Effect of hydrophilic nanosilica fillers on thermal properties of thermoplastic polyurethane-silica nanocomposites

VEGA-BAUDRIT, J.,; VÁZQUEZ, P.; MARTÍN-MARTÍNEZ, J.M.,

Barcelona - España

Conferencia; Fourth International Conference on Polymer Modification, Degradation and Stabilization, MODEST 2006, Madrid (España) (2006).; 2006

MODEST

Thermoplastic polyurethane (TPU) adhesives containing pyrogenic nanosilicas with different specific surface and silanol group content were prepared and characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TGA), X-ray diffraction, plate-plate rheology, dynamical–mechanical and thermal analysis (DMTA), transmission electron microscopy (TEM), and strain-stress testing. Adhesive strength was obtained from T-peel tests of PVC/polyurethane adhesive joints.     It has been shown a relationship between the degree of polyurethane phase segregation and the silica specific surface area. The characterization of nanosilicas with different specific surface areas has shown that increasing the nanosilica specific surface area facilitates agglomerate formation due to interactions with hydrogen bonds between the silanol groups in silica. The increase in phase segregation values (DPS) is because the presence of silanol groups in silica encourages hydrogen bonding. As interurethane bonds rather than esterurethane bonds are favored, soft segment chains are freer to interact between them, so that silica favors phase segregation.   The pyrogenic silica dispersion in polyurethane improves mechanical and rheological properties. The comparison of T-peel strength values of the PVC/silica-containing polyurethane joints shows an increase in initial adhesion. In the initial phases after adhesive joints have been made, the adhesive does not crystallize in some joints. After some time, the presence of pyrogenic silica improves the cohesion properties of all polyurethane adhesives since most of the joints made with adhesives containing silica mainly display cohesion failures in PVC, regardless of the silica surface area.   Keywords: Nanosilicas, thermoplastic polyurethane adhesives, specific surface area, FTIR, phase segregation, TEM.