Effects of Phosphorus and Boron Compounds on Thermal Stability and Flame Retardancy Properties of Epoxy Composites

Abstract

While plastics are regarded as the most resourceful materials nowadays, ranging from countless utilities including protective or decorating coatings, to adhesives, packaging materials, electronic components, paintings, furniture, insulating composites, foams, building blocks and so on, their critical limitation is their advanced flammability, which in fire incidents can result in dramatic human fatalities and irreversible environmental damage. Herein, epoxy-based composites with improved flame-resistant characteristics have been prepared by incorporating two flame retardant additives into epoxy resin, namely 6-(hydroxy(phenyl)methyl)-6H-dibenzo[c,e][1,2]oxaphosphinine-6-oxide (PFR) and boric acid (H3BO3). The additional reaction of 9,10-dihydro-oxa-10-phosphophenanthrene-10-oxide (DOPO) to the carbonyl group of benzaldehyde yielded PFR, which was then used to prepare epoxy composites having a phosphorus content ranging from 1.5 to 4 wt%, while the boron content was 2 wt%. The structure, morphology, thermal stability and flammability of resulted epoxy composites were investigated by FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry (MCC). Thermogravimetric analysis indicated that the simultaneous incorporation of PFR and H3BO3 improved the thermal stability of the char residue at high temperatures. The surface morphology of the char residues, studied by SEM measurements, showed improved characteristics in the case of the samples containing both phosphorus and boron atoms. The MCC tests revealed a significant reduction in flammability as well as a significant decrease in heat release capacity for samples containing both PFR and H3BO3 compared to the neat epoxy thermoset.

Tailoring Thermal and Electrical Properties of Jeffamine Segmented Polyetherimide Composite Films Containing BaTiO3 particles

“…Recent research has focused on the impact of incorporating inorganic fillers into various high-performance polymer composites [ 23 , 24 , 25 ]. Barium titanate (BaTiO 3 ) is an inorganic filler of interest due to its high dielectric constant and ferroelectric properties.…”

Esterification Oligomerization of Phosphaphenanthrene Biphenol Caused Efficient Flame Retardant Effect of Group Aggregation in Epoxy Resin

“…14,15 Some DOPO derivatives have been reported as effective flame retardants in epoxy resin. 16 For example, the P−H bond of DOPO can react with a Schiff base, 17 unsaturated double bond, 18,19 and carbonyl group 20 to prepare curing agents of epoxy resins; the additive-type flame retardants were synthesized by combining the phosphaphenanthrene group and other groups with a flame retardant feature. 21−24 In addition, the flame retardancy of some phosphorous polyester compounds prepared by DOPO or its derivatives have been widely studied.…”

“…As one of the efficient flame retardant groups, phosphaphenanthrene group can quench free radical chain reactions in the gas phase during combustion. , 6 H -Dibenz­(C,E)­(1,2)­oxaphosphorin-6-oxide (DOPO) and 2-(6-oxid-6 H -dibenzo­[c,e]­[1,2]­oxaphosphorin-6-yl)-1,4-benzenediol (DOPO-HQ) with phosphaphenanthrene structures have a considerable position in the field of flame retardant polymer materials. , Some DOPO derivatives have been reported as effective flame retardants in epoxy resin . For example, the P–H bond of DOPO can react with a Schiff base, unsaturated double bond, , and carbonyl group to prepare curing agents of epoxy resins; the additive-type flame retardants were synthesized by combining the phosphaphenanthrene group and other groups with a flame retardant feature. − In addition, the flame retardancy of some phosphorous polyester compounds prepared by DOPO or its derivatives have been widely studied. Wang et al used DOPO, paraformaldehyde, diethanolamine, and alkyd resin to obtain flame retarded alkyd resin.…”

Thermal Properties and Flammability Characteristics of a Series of DGEBA-Based Thermosets Loaded with a Novel Bisphenol Containing DOPO and Phenylphosphonate Units

“…However, a high content of DOPO groups is required to achieve a significant improvement in the flame resistance of epoxy resins, which can lead to a deterioration of the end-use product’s characteristics. Therefore, the DOPO monomer has been frequently appealed in the synthesis of various flame retardants containing nitrogen, sulfur, silicon, or boron in the structure, elements well-known for their synergistic effect in terms of flame retardancy when used along with phosphorus, thus, showing better flame retardancy in epoxy-resin-based materials [ 15 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Various diamines and bisphenols containing phosphorus and nitrogen as reactive flame retardants for crosslinking epoxy resin have been reported [ 24 , 25 , 26 , 27 , 28 , 29 ].…”