Thermal Degradation Of Epoxy Resin Research Articles

Influence of heating rate and atmospheric conditions on the thermal response of CFRP and its constituents

The thermal stability of carbon fibre-reinforced polymer (CFRP) and its constituents (neat epoxy resin and carbon fibre) are studied in terms of mass loss using a thermogravimetry technique at different heating rates and two atmospheric conditions (air and pure nitrogen). By interpreting the mass loss over a temperature range of 25–900 °C, it was possible to identify the specific mechanisms of polymer degradation. In an oxygen-free pure nitrogen atmosphere, the thermal degradation of epoxy resin used as the composite's matrix is strongly inhibited up to the temperature of 400 °C, after which it undergoes thermal decomposition, in contrast to the carbon fibre reinforcement that does not degrade in nitrogen. In an air atmosphere, however, the CFRP and its constituents degrade via a complex reaction pathway encompassing three endothermic reactions (pyrolysis of the epoxy resin, oxidation of the residue from the first pyrolysis reaction and carbon fibre oxidation) that overlap and one endothermic reaction in nitrogen (pyrolysis of the epoxy resin). A deconvolution technique based on fitting log-normal distributions to the first derivative of the mass loss data has also been undertaken to separate the thermal decomposition reactions for each CFRP to understand the effect of each reaction's contribution. It can be used to evaluate complex thermal degradation processes that can be characterised by finding the respective kinetic parameters of each reaction, e.g. by using combined kinetics analysis.

Effect of a Novel Polysilicone on the Flame Retardancy and Thermal Degradation of Epoxy Resin

Effect of a Novel Polysilicone on the Flame Retardancy and Thermal Degradation of Epoxy Resin

Kinetic simulation and prediction of pyrolysis process for non-metallic fraction of waste printed circuit boards by discrete distributed activation energy model compared with isoconversional method.

Kinetic studies on the pyrolysis process for non-metallic fraction (NMF) of waste printed circuit boards (WPCBs) were conducted using both the isoconversional SKAS method and the discrete distributed activation energy model (discrete DAEM). The pyrolysis process of the NMF sample could be classified into three stages, and a large mass loss was observed from 98 to 570°C, attributed to thermal degradation of epoxy resins in the NMF sample. The kinetic parameters, including activation energies (E i), pre-exponential factors (A i), and contributed fractions (f i,0), were determined. It indicated that the discrete DAEM could predict the pyrolysis process of the NMF more accurately and completely when compared with the isoconversional SKAS method. In the discrete DAEM, E i and A i values were evaluated at 99 equally spaced intervals of conversion. The E i and A i (in the form of lnA i) transformed with reaction progress, ranging from 80.9 to 240.5kJ/mol and 19.07 to 39.55s-1, respectively, with the conversion increased from 0.01 to 0.99. The pyrolysis of the NMF of WPCBs could be accurately characterized as 17 dominating reactions from f i,0 results. Graphical abstract ᅟ.

Kinetic study of the stabilizing effect of aluminum trihydroxide on thermal degradation of epoxy resin

AbstractThe stabilizing effect of epoxy resin (EP)/aluminum trihydroxide (ATH) was measured by thermogravimetric analysis (TGA) in an N2 flow. The Kissinger and Flynn-Wall-Ozawa methods were used to determine the activation energy of non-isothermal degradation at different stages. The results showed that there was a slight increase in activation energy after ATH was added. It confirms the fire-retardant effect of ATH on the thermal degradation behaviour of pure EP. The Flynn-Wall-Ozawa method showed that flame-retardant ATH remarkably enhanced the activation energy of the thermal degradation process for EP, albeit the conversion rate being only 10%, which demonstrated the stabilization of ATH to the char layer of EP.

Effect of graphene nanosheets and layered double hydroxides on the flame retardancy and thermal degradation of epoxy resin

Graphene nanosheets and layered double hydroxides showed a synergistic effect on improving the flame retardancy of epoxy resin.

