Thermal degradation of POSS-containing nanohybrid linear polyurethanes based on 1,6-hexamethylene diisocyanate

Synthesized from 1,6-hexamethylene diisocyanate (HDI), 1,4-butanediol (BDO), poly(tetramethylene)glycol (PTMG), and propanediolisobutyl-POSS (PHI-POSS) nanohybrid polyurethanes (PU) were examined by TG/FTIR/MS coupled method to determine the mechanism of thermal improvement caused by POSS addition. The measurements were made in both; inert and oxidizing atmosphere for composites containing 0, 6, and 10 % of PHI-POSS. Depending on the concentration of additive, and the surrounding atmosphere we noticed from 5 to 15 degrees C improvement on different stages of degradation. Among the released gases, mostly tetrahydrofuran (THF), butanediol (BDO), and HDI were recorded, as well as various PTMG-derived ethers and alcohols formed during the depolymerization of segments present in the amorphous phase, as well as amines and amides as decomposition products of segments in the crystalline phase. Interestingly, the release of formates and formaldehyde before the first stage of degradation was observed in the oxidizing atmosphere. The effect of POSS addition causes: (i) reduction of the number of hard domains intensifies the first stage of degradation, but simultaneously increases the onset and the temperature of the maximum rate of decomposition at different stages through preventing some rearrangements leading to breaking of chain, and (ii) formation under elevated temperature conditions of silica-rich char residues that act as a barrier for gas and mass transport.