Poly(methyl methacrylate)-modified vinyl ester thermosets: Morphology, volume shrinkage, and mechanical properties (original) (raw)
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AFM fracture surface study of vinylester and unsaturated polyester based thermosets
2006
The study and understanding of the structure and properties of styrene/vinylester (St/VE) and styrene/unsaturated polyester (St/UP) cross-linked thermosets has received technologic and scientific attention, because these resins are widely used as matrices in composites formulations, sharing advantages, such as low room temperature viscosity coupled with good mechanical properties and low cost, plus the added chemical resistance in the case of VE. To investigate the morphologies of these systems, scanning electron microscopy (SEM) offers an useful tool at a micron scale, while the atomic force microscopy (AFM) allows to reach the detail of the topography at a nanometric scale and also to determine the nanostructures of the surface [1].
Journal of Thermal Analysis and Calorimetry, 2010
The mechanical properties of poly(vinyl acetate) (PVAc)/epoxy thermosets as a function of the PVAc content were investigated through dynamic mechanical thermal analysis from-100 to 220°C and through tensile tests at room temperature. The morphology of the thermosets was examined by scanning electron microscopy. Cured PVAc/epoxy blends are phase separated, arising two phases that correspond to a PVAc-rich phase and to the epoxy rich-phase. The morphology evolves from nodular to inverted as the PVAc content increases. Intermediate compositions present combined morphologies, in which nodular and inverted regions are detected. The tensile properties at room temperature reveal that combined morphologies present the most ductile behaviour. The glass transition temperatures (T g) of PVAc and of epoxy phases in the blends are different from those of the neat polymers. The profile of the loss modulus (E 00)-temperature curves are correlated with the change in morphology that appears increasing the PVAc content. The storage modulus (E 0)-temperature curves are highly dependent on the morphology of the samples. The E 0-composition dependence is predicted using several models for two-phase composites. The low-temperature b-relaxation of the epoxy is slightly modified by the presence of PVAc. The activation energies of the a and b-relaxations are not dependent on the blend morphology.
Liquid rubber modified vinyl ester resins: fracture and mechanical behavior
Polymer, 2001
The fracture and mechanical behavior of vinyl ester resins (DVER) cured with styrene (S) and modi®ed with two different liquid rubbers has been determined and related to the microstructure of the resulting modi®ed thermosets. Carboxyl terminated poly(butadiene-co-acrylonitrile) (CTBN), a common toughening agent for epoxy resins, is an almost unreactive rubber with the DVER and S comonomers. During crosslinking the system undergoes a phase separation mechanism similar to that occurring in unsaturated polyester resins (UPE) modi®ed with a low pro®le additive (LPA), such as polyvinyl acetate (PVAc). This process leads to materials, which exhibit a sharp drop in density at high CTBN concentrations ($10% by weight) and to the development of a co-continuous microstructure in these materials. This feature is consistent with a maximum in fracture toughness as a function of the additive (CTBN) content, followed by a rapid deterioration in toughness at higher concentrations. On the other hand, the use of a reactive rubber, vinyl terminated poly(butadiene-co-acrylonitrile, VTBN, as the additive leads to a different morphology consisting on rubber inclusions in the thermoset matrix. This structure gradually reduces the fracture and mechanical performance of the resins modi®ed with increasing concentration of reactive elastomer. q .ar (M.I. Aranguren).
Effect of Thermoplastic Incorporation on the Performance of Thermosetting Matrix
Materials Sciences and Applications, 2012
In this work, the morphology, thermal and viscoelastic properties, deformation and fracture behaviour of a commercial vinylester resin modified with a biodegradable polymer was investigated. Flexural, impact and fracture tests were performed on the blends with different polycaprolactone (PCL) contents. They exhibited improved stiffness and fracture properties in comparison to the neat resin. From SEM analysis of fracture surfaces, stress whitening and branced fracture paths toughening mechanisms were identified. The dependence of the glass transition temperature with PCL content was adequately fitted by simple models available in the literature. From the results of these models along with the results of calorimetric studies and SEM analysis, it can be concluded that the interaction between vinylester and PCL is strong enough to avoid phase separation.
Journal of Applied Polymer Science, 2011
Polystyrene/Styrene-Ethylene-Propylene-Styrene/Vinyl Ester Resin (PS/SEPS/VER) blends used as matrix of ultra high molecular weight polyethylene (UHMWPE) fiber-reinforced composites, which included both physical crosslinking points of thermoplastic resin SEPS and chemical crosslinking network of thermosetting resin PS/VER, were prepared by solution blending and hot-molding. Morphology and mechanical properties of the PS/SEPS/VER composites were investigated in this work. The microstructure of PS/SEPS/VER composites observed by means of scanning electron microscopy (SEM) was correlated with mechanical properties. It is worth noting that, stiffness increased sharply with the addition of VER within a certain range. Impact properties verified the structure that the physical crosslinking points of SEPS were immersed in the chemical crosslinking network of PS/VER. Dynamic mechanical analysis revealed that, incorporation of VER changed the storage modulus and loss tangent. In brief, addition of VER had improved mechanical properties, thermal stability, and fluidity of the composites during processing, indicating a successful result for preparing resin matrix material with outstanding comprehensive performances. Analog map was presented to facilitate better understanding of the special structure of PS/SEPS/VER.
