Study on curing kinetics and curing mechanism of epoxy resin based on diglycidyl ether of bisphenol a and melamine phosphate

Preparation and Properties of Toluene-Diisocyanate-Trimer-Modified Epoxy Resin

In this paper, a novel modified epoxy resin with an interpenetrating network structure for use as a grouting material with high toughness was prepared by a method of graft copolymerization between polyurethane prepolymer (PUP) trimer and epoxy resin (E-44). Polyurethane prepolymer was synthesized using poly(propylene glycol) (PPG) and 2,4-toluene diisocyanate trimer (TDIT) at 70 °C for 3 h. The graft copolymer was prepared by grafting polyurethane prepolymer onto the side chain of epoxy resin at 110 °C. The mechanical properties, fracture surface morphology, chemical structure, thermal properties, and corrosion resistance of the modified epoxy resin curing products were studied. Due to the beneficial flexible segments and the interpenetrating network structure, the results show that when the ratio of epoxy resin to polyurethane prepolymer is 10:2, the optimum mechanical properties are obtained; these include a compressive resistance of 184.8 MPa, impact property of 76.6 kJ/m², and elongation at break of 31.5%. At the same time, the modified epoxy resin curing product also has excellent heat and corrosion resistance. This work provides a new method for the study of epoxy resins with high performance.

Bulk cure study of nanoclay filled epoxy glass fiber reinforced composite material

The correlation between cure properties and structure of nanoclay filled composite laminate has not been studied extensively. Most of the cure studies were preferably done using small samples through a calorimetric method. In this study, the effect of varying weight ratio of nanoclay (1–5 wt%) on bulk cure properties of epoxy glass fiber reinforced composite (GFRC) laminates was studied. Bulk cure of unfilled and clay filled GFRC laminates was determined using the dynamic mechanical analysis-reheat method (DMA-RM). DMA-RM cure properties gave a better coordinate method, with better cure efficiency achieved in clay filled GFRC laminates when compared to unfilled GFRC laminates. The correlation between nanoclay and DMA-RM degree of cure was coordinated with compressive and in-plane shear strength properties. The degree of cure value of 78% by DMA-RM at 1 wt% clay filled GFRC corresponds with the compressive modulus and in-plane shear strength highest values, which are 20% and 14% increase, respectively, also at 1 wt% clay filled GFRC. The structures of the unfilled and clay filled epoxy were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Clay filled epoxy up to 3 wt% showed no distinct diffraction peak, which suggested that nanoclay is randomly dispersed in the matrix.

Structural Analysis of a Melaminium Polyphosphate from X-ray Powder Diffraction and Solid-State NMR Data

The crystal structure of the environmentally friendly flame retardant melaminium polyphosphate (MPoly) (2,4,6-triamino-1,3,5-triazinium x PO(3))(n)was determined by a direct-space global optimization technique from X-ray powder diffraction data. Solid-state NMR was used to corroborate the proposed hydrogen-bonding model and to determine the average degree of polymerization (n > 100). An analysis of the crystal structure of MPoly reveals aspects of molecular geometry and packing that are characteristic for melamine-containing compounds and polyphosphate salts. A comparison of MPoly with the crystal structures of its precursors melaminium orthophosphate (MP) and melaminium dihydrogenpyrophosphate (MPy) provides insight in the mechanism of the endothermic dehydration processes that takes place in the reaction path MP --> MPy --> MPoly. Solid-state NMR characterization of various samples of the same batch showed inhomogeneities in the MPoly composition. Various quantities of orthophosphates were found, which cannot be assigned to be MP.