Thermal Degradation of Epoxy Resins Containing Aluminum Compounds

A novel cheap macromolecular intumescent flame retardants (Al-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-aluminum characterized by IR. Epoxy resins (EP) were modified with Al-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Al contents of 4.0 % get a LOI of 26.8% and char yield of 19.5%. Dilatation, SDR and MSD of EP/Al-MIFR decreased. The degradation behavior of the EP/Al-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Al and P at the residue were increased.

Thermal degradation of epoxy resin grafted with polyurethane

Abstract Epoxy resin grafted with polyurethane was synthesized and characterized through a series of tests. The grafting reactive process between the pendant secondary hydroxyl groups on the side chains of epoxy resin and the isocyanate groups of pre-polyurethane were investigated by Fourier transform infrared spectroscopy. Thermal behavior of the grafted epoxy resin was investigated by thermogravimetric analysis within 40–500°C. The degradation of grafted epoxy resin involved two stages. Microstructures of the polyurethane section and grafted epoxy resin were observed by field emission scanning electron microscopy. Model fitting method was employed to calculate the thermal degradation model of grafted epoxy resin. In this paper, 15 typical kinetic mechanisms were introduced into the model fitting method, such as Coats-Redfern method and Achar-Brindley-Sharp-Wendworth method, to obtain the kinetic function of thermal degradation for grafted epoxy resin.

Thermal Degradation of Epoxy Resins Containing Copper Compounds

A novel cheap macromolecular intumescent flame retardants (Cu-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-copper characterized by IR. Epoxy resins (EP) were modified with Cu-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Cu contents of 3.0 % get a LOI of 27.0% and char yield of 19.4%. Dilatation, SDR and MSD of EP/Cu-MIFR decreased. The degradation behavior of the EP/Cu-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Cu and P at the residue were increased.

Effect of nanosilica on the kinetics of cure reaction and thermal degradation of epoxy resin

Nanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol-A based epoxy (DGEBA), and 3,5-diamino-N-(4-(quinolin-8-yloxy) phenyl) benzamide (DQPB) as curing agent were obtained from direct blending of these materials. The effect of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique. The activation energy (Ea) was obtained by using Kissinger and Ozawa equations. The Ea value of curing of DGEBA/DQPB/10% NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction. The Ea values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol, respectively. The addition of 10% of NS to the curing mixture did not have much effect on the initial decomposition temperature (Ti) but increased the char residues from 20% to 28% at 650°C.

Thermal degradation of epoxy resin reinforced with polypropylene fibers

AbstractThe influence of polypropylene fibers on the thermal degradation of epoxy composites was investigated with thermogravimetric analysis. Three composites with 5, 10, or 15 wt % polypropylene fibers were prepared with epoxy as a matrix material. The polypropylene fibers, used as reinforcing materials, retarded the thermal decomposition, and increasing the weight percentage of the fiber material increased the thermal stability to a certain extent. Of the three composites, the 10 wt % polypropylene fiber/epoxy resin composite showed very good thermal stability, which was indicated by the increase in the resin decomposition temperature from 280°C for the 5 wt % polypropylene fiber/epoxy resin composite to 375°C for the 10 wt % polypropylene fiber/epoxy resin composite. The Horowitz–Metzger method was used to calculate the activation energies, and the results were tabulated. A morphological analysis was carried out with scanning electron microscopy to evaluate the dispersion of the fibers in the epoxy matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 500–503, 2007

Thermal degradation kinetics of epoxy-anhydride resins: II. Influence of a reactive diluent

The effect of reactive diluent on the thermal degradation kinetics of epoxy-anhydride resins has been studied by thermogravimetry in both isothermal and non-isothermal conditions. It was found that the kinetics of thermal degradation can be described well by a simple reaction order model. The addition of reactive diluent increases the apparent activation energy and the kinetic exponent. A difference was also observed between the set of kinetic parameters obtained by kinetic analysis of isothermal and non-isothermal data. Such behavior indicates a more complex mechanism of thermal degradation of epoxy resin.

