Some structure‐property relationships in polymer flammability: Studies of phenolic‐derived polymers

Abstract

SynopsisThe investigation of the thermal degradation of the char-forming phenol-formaldehyde resins is conducted to provide information for the systematic design of high temperature flame-resistant phenolics. Three different processes of curing are used (1) Formaldehyde or s-trioxane is reacted with m-substituted phenol-formaldehyde oligomers under acidic conditions to give the methylene bridged-novolac resins. (2) Phenol and rn-substituted phenols are reacted with CH20 under basic conditions and then heated to give the methylene bridged resol resins. (3) p-Terephthaloyl chloride and m-and p-substituted novolac oligomers are reacted to give cured resins with ester linkages. The evaluation of the effect of various substituents indicates that the oxygen index (01) increases from about 33 for unsubstituted phenolics to about 75 for meta-halogen substituted phenolics. The evaluation of the effect of various crosslinking agents shows that the 01 for CHzO-cured phenolics is 75 as compared to 50 for the trioxane cured phenolics and to 40 for the terephthaloyl chloride cured phenolics. A set of phenolic copolymers with different weight percentage content of halogen substituted phenols are synthesized as novolacs and resols. The results surprisingly indicate no increase of 01 for the cured novolac copolymers, whereas the increase is observed for the cured resol copolymers. The activation energy for the thermooxidative degradation of the cured novolacs is about 12-15 kJ/mol lower as compared to tpt of the cured resols.

Iron-based soft magnetic composites with Mn–Zn ferrite nanoparticles coating obtained by sol–gel method

“…Organic coatings are widely applied in SMCs due to their rapid and nonhazardous coating process and largely improved cured-film properties. These include epoxy, polyamide, silicone resins and polyvinyl alcohol [8][9][10]. The thermal treatment temperature for these materials is limited by the thermal resistance of the organic insulating layer between the magnetic particles; therefore phosphates (zinc/iron/manganese) and oxides (MgO) with high resistance temperatures were selected instead of organic coatings [11,12].…”

Electrical, mechanical, and thermal properties of exfoliated graphite/phenolic resin composite bipolar plate for polymer electrolyte membrane fuel cell

“…Natural flake graphite (NFG) (purity, 99.61 wt%; average flake size, 500 mm) and potassium permanganate (99 wt%) were added to a solution of perchloric acid (60 wt%) and acetic anhydride (97 wt%) at 25 C. The total precursor that is mixture was mixed with the help of a glass rod in a porcelain dish for 10 sec. Less than 2 g of the mixed precursor was taken in a glass beaker and directly placed into a domestic microwave oven (Samsung CE103VD) and was allowed to irradiate at 600 W for 50 sec.…”

Studies and characterization of RESOL/VAc–EHA/HMMM IPN systems in aqueous medium

“…1,2 Thermoset phenolic resin is one of the earliest synthetic resins to possess good fire retardancy and a low smoke and toxicity index. [3][4][5] It is widely used in construction, electrical, and other industries. However, unmodified phenolic resin is a brittle material, with limited application.…”