Polyhedral Oligomeric Silsesquioxane Poly Urethane Research Articles

Silicone-enriched surface of immersed polyurethane-POSS antifouling coating

A series of waterborne polyurethane-polyhedral oligomeric silsesquioxane (WBPU-POSS) dispersions were synthesized. Different POSS contents were used to evaluate the effect of POSS content on silicone enrichment under both nonimmersed and immersed conditions. The impact of silicone enrichment under immersed conditions on antifouling properties was also evaluated. The structure of the WBPU-POSS coating was identified by FT-IR and 29Si-NMR. X-ray photoelectron spectroscopy (XPS) analysis confirmed a silicone-enriched surface with a certain composition of the WBPU-POSS coating under both nonimmersed and immersed conditions. The mechanical properties, hydrophilicity and hydrolytic degradation of the coating all varied with POSS content. The long-term antifouling performance of immersed coatings depends on surface silicone enrichment, which was found to be above 0.0021 mole POSS content in WBPU-POSS coatings.

Synthesis and properties of hydroxyl-terminated polybutadiene-based polyurethanes reinforced with polyhedral oligomeric silsesquioxanes.

Polyurethane/polyhedral oligomeric silsesquioxane (PU/POSS) hybrid composites are prepared by a one-step PU reaction using hydroxyl-terminated polybutadiene (HTPB) prepolymer, isophorone diisocyanate (IPDI) and either non-reactive or reactive POSS molecule. The effect of incorporation of functionalized POSS molecules covalently bonded or physically blended into PU matrix is investigated in terms of mechanical reinforcement and thermal stability of these resulting PU/POSS hybrid composites. PU/POSS hybrid composites prepared with reactive POSS molecules exhibit the mechanical reinforcement while maintaining low glass transition temperataure (T(g)), probably due to the fact that reactive POSS molecules chemically incorporated in PU are aggregated to crystallize, effectively working as a physical crosslinking in PU/POSS hybrid composites. This can be advantageous in that mechanical reinforcement of PU/POSS hybrid composites can be achived without sacrificing the low temperature properties of these composites. However, the contribution of POSS molecules incorporated covalently into PU matrix is virtually absent on the thermal decomposition temperature (T(d,max)) measured using TGA/DTG. Thermal degradation behavior of these hybrid composites in the early stage rather appears to depend preferably on characteristics of POSS molecules incorporated.

A Kinetic Analysis of the Thermo-Oxidative Degradation of PU/POSS nanohybrid Elastomers

A series of polyurethane/polyhedral oligomeric silsesquioxane (PU/POSS) nanohybrid elastomers, synthesized from diphenylmethane-4,4’-diisocyanate (MDI), po- lyoxytetramethylenediol (PTMG), 1,4-butanediol (BD) and 1-(1-(2,3-dihydroxypropoxy)butyl)-3,5,7,9,11,15-isobutyl- pentacyclo-[9.5.1.13,9.15,15.17,13]-octasiloxane(PHIPOSS), have been submitted to thermal stability investigations under an oxidizing atmosphere. The polymers were prepared with differing amounts of silsesquioxane units in their hard segments (0, 4 and 10 wt. %). It was observed that POSS influenced the thermal stability of PU/POSS nanohybrid systems both in the first and second stage of the degradation process. Ozawa–Flynn–Wall and Friedman Kinetic analyses revealed that the activation energy (Ea) and pre-exponential factor (A) increased in the first stage and decreased in the second stage of the thermal degradation as a result of PHIPOSS introduction into PU elastomers. The best approximation of the f(α) function was found for the reaction of nth order with autocatalysis/n-dimensional nucleation model in case of neat PU and reaction of nth order with autocatalysis/reaction nth order model for the nanohybrid elastomers