Degradation of epoxy polymers: Part 4—Thermal degradation of bisphenol-A diglycidyl ether cured with ethylene diamine
Abstract
The principal characteristics and products of thermal degradation of a commercial epoxy resin prepared by reaction of 2,2-bis-(4′-hydroxyl phenyl)propane (bisphenol-A) with 1-chloro-2,3-epoxy propane (epichlorhydrin) and cross-linked (cured) with ethylene diamine have been studied. The principal products are small amounts of hydrogen and methane, ethane, propene, ammonia, methylamine with a trace of trimethylamine, water, phenol, cresols, 4-isopropyl phenol, 4-isopropenyl phenol, bisphenol-A, 2-(benzo-fur-5-yl)-2-(p-hydroxy phenyl)propane and 2-(benzo-pyran-6-yl)-2-(p-hydroxy phenyl)propane. These products appear from about 300°C and mechanisms for their formation are proposed.
References (4)
- N. Grassie et al.
Poly. Deg. and Stab.
(1985) - N. Grassie et al.
Poly. Deg. and Stab.
(1985)
Cited by (139)
Product-specific kinetics reveal effect of epoxy crystallization on thermoset thermal degradation
2024, PolymerCrystallization is a common problem for epoxy resins, which are ubiquitous in industrial and commercial use. Integration of crystallized epoxy monomers into cured thermosets has been shown to alter the thermosets’ final mechanical properties. However, no studies have investigated the impact of these crystals on the thermal stability of the thermoset. Here we investigate the degradation kinetics of a bisphenol F–based epoxy thermoset with and without crystallized monomers using Product-Specific Kinetic (PSK) analysis coupled with Evolved Gas Analysis-Mass Spectrometry (EGA-MS). PSK analysis revealed significant differences in evolved product ion kinetics, suggesting changes in the degradation kinetics between thermoset configurations. It was concluded that early stages of degradation are influenced most by crystal presence due to the high concentration of unreacted epoxy monomers and lower cross-linking density of the cured network. After post-cure annealing, significant changes are observed in the degradation kinetics of thermosets without crystal inclusions. Conversely, post-cure annealing procedures of crystal integrated thermosets showed little change in the thermoset degradation kinetics across all conversion extents. These findings suggest that post-cure annealing of thermosets with crystals present at the onset does not alter the cross-linking density of the polymer network enough to significantly change the degradation kinetics. We hypothesize this is because the excess monomers from the melted crystals are unable to find suitable reaction sites for complete binding into the polymer network, which has direct implications for the material properties and final thermal stability of the thermoset.
Experimental study on the thermal decomposition of epoxy/anhydride thermoset matrix in composite insulator core rods
2024, Polymer Degradation and StabilityEpoxy/anhydride thermoset matrix within composite insulator core rods may thermally decompose by temperature rise caused by partial discharge. The thermal decomposition characteristics of the epoxy/anhydride thermoset was analyzed using pyrolysis-gas chromatography-mass spectrometry (PY–GC–MS) from 200 to 1000 °C, including the mechanisms of crosslinked network scission and the formation of gaseous or liquid products with potential secondary effects on surrounding materials. Below 360 °C, scission at crosslinking points predominates by ceiling temperature behavior, forming anhydrides. Above 380 °C, scission of main chains leads to the production of corresponding fragments. Beyond 600 °C, decomposition of anhydrides and fragments from main chains leads to the formation of lower molecular weight substances. During the pyrolysis process, organic acids are formed from 240 °C to 1000 °C. Above 600 °C, gases with high vapor pressures and liquids that can induce swelling are produced. These byproducts can have secondary effects on surrounding materials, including the failure of interfacial adhesion, swelling of silicone rubber sheaths, and a reduction in the mechanical strength of glass fibers. Consequently, these effects may accelerate the decay-like deterioration of core rods, characterized by a surface morphology reminiscent of rotting wood. These findings will inform the optimization of materials for enhanced electrical equipment performance and facilitate the evaluation of potential environmental impacts posed by the thermal decomposition of epoxy/anhydride thermosets in future applications.
