Epoxy resins radiation effects

The epoxy resin formed by tetraglycidyl 4,4 -diamino diphenyl methane and 4,4 -diamino diphenyl sulfone was characterized by dynamic mechanical analysis. Epoxy specimens were exposed to varying dose levels of ionizing radiation (0.5 MeV electrons) up to 10,000 Hrads to assess their endurance in long-term space applications. Ionizing radiation has a limited effect on the mechanical properties of the epoxy. The most notable difference was a decrease of approximately 40°C in Tg after an absorbed dose of 10,000 Mrads. Sorption/desorption studies revealed that plasticization by degradation products was responsible for a portion of the decrease in Tg. 

Wilson, W.T. "Effect of Radiation on the Dynamic Mechanical Properties of Epoxy Resins and Graphite Fiber/Epoxy Composites", 1986, Ph.D. Thesis, North Carolina State University, Raleigh, NC. 

The mechanisms of radiation damage and effects of hardeners were studied recently by pulse radiolysis [89], The epoxy resins require a relatively large amount of curing agents (hardeners), most of them are aromatic and aliphatic amines such as diamino diphenyl methane or triethylene tetramine. On the basis of the emission spectra and kinetic behavior of excited states observed, the radiation resistance of aromatic and aliphatic amine curing epoxy resin was explained by internal radiation protection effects due to energy transfer. 

A number of investigations on radiation effects of polymers at ambient temperature have been carried out and summarized in some recent publications [38-40]. However, there are very few experimental results on cryogenic temperature irradiation of conventional polymers. Figure 5 shows the summary of early experiments on irradiation of polymers at 77 K up to y-ray dose of 2 x 106 Gy [41,42]. As is evident from Fig. 5, the candidate polymers that can be used at cryogenic temperatures are only aromatic based epoxy resins, poly-imides, and polystyrene. This means that the choice of polymers for superconducting magnets to be operated in a radiation environment is rather limited. Therefore, the intention of this chapter is to give information on the radiation tolerance of recently developed polymers. 

Recently Nishijima et al. investigated the radiation effects of three-dimensional glass-fabric reinforced plastics (3DFRP) mentioned in the preceding section, since the interlaminar shear strength of composites was expected to be greatly enhanced by the presence of Z-axis reinforcement [78]. Two kinds of 3DFRP were newly developed and named as ZI-003 and ZI-005 of which the matrices were epoxy and BT resins, respectively [28]. The compressive tests... 

The radiation effects on dielectric properties of an epoxy resin (Epilox EG 34 with aromatic amine hardener Nr 105) were studied by Jahn et al. with electron,... 

For the less critical applications, standard (epichlorhydrin/bisphenol A) epoxy resins retain their physical properties well, but are particularly subject to the adverse effects of UV radiation on their appearance. This causes rapid yellowing and chalking due to their aromatic structure and UV agents are ineffective. Therefore, aU mouldings made with these resins which are to be subjected to extended outdoor exposure will benefit from protection by surface coating or shading. 

IR spectroscopy was used to follow the ageing processes of two types of epoxy resins. Resin samples were exposed to ionising radiation and the effects at the molecular level were determined. Aromatic amine cured resins were oidy slightly affected by the radiation, but those cured by alkyl diamines were more sensitive and thus absorbed more water molecules (41). 

When used for space structural applications in outer space, epoxy composites are exposed to -rays, electrons, protons, ultraviolet light and heat. It is therefore important to determine the long term effects of this radiation on epoxy resin. 

Rosu, D., Rosu, L., Mustata, E., Varganici, C.-D. Effect of UV radiation on some semi-interpenetrating polymer networks basedon polyurethane and epoxy resin. Polym. Degtad. Stab. 97, 1261-1269 (2012)... 

Giori C, Yamauchi T. Effects of ultraviolet and electron radiations on graphite-reinforced polysulfone and epoxy resins. J Appl Polym Sci 1984 29 237-249. Haliwell SM. Weathering of polymers. RAPRA Review Reports 1992 53. 

The microwave and thermal cure processes for the epoxy-amine systems (epoxy resin diglycidyl ether of bisphenol A, DGEBA) with 4,4 -diaminodiphenyl sulfone (DDS) and 4,4 -diaminodiphenyl methane (DDM) were investigated for 1 1 stoichiometries by using fiber-optic FT-NIR spectroscopy. The kinetic rate parameters for the consumption of amines were determined by a least squares curve fit to a model for epoxy/amine cure. The activation energies for the polymerization of the DGEB A/DDS system were determined for both cure processes and found to be 66 and 69 kJ/mol for the microwave and thermal cure processes, respectively. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect [99]. 

FTIR techniques in combination with or as complement to other measurement techniques have been used in a wide range of photochemistry studies on polymers. These include bisphenol-A polycarbonate [173], polycarbonate coatings on mirrors [174], PMMA [175], poly( -butyl acrylate) [176] and polypropylene [177]. DSC and FTIR studies have been used in conjunction to investigate the nature of y-radiation-induced degradation and its effect on the 19°C and 30°C phase transitions in PTFE [178]. IR studies of the hydrolysis of melamine-formaldehyde crosslinked acrylic copolymer films have shown that copolymer-melamine formaldehyde crosslinks are broken and that crosslinks between melamine molecules are formed [179]. The thermal and photo-degradation mechanisms in an IR study of cured epoxy resins were found to be related to the autoxidative degradation processes for aliphatic hydrocarbons [180]. 

Details are given of the effects of strong ionising radiations on the physico-chemical modifications of epoxy resins. The sensitivity of the epoxy resins to radiation was determined using carbon 13 NMR. 20 refs. 

The initial step in the program is the development of a characterization project to assess the effect of a number of primary variables on the performance of laminates under irradiation and at 4 K. Typical variables are reinforcement type, resin system, and cure cycle. The materials will represent a cross section of the existing commercial laminate production. Several laminates will be specially fabricated to provide increased radiation resistance. They will utilize commercial, boron-free glass for reinforcement and epoxy systems cured with aromatic amines. All test laminates will be made by a commercial producer under conditions dupli-... 

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