Dynamic Mechanical Properties Of Polyurethane Elastomers

The dynamic mechanical property and its influencing factors of polyurethane elastomers were studied. The work consists of two main parts:(1) PU elastomers with high value of micropgase separated degrees were prepared using low unsaturated polyether polyols with different molecular weight and different chain extenders. (2) PU elastomers with cross-linked hard segment were prepared using crosslink agents, isocyanurate grups and the modified method of irradiation.A series of PU elastomer samples were synthesized using four kinds of low unsaturated polyether polyols with different molecular weight as soft segments. The phase separated degrees of the PU elastomers increased with increase of the soft segment molecular weight. The samples with soft segment molecular weight at 4000 and 8000 had the lowest value of tanδat above the ambient temperature.The microphase separated degrees of PU elastomers based on aromatic chain extenders were found to be obviously higher than those based on aliphatic chain extenders and the order of the value was that PU-HQEE>PU-HER>PU-BDO>PU-BD. The sample of PU-HQEE had the lowest value of tan8 at above the ambient temperature.A series of cross-linked PU elastomer samples with various crosslink density were synthesized using trimethylolpropane (TMP) and glycerin as crosslink agents. The partial micro phase separated degrees might be partly influenced by the cross linked structure. The samples containing a small amount of crosslink agent (TMP or glycerin) could make tanδto a very low value at above the ambient temperature. For PU elastomer samples using glycerin as crosslink agent, the tanδvalue at the same temperature was lower than those using TMP as crosslink agent.Poly(urethane-isocyanurate)(PUIR) elastomers with different extent of urethane group and isocyanurate ring were synthesized by changing the NCO/OH ratios. The isocyanurate ring had a little influence on the micro phase separated degrees of PUIRs and could make the tanδto a low value above the ambient temperature.PU elastomers were prepared with 1,4-butynediol as the chain extender and were then treated by the high energy electron beam. Hydrogen bond rearrangement in the hard segments of PU was found when the irradiation dose was low. The carbon-carbon triple bonds in the PU were broken and the structure of network was formed when the irradiation dose was high. The radiation treatment could make the tan8 of PUs to a certain low value at above the ambient temperature.