Studies on the Thermal Properties and Flame Retardancy of Epoxy Resins Modified with Polysiloxane Containing Organophosphorus and Epoxide Groups

Abstract

ABSTRACT:A novel epoxy resin modifier, phosphorus-containing epoxide siloxane (PES) with pendant epoxide and cyclic phosphorus groups on the side chain of the polysiloxane backbone, was synthesized by the ring-opening reaction of epoxy-siloxane with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). PES was characterized by 1 H NMR and FT-IR measurements, and then it was employed to modify an epoxy resin at various ratios via prereaction with 4, 4 0 -diaminodiphenyl-methane (DDM) as curing agent. In order to compare with the epoxy resins modified with PES, DOPO-containing epoxy resins also cured under the same conditions. The thermal, thermomechanical, and flame-retardant properties of all cured polymers were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), the limited oxygen index (LOI) and cone calorimetry. The results showed that the epoxy resins modified with PES exhibited much better thermal properties and flame retardancy than the DOPO-containing epoxy resins at the same phosphorus content and the neat epoxy resin. In recent years, epoxy resins have been widely used in coatings, adhesives, aerospace and electronic industries, especially in microelectronic field. However, with the rapid development of electronic technology, the heat resistance and flame retardancy of conventional epoxy resins couldn't meet the requirements of these applications. 1,2 Much work has been done in an attempt to make epoxy resin more flame retardancy and great progress has been achieved so far. [3][4][5][6][7][8][9][10] At present, with the consideration of avoiding the generation of toxic and halogenated gases, the trend is toward using environment-friendly flame retardant to modify the epoxy resins. One example is the use of organophosphorus, which shows evident effectiveness as a flame retardant. [4][5][6][7][8] However, this increase in flame retardancy is always accompanied by a decrease in the initial decomposition temperature, which makes the modified epoxy resins unfit for those applications requiring critical thermal stability. Moreover, due to the limit from chemical structures in molecular design during the introduction of phosphorus, the low crosslink density of the cured epoxy resin often decreases T g of the epoxy resin. 9,10 According to a previous report, 11 the flame retardancy of phosphorus could be improved if providing an environment to reduce the thermal oxidation of phosphorus char at the high temperature region. Organosiloxanes possess many properties, including hydrophobic property, non-flammability, excellent thermo-oxidative stability and electronic property, which can compensate for the disadvantages of phosphorus flame retardant. Thus, organosiloxanes would be one of choices for enhancing the flame retardancy and heat resistance. [12][13][14] In this paper, a novel modifier for epoxy resins, epoxy oligomer containing organophosphorus and organosilicon, was synthesized by the reaction of methylhydrosiloxane-dimethylsil...

New Reactive Isoeugenol Based Phosphate Flame Retardant: Toward Green Epoxy Resins

“…40 Furthermore, in the case of DOPO addition, an unintended consumption of epoxy group was reported, leading to a lower network density and a subsequent decrease of the thermoset Tg. 41,42 Thus, the route which uses reactive organophosphorus FRs monomer is preferred in order to maximize the fire retardancy and to reduce the evolution of toxic species. Wang et al [43][44][45] have prepared epoxy resins containing phosphorus groups and some other groups (piperidine, imidazole, benzimidazole) to combine char promotion, radical quenching and fuel dilution effects.…”

Impact of halogen-free flame retardant with varied phosphorus chemical surrounding on the properties of diglycidyl ether of bisphenol-A type epoxy resin: synthesis, fire behaviour, flame-retardant mechanism and mechanical properties

“…[1][2][3] Bifunctional diglycidyl ester of bisphenol A (DGEBA) based epoxy resins, are often utilized for semiconductor encapsulation in EE applications. [5][6][7][8][9][10][11][12][13][14][15][16][17] Generally, phosphorous containing flame retardants (P-FRs) are always regarded as one of the best choices to reduce flammability of epoxy resin since lots of halogenated flame retardants (H-FRs) are forbidden owing to their serious hazards for environment and human. Nevertheless, the intrinsic flammability of DGEBA/DDS is one of challenges for their products.…”

Study on the modification of epoxy resin by a phosphorus‐ and silica‐containing hybrid

“…The limited oxygen index was a measuring method for the flame retardant, which was defined as the minimum oxygen content in oxygen and nitrogen mixture to sustain combustion 18, 22, 23. Compared with the unmodified epoxy resin, the LOI values of the epoxy resin modified by DPS with or without the catalyst were relatively higher, indicating more oxygen needed to support flammable after the determined bar ignited.…”