Interfacial Interactions in Polymer-Layered Silicate Nanocomposites

Abstract

Interactions between sodium montmorillonite (Na-MMT) and a variety of probes, some of which are intended to model components of a polyurethane system, have been studied. Particular attention was given to the effect of preadsorbed water on the adsorption behavior of the probes. Flow microcalorimetry (FMC), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and wide-angle X-ray scattering (WAXS) were used to monitor the adsorption process. The probe set included alcohols, amines, ethers, poly(propylene glycol) monobutyl ethers (PPG), and 4-ethylphenyl isocyanate (4-EPI). FMC revealed that the preadsorbed water molecules on undried Na-MMT hindered the adsorption of alcohol and ether probes, but had little effect on the adsorption of amines. Drying of Na-MMT to less than 0.3% w/w H2O led to an increase in heat of adsorption and generally greater retention of the probes. PPG showed strong interaction with Na-MMT due to multipoint adsorption. With dried Na-MMT, WAXS revealed that PPG of molecular weight (MW) 1000 was partly intercalated into the gallery while lower molecular weight PPG (MW 340) did not intercalate the Na-MMT. DRIFTS spectra of 4-EPI adsorbed on undried Na-MMT revealed urea linkages, indicating formation of N,N'-bis(4-ethylphenyl) urea. In contrast, with dried Na-MMT the 4-EPI formed a urethane linkage with hydroxyl groups present at the edges of the silicate platelets.

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

“…However, reaction products of similar refractive index to 4-EPI could also be present. The quantity of 4-EPI adsorbed onto Na-MMT and the adsorption energy (approximately 0.7 J/g of Na-MMT) were both relatively small, compared to that of other model probes [25]. However, no desorption of 4-EPI from non-dried Na-MMT was observed, indicating very strong interaction.…”

“…The data presented here are preliminary results of solely isocyanate-montmorillonite interactions, a complementary publication [25] will present studies of a wide range of model probes designed to mimic the components of reactive PU systems.…”

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.…”

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.…”