M. J. Shim

Kinetic studies of an epoxy cure reaction by isothermal DSC analysis

Abstract Autocatalytic cure kinetics for an epoxy system was studied by isothermal DSC analysis. The system used in this study was the diglycidyl ether of bisphenol A(DGEBA)/4,4′-methylene dianiline (MDA) system with various contents of phenyl glycidyl ether (PGE)-acetamide (AcAm). Regardless of the PGE-AcAm content, the shape of the conversion curves was sigmoid, and this meant that DGEBA/MDA/PGE-AcAm system underwent an autocatalytic cure reaction. When the PGE-AcAm content increased, the cure rate increased due to the catalytic role of hydroxyl groups of PGE-AcAm. From the comparison between theoretical prediction and experimental data, it was found that the autocatalytic expression correctly represented to analyze the cure kinetics of these systems.

Curing behavior of an unsaturated polyester system analyzed by Avrami equation

The isothermal cure behavior of an unsaturated polyester resin system is studied by differential scanning calorimetry. The reaction heats (at different curing temperatures) are presented and compared to the results of the previous studies. Various kinetic parameters as well as details of the curing process can be obtained and elucidated, based on the Avrami theory. The experimental results reveal that this analytical method is valid for describing the curing behavior of unsaturated polyester resins.

Curing Reaction and Phase Change in a Liquid Crystalline Monomer

An epoxy monomer was cured in liquid crystalline phase with three different amines to form (LCT). The thermal transitions of the LCT were studied by differential scanning calorimetry (DSC), wide angle X-ray diffraction. (WAXD) and polarized optical microscopy (POM). Different curing features are observed depending on the curing agent and reaction condition, which is related to the formation and development of LC phase during cure. An isoconversional analysis is used to characterize the cure process.

Dynamic DSC Characterization of Epoxy Resin by Means of the Avrami Equation

A phenomenological approach was used to characterize the cure processes of epoxy resins (a diglycidyl ether of bisphenol A and its modifier CTBN) from dynamic experiments by DSC. Various kinetic parameters were obtained by using a modified Avrami expression. The resulting overall activation energies for the two systems agreed very well with the published data in the whole cure temperature range. In contrast with the isothermal results and the general dynamic models, a change in the exponent and the non-linear temperature dependence of the rate constant were also observed.

Studies on Immuno-Modulatory and Antitumor Effects of Crude Polysaccharides Extracted from Paecilomyces sinclairii

Neutral salt soluble [0.9% NaCl (Fr. NaCl)], hot water soluble (Fr. HW) and methanol soluble (Fr. MeOH) materials were extracted from Paecilomyces sinclairii. In vitro cytotoxicity tests. Fr. HW was not cytotoxic against MH3T3, Sarcoma 180 and HepG2 cancer cell lines at the concentration of , while HT-29 cell line was cytotoxic at the concentration of . Fr. NaCl and Fr. MeOH were slightly cytotoxic to the cell lines. Intraperitoneal injection with Fr. NaCl and Fr. MeOH exhibited antitumor activity with life prolongation effect of 32.3% in mice inoculated with Sarcoma 180. Fr. NaCl improved proliferation of spleen cells and the immunopotentiation activity of B lymphocyte by increasing spleen cell numbers and the alkaline phosphatase activity by folds, respectively. Fr. NaCl generated of nitric oxide (NO) when cultured with RAW 264.7, a mouse macrophage cell line, at the concentration of , while iipopolysaccharide, a positive control, produced . The Fr. NaCl showed the hightest antitumor effect and activation of B lymphocytes and macrophage. From these results, antitumor effect of P. sinclaitii was likely due to immunopotentiation activity.

Thermal degradation of LC epoxy thermosets

A novel liquid crystalline (LC) epoxy monomer was cured with different types of hardeners. The thermal-degradation properties of cured thermosets were evaluated by thermogravimetric (TG) analysis. Several widely used kinetic models were reviewed and used to fit the TG data. The experimental results showed that the methods from one constant heating rate are insensitive to the magnitude of reaction order n. The Kissinger and Osawa methods from multiple processes would give more confident kinetic parameters in these observed systems.

Effects of CTBN on the cure characteristics of DGEBA/MDA/PGE-AcAm system

Abstract Effects of carboxyl-terminated butadiene acrylonitrile rubber (CTBN) on the cure characteristics of diglycidyl ether of bisphenol A (DGEBA)/4,4′-methylene dianiline (MDA)/phenyl glycidyl ether (PGE)-acetamide (AcAm) system were studied by autocatlytic cure rate expression. Cure rate at initial stage increased with the increment of the CTBN content, however, at some high stage cure rate was inverted due to the diffusion control of formed CTBN domain. The total conversion was also decreased with the increase of the CTBN content.

Antitumor and Immuno-modulatory Effect of Crude Polysaccharides from Fruiting Body of Tremella aurantialba Against Mouse Sarcoma 180

Tremella aurantialba, one of edible and medicinal mushrooms belonging to Tremellaceae of Basidiomycota, has been known to have outstanding curing effects on coughing, tracheitis and hypertension of humans and antitumor activity on the sarcoma 180 and Erhrlich carcinoma of mice. Neutral saline soluble (0.9% NaCl), hot water soluble and methanol soluble substances (hereinafter referred to Fr. NaCl, Fr. HW and Fr. MeOH, respectively) were extracted from fruiting body of the mushroom. In vitro cytotoxicity tests showed that all crude polysaccharides extracted from the fruiting body were not cytotoxic against cancer cell lines such as RAW 309 CR.1 and Sarcoma 180 at the concentration of . Intraperitoneal injection with crude polysaccharides exhibited life prolongation effect of in mice inoculated with Sarcoma 180. Fr. MeOH improved the immunopotentiation activity of B lymphocyte by increasing the alkaline phosphatase activity by 1.16 folds at the concentration of . In case of Fr. HW, the numbers of peritoneal exudate cells and circulating leukocytes were increased by 1.42 and 2.87 folds, respectively.

Bulk properties of epoxy resin modified by epoxy–aminosilane copolymers

A linear epoxy-aminopropyltriethoxysilane addition polymer was used as a new epoxy modifier. In this paper, the thermal and mechanical properties have been determined by differential scanning calorimetry (DSC) and mechanical testing. The experimental results show that this copolymer modifier can effectively improve the toughness of resins without sacrificing their thermal resistance, stiffness and strength. As a comparison, the properties of epoxy resin blended with aminopropyltriethoxysilane (γ-APS) have been carried out simultaneously.

The macrokinetic model of thermosetting polymers by phase-change theory

Abstract The general rate law frequently used to describe the cure process of thermosetting polymers (thermosets) can be deduced by analysing the Avrami theory. Every parameter in it can be given reasonably. From the macrokinetic model, it is also possible to describe the non-isothermal cure process of thermosets. A comparative example shows that the theoretical prediction is in good agreement with the experimental data.