Glass-reinforced polyesters (GRPs) are attractive in structural applications due to their strength-to-weight ratio and resistance to chemical attack. For marine and processing applications, in particular, GRPs must withstand long-term exposure to brine and either highly acidic or basic aqueous solutions. In this work, we report on the degradation of two GRP laminates, a pultruded isophthalic polyester (IPE) and a hand-moulded vinyl ester (VE), in brine (5% w/v NaCl) and a 10% w/v NaOH(aq) solution over the course of 270 days at 25°C. Tensile and flexural strengths have been measured as a function of immersion time and reveal that the IPE resin is more susceptible to water permeation and fibre-resin debonding than the VE. While the IPE laminate undergoes dramatic tensile strength deterioration in NaOH(aq) within the first 30 days of immersion, the VE resin is far more resistant to degradation in either solution. These measurements are consistent with surface features imaged with electron microscopy. Incorporation of polyethylene terephthalate (PET) or C-glass surface veils into these laminates is not generally beneficial for property retention, since the veils produce more interfaces and enhance water absorption through wicking.

Degradation kinetics of glass-reinforced polyesters in chemical environments

The effects of variation of styrene content on the thermal, mechanical and morphological behaviours of epoxy novolac vinyl ester resin (EVER)/glass fabric laminate have been investigated. The vinyl ester resin matrix was synthesized indigenously using epoxy novolac resin and methacrylic acid catalyzed by triphenylphosphine at a temperature of 85 °C in nitrogen atmosphere. Fourier-transform infra-red spectroscopic (FT-IR) analysis was used to see the structural changes during the synthesis of the EVER. Differential scanning calorimetric (DSC) technique was used to investigate the curing behaviour of the EVER matrix. Exothermic peaks (Tp) appeared in the range of 117–127 °C for all the samples of epoxy resin and EVERs. Thermal stability of the prepared samples was analyzed by dynamic thermogravimetric runs. The TG/DTG trace of epoxy showed two-step mass loss decomposition behaviour whereas that of vinyl ester resin exhibited a single step mass loss. Mechanical properties such as tensile, flexural and impact strengths of the prepared laminates were determined and it was found cured resin containing 40% styrene showed the best balance of properties and EVER/glass fabric laminates exhibited better properties as compared to the epoxy/glass fabric laminates Dynamic mechanical analyses of the samples were done to determine the viscoelastic properties. Tg decreased significantly with increased styrene concentration due to increase in cross-linking density. Cross-sections of the cured samples, which failed during impact testing, have been critically studied through scanning electron microscopic (SEM) analysis to gain insight into the phase morphology.

Laminates based on vinyl ester resin and glass fabric: A study on the thermal, mechanical and morphological characteristics

The relationship between observed swelling of two cross-linked polystyrene resins and the microenvironment within polymer matrixes has been examined. Polystyrene cross-linked with either divinyl benzene (Merrifield resin) or 1,4-bis(4-vinylphenoxy)butane (JandaJel) was investigated with fluorescence and electron-paramagnetic resonance spectroscopy. Fluorescence spectroscopy revealed a superior correlation between observed swelling and solvation effects using a dansyl probe with JandaJel than with Merrifield resin. However, the internal viscosity of pre-swollen JandaJel is higher than Merrifield resin, as determined by EPR measurements. The combination of these two analytical methods provides insights into the physical differences observed between these two chemically similar resins and suggests caution should be used if using singular physical techniques to probe the microenvironment of polymeric matrixes.

Investigating resins for solid phase organic synthesis: the relationship between swelling and microenvironment as probed by EPR and fluorescence spectroscopy.

The sorption and desorption kinetics of water into polyetherimide (ULTEM 1000) were studied at various temperatures ranging from 20 to 100°C. The water equilibrium concentration increases slightly with temperature from 1.39% (by weight) at 20°C to 1.50% at 100°C. The solubility coefficient, S, calculated from these data, and the water vapor pressure decrease with temperature. The calculated heat of dissolution Hs is close to −43 kJ mol−1, which explains the low effect of temperature on the equilibrium concentration. The diffusion coefficient, D, varies from about 1.10−12 m2 · s−1 at 20°C to about 16.10−12 m2 · s−1 at 100°C. The apparent activation energy of diffusion, ED, and the heat of dissolution, Hs, of water in the polymer have opposite values (respectively, +43 and −42 kJ · mol−1). From this observation and a comparison of these data with water diffusion characteristics in other glassy polar polymers, it is hypothesized that the transport rate of water is kinetically controlled by the dissociation of water–polymer complexes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1439–1444, 2000

Humid aging of polyetherimide. I. Water sorption characteristics

Interactions of solvents with poly(methyl methacrylate)

Six di- or tetramethacrylates based on respectively bisphenol A diepoxides or phenol-epoxynovolacs were crosslinked by styrene in optimized conditions. Density, T g , propagation rates of ultrasonic waves, tensile properties and rubbery modulus were then experimentally determined. A constitutive repeat unit of the network was written on the basis of the hypothesis that the conversion of the styrene-methacrylate copolymerization was complete and that the resulting network was homogeneous. The relationships between the corresponding (theoretical) structure and the physical properties were then studied

Styrene crosslinked vinylesters. I: Correlation between the theoretical structure and some thermophysical properties

The sorption characteristics (water equilibrium concentration W m and coefficient of diffusion D) were determined gravimetrically for six styrene crosslinked vinylester networks at 30, 40 and 50°C, 95% RH The equilibrium water concentration (05-18% by weight) is independent of the temperature and appears to be closely related to the concentration of polar groups (especially hydroxyls) in the polymer It is an increasing function of the solubility parameter The water diffusivity is of the same order of magnitude as that of unsaturated polyesters but considerably higher than that of hydrophilic amine crosslinked expoxies

Styrene crosslinked vinylesters. II: Water sorption, water diffusion and cohesive properties

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Styrene crosslinked vinylesters. I: Correlation between the theoretical structure and some thermophysical properties

Styrene crosslinked vinylesters. II: Water sorption, water diffusion and cohesive properties