Synthesis and characterization of linseed vinyl ester fatty amide-modified epoxy layered silicate nanocomposites

Bio-based epoxy/clay nanocomposites were prepared by swelling organoclay in an epoxy (DGEBA)/linseed vinyl ester fatty amide (LVEFA), followed by curing with an aromatic hardener, 4,4′-diaminodiphenylmethane (DDM). The X-ray diffraction showed the existence of intercalated clay in the polymer matrix. Differential scanning calorimetry (DSC) indicated a gradual increase in the glass transition temperature as the organoclay loading increased. The tensile strength, flexural strength and impact strength of 20 wt.% linseed vinyl ester-modified epoxy composites significantly increased by 23.65, 13.19 and 40.7%, respectively, with increasing organoclay concentration. The tensile modulus and flexural moduli were enhanced by 14 and 9.28%, respectively.

Application of Ketone-Based Resins as Anticorrosive Coating

Effect of some newly synthesized modified ketonic resins on corrosion inhibition of stainless steel (SS) and copper (Cu) was investigated in acidic medium. Carboxyl, hydroxyl, and carbonyl functionalized resins have been coated on metal electrode as a thin film by dipping method. Corrosion characteristics of coating on SS (304 L) and Cu were investigated by polarization, open-circuit, and impedance measurement. These measurements performed at different time and the stability of polymeric coating were tested with time in acidic medium. The resin coating was able to protect both the SS and copper.

Synthesis and Characterization of 3,3′-bis (3-maleimidophenyl) Phenyl Phosphine Oxide (BMI)/1, 3-Cyanatobenzene Epoxy Inter-crosslinked Matrices for Engineering Applications

Cyanate ester (CE) -3,3′-bis (3-maleimidophenyl) phenyl phosphine oxide (BMI)-modified epoxy matrices were made by using epoxy resin (DGEBA) and 1,3-dicyantobenzene and diaminodiphenyl methane as a curing agent. The properties of BMI-CE epoxy matrices were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis, scanning electron microscopy, water absorption behavior and heat deflection temperature. The matrices were also characterized for their mechanical properties such as tensile strength, flexural strength and unnotched Izod impact strength by ASTM methods. The mechanical and tensile properties were improved by increasing the percentage of the CE in the epoxy resin. DSC thermograms of 1,3-dicyantobenzene as well as BMI-modified epoxy resin showed an unimodal reaction exothermicity.

Preparation and Properties of Polybenzoxazinepoly(dimethylsiloxane-co-diphenylsiloxane) Hybrids as High Performance Polymers

Polybenzoxazine, poly(B-a), was hybridized with polysiloxanes by synchronizing two reactions; ring-opening polymerization of benzoxazine (B-a) and the sol—gel process of diethoxysilanes. As diethoxysilanes, mixtures of diethoxydimethylsilane and diethoxydiphenylsilane in various ratios were used to prepare polysiloxane copolymers, poly(dimethylsiloxane- co-diphenylsiloxane), P(DMS/DPS). The effect of diphenylsiloxane (DPS) content of polysiloxane copolymer on the optical, mechanical, and thermal properties of the hybrids was studied. The progress of the sol—gel process was confirmed by IR, 1H-NMR and size exclusion chromatography. Opaque poly(B-a)-P(DMS/DPS) hybrid films were obtained at high dimethylsiloxane (DMS) content corresponding to the phase separation. The domain size of the polysiloxane was evaluated from the scanning electron microscope. Meanwhile, transparent hybrid films were obtained at high DPS content, corresponding to the homogeneous phase as observed from the scanning electron microscope. The hybrid films revealed higher tensile strength and elongation at break than pristine poly(B-a) as a function of DPS content. Dynamic viscoelastic analyses of the hybrids at high DMS content revealed two glass transition temperatures ( Tg) corresponding to polysiloxane and poly(B-a) components, while one Tg was observed at high DPS content. Thermogravimetric analysis of the hybrids revealed that the thermal stability of the poly(B-a)-polysiloxane hybrids was higher than pristine poly(B-a) depending on the DPS content.

Synthesis and Characterization of Bismaleimide-modified, Soy-based Epoxy Matrices for Flame-retardant Applications

Epoxidized soybean oil at various concentrations was cured with amine curing agent. The prepared matrices were chemically modified with three types of bismaleimides, namely N, N′ -bismaleimido4,4 ′ -diphenylmethane (BMI-1), 1,3-bis(maleimido)benzene (BMI-2) and 3,3′ -bis(maleimidophenyl) phenylphosphine oxide (BMI-3). The interpenetrating networks thus developed were characterized for glass transition temperature, thermal stability, dynamic mechanical analysis, heat distortion temperature, flame retardancy and water absorption behavior. The incorporation of bismaleimides in the soy-based epoxy matrices significantly enhanced thermal stability and flame retardancy. The excellent flame retardant properties of the BMI-3 incorporated system were also demonstrated by high char yield and high limiting oxygen index. Dynamic mechanical analysis studies showed that the storage modulus increased with the increase in the concentration of bismaleimides and a reduction in the tan δ value for the bismaleimide-modified, 30 wt.% soy-based epoxy system due to enhanced cross-linking density and rigidity.

Synthesis and Characterization of N,N'-bismaleimido-4,4'-diphenyl methane — Vinyl Ester Oligomer Modified Unsaturated Polyester Interpenetrating Matrices for Advanced Composites

An intercrosslinked network of hybrid bismaleimide-modified vinyl ester oligomer—unsaturated polyester matrix systems were developed. Vinyl ester oligomer was used as a toughening agent for unsaturated polyester resin and was added in 10, 20 and 30% (by weight). Benzoyl peroxide was used as curing agent. The vinyl ester oligomer-toughened unsaturated polyester matrix systems were further modified with 5, 10 and 15% (by weight) of bismaleimide. Bismaleimide-modified vinyl ester— unsaturated polyester matrices were characterized by mechanical (tensile strength, flexural strength, tensile modulus, flexural modulus and impact strength), thermal [differential scanning calorimetry (DSC) thermogravimetic analysis (TGA) and heat deflection temperature analysis (HDT)] and morphological studies [scanning electron microscope (SEM)] and water absorption. Data obtained from mechanical and thermal studies indicated that the introduction of vinyl ester oligomer into unsaturated polyester resin improved the fracture toughness with marginal reduction in the values of heat deflection temperature and glass transition temperature. The introduction of bismaleimide into vinyl ester oligomer-incorporated unsaturated polyester resin enhanced both thermal and mechanical behavior. The SEM micrographs of fractured surfaces of vinyl ester oligomer modified unsaturated polyester systems and BMI modified vinyl ester—unsaturated polyester matrices illustrate the presence of heterogeneous morphology.