Flexible photoresponsive transparent wood (FPTW) has potential applications in electronic equipment, sensors, and other fields. In this study, flexible and photoresponsive transparent wood was synthesized through the impregnation process, utilizing epoxy resin and a spiropyran solution. This process endowed the wood with intelligent response and flexible capabilities. Scanning electron microscopy (SEM) revealed the impregnation of the flexible polymer into the porous structure of natural wood. Further validation was conducted to affirm the sample responds to ultraviolet light, employing analyses of infrared spectroscopy, UV–visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). Through the measurement of chromaticity parameters, encompassing lightness (L*), redness (a*), yellowness (b*), and total color difference (ΔE*), before and after UV irradiation, it is indicated that the wooden samples manifest commendable photoresponsive properties. Testing the fluorescence properties of the samples, the spiropyran completed the opened-loop and closed-loop transitions under irradiation with UV and visible light. In addition, the FPTW has excellent mechanical properties, with a tensile strength of 0.98 GPa and an elastic modulus of 0.65 GPa.
Hygrothermal aging of particle-filled epoxy-based composites
2023, Polymer Degradation and StabilityIn this study hygrothermal aging in two particle-filled epoxy-based composites was investigated. The filler loading of both composites was comparable but differed in the filler type (portland cement; quartz). The influence of 10 different climates with varying humidities and temperatures on mechanical properties was examined periodically with tensile tests. The changes in structure and composition were investigated with microscopy, EDX, TGA, and XRD. Elastic properties were calculated with a Halpin-Tsai model and the tensile strength with an interface-dependent model proposed by Pukanszky. Here we suggest that physical aging and the growth of crystals within cement fillers contribute to stiffening effects. Water uptake by cement fillers also led to an increase in modulus and was ascribed to the formation of hydration products. The results indicate that the degradation of Young’s modulus is not affected by the filler type, whereas the degradation of the tensile strength is substantially influenced.
Chemical structure construction of DOPO-containing compounds for flame retardancy of epoxy resin: A review
2023, Progress in Organic CoatingsFire-safety epoxy resin with excellent comprehensive performance becomes the requirement for further application in the industry. As a commercially available compound, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) exhibits strong potential to develop effective flame retardants for epoxy resin due to its reactive group of P
H and dominant function in gas phase. In order to overcome the adverse effect on mechanical properties and improve flame-retardant effectiveness, DOPO has been used as an initial reactant to synthesize various compounds for epoxy resin. In terms of the different substituents at phosphorus atom in DOPO including PC, PO/PN, and P-ring structure, this work reviews the research progress of these derivatives with the phosphorus element only from DOPO structure in the last decade. Around the relationship between chemical structure and properties, the effect of DOPO-containing compounds on the properties of epoxy resin is discussed, mainly involving flame-retarded performance, heat resistance, and mechanical properties. Although a large number of DOPO derivatives has been designed and used for epoxy resin, some issues still need to be improved, such as migration of flame retardants, deterioration of mechanical properties, processibility, economic competitiveness, and so on. Therefore, an efficient flame retardant can not only improve the flame retardation at low loading but also maintain original outstanding properties of epoxy resin. Through tailoring the chemical structure, to endow epoxy resin with outstanding comprehensive performance in an eco-friendly and economic manner is the further development tendency for DOPO-based flame retardants.Preparation and properties of hydrophobic and transparent wood
2022, Journal of Bioresources and BioproductsNatural wood (NW) was treated with sodium chlorite to obtain delignified wood (DW) in this study, then epoxy was impregnated to get transparent wood (TW), and finally the TW was coated with perfluorodecyltriethoxysilane (FAS) to acquire hydrophobic and transparent wood (HTW). The hydroxyl group generated by the hydrolysis of the FAS and the hydroxyl group of the epoxy underwent a dehydration condensation reaction to generate a Si–O–C bond, while the FAS molecules were also dehydrated and condensed to form a Si–O–Si bond according to Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Therefore, the mechanical property and thermal stability of the HTW were better than the TW based on their tensile tests and thermogravimetric analysis (TGA). Due to the large reduction of hydroxyl in epoxy, the hydrophobicity of the HTW was greatly improved compared with the TW, and their contact angles were 113° and 77°, respectively. The results of scanning electron microscopy (SEM) showed that epoxy was filled in the voids of wood. In addition, the coating of the FAS did not obviously reduce the transmittance, and the transmittance of the TW and HTW was 69% and 67% at 750 nm. All in all, the HTW has potential for application in transparent decoration.