HER- LIQ 

These calculations were based on the reaction scheme (8.1) shown opposite and an idealised polyurethane structure from this scheme and the details are given in Table 8.4. 

In general, the contributions of both the soft and hard segments in the polyurethanes can be correlated with the properties observed. The soft rubbery block primarily affects resiliency, wear, tear, compression set and low temperature properties, while the hard block affects hardness, modulus and tensile properties [11]. 

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