Synthesis and Properties of Benzoxazinyl siloxane from Bisphenol-A on Polyurethane

• Main Authors: Yuan-Peng Chen, 陳鵬元
• Other Authors: Sheng-Hong Dai
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/21118834021910247313

碩士 === 國立中興大學 === 化學工程學系所 === 104 === Benzoxazines are useful thermosetting intermediates which can enhance mechanical properties and impart thermal stability to polymers through heat-curing crosslinking in absence of any catalyst. However, their shortcomings appear to be consisting in their high-curing temperatures with their products becoming brittle and non-transparency. These issues have been addressed partially in my present research. In my research, I carried out the following study dealing with benzoxazine-functionalization in polyurethanes (PUs). Firstly, two different chain-lengths of benzoxazinyl siloxane intermediates with amine-end groups were successfully synthesized in high yields from diamino-siloxanes as the starting materials. Secondly, the benzoxazinyl siloxane intermediates were formulated into PU formulations by reaction of benzoxazinyl siloxane intermediates with diisocyanate prepolymers. Then, the curing onset-temperatures and their effects to PUs’ thermal and physical properties were examined. Thirdly, TEOS of concentrations in 0, 2, 4, and 6 wt% were added to the above PUs formulations also to examine their combined effects to PUs after curing processes. In the synthesis of benzoxazinyl siloxane amine intermediates, two diamino-siloxanes with amine equivalent weights of 130 and 430 were used as the starting materials for condensation with amino-phenols and formaldehyde. It was found that dual function intermediates with isopropylidene diethylaniline-phenol, DP-H-DEA, have been found to react with formaldehyde/diamino-siloxanes selectively at phenol site of DP-H-DEA into benzoxaznyl siloxnes with two hindered amino-groups as their termination groups. In other words, the selective benzoxazinyl functionalization was achieved at phenol side of DP-H-DEA especially in the mixed solvent systems of toluene and ethanol. In both syntheses, high yields of amino-group terminated benzoxazinyl siloxanes in over 90%” were achieved. Benzoxazinyl siloxane intermediates were then added to isocyanate prepolymers which were prepared by reacting MDI, HDI, IPDI or TXMDI with a long-chained carbonate diol to form TPU elastomers. In all cases, curing of PUs through ring-opening reactions of benzoxazine rings in this study have universally enhanced mechanical properties of all PUs, but the onset temperatures of PUs varied in all cases which was determined by DSC analyses. It was found that PUs made from benzoxazinyl silaxane of eq.130 and diisocyanate prepolymers appear to be phase-mixed polymers, where symmetrical MDI and HDI based PU have higher onset temperature of 160.0℃ and 181.3℃respectively. In the same comparison, those of PUs prepared from IPDI and TMXDI were comparatively lower at 165.0℃and 138.6℃respectively. Interestingly, in case with PU made from benzoxaznyl silaxane of eq.430, the order of the on-setting temperatures were reversed possibly because of the degree of phase-segregated morphologies being observed in PUs particularly in HDI and MDI based polymers. As the result, the curing onset temperature of PU of MDI and TMXDI became comparatively lowered at 160.0℃ and 138.6℃respectively. Close proximity of benzoxazinyl groups seems to be giving the advantages in these cases. When TEOS was introduced into PU polymer chains, the double crosslinked PUs seemed to enhance mechanical properties and thermal stability in PUs from benzoxazinyl silaxane(eq=130). It is interesting to observe that onset temperatures to PUs were found to be less predictable, but in the case of 130DI with 4 wt.% of TEOS the onset temperature at 125℃was observed. This on-set temperature has been the lowest in record so far, and the root cause of it is unknown but seems worthy of further study.