The Interactions of Water with Epoxy Resins

Moy, P.; Karasz, F. E.

doi:10.1021/bk-1980-0127.ch030

Cited by 41 publications

(15 citation statements)

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“…Values close to that obtained here were published. 19 As Figure 4 shows, both equations provide a good description of experimental data for low water uptakes. As water content increases, eq.…”

Section: Resultsmentioning

confidence: 88%

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Water effect on the morphology of EVOH copolymers

Aucejo

Marco

Gavara

1999

J. Appl. Polym. Sci.

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ABSTRACT:The effect of water on the morphology of four ethylene vinyl alcohol copolymers (EVOH) with different ethylene contents was studied by differential scanning calorimetry (DSC). EVOH film samples equilibrated in controlled atmospheres at different relative humidities (RH) and 23°C were analyzed. Under dry conditions, the glass transition temperature (T g ) was unaffected by copolymer ethylene content. As RH increases, T g decreases. It seems that the presence of water within the polymer matrix results in plasticization of the polymer. T g varies from around 50°C (dry) to below room temperature. EVOH copolymers are glassy polymers when dry and rubbery polymers at high RHs. Fox and Gordon-Taylor's equations well describe T g depletion at low water uptake, although severe water gain results in a considerable T g decrease, which is not predicted by these theories. Melting temperature, T m , and enthalpy, ⌬H m , were also analyzed. When dry, T m decreases as ethylene content increases. No significant water effect was found on either T m or ⌬H m . Hence, crystallinity seems to be unaffected by water presence.

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Section: Resultsmentioning

confidence: 88%

“…(2), which agreed better with the experimental values, was 0.2. Some authors 19 related the value of k to the heat capacity increments at the glass transition of the pure components (k ϭ ⌬C p p /⌬C p s ). Values close to that obtained here were published.…”

Section: Resultsmentioning

confidence: 99%

Water effect on the morphology of EVOH copolymers

Aucejo

Marco

Gavara

1999

J. Appl. Polym. Sci.

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“…In these systems, the measured enhancement of toughness (usually in terms of fracture energy) is typically found to reach a factor of three or four times the matrix toughness, and is attributed to plastic deformation of bridging ligaments. This view is supported by analytical models of toughening due to crackface tractions [23,24], but ignores the possible contribution from the crack-trapping mechanism. In brittle matrices containing ductile particles this omission is probably justified, since any crack trapping which occurs would be prematurely terminated by relaxation of the opening constraint as the highly stressed particles deform.…”

Section: Ceramic Matricesmentioning

confidence: 99%

Experimental investigations of crack trapping in brittle heterogeneous solids

Mower

Argon

1995

Mechanics of Materials

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Over the past two decades many mechanisms of toughening have been considered for brittle solids. Some of the most prominent ones applicable to either monolithic materials or fiberreinforced composites include deformation-induced local transformations, micro-cracking, crack trapping, crack bridging, and fiber pull-out. Few if any of these have been studied in the past in a manner which permitted evaluation of the effects of individual mechanisms in the absence of other interacting mechanisms. Here we present the development, analysis and results of an experimental study of toughening by the process of crack trapping by second-phase particles (spheres and fibers) of such toughness that make them impenetrable by probing cracks, forcing the cracks to bow around the obstacles with increasing applied load.The model fracture specimens employed here were wedge-loaded double cantilever beams cast of a brittle epoxy, containing macroscopic (3mm-diameter) inclusions of Nylon or polycarbonate having similar elastic properties to the matrix. The tests were performed at -60*C to achieve controlled, stable crack propagation. Images of the crack fronts advancing at velocities of about 10-4 M/s were recorded with good resolution, providing a continuous record of crack-front shapes during the evolution of the crack-trapping process from the initial pinning configuration through the transition to crack-flank bridging. Remarkable agreement between these images and crack-front shapes predicted by the numerical simulation of Bower & Ortiz is demonstrated. A parametric approach was adopted to study the influence of obstacle spacing, surface adhesion and thermally-induced residual stresses upon the observed crack-front behavior and enhanced stress intensity required to propagate the cracks past these obstacles. Analysis of the quantitative data has demonstrated that, in brittle matrices containing particle volume fractions of approximately 0.2, toughness enhancement by over a factor of two, relative to neat matrix values, may be achieved through the crack-trapping mechanism alone, provided that a high level of adhesion can be maintained between the matrix and the tough reinforcing particles.

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“…[11][12][13] When the T g drops below storage temperature, a substantial increase in oxygen permeability is expected, resulting in a shorter shelf life for oxygen-sensitive foods packaged in the plastic material. Wachtel et al 14 reported that the T g of dry EVOH was approximately 70°C; however, T g of EVOH in the presence of 8% water was below room temperature.…”

Section: Introductionmentioning

confidence: 99%

Water absorption in EVOH films and its influence on glass transition temperature

Zhang

Britt

Tung

1999

J. Polym. Sci. B Polym. Phys.

110

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Moisture sorption kinetics of nonoriented ethylene vinyl alcohol copolymer (EVOH) film (EF‐E15) were studied at 25, 35, and 45°C. Anomalous diffusion was observed for the polymeric film at high relative humidities (RH) and higher temperatures. Diffusion and solubility coefficients of water were found to be concentration dependent. The moisture sorption isotherms of three types of EVOH films (EF‐E15, EF‐F15, and EF‐XL15) determined at 25, 35, and 45°C, were well described using the GAB equation. Glass transition temperatures (Tg) of the EVOH films, as influenced by RH, were measured using differential scanning calorimetry. Tg values decreased with increasing RH due to the plasticization effect of water, and were found to be dependent on ethylene content and orientation of the EVOH films. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 691–699, 1999

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The Interactions of Water with Epoxy Resins

Cited by 41 publications

References 0 publications

Water effect on the morphology of EVOH copolymers

Water effect on the morphology of EVOH copolymers

Experimental investigations of crack trapping in brittle heterogeneous solids

Water absorption in EVOH films and its influence on glass transition temperature

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