The effect of moisture on the physical and mechanical integrity of epoxies

The effect of specific combinations of moisture, heat, and stress on the physical structure, failure modes, and tensile mechanical properties of diaminodiphenyl sulphone (DDS)-cured tetraglycidyl 4,4′diaminodiphenyl methane (TGDDM) epoxies [TGDDM-DDS (27 wt% DDS)] are reported. Sorbed moisture plasticizes TGDDM-DDS epoxies and deteriorates their mechanical properties in the range 23 to 150° C. Studies of the initiation cavity and mirror regions of the fracture topographies of these epoxies indicate that sorbed moisture enhances the craze initiation and propagation processes. The effect of tensile stress-level, applied for 1 h on dry epoxies, on the subsequent moisture sorption characteristics of the epoxies was also investigated. Such studies indicate that the initial stages of failure that involve both dilatational craze propagation and subsequent crack propagation enhance the accessibility of moisture to sorption sites within the epoxy to a greater extent than in the latter stages of failure which involve crack propagation alone. The amount of moisture sorbed by TGDDM-DDS epoxies is enhanced by ∼ 1.6 wt% after exposure to a 150° C thermal spike, as a result of moisture-induced free volume increases in the epoxies that involve rotational—isomeric population changes.

[1]  L. Pauling.  The Nature Of The Chemical Bond , 1939 .

[2]  E. Hückel,et al.  The nature of the chemical bond and the structure of molecules and crystals. — An Introduction to modern structural chemistry. von Linus Pauling. 429 S.mit 72 Fig. Ithaka, New‐York. Cornell University Press. Preis geb. 4,50 Dollar , 1940, Zeitschrift für Elektrochemie und angewandte physikalische Chemie.

[3]  John Crank,et al.  The Mathematics Of Diffusion , 1956 .

[4]  G. J. van Amerongen,et al.  Diffusion in Elastomers , 1964 .

[5]  A. Michaels,et al.  Controllably crazed polystyrene: Morphology and permeability , 1968 .

[6]  V. Stannett,et al.  The effect of penetrant activity and temperature on the anomalous diffusion of hydrocarbons and solvent crazing in polystyrene part I: Biaxially oriented polystyrene , 1969 .

[7]  V. T. Stannett,et al.  Anomalous transport of hydrocarbons in polystyrene , 1970 .

[8]  V. Stannett,et al.  The effect of molecular weight and orientation on the sorption of n-pentane by glassy polystyrene , 1971 .

[9]  S. Mostovoy,et al.  The fracture toughness and stress corrosion cracking characteristics of an anhydride‐hardened epoxy adhesive , 1971 .

[10]  Effect of solvents on the cryogenic dynamic mechanical properties of polystyrene , 1972 .

[11]  A.D.S. Diggwa.  Fracture properties of thermosets , 1974 .

[12]  V. Stannett,et al.  The effect of orientation on the morphology and kinetics of solvent crazing in polystyrene , 1974 .

[13]  R. M. Verette.  Temperature/humidity effects on the strength of graphite/epoxy laminates , 1975 .

[14]  The effect of temperature on the deformation and fracture of polystyrene , 1975 .

[15]  J. E. Halkias,et al.  Moisture in Composites: The Effect of Supersonic Service on Diffusion , 1975 .

[16]  J. B. Shortall,et al.  The fracture toughness and fracture morphology of polyester resins , 1976 .

[17]  G. Springer,et al.  Moisture Absorption and Desorption of Composite Materials , 1976 .

[18]  R. Young,et al.  Crack propagation and arrest in epoxy resins , 1976 .

[19]  G. Pritchard,et al.  The effect of water on the critical stress intensity factor of unsaturated polyester resins , 1976 .

[20]  R. Bohlmann,et al.  Moisture diffusion in graphite/epoxy laminates - Experimental and predicted , 1977 .

[21]  J. Kardos,et al.  Sorption and diffusion of water in glass ribbon‐reinforced composites , 1977 .

[22]  Dj Wilkins.  Environmental Sensitivity Tests of Graphite-Epoxy Bolt Bearing Properties , 1977 .

[23]  R. J. Morgan,et al.  The microscopic failure processes and their relation to the structure of amine-cured bisphenol-A-diglycidyl ether epoxies , 1977 .

[24]  J. Whiteside,et al.  Effects of environment on advanced composites structures , 1977 .

[25]  Robert J. Young,et al.  Stability of crack propagation in epoxy resins , 1977 .

[26]  Mechanism of Epoxy Moisture Effects , 1977 .

[27]  M. R. Louthan,et al.  Proceedings of conference environmental degradation of engineering materials, October 10-12, 1977, College of Engineering, Virginia Tech, Blacksburg, Virginia , 1977 .

[28]  C. Browning,et al.  The mechanisms of elevated temperature property losses in high performance structural epoxy resin matrix materials after exposures to high humidity environments , 1978 .

[29]  J. Vinson,et al.  Advanced Composite Materials—Environmental Effects , 1978 .

[30]  L. Broutman,et al.  Effect of an External Stress on Moisture Diffusion and Degradation in a Graphite-Reinforced Epoxy Laminate , 1978 .

[31]  Method for casting epoxy tensile coupons. , 1978, The Review of scientific instruments.

[32]  J. E. O'neal,et al.  Effect of epoxy monomer crystallization and cure conditions on physical structure, fracture topography, and mechanical response of polyamide-cured bisphenol-A-diglycidyl ether epoxies , 1978 .

[33]  R. J. Morgan,et al.  The Durability of Epoxies. , 1978 .

[34]  Roger J. Morgan,et al.  The structure, modes of deformation and failure, and mechanical properties of diaminodiphenyl sulphone-cured tetraglycidyl 4,4′diaminodiphenyl methane epoxy , 1979 .