| Polyether polyols is one of the important raw materials for preparing polyurethaneelastomers (PUE), and the star-shape polyether polyols, with its unique three-dimensionalstructure as well as its higher functionality and lower viscosity compared with linear polyolshaving same molecular weight, is a kind of special morphological polymer in polyetherpolyols. In this research, linear polyethylene glycols (PEG) and four-arm polyethylene glycols(4aPEG) were used as raw materials respectively to synthesize multi-hydroxyl polyethyleneglycols derivatives and multi-hydroxyl star-shape block four-arm polyethylene glycols/tetrahydrofuran (4aPEG/THF) copolyether, and then these multi-hydroxyl copolyethers wereused to prepare PUE without additional cross-linker. The optimal experimental conditions tosynthesize the multi-hydroxyl copolyethers and the PUE were investigated, and infraredspectroscopy (IR), nuclear magnetic resonance spectroscopy (1H-NMR and13C-NMR),viscosity meter, gel permeation chromatography (GPC), differential scanning calorimeter(DSC), thermo gravimetric analyzer (TGA) and tensile testing machine were used tocharacterize the multi-hydroxyl copolyethers and the PUE. The main results are as follows:The multi-hydroxyl polyethylene glycols derivatives, which was synthesized with PEGand epoxy chloropropane (ECH) and was used as macromolecular cross-linker, could reactwith PEG,1,4-butanediol (BDO) and toluene diisocyanate (TDI) to prepare PUE by one-stepmethod. The results show that the curing parameter R has the greatest influence on the tensilestrength of the PUE, while the curing temperature influence the elongation at break of thePUE mostly. The optimal reaction conditions for preparing PUE using the macromolecularcross-linker are shown as follows: R value is1.2, mole ratio of BDO/PEG is3, mole ratio ofBDO/macromolecular cross-linker is9, curing temperature is70℃. The tensile strength of thePUE prepared in optimal conditions is12.93MPa, glass transition temperature (Tg) is-34℃,thermal decomposition temperature (Td) is248℃ Using4aPEG as initiator, propylene oxide (PO) and ECH as ring-opening assistantrespectively, tetrahydrofuran (THF) was triggered to take cationic ring-openingpolymerization to synthesize4aPEG/THF copolyether. Results show that both two kindsring-opening assistant can trigger THF’s polymerization and polyether polyols with goodpurity can be obtained. When using PO and ECH as ring-opening assistant to trigger THF’spolymerization to synthesize4aPEG/THF copolyether polyols, the optimal conditions are thatthe mass ratio of THF/4aPEG is3:1, PO mole percent is10%and ECH mole percent is4%based on THF molar quantity, initiator dosage is4%mole percent of THF and reaction time is1.5h. Besides, DSC curve shows that THF’s polymerization into copolyether triggered by thetwo kinds of ring-opening assistant can inhibit the crystallization of4aPEG chain. Under theoptimal conditions, the functionality of copolyether synthesized by PO as ring-openingassistant is3.29, number-everage molecular weight is8122, while the functionality ofcopolyether synthesized by ECH as ring-opening assistant is2.95, number-everage molecularweight is5430, so that the comprehensive performance of copolyether synthesized by PO asring-opening assistant is better than that of ECH as ring-opening assistant.When preparing PUE by one step method with4aPEG/THF copolyether as raw material,which was synthesized by PO as ring-opening assistant, the obtained PUE has lower Tg(-30℃)and higher Td(234℃) and shows excellent performance of thermal property, with theincreasement of R value the tensile strength of the PUE prepared increases, while theelongation at break decreases. The optimal conditions for getting excellent mechanicalproperties of PUE are as follows: mole raito of BDO/(4aPEG/THF) is between2and3,dosage of catalyst is0.2%of the total mass, curing temperature is between50℃and70℃. Inaddition, when using the copolyether to prepare PUE, the viscosity of copolyether should notbe too large. |
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