In this study, the various combinations of low- and high-decomposition temperature initiators and dual promoters were used to cure an unsaturated polyester resin. Methyl ethyl ketone peroxide (MEKP) and acetyl acetone peroxide (AAP) solutions were used as low-temperature initiators. Benzoyl peroxide (BPO) and t-butyl perbenzoate (TBPB) were used as medium and high-temperature decomposition initiators, respectively. Gel time and pseudo-adiabatic exotherm measurements have been used to study the curing behaviour. It has been demonstrated that the low-temperature initiator decomposition does not interfer with the high-temperature initiator decomposition. It was found that the exotherm peak and cure rate have been affected by the decomposition rate of low-temperature initiator in different ways. It is shown in this study that for cobalt naphthenate and dimethyl aniline (DMA) dual promoter systems that, with the increasing of DMA concentration, namely high reactive promoter, exotherm parameters sharply change. It might be due to the more reactive nature of DMA in comparison with the cobalt naphthenate reactivity. Now we can say, a judicious choice of a dual initiator or a dual promoter can avoid short time exothermic reactions, so a dual system can be much more effective than a single one.

A detailed study on the curing of Bisphenol A-based liquid epoxy resin such as Lapox B-13 (Viscosity 12000-16000 mpos) and Lapox B-11 (Viscosity 9000-12000mpos) with various amines like EDA (Ethylenediamine),DETA (Diethylenetriamine), TETA (Triethylenetetramine), AEP (Aminoethylpiperazine) and IPDA (Isophoronediamine) as curing agents have been carried out. The curing rates and the exotherm have been determined. The effect of various accelerators or modifiers on the curing rate is also worked out using salicylic acid, phenol and nonylphenol. The results obtained reveal that the curing rates are faster in the case of tertiary amines compared to secondary and primary amines. The high exotherm and the least curing time in the case of AEP can be attributed to the tertiary nitrogen group present and which can act as a catalyst for the curing process. It is also observed that a cyclic amine like Isophoronediamine which has only primary amine group takes a longer time for curing with a low isotherm. The data obtained with accelerators on the curing studies clearly indicate that they enhance the curing rate and the exotherm in all the cases. In majority of the cases the cured samples obtained were hard and polymeric transparent materials. The effect of mass of the sample on the curing rate and isotherm has also been observed. All the cured samples show good resistance to moisture absorption and show high chemical resistance.    

The diglycidyl ether of bisphenol A and boron trifluoride-diethylamine, mono-allylamine and piperidine complexes are used in a model system to investigate the cure reaction which occur during polymerization. Experiments using FT-IR at different temperatures show that boron trifluoride-amine complexes break down rapidly to tetrafluoroboric acid at 100 degrees C and above. Tetrafluoroboric acid forms complexes with epoxy groups, producing an activated monomer that reacts with epoxy in an etherification reaction. Dynamic DSC thermograms also show a small exotherm peak due to complex formation before the large exotherm peak of etherification reaction. A phenomenological approach is used to characterize the cure kinetics. Kinetic analysis, using integral procedure on dynamic data, indicates that the cure reaction data of diglycidyl ether of bisphenol A with boron trifluoride-amine complexes can be described well with the homogeneous first-order reaction model. The activation energies are found to be in the range of 90.85 kJ/mol for boron trifluoride-diethylamine; 96.88 kJ/mol for boron trifluoridemonoallylamine; and 94.45 kJ/mol for boron trifluoride-piperidine complexes.

Simultaneous thermal analysis (STA) method has been applied to study decomposition reactions of AP under a flowing nitrogen atmosphere and static air. Results obtained indicate that a phase transformation occurs prior to the decomposition reaction. Decomposition takes place exothermally in two stages, first stage of decomposition could be suppressed by the controlled heating programme. Addition of a small amount of boron lowered the temperature of the exotherm and increased the overall enthalpy of reactions.

Epoxies are generally cross-linked by the addition of a hardener, most of the time a diamine such as diamine diphenyl sulphone, oxydianiline or methylene diamine, and then thermocured. These formulations are quite often used, particularly in the aerospace industry for making structural materials, prepregs or composites. In this paper we have investigated the cross-linking reactions of a difunctional cycloaliphatic epoxide monomer 3,4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexane carboxylate initiated by UV-irradiation and compared the kinetics with N,N-diglycidyl- 4-glycidyloxyaniline (a nitrogen-containing monomer with a functionality of three) and 4,4'-methylenebis (N,N-diglycidylaniline) (another nitrogen-containing monomer with a functionality of four). Kinetics is followed using a differential photocalorimetry (DPC) technique. Upon UV irradiation in the presence of cationic photoinitiator, the difunctional cycloaliphatic epoxide monomer shows an exotherm peak whereas for the latter two monomers, no exotherm peaks were observed from the sample as a result of exposure to the UV source. To explain the phenomenon observed, the effect of addition of two amines with wide difference in the basicity of p-nitroaniline and pyridine, has been studied on the UV-curing of epoxy resins. It has been found that the presence of amines does retard the rate of photopolymerization and the extent of retardation is dependent on the basicity of the amine. Of the two amines used, pyridine and p-nitroaniline, the former is a stronger inhibitor, because of the ready availability of the lone pair of electrons. The results explain the non-reactivity of nitrogencontaining epoxy monomers N,N-diglycidyl-4-glycidyloxyaniline and 4,4'-methylenebis (N,N-diglycidylaniline) to cationic polymerization upon exposure to UV-radiation.

Acid-activated corn husk waste (CHW) was used to investigate the adsorption mechanism of Indigo Carmine (IC) dye from an aqueous solution. The effect of different operating parameters such as pH (1-7), initial IC dye concentration (40-400 mg/L), contact time (5-75 min), and heating temperature (25–200 °C) was measured on the removal of IC dye by the CHW. The maximum uptake of IC dye was observed at an initial pH of 2. The maximum capacity of 13.57 mg/g and the maximum dye removal of 89.01 % in wastewater. The adsorbents were characterized using Fourier Transforms Infrared Spectrophotometry (FTIR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray Fluorescence (XRF), and Thermogravimetry Analysis. The characterization process reveals the differences in adsorbent characteristics before and after the adsorption processes. The Langmuir showed the best fitting (R2 = 0.977) and described multilayer adsorption on diverse surfaces. The pseudo-second-order kinetic model best correlated with the experimental data (R2 = 0.981). Thermodynamics revealed that adsorption was favorable spontaneous and exotherm. The study's results indicated that using CHW as a low-cost adsorbent to treat IC dye was efficient and beneficial to the environment.