Amar Nath Banerjee

Photopolymerization of methyl methacrylate with the use of bromine as photoinitiator

Low concentrations of bromine (0.008–0.06M) were used to initiate photopolymerization of MMA in bulk and in diluted (near bulk) systems, the diluents or solvents used being benzene, toluene, dioxane, tetrahydrofuran, carbon tetrachloride, chloroform, methylene chloride, and methanol. Polymerization in bulk follows usual free-radical kinetics. Inert solvents (benzene, toluene) as well as the other solvents used enhance the rate of polymerization MMA even when used in the range of catalytic concentrations (0.04–0.4M). An initiation mechanism involving solvent molecules appears to be predominant in diluted systems.

Tensile behaviour of unidirectional polyethylene-glass fibres/PMMA hybrid composite laminates

Abstract Unidirectional hybrid composite laminates based on high-performance polyethylene fibres and glass fibres were prepared with partially polymerized methyl methacrylate at room temperature, followed by heating at 55°C (well below the softening point of polyethylene fibres) for a stipulated time. It was observed that the tensile strength, modulus of elasticity and hybrid effect of the laminates depend on the relative proportion of both the fibres.

Stress relaxation behaviour of unidirectional polyethylene-glass fibres PMMA composite laminates

Abstract Unidirectional composite laminates based on glass fibres (GF) and high performance polyethylene fibres (PEF) and their hybrids were prepared with partially polymerized methyl methacrylate at room temperature, followed by heating at 55°C (well below the softening point of PEF) for 2 h. The stress relaxation behaviour of the composites were determined and analysed. It was found that at all strain levels, the rate of stress relaxation decreased by incorporation of GF in GF-reinforced composite laminates (GFRC) but the reversed behaviour was found in the case of PEF-reinforced composite laminate (PEFRC). An interesting observation of the study was that the rate of stress relaxation decreased linearly in two steps in the case of PEFRC, whereas in the case of GFRC, it decreased in one step. The rate of stress relaxation was increased with the increase of relative proportion of PEF in the hybrid composites and at a higher proportion of PEF, it decreased in two steps like PEFRC.

Graft copolymerization of methyl methacrylate on silk fiber using mohr's salt—potassium persulfate as redox initiator under visible light in a limited aqueous medium

Graft copolymerization of methylmethacrylate onto mulberry silk fibers was studied under photoactive conditions with visible light using the Mohrs salt-potassium persulfate as the redox initiator in a limited aqueous medium. Polymerization in the presence of light at 40 ± 1°C was found to be more pronounced than that in the dark at 40 ± 1°C. Percent grafting, percent total conversion, and grafting efficiency under different sets of conditions were studied, and the mechanisms of polymerization and graft copolymer formation were discussed. Characterization of the grafted fibers was done by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and thermogravimetry.

Photograft copolymerization of methyl methacrylate on silk fiber using titanium(III) chloride–potassium persulphate redox initiator in a limited aqueous system. I

Graft copolymerization of methyl methacrylate (MMA) onto mulberry silk fibers has been investigated in a limited aqueous system employing titanium(III) chloride-K 2 S 2 O 8 as the redox initiator under a photoactive condition with visible light. Polymerization in the presence of light at 32 ± 1°C has been found to be more pronounced than in the dark under identical conditions. The percentage of grafting, the percentage of total conversion, and the percentage of grafting efficiency have been studied by varying the reaction time, concentration of monomer, initiator concentration, solvent composition, and pH of the medium. A high percentage of grafting (∼ 93%), high grafting efficiency (∼ 97%), and the percentage of total conversion (∼ 25%) have been obtained with little homopolymer formation. Characterization of the grafted fibers has been investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. Finally, the reaction mechanism has been discussed by considering hydrogen bonding.

Stress-relaxation behavior of Unidirectional polyethylene-carbon fibers : PMMA hybrid composite laminates

Unidirectional composite laminates based on carbon fibers (CF) and high-performance polyethylene fibers (PEF) and their hybrids were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF, 147°C) for 2 h. The stress-relaxation behavior of the composites were determined and analyzed. It was found that at all strain levels the rate of stress relaxation decreased by the loading of CF in CF-reinforced composite laminates (CFRC); however, the reverse behavior was found in the case of PEF-reinforced composite laminate (PEFRC). An interesting observation of the study was that the rate of stress relaxation decreased linearly in two steps in the case of PEFRC, whereas in the case of CFRC, it decreased in a single step. In the case of hybrid composites, the stress relaxation decreases in two steps as in PEFRC.

Impact behavior of unidirectional polyethylene–glass fibers: PMMA hybrid composite laminates

Unidirectional (UD) hybrid laminates based on glass fibers (GF) and high performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature followed by heating at 55°C (well below the softening point of PEF) for 2 h. Izod impact strength of the composites was then measured. An interesting observation of the study was the change in impact strength that was largely dependent on the position of GF and PEF ply/plies present within the hybrid laminates. When the ply/plies of PEF were at the impacted surface, the impact strength showed a higher value than that of the case when GF ply/plies were at the impacted surface of the hybrid laminates.

Polymerization of methyl methacrylate using isatin and benzoyl peroxide combination as photoinitiator

Photopolymerization of methyl methacrylate in visible light was studied at 40° under N2 using isatin-(benzoyl peroxide) combination as the initiator. The photopolymerization by a free radical mechanism and radicals are generated by an initial complexation between the initiator components and the monomer. Kinetic data indicate a low order dependence of Rp on initiator concentration (initiator exponent <0.5). Initiator-dependent chain termination was significant, with bimolecular termination.

Polymerization of Methyl Methacrylate Using Acridone-Bromine Combination as the Photoinitiator

Abstract The photopolymerization of methyl methacrylate (MMA) in visible light was studied at 40°C using the acridone-bromine (acridone-Br2) combination as the photoinitiator. The polymerization was found to proceed via a free radical mechanism, and the radical generation process was considered to follow an initial complexation reaction between monomer and each initiator component (acridone and Br2), followed by further interaction between these two initiator-monomer complexes. Kinetic data indicated a lower-order dependence of R on initiator concentrations (initiator exponent < 0.5). Initiator-dependent chain termination was signifi-cant along with the usual bimolecular mode of chain termination. The monomer exponent varied from about 1.00 to 2.00, depending on the nature of solvents used. The nonidealities in this system were also analyzed.

Tensile behavior of unidirectional polyethylene fibers PMMA and glass fibers—PMMA composite laminates

Unidirectional (UD) composite laminates based on glass fibers (GF) and high-performance polythylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF) for 2 h. The tensile strength, modulus of elasticity, fiber efficiency and strength efficiency of both the composite laminates, loaded parallel to the fibers, at the same volume fraction range, were investigated. All the properties were compared between the two composite laminates. It was observed that the measured tensile strength and modulus of elasticity deviated from the values calculated from the Rule of Mixture (ROM). The deviation was minimal at the lower volume fraction of fibers, and increased with the fiber volume. An interesting feature that was observed was that the efficiencies of PEF-reinforced composite was higher than that of the GF-reinforced composite at the same volume fraction of the fibers.