A variety of toughening agents are used to modify epoxy resins that improve the fracture toughness of the epoxy systems. The basic goal in toughening cross-linked epoxy resins that are normally brittle at room temperature is to improve crack resistance and toughness without significantly decreasing other important inherent properties, such as the flexural modulus and the thermomechanical properties of the original epoxy resins.In the present study, thermally stable epoxy resin modified urea-formaldehyde/silicon blends have been prepared by in situ polymerization technique. The materials were modified with triethylenetetramine (hardener) to obtain highly cross-linked thermosetting resins. The physical properties of the resulting blends were evaluated by measuring the impact strength, which is found to be increased by more than 25% of that of the cured and blank epoxy resin. The impact fracture surfaces are examined using scanning electron microscopy (SEM) to reveal the morphological changes.The hardness was found to be high in the case of modified epoxy resin as compared to blank epoxy. The influence on the thermal properties and the behavior of different curing agents on resins were investigated by thermogravimetrc analysis (TGA) and differential scanning calorimetry (DSC). The results of the modified epoxy resins showed remarkably high thermal stability as well as a higher degree of solvent resistance as compared with blank epoxy resin.

No abstract

Novel epoxy resins with high impact strength and hardness have been synthesized by the bulk polymerization method. These materials were modified with styrene, polymethylmethacrylate, methylmethacrylate, and acrylonitrile to obtain both thermoplastic and thermosetting resins. Physical properties of the resulting mixtures were evaluated by measuring the impact strength, hardness and the degree of compression. Thermograms were used to investigate the behavior of different curing agents with resins. Comparison of results of modified epoxy resin with blank epoxy resin reveals that modified resins show remarkably high glass transition temperatures and thermal stability, as well as hardness. These materials exhibit a higher degree of solvent resistance.

The synthesis of thermally stable Tetra-di-glycidyl ether bisphenol-A (TDGEBA) Epoxy resin and Sulphanilamide (SAA) have been synthesized from (SAA) and TDGEBA by in situ polymerization technique to obtain Tetra-di-glycidyl ether bisphenol-A Sulphanilamide (TDGEBA/SAA) Epoxy resin and modified with various percentages of polyester (PE) to obtain Tetra diglycidyl ether bisphenol-A Sulphanilamide polyester (TDGEBA/SAA-PE), highly cross-linked thermosetting polymer network. These materials were cured with triethylenetetramine TETA (hardener) to obtain highly cross-linked thermosetting resin. The physical properties of the resulting blends were evaluated by measuring the impact strength of (TDGEBA/SAA-PE) (increased more than 30% than the unmodified epoxy resin) and hardness that is found to be higher than unmodified epoxy resin. Differential scanning calorimetry (DSC) and thermo gravimetric (TGA) analysis were also cured to assess the thermal behavior of the samples. DSC of the (TDGEBA/SAA) Epoxy resin cured with TETA showed exothermic reactions and the glass transition temperature (Tg) shifted from 350˚C to 400˚C compared with uncured epoxy and the thermal stability of the TDGEBA/SAA epoxy resin modified increased with increasing of PE. Scanning Electron Microscopy (SEM) studied the morphology of the samples after unnotched impacts on fracture surfaces. These materials exhibited a higher degree of solvent resistance.

No abstract