Studies On Polyurethane/Polysiloxane IPNs Damping Elastomers

In this paper, a series of polysiloxanes crosslinked by tetraethyl orthosilicate, polyurethanes crosslinked by trimethanol propane, and polyurethane/polysiloxane IPNs were synthesized at the existence of catalyst at room temperature. The mechanic properties and dynamic mechanical behaviors of polysiloxanes, polyurethanes and JPNs were investigated. The chemical structure and vulcanization kinetics of polysiloxanes, polyurethanes and polyurethane/polysiloxane IPN were studied by FTIR. The thermal stability, pyrolysis product, pyrolysis reaction kinetics and pyrolysis mechanism of polysiloxanes, polyurethanes and polyurethanelpolysioxane IPNs in nitrogen atmosphere were analyzed by TG-IR. Morphology in surface and interior of polysiloxanes, polyurethanes and IPNs were studied by SEM and AFM. The distribution of main elements in surface and interior of IPNs were also analyzed by XPS. Morphology and performance of polysiloxanes, polyurethanes affected by chemical structure, as well as morphology and performance of polyurethane/ polysiloxane IPNs influenced by polymer chemical structure and composition were discussed. The vulcanization reaction kinetics of polysiloxane, polyurethane and polyurethane /polysiloxane IPN catalyzed by di-n-butyltindilaurate at room temperature were determined by FTIR. Both vulcanization reactions of polysiloxane and polyurethane were second order reaction, reaction rate constants were 2.05>( 102g(mol?mini?and l.73x10抔(mol.min)1, and reaction activity energy were 76.59 kJ昺oV抋nd 22.7 kJ. moV1 respectively. In polyurethane/polysiloxane IPN, the vulcanization reaction of polyurethane was also second order reaction, but reaction rate constant was 6.25 X 103g(mol.min)? far below that of pure polyurethane result of the existence of polysiloxane, and its reaction activity energy was 30.7 ld?mol? Polydimethylsiloxane with 16% phenyl (lateral group) (PS2) had better damping behavior, and its surface structure was also analyzed with AFM. The compatibility difference between polydiphenylsiloxane segments and polydimethylsiloxane segments was the reason that leaded microphase separation and broadened the glass transition region of PS2. The mechanical performance and dynamic mechanical behavior of polyurethanes based on MDI were better than polyurethanes based on TDI, and polyurethane based on PEG and TDI had poor mechanical property, while had good damping behavior. This results demonstrated that mechanical and damping properties of polyurethane had relationship with structure and interaction between soft segments and hard segments in polyurethane, MDI had symmetrical structure and piled regularly could reinforce the strength of polyurethane, compatibility and strong interaction between soft and hard segments could increase the damping performance of polyurethane. The molecular weight of polyether and structure of hard segments had great iii influence on morphological structure of polyurethane elastomer. AFM analysis discovered that soft segments tended to distribute in polyurethane surface, but only very little hard segments stuck out of surface. Molecular weight of polyether had no effect on thermal stability of polyurethane, the main pyrolysis products of polyurethane in nitrogen atmosphere were carbon dioxide, isocyanate, tetrahydrofuran, alcohol and ester. The main pyrolysis product of polysiloxanes was hexamethyl- trisiloxane (D3) . The pyrolysis reaction order and ac...