Sritama Kar

Effect of aluminum silicate on the impact and adhesive properties of toughened epoxy resins

Carboxyl randomized poly(2-ethyl hexyl acrylate) (CRPEHA) and epoxy randomized poly(2-ethylhexyl acrylate) (ERPEHA) have been used to toughen aluminum silicate filled epoxy resin cured with 4,4′-diaminodiphenyl methane. CRPEHA (A-1) and ERPEHA (B-1) were synthesized by solution polymerization technique in the form of liquid rubbers. The toughened epoxy networks were evaluated for their impact and adhesive properties. The epoxy/liquid rubber compositions were varied to study the effect of toughener concentration on the adhesive and impact properties for both filled and unfilled systems. Improved properties were obtained for epoxy resins toughened with (1 : 1) mixture of CRPEHA and ERPEHA. Lap shear strength of filled epoxy resins was higher than that of unfilled ones but the reverse was the case for impact strength. Analysis of adhesive failure surfaces by scanning electron microscopy (SEM) indicated the presence of a two-phase microstructure.

Amine‐randomised poly(2‐ethylhexyl acrylate) as impact and adhesive modifier for epoxy resin

The adhesive and impact properties of cured epoxy resins, modified with amine‐randomised poly(2‐ethylhexyl acrylate) (ARPEHA) liquid rubber, as a function of the concentration of the liquid rubber, have been investigated. ARPEHA was synthesised by the reaction of the carboxyl‐randomised poly(2‐ethylhexyl acrylate) (CRPEHA) liquid rubber with 4,4′‐diaminodiphenyl sulphone. CRPEHA was synthesised by solution co‐polymerisation of 2‐ethylhexyl acrylate and acrylic acid. ARPEHA modified cured epoxy resins were formed by curing with an ambient temperature‐curing agent, triethylene tetramine. The modified epoxy resins were evaluated with respect to their adhesive and impact properties. The optimum properties were obtained at around 12.5 phr (parts per hundred parts of epoxy resin) of modifier. Analysis of the fracture surface using scanning electron microscopy indicated the presence of two‐phase microstructures.

Synthetic Zinc Oxide Nanoparticles as Curing Agent for Polychloroprene

Zinc oxide nanoparticles were synthesised by a homogeneous precipitation and calcination method. Their dimensions were in the range of 30 – 50 nm. Their performance as curing agent for polychloroprene rubber was compared to that of rubber grade zinc oxide. The tensile strength was observed to increase by 30% and elongation at break by 10%, with the tensile modulus almost unaltered. The crosslink density was increased by 15% and the dynamic modulus at 25 °C was also 10% higher for the nanocomposites. The results from FTIR spectrometry and volume fraction of rubber in the swollen gel supported the fact that there was an increased interaction between the rubber and ZnO for the nanocomposites.

Toughened epoxy modified with phenol‐nonyl phenol based polymer

Purpose – To evaluate the efficiency of modifying epoxy resin using phenol-nonyl phenol based polymer (PNPF) for toughness improvement and optimise the results of such a modification. Design/methodology/approach – For effective toughening, various compositions were made by incorporating PNPF at different concentrations. The impact and adhesive strengths of the unmodified and modified epoxy networks were characterised. Findings – The modification of epoxy resin using PNPF showed significant enhancement of impact and adhesive strengths over the unmodified one. The modification caused the formation of a chemical linkage between PNPF and resin which led not only to a phase separation, but also to formation of intrinsically strong chemical bonds across the PNPF phase/resin matrix interphase, which was the main cause of the improved impact and adhesive strengths. The optimum results were obtained at 10 phr (parts per 100 parts of epoxy resin) of modifier. Research limitations/implications – The modifier, PNPF, used in the present context was synthesised from phenol, nonyl phenol and formalin using oxalic acid as catalyst. Practical implications – The developed method provided a simple and practical solution to improving the toughness of a cured epoxy. Originality/value – The method for enhancing toughness of a cured epoxy was novel and could find numerous applications in the surface coating and adhesive.

Amine terminated poly(ethylene glycol) benzoate modified epoxy networks

Purpose – To evaluate the efficiency of modifying epoxy resin using amine terminated poly(ethylene glycol) benzoate (ATPEGB) for improved toughness and to optimise the results of such a modification.Design/methodology/approach – For effective toughening, various compositions were made by incorporating different concentrations of ATPEGB. The impact and adhesive strengths of the unmodified and modified epoxy networks were characterised.Findings – The modification of epoxy resin using ATPEGB showed significant enhancement of impact and adhesive strengths over the unmodified one. The modification caused a chemical linkage between ATPEGB and resin which led not only to a phase separation but also to ensuring the intrinsically strong chemical bonds across the ATPEGB phase/resin matrix interface, which was the main cause to the improved impact and adhesive strengths. The optimum results were obtained at 12.5 phr (parts per hundred parts of epoxy resin) of modifier.Research limitations/implications – The modifier...

Chain-extended epoxy-functionalised poly-(2-ethylhexylacrylate) as impact and adhesive modifier for epoxy resin

Abstract Epoxy resin is widely used for coatings, adhesives, casting, electrical insulation materials and other applications. However, unsolved problems still remain in its applications. The main problem is low toughness: cured epoxy resin is rather brittle with poor resistance to the propagation of cracks, derived from the internal stress generated by shrinkage in the cooling process from cure temperature to room temperature. The objective of this study was to improve the flexibility of diglycidyl ether of bisphenol-A based epoxy resin by using a liquid rubber. For this purpose, epoxy functionalised poly-(2-ethylhexylacrylate) (EFPEHA) and chain extended poly-(2-ethylhexylacrylate) (CEEFPEHA) based on the EFPEHA and Tris-2,4,6-(N,N-dimethyl amino methyl) phenol have been synthesised. The products were characterised by IR spectroscopy, non-aqueous titration, viscosity measurement and solubility characteristics. The developed CEEFPEHA was incorporated as a modifier into the epoxy matrix and its effect was studied by impact and adhesive strength measurements. Fractographic examinations under scanning electron microscope indicated the formation of rubber domains in the epoxy matrix.