Composites with good toughness properties were prepared from chemically modified soy epoxy resin and glass fiber without additional petroleum based toughening agent. Chlorinated soy epoxy (CSE) resin was prepared from soybean oil. The CSE was characterised by spectral, and titration method. The prepared CSE was blended with commercial epoxy resin in different ratios and cured at 858C for 3 h, and post cured at 2258C for 2 h using m-phenylene diamine (MPDA) as curing agent. The cure temperatures of epoxy/CSE/ MPDA with different compositions were found to be in the range of (151.2-187.58C). The composite laminates were fabricated using epoxy /CSE/MPDA-glass fiber at different compositions. The mechanical properties such as tensile strength (248-299 MPa), tensile modulus (2.4-3.4 GPa), flexural strength (346-379 MPa), flexural modulus (6.3-7.8 GPa) and impact strength (29.7-34.2) were determined. The impact strength increased with the increase in the CSE content. The interlaminor fracture toughness (G IC ) values also increased from 0.6953 KJ/m 2 for neat epoxy resin to 0.9514 KJ/m 2 for 15%CSE epoxy-modified system. Thermogravimetric studies reveal that the thermal stability of the neat epoxy resin was decreased by incorporation of CSE.

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Anthraquinone dicyanate was prepared by treating CNBr with 1,4 dihydroxy anthraquinone in the presence of triethylamine at -5 to 5°C. The dicyanate was characterized by Fourier transform infrared (FT-IR) spectroscopy. The prepared dicyanate was blended with commercial epoxy resin in different ratios and cured at 120 °C for 1 h, 180 °C for 1 h and post-cured at 220 °C for 1h using diamino diphenyl methane as the curing agent. Castings of neat resin and blends were prepared and characterized by FTIR analysis. The composite laminates were also fabricated from the same composition. The mechanical properties such as tensile strength, flexural strength and fracture toughness were measured as per ASTM D 3039, D 790 and D 5528, respectively. The tensile strength increased with increasing cyanate content (3, 6, and 9%) from 52.1 to 80.1 MPa. The values of fracture toughness also increased from 0.7671 kJ m-2 for the neat epoxy resin to 0.9168 kJ m-2 for the 9% cyanate ester epoxy-modified system. The thermal properties were also studied. The 10% weight loss temperature of pure epoxy was 358 °C and it increased to 381 °C with incorporation of cyanate ester resin. The incorporation of cyanate ester up to a 9% loading level did not affect the glass transition temperature to a very great extent.

Bis(4-cyanato 3,5-dimethylphenyl) naphthylmethane was prepared by treating CNBr with bis(4-hydroxy 3,5dimethylphenyl) naphthylmethane in the presence of triethylamine at À5 to 58C. The dicyanate was characterized by FT-IR and NMR techniques. The prepared dicyanate was blended with commercial epoxy resin in different ratios and cured at 1208C for 1 hr, 1808C for 1 hr, and post cured at 2208C for 1 hr using diamino diphenyl methane (DDM) as curing agent. Castings of neat resin and blends were prepared and characterized by FT-IR technique. The morphology of the blends was evaluated by SEM analysis. The composite laminates were also fabricated from the same composition using glass fiber. The mechanical properties like tensile strength, flexural strength, and fracture toughness were measured as per ASTMD 3039, D 790, and D 5528, respectively. The tensile strength increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m 2 for neat epoxy resin to 0.8615 kJ/m 2 for 9% cyanate ester epoxy modified system. The thermal properties were also studied. The 10% weight loss temperature of pure epoxy is 3588C and it increased to 3988C with incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% loading level does not affect the T g to a very great extent. POLYM. COMPOS., 29:709-716, Synthesis of Monomer PrecursorSynthesis of Bis(4-hydroxy 3,5-dimethylphenyl) Naphthyl Methane. Into a three-necked flask equipped with a condenser, a Dean-stark water separator and a nitrogen Correspondence to: M. Sarojadevi;

A novel siloxane containing dicyanate was synthesized from the condensation reaction of dichloro methyl phenylsilane with 1, 5 dihydroxynaphthalene in a 1 : 2 ratio using triethylamine as catalyst. A new dicyanate was prepared by treating CNBr with synthesized silane containing diol in the presence of triethyl amine as catalyst at —10 to 5 °C. The dicyanate was characterized by Fourier transform infrared spectroscopy (FTIR) and NMR. The curing reaction of the prepared dicyanate and epoxy blends was studied using differential scanning calorimetry. The prepared dicyanate was blended with commercial epoxy resin in different ratios (3, 6 and 9%) and cured at 120 °C for 1 h, 150 °C for 1 h, 220 °C for 1 h using diamino diphenyl methane as the curing agent. The composite laminates with glass fiber were also fabricated using the same composition. Cured neat resin and epoxy blends were characterized by FTIR. The mechanical properties such as tensile strength, flexural strength, and fracture toughness of the composites were measured by adopting ASTM D 3039, D 790, and D 5528, respectively. The tensile strength increased with increasing cyanate content (3, 6, and 9%) from 55 to 62 MPa. Dynamic mechanical analysis shows that with increasing cyanate content in the composite the storage modulus moderately increased in comparison with the neat epoxy composite. There was not much difference in the values of storage modulus at 50 °C and that at 100 °C, showing that the synthesized cyanate has better thermo mechanical characteristics. The flame retardant property of epoxy—cyanate blend was observed to be 50, 36 and 25 s for 3, 6 and 9%, respectively, which showed that the silane-containing cyanate polymer had better flame retardant properties.

A series of azo functionalized diols were synthesized through diazotization which involves the reaction of amine with phenol and 2,6-dimethyl phenol. Four different amines have been used to prepare five bisphenols. These bisphenols were converted to their corresponding cyanate esters by treatment with cyanogen bromide (BrCN) in the presence of triethylamine (Et 3 N). The chemical structures of the prepared compounds were characterized with Fourier Transform Infrared, 1 H-NMR, 13 C-NMR spectroscopy, and elemental analysis. Dynamic curing behavior was investigated using differential scanning calorimetry. The maximum curing temperature of these cyanate esters are in the range of (186-208 C). T g values of the polycyanurate networks are in the range of 245-276 C. The thermal properties of cured cyanate ester were studied at a heating rate of 10 C min 21 in N 2 atmosphere. The polymers showed excellent thermal stability (T 10 was found to be in the range 405-438 C) and the percentage of char yield at 800 C were found to be 30-49. The flame retardancy of the cyanate ester resins have been studied using limited oxygen index value which is in the range of 29.5-37.1 at 800 C. POLYM. ENG. SCI., 55:47-53, 2015.

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