Structure Development and Interfacial Interactions in Flexible Polyurethane Foam-Layered Silicate Nanocomposites

Abstract

Unmodified Na-montmorillonite (MMT) was swollen in a polyol/water mixture using an ultrasound technique. Polyurethane (PU) foam nanocomposites were formed via reaction of these polyol/water/Na-MMT mixtures with toluene diisocyanate (TDI). Forced-adiabatic attenuated total reflectance FTIR spectroscopy was used to determine the kinetics of both the PU copolymerisation and of the microphase separation between poly(ether-urethane) soft segments and polyurea hard segments. Consumption of TDI during the initial stages of the copolymerisation was accelerated significantly by the addition of 10 wt% Na-MMT. The initial rate of formation of urea groups also increased significantly upon addition of Na-MMT, but at reaction times >100 s a significant retardation occurred in the development of hydrogen bonding within the urea groups of the hard-segment phase that was recovered only after 1000 s. The reasons for this extensive disruption in structure development were investigated using flow microcalorimetry (FMC), diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS), and wide angle X-ray scattering (WAXS) to monitor the adsorption process and any chemical reaction between hydrated Na-MMT and a model monoisocyanate; 4-ethylphenyl isocyanate (4-EPI). DRIFTS spectra of 4-EPI adsorbed on Na-MMT revealed urea groups, indicating formation of N,N -bis(4-ethylphenyl) urea. FMC indicated that a significant quantity of this urea formed at the surface and then desorbed. In addition, DRIFTS spectra indicated that the 4-EPI reacted with hydroxyl groups present at the edges of the silicate platelets to form urethane linkages. Thus, in a PU-foam reaction mixture, the water will tend to associate with the Na-MMT, either within the galleries or on the surfaces of silicate lamellae. Upon reaction with isocyanate, the presence of the Na-MMT both promotes the formation of urea and generates urethane linkages between silicate lamellae and the polyurethane.

Flow Micro‐Calorimetry and FTIR Spectroscopy Study of Interfacial Interactions in Uncoated and Coated Calcium Carbonate Filled Polyurethane Adhesives

“…The butan‐2‐one and heptane were HPLC grade and dried over 3A molecular sieves. The adsorption and desorption of dimethyl adipate (99%, Aldrich, UK), from both heptane and butan‐2‐one, on to the calcium carbonate samples was investigated at 20 °C according to established FMC methods . After completion of the FMC experiments, the fillers were oven dried at 70 °C for 20 hours, and were examined using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS).…”

“…They concluded that the conformation of the macromolecules on silica depends on the silica surface area which was correlated with surface‐polymer interactions. During the last five years, FMC has been used in studies of: bio‐diesel fuel manufacture, waste control, organic pollutants and catalysts, within the pharmaceutical, chemical and polymer industries . However, the use of FMC in studies of interfacial interactions in thermoplastic polyurethane (TPU) composite adhesives has not been reported in the literature.…”

Shape memory properties of electrically conductive multi-walled carbon nanotube-filled polyurethane/modified polystyrene blends

“…Desired properties can be induced in polymeric chain via chain extenders. 2,3 Soft segments give extensibility, while hard segments can promote physical cross linking. Relative hard and soft segment content is responsible for morphological variation.…”

Flow micro-calorimetry and diffuse reflectance Fourier transform infrared spectroscopy studies in filled polyurethane adhesives by using dimethyl adipate as a model compound

“…Within the last five years FMC has been applied to studies of bio-diesel fuel manufacture, waste control, organic pollutants and catalysts, within the pharmaceutical, biochemical, chemical and polymer industries [21][22][23][24][25]. However, the use of FMC in studies of interfacial interactions in nanofilled thermoplastic polyurethane adhesive has not yet been reported in the literature.…”

“…,[13][14][15][16][17]19,20,24,25]. After completion of the FMC experiments, the nanofillers were oven dried at 70 ºC for 20 hours, and then examined using diffuse reflectance Fourier transform infrared spectroscopy (DRFTIRS).…”