Synthesis, Characterization And Properties Of Carborane-Containing Polyurethanes

Polyurethanes (PURs) actually can be designed in various forms of products with excellent properties such as peel strength, ultra-low temperature, oil and abrasion resistance and by tuning the characteristics of the hard and soft segments, different properties can be realized from PURs. As a result, PURs find their use in variety of applications including foams, elastomers, coatings, adhesives and fibers. Polyurethanes, however, are well known to exhibit poor heat resistance that largely limits their use as engineering materials. Attempts to improve the thermal stability of polyurethane have been made by introduction of heat resistant groups into the main chain of polyurethanes. Carboranes have been one of the most extensively investigated of all known new chemicals during last 50 years, especially dicarba-closo-dodecaboranes (carboranes for short). Carboranes have been regarded as excellent groups to construct polymers with remarkable thermal stability due to their stable cage-like structures and thermal isomerization shift behavior.In this study, carborane was patronized as a raw material. A series of caborane derivatives were synthesized via anion reaction to prepared carborane-containing polyesters, at the same time, carborane-containing polyarylester were synthesized via sulfonylation method. Comparing and selecting the carborane-containing polyarylester with the best thermal property, the chosen polyarylester was to react with polyester and diisocyanate for the preparation of carborane-containing hydroxy-terminated prepolymer (PUA2). While carborane-containing isocyanate-terminated prepolymer (PUB2) was prepared from diisocyanate, polyol and 1,2-carborane bisphenol. Afterwards, carborane-containing polyurethane (PUR2) was obtained by mixing PUA2 and PUB2 at a certain ratio of weight. The prepared carborane-containing polyurethane was characterized by conventional methods to guarantee the effect of modification.1.1,2-,1,7-bi-hydroxymethyl-carborane were synthesized by n-BuLi, carborane and paraformaldehyde via anion reaction. 1,7-bis-carboxyl-carborane was synthesized with 1,7-carborane by the way of carbon dioxide.1,7-bis-acyl chloride-carborane was prepared with 1,7-bis-carboxyl-carborane via acylating chlorination of PC15 and POC13 system. A series of caborane derivatives were confirmed by FTIR, ’H-NMR, and the results demonstrated carborane derivatives were successfully derivatives.2. Carborane-containing polyesters were synthesized by the derivatives obtained, and carborane-containing polyarylesters were synthesized by 1,7-carboxyphenyl-carborane and different kinds of biphenolsl via sulfonylation method. According to the results of GPC and TGA, the carborane-containing polyarylester synthesized by 1,7-carboxyphenyl-carborane and 4,4-oxydiphenol was chosen as one of raw materials to prepare carborane-containing hydroxy-terminated prepolymer.3. Carborane-containing hydroxy-terminated prepolymer was successfully prepared from poly-1,4-butylene adipate (PBA), carborane-containing polyarylester and 4,4-diphenylmethane diisocyanate (MDI) at the molar ratio of OH/NCO=1.5. And confirmed the reaction conditions:solvent acetone, time 1.5h, temperature 80℃. Furthermore, the more carborane-containing polyarylester, the higher molecular weight, but polyarylester had a small part to play in improving the thermal stability of PUAs.4,4-diphenylmethane diisocyanate, trimethylolpropane and 1,2-carborane bisphenol were employed as raw materials of carborane-containing isocyanate-terminated prepolymer. And confirmed the reaction conditions are solvent acetic ether, nMDI/nTMP=3.1～3.2, reaction temperature 65℃, and holding temperature 75℃.4. At room temperature, carborane-containing polyurethane (PUR2) was obtained by mixing carborane-containing hydroxy-terminated prepolymer and carborane-containing isocyanate-terminated prepolymer at a certain weight ratio. Mechanical properties, thermal stability, chemical resistance were improved a lot. Tensile strength had 15MPa higher than that of carborane-free polyurethane (PUR1), break at elongation had 10 times higher than that of PUR 1, chart yield increased from 0% to 60%, and decomposition temperature had 100℃ higher than that of PUR1. It indicated that when the dosage of carborane bisphenol was 10wt%, m(PUA2:PUB2)=100:30, carborane-containing polyurethane possesses better performance.