The Analysis of Variance.

Effects of resin hydrophilicity on water sorption and changes in modulus of elasticity.

Epoxy resins are a family of thermosetting materials widely used as adhesives, coatings and matrices in polymer composites because of the low viscosity of the formulations, good insulating properties of the final material even at high temperatures and good chemical and thermal resistance (May, 1988). Epoxy thermosets can be described as 3D polymer networks formed by the chemical reaction between monomers (“curing”). This 3D covalent network structure determines the properties of thermosetting polymers: unlike thermoplastics, this kind of polymers does not melt, and once the network has been formed the material cannot be reprocessed. Maybe one of the main advantages of epoxy thermosets is that the starting monomers have low viscosity so that complex geometries can be easily shaped and fixed after curing the monomers. Thus the formation of the network via chemical reaction is a key aspect in this kind of materials.

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Applications of FTIR on Epoxy Resins - Identification, Monitoring the Curing Process, Phase Separation and Water Uptake

Polyhedral oligosilsesquioxane (POSS)-based hybrid polymers have generated much interest recently, both from the academic and industrial points of view. POSS are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic–inorganic hybrids, thus providing the opportunity to design and build materials with extremely well-defined dimensions possessing nanophase behavior. POSS have been successfully incorporated into common polymers via copolymerization, grafting or blending. A variety of POSS-containing copolymers have been prepared and they have displayed great potential in the development of a wide range of hybrid nanomaterials with diverse properties. This work has critically evaluated the recent developments in syntheses of POSS polymer materials leading to POSS nanocomposites. The syntheses of POSS cages, monomers containing POSS cages, POSS-dendrimers' cores, POSS-containing polymers (nanobuilding blocks) and POSS nanocomposites are described in detail. This work also assesses the properties of POSS nanobuilding blocks that can be otherwise used for developing nanocomposites. Such properties include mechanical, thermal, flame-retardant and viscoelastic properties. Investigations into the structure, morphology and compatibility of POSS nanobuilding blocks have been reviewed. Other properties covered include the ion-mobility and swelling characteristics as well as porosity of POSS nanobuilding blocks. Lastly, existing and possible future applications are highlighted and final conclusions are drawn.

Polyhedral Oligomeric Silsesquioxanes (POSS)-Containing Nanohybrid Polymers

Modification of epoxy resins with functional silanes, polysiloxanes, silsesquioxanes, silica and silicates

The characteristics of sorption and diffusion of water in an amine-cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water-sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water-sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001

Effect of water sorption on the structure and mechanical properties of an epoxy resin system

Using dynamic mechanical analysis (DMA) we have studied thermal degradation for a system containing a diglycidyl ether of bisphenol A (DGEBA) and 1,3-bisaminomethylcylohexane (1,3-BAC). The changes of dynamic mechanical properties during thermal degradation indicated a shift of the glass transition temperature (Tg) to higher temperatures and a decrease in the peak value of the dynamic loss factor (tan δ) with an increasing of aging time. The value of dynamic storage modulus (E′) at the rubbery state showed an increase with aging time, whiteE′ at the glassy state only underwent a moderate change with increased thermal degradation. From these results it can be argued that thermal degradation during the stage prior to the onset of the severe degradation involves structural changes in the epoxy system, as further crosslinking and loss of dangling chains in the crosslinked network.

Dynamic mechanical analysis

Composite materials were prepared by mixing fly ash obtained from biomass combustion as filler and isotactic polypropylene (PP) as matrix. Three silane-type coupling agents mainly differing in the size of their functional groups were used to improve the compatibility between both components. Uniaxial tensile tests showed that the incorporation of untreated ash into PP led to stiffer but also more brittle and weaker materials, as Young's modulus significantly increased and tensile strength and elongation at break decreased. Furthermore, an enhancement in storage and loss moduli as well as in composite viscosity was observed with the addition of fly ash. Hardness tests and thermal and fracture surface analyzes revealed tensile test results similar to those mentioned earlier. In summary, after analyzing the effects of the three silanes on mechanical, thermal, morphological, and rheological properties, the silane containing the vinyl functional group (XL10) was selected as the most appropriate for the PP/ash composites investigated. POLYM. COMPOS., 31:1722–1730, 2010. © 2010 Society of Plastics Engineers.

Rheological, thermal, and mechanical characterization of fly ash-thermoplastic composites with different coupling agents

Using differential scanning calorimetry (DSC), we have studied, under isothermal and dynamic conditions, the kinetics of the cure reaction for an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) modified with different contents of acrylonitrile-butadiene-styrene (ABS) and cured with 1,3-bisaminomethylcyclohexane (1,3-BAC). Kinetic analysis were performed using three kinetic models: Kissinger, Flynn-Wall-Ozawa, and the phenomenological model of Kamal as a result of its autocatalytic behavior. Diffusion control is incorporated to describe the cure in the latter stages, predicting the cure kinetics over the whole range of conversion. The total heats of reaction were not influenced by the presence of ABS. The autocatalytic mechanism was observed both in the neat system as well as in its blends. The reaction rates of the blends and the maximum conversions reached did not change too much with the ABS content. Blending ABS within the epoxy resin does not change the reaction mechanism of the epoxy resin formation.

J. Cano

Papers

Effect of water sorption on the structure and mechanical properties of an epoxy resin system

Dynamic mechanical analysis

Rheological, thermal, and mechanical characterization of fly ash-thermoplastic composites with different coupling agents

Kinetic studies of the effect of ABS on the curing of an epoxy/cycloaliphatic amine resin

Effect of poly(styrene-co-acrylonitrile) on the curing of an epoxy/amine resin