No abstract

No abstract

No abstract

No abstract

The organic—inorganic hybrid involving hydroxyl-terminated polydimethylsiloxane (HTPDMS)-modified epoxy, filled with organo-modified flurohectorite clay of various percentages (1—5 wt%) were prepared via in situ polymerization using γ-amino propyltriethoxysilane as cross-linking agent in the presence of dibutyltindilaurate catalyst. The reactions involved during the curing process between epoxy and siloxane were confirmed by FT-IR. The results of differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperatures of the clay-filled hybrid epoxy systems are lower than that of neat epoxy. The data obtained from the thermal studies indicated that improved thermal stability was due to the incorporation of nanoclay into siloxane-modified epoxy hybrid systems. The morphologies of the siloxane containing epoxy—clay hybrid systems show heterogeneous character, due to the partial incompatibility of HTPDMS. Scanning electron microscopy indicates the phase separation, induced by the polymerization, occurs in the HTPDMS-modified epoxy hybrids to yield spherical particles of siloxane-rich phase, which are uniformly dispersed in the continuous epoxy matrix. Microstructures of nanocomposites were ascertained from X-ray diffraction (XRD) and transmission electron microscopy. The formation of exfoliated structure of organoclay was confirmed from the XRD pattern and shows interlayer spacing between 3.42 and 8.50 Å. Hybrid epoxy nanocomposites containing higher percentage composition of organo-modified flurohectorite clay contents (up to 5 wt%) display more pronounced improvements in thermal properties and moisture resistance than corresponding unmodified epoxy matrices.

Organic-inorganic hybrids involving organo-modified montmorillonite (OMMT) clay and tetraglycidyl diamino diphenyl methane epoxy (TGDDM) were prepared via in situ polymerization by the homogeneous dispersion of various percentages (1-5% w/w) of clay in epoxy matrix resin. The resulting homogeneous epoxy-clay hybrids were modified with 10 wt% of hydroxyl terminated polydiemthyl siloxane (HTPDMS) using γ-aminopropyltriethoxysilane (γ-APS) as coupling agent in the presence of tin catalyst. The siliconized epoxy-clay prepolymers were further modified separately with 15 wt% of bismaleimide (BMI) monomers and cured with diaminodiphenylmethane. The reactions involved during the curing process between epoxy resin, siloxane and BMI were confirmed by using FTIR and DSC curing analysis. The differential scanning calorimetry (DSC) show that the significant increase in glass transition temperatures in the clay filled hybrid epoxy systems than that of neat epoxy resin. The data obtained from thermal studies indicates that the appreciable improvement in hybrid systems was due to the incorporation of MMT clay, BMI and siloxane into epoxy systems. Scanning electron microscopy (SEM) of the hybrid systems show that the homogenous morphology. X-ray diffraction analysis of the clay hybrid systems shows that the amorphous diffraction patterns and the peaks are broadened and nearly disappeared after 24 h swelling, suggesting the formation of exfoliated structure.

No abstract

Free-radical copolymerization of 4-nitrophenyl acrylate (NPA) with n-butyl methacrylate (BMA) was carried out using benzoyl peroxide as an initiator. Seven different mole ratios of NPA and BMA were chosen for this study. The copolymers were characterized by IR, 1 H-NMR, and 13 C-NMR spectral studies. The molecular weights of the copolymers were determined by gel permeation chromatography and the weight-average (M w ) and the numberaverage (M n ) molecular weights of these systems lie in the range of 4.3-5.3 ϫ 10 4 and 2.6 -3.0 ϫ 10 4 , respectively. The reactivity ratios of the monomers in the copolymer were evaluated by Fineman-Ross, Kelen-Tudos, and extended Kelen-Tudos methods. The product of r 1 , r 2 lies in the range of 0.734 -0.800, which suggests a random arrangement of monomers in the copolymer chain. Thermal decomposition of the polymers occurred in two stages in the temperature range of 165-505°C and the glass transition temperature (T g ) of one of the systems was 97.2°C.