Journal of Materials Science, 2002
Micron-and nanometer-sized aluminum particles were used as reinforcements to enhance the fracture toughness of a highly-crosslinked, nominally brittle, thermosetting unsaturated polyester resin. Both particle size and particle volume fraction were systematically varied to investigate their effects on the fracture behavior and the fracture toughness. It was observed that, in general, the overall fracture toughness increased monotonically with the volume fraction of aluminum particles, for a given particle size, provided particle dispersion and deagglomeration was maintained. The fracture toughness of the composite was also strongly influenced by the size of the reinforcement particles. Smaller particles led to a greater increase in fracture toughness for a given particle volume fraction. Scanning electron microscopy of the fracture surfaces was employed to establish crack front trapping as the primary extrinsic toughening mechanism. Finally, the effects of particle volume fraction and size on the tensile properties of the polyester-aluminum composite were also investigated. The measured elastic modulus was in accordance with the rule-of-mixtures. Meanwhile, the tensile strength was slightly reduced upon the inclusion of aluminum particles in the polyester matrix. C 2002 Kluwer Academic Publishers
With a global annual output of over 65 million tons and accounting for over 20% of all polymeric materials made today, thermoset polymers serve a significant role in modern industrial applications such as plastic and rubber. The high-density crosslinks not only give useful properties like as chemical and thermal resistance to the thermoset, but also make it difficult to modify. Here, using a maleated eco-thermoset blend additive (50% v/v) synthesized from epoxidized corn oil and epoxy resins (MEPECO), we show that adding an optimal amount of 5% MEPECO to vinyl ester (VE) resin improved flammability properties as analyzed by microcalorimeter, contact angle, and thermogravimetric analyzer. Using flexural testing and spectral analysis, the mechanical properties enhanced considerably in terms of strength and modulus with the same optimal amount of MEPECO. However, impact energy is much lower during digestion of the eco-thermoset resin due to shear yielding localization, as demonstrated ...
Studies on Viscoelastic, Thermal and Morphological Properties of Vinyl Ester – Mixed Diluents System
Archives of Metallurgy and Materials
Vinyl ester resin networks formed by using mixture of diluents were prepared. Methyl methacrylate (MMA) diluent was mixed in various proportions with vinyl ester resin which was already premixed with styrene diluent (45 wt. %). Weight ratios e.g. 80:20, 70:30 and 60:40 of VE resin: MMA diluents were studied. Viscoelastic properties of the cross-linked resin were studied by dynamic mechanical analyzer in terms of storage modulus and tanδ. Thermal analysis was performed using non-isothermal mode of Differential scanning calorimetry. The samples with mixed diluents, showed higher modulus, and glass transition temperature in comparison to that of the pure vinyl ester-styrene resin cross-linked in presence of styrene only. The difference in thermal stability between vinyl ester-styrene and vinyl ester-MMA-styrene was checked. Vinyl Ester - 20 wt. % MMA-Styrene samples have the best thermal property among all other prepared samples. Multiphase morphology was formed for the thermoset cross...
Vinyl ester resin: Rheological behaviors, curing kinetics, thermomechanical, and tensile properties
AIChE Journal, 2014
The effects of isothermal temperature on the curing extent, gel time, dynamic rheological behaviors, and mechanical properties of vinyl ester resins (VERs) were systematically studied. Although, the curing extent was observed increase with increasing the operating temperature, the study of residual heat of cured VERs indicated that the final curing extent depended on the postcuring process. The values of shear storage and loss modulii at gel point were observed to decrease with increasing both the isothermal temperature and heating rate, which were associated with the formation of microgels during the gelation process. With increasing isothermal temperature and heating rate, the microgel did not have enough time to grow well, causing a reduced shear storage and loss modulii at the gel time. The storage and loss modulii of the cured VERs were also studied and shown that with temperature increased to the glass transition, both modulii were first decreased and then increased. V C 2013 American Institute of Chemical Engineers AIChE J, 60: [266][267][268][269][270][271][272][273][274] 2014
Chemical modification of matrix Resin networks with engineering thermoplastics
Polymer Bulletin, 1985
Bisphenol A-based epoxy resins were modified with either phenolic hydroxyl or aromatic amine functionally-terminated poly(arylene ether sulphone) oligomers and thermally cured with 4,4' diaminodiphenyl sulphone. The resulting networks displayed significantly improved fracture toughness, with little sacrifice in modulus. The bisphenol A-based polysulphones were molecularly miscible with the epoxy precursors over the entire range of compositions and molecular weights investigated, but developed a two phase structure upon network formation. The molecular weights and composition of polysulphone chemically incorporated into the network were varied and their effect on several important physical properties was investigated. The dynamic mechanical analysis and scanning electron microscopy (SEM) studies showed that it is possible to generate a two-phase morphology in the cured networks wherein polysulphone composite particles are dispersed in the epoxy matrix. Despite the two-phase structure, the modified crosslinked systems are nearly transparent, due to a similarity in component refractive index values. The fracture toughness of these modified networks under plane strain conditions improved significantly with minimal sacrifice of the flexural modulus.