Studies on thermal degradation of epoxy resins by high-resolution pyrolysis-gas chromatography

The optimum pyrolytic conditions for thermosetting epoxy resin samples were first empirically studied. On the basis of the optimized pyrolytic conditions, epoxy prepolymers and epoxy resin samples cured with and without curing agents, such as diamine and dicarboxylic acid anhydride, were studied using high-resolution pyrolysis-gas chromatography. In addition to some intact prepolymer molecules, various degradation products characteristic of the prepolymers, up to diglycidyl ether of bisphenol A, were detected on the pyrograms of the prepolymers. On the other hand, various phenols characteristic of the prepolymers and a variety of pyrolyzates characteristic of the reacted curing agents, including intact dicarboxylic acid anhydride, were observed on the programs of the cured resin samples. The potential of this technique for studying the curing process of the epoxy resins is discussed.

Combined pyrolysis and radiochemical gas chromatography for studying the thermal degradation of epoxy resins and polyimides. I. The degradation of epoxy resins in nitrogen between 400°C and 700°C

AbstractThe thermal degradation of a bisphenol A‐based epoxy resin (EP 274) cured with 4,4′‐diaminodiphenyl methane (DDM) and with phthalic anhydride (PA) was studied using a radiochemical pyrolysis gas chromatography technique. Conclusive evidence for some of the degradation mechanisms of these resins was obtained by pyrolyzing samples containing various 14C‐labelled groups and analyzing the products using this method.

Mechanisms for initiating thermal degradation of certain anhydride‐cured epoxides

AbstractThe mechanisms initiating the unusual thermal degradation of epoxy resins cured with methylbicyclo [2.2.1] hept‐5‐ene‐2, 3‐dicarboxylic anhydride were investigated. Two mechanisms were elucidated, each assuming greater importance than the other depending upon the severity of the thermal environment. One is an internal acid‐initiated mechanism operating from 240 to 350°C. under slow heating rates. The other is a reverse Diels‐Alder reaction which operates above 350°C., usually under instantaneous pyrolysis conditions such as encountered in ablation. These two mechanisms, working simultaneously, promote further crosslinking of the resin system giving rise to a greater amount of carbonaceous residue than would otherwise be expected.

The thermal degradation of some epoxy resins

AbstractThe thermal degradation of epoxy resins was studied in a static system over the temperature range 300–450°C. The reaction proceeds without an induction period, the initial rate being maximum. The rate W increases with temperature according to the law W = Ae–E/RT. The effective activation energy was 35 kcal./mole. The reaction products consist of gases, a resinous liquid, and a solid residue. The liquid has practically the same spectral characteristics in the infrared as the initial epoxy compound. In the infrared spectrum of the residue the bands characteristic of the epoxy group are absent. Water and formaldehyde were found among the liquid products. Methane and carbon monoxide were found in large amounts by means of a chromatographic method. In the thermal degradation of the unhardened epoxy resin the low molecular fraction volatilizes, and the high molecular fraction degrades liberating the radical which isomerizes and decomposes to CO and ĊH3. The methyl radical abstracts a hydrogen atom from the polymer and is converted to methane. The ROĊH2 radical formed on liberation of the epoxy group yields formaldehyde. Among the gaseous products formed in the thermal degradation of the epoxy resin hardened by polyethylene polyamine (PEPA) were found H2, CO, CH4, C2H6, C2H4, C3H6, and C3H8. Ethane, ethylene, propylene, and propane are possibly produced by decomposition of the PEPA radical. The thermooxidative degradation of epoxy resins was investigated in a static system. The reaction was shown to be of the degenerate branching chain type. The dependence of the induction period on the oxygen pressure and on the temperature was determined.