Nantaya Yanumet

Thermal conductivity and mechanical properties of BN-filled epoxy composite: effects of filler content, mixing conditions and BN agglomerate size

Thermal conductivity and mechanical properties of boron nitride (BN)-filled epoxy composite as a function of filler content, mixing conditions, and BN agglomerate size were studied. Both thermal conductivity and mechanical properties of the composite were found to increase with increases in filler content, mixing speed, mixing time, and mixing temperature, but with decrease in BN agglomerate size. Sonication was found to be more effective in decreasing the BN agglomerate size than mechanical mixing. Viscosity of the BN—epoxy mixture was also studied under various mixing and sonicating conditions. A maximum thermal conductivity of 1.97 W/mK was obtained at 28 vol.% filler content and the mixing conditions of 80 rpm, 30 min, followed by sonication.

The effect of polymerization conditions on the density and Tg of bisphenol-A and hexafluoroisopropylidene-containing polybenzoxazines

The volumetric expansion of bisphenol-A and aniline-based benzoxazine (BA-a) has been studied by comparing the room temperature density of the cured BA-a under different polymerization conditions with the amorphous BA-a monomer. The glass transition temperatures (Tg) of BA-a at various degrees of polymerization have been investigated by differential scanning calorimetry (DSC). The degrees of conversion at different polymerization temperatures were compared with the respective glass transition temperatures. It was found that substantial development of Tg occurs at low degrees of conversion. A fluorinated polybenzoxazine was synthesized from the ring-opening polymerization of hexafluoroisopropylidene-containing benzoxazine monomer. The properties of the fluorine-containing polymer were compared to those of nonfluorinated polybenzoxazine. Fluorine incorporation had a profound effect on the glass transition temperature of polybenzoxazine. The thermal stability also improved upon fluorination.

A study on sisal fiber-reinforced benzoxazine/epoxy copolymer based on diamine-based benzoxazine

A diamine-based benzoxazine monomer has been synthesized via the Mannich condensation reaction of ethylenediamine, phenol and formaldehyde. The effect of solvent was investigated. The chemical structure and thermal properties of the diamine-based benzoxazine were characterized by FT-IR, NMR, DSC and TGA. Sisal fibers are incorporated in a mixture of benzoxazine and bisphenol-A type epoxy resins to form a unidirectionally reinforced composite. The effects of varying fiber contents and matrix composition on the mechanical properties of the composites are studied.

Surfactant Effects on Application of a Hydrophobic, Fluoropolymer Coating to Cotton by Admicellar Polymerization

Various methods have been used previously to impart hydrophobicity to cotton. In this study, thin co-polymer films of trifluoroethyl acrylate (TFEA) and octafluoro pentyl methacrylate (OFPM) were formed on cotton using individual fluorosurfactants and surfactant mixtures through the process of admicellar polymerization. Efficacy of 6 different fluorosurfactant systems and process conditions including surfactant type, concentration, adsorption/adsolubilization time, polymerization time, and monomer concentration have been investigated in order to obtain hydrophobic coatings on woven cotton fabric. Adsolubilization times as short as 2 h and polymerization times as short as 1 h yielded satisfactory performance. Characterization of the hydrophobic polymer films obtained included static contact angles, SEM imaging, elemental analysis and XPS analysis. Treated fabrics exhibited good water repellency for several surfactants and surfactant mixtures with initial supernatant monomer concentrations of 4 mM. Surfactant mixtures were able to outperform the separate individual species in admicellar polymerization.