Yie-Shun Chiu

Phosphorus-containing epoxy for flame retardant. III: Using phosphorylated diamines as curing agents

Two phosphorus-containing diamine compounds, bis(4-aminophenoxy)-phenyl phosphine oxide and bis(3-aminophenyl)phenyl phosphine oxide, were synthesized for use as curing agents of epoxy resins. Phosphorylated epoxy resins were obtained by curing Epon 828 and Eponex 1510 with these two diamine agents. For raising the phosphorus contents of the resulting epoxy resins, the phosphorus-containing epoxy, bis(glycidyloxy)phenyl phosphine oxide (BGPPO), was also used. These two diamine agents showed similar reactivity toward epoxies. Their reactivities were higher than DDS and lower than DDM. High char yields in TGA evaluation were found for all the phosphorylated epoxy resins, implying their high flame retardancy. The excellent flame-retardant properties of these phosphorylated epoxy resins were also demonstrated by the high limiting oxygen index (LOI) values of 33 to 51.

Phosphorus-containing epoxy for flame retardant. I. Synthesis, thermal, and flame-retardant properties

A new phosphorus-containing oxirane, bis-(3-glycidyloxy)phenylphosphine oxide (BGPPO), was synthesized. Further curing BGPPO with diamine curing agents, dicyanodiamide (DICY), 4,4′-diaminodiphenylmethane (DDM), and 4,4′-diaminodiphenylsulfone (DDS), respectively, resulted in several phosphorylated epoxy resins. Compared with Epon 828, Eponex 1015, and DER 732, BGPPO showed relatively high reactivity toward diamine agents via DSC studies. Furthermore, the reactivity of the three curing agents toward BGPPO were found to be in the order of DDM > DICY > DDS. Thermal stability and the weight loss behavior of the cured polymers were studied by TGA. The phosphorylated resins showed lower weight loss temperatures and higher char yields than did the Epon 828-based resins. The high char yields as well as high limited oxygen index (LOI) values of the BGPPO-based resins confirmed the effectiveness of phosphorus-containing epoxy resins as flame retardants.

Synthesis, characterization, thermal, and flame retardant properties of phosphate-based epoxy resins

A new phosphorus-containing oxirane bis-glycidyl phenylphosphate (BGPP), and a diamine, bis(4-aminophenyl)phenylphosphate (BAPP), were synthesized. Both of these two phosphorus-containing compounds lead to phosphate-containing epoxy resin via curing reaction. The kinetics of the curing reaction of BGPP with various curing agents, including BAPP, were studied. The introduction of electron-withdrawing group into the compounds increases the BGPP and decreases the BAPP reactivity in the curing reaction. The thermal and the weight loss behavior of the cured epoxy resins were studied by TGA. High char yields (32–52%) as well as high limiting oxygen index (LOI) values (34–49) of these phosphorylated resins were found, confirming the usefulness of these phosphorus-containing epoxy resins as flame retardants.

Phosphorus-containing epoxy for flame retardance: IV. Kinetics and mechanism of thermal degradation

Abstract The kinetics and mechanisms of thermal degradation of a phosphorus-containing epoxy based on bis-(3-glycidyloxy)phenylphosphine oxide (BGPPO) and 4,4′-diaminodiphenylsulfone (DDS) were studied. Two and four stages were found for BGPPO/DDS degradation in nitrogen and air, respectively. The degradation activation energies calculated from the methods of Kissinger, Friedman and Ozawa were obtained. The first stage of degradation, which results from the decomposition of phosphorous groups, showed lower activation energy than the other stages. Furthermore, via FTIR and TG-FTIR investigations, the degradation of this phosphorus-containing epoxy was determined to begin by the breaking of PPh bonds, followed by dehydration reactions breaking POC bonds, and elimination of propyl groups. Therefore, the degradation of the epoxy resulted in high char yields and residues with high phosphorus contents.

Flame retardant epoxy polymers based on all phosphorus-containing components

A phosphorus-containing epoxy resin, bis(3-t-butyl-4-glycidyloxyphenyl-2,4-di-t-butylphenyl)resorcinol diphosphate, was synthesized and subsequently cured with non-phosphorus containing amines, and/or novel phosphorus-containing aromatic or polyoxyalkylene amines. Chemical structures of these materials were characterized with FTIR, NMR, elemental analysis, and amine titration. The introduction of soft –P–O– linkage, polyoxyalkyene, or hard aromatic group into the backbones of the synthesized phosphorus-containing amines provides epoxy polymers with high phosphorus contents and tailored flexibility. Thermal analysis of differential scanning calorimeter and thermal gravimetric analysis (TGA) reveals that these resulted epoxy polymers possess moderate Tgs and thermal stability. Furthermore, high char yields in TGA analysis and high limited oxygen index values indicate that these phosphorus-containing epoxy polymers possess excellent flame retardant properties.

Synthesis and flame-retardant properties of phosphorus-containing polymers based on poly(4-hydroxystyrene)

Phosphorus-containing polystyrene was obtained through incorporating phosphate groups onto poly(4-hydroxystyrene). This was achieved by esterification with diethylchlorophosphate. The phosphorylation was confirmed by IR, 1H-NMR, and 31P-NMR analysis. By varying the feeding ratios of the reactants, the phosphorus content in the polymers could be successfully tailored and gave values of 12.8 to 4.9% by weight. This was further corroborated by elemental analysis. Thermal characteristics and temporal stability of the phosphorylated polymers were evaluated by DSC and TGA. High char yields (64% by weight) and LOI values of 41 were found for these polymers. Such properties make these polymers useful in flame retardants.

Flame-retardant polyurethanes from phosphorus-containing isocyanates

Phosphorus-containing polyurethanes are synthesized by reacting phosphorus-containing diisocyanates, bis (4-isocyanatophenoxy) phenyl phosphine oxide (BIPPO) and bis (3-isocyanatophenyl) phenyl phosphine oxide (BIPPPO), with various diols. The chemical structures of the obtained monomers and polymers are characterized by IR, 1H- and 31P-NMR spectroscopy. Thermal analysis of the phosphorus-containing polyurethanes reveals that incorporating phosphorus into the polymers increases exothermicity during their decomposition. According to these results, the phosphorus-containing polyurethanes are less thermally stable than conventional polyurethanes. Char yield and LOI measurements demonstrate that incorporating phosphorus into polyurethanes markedly improves their flame retardancy.

Phosphorus containing epoxy for flame retardant II: Curing reaction of bis‐(3‐glycidyloxy) phenylphosphine oxide

The curing reaction of a phosphorus containing epoxide, bis-(3-glycidyloxy) phenylphosphine oxide (BGPPO), was studied by differential scanning calorimeter (DSC) using dynamic and isothermal methods. Kinetic parameters and activation energy of the BGPPO cured with diamine or dianhydride curing agents were determined. The dynamic activation energies were significantly larger than the isothermal ones. Via isothermal analysis technique, the activation energies of BGPPO cured with 4,4′-diaminodiphenylmethane, dicyanodiamide, methyl tetrahydrogen phthalic anhydride, and phthalic anhydride were found to be 69.5, 83.5, 93.6, and 90.6 kJ/mol, respectively. These values were comparable with those of other commercial epoxy curing system.

Synthesis, thermal properties, and flame retardancy of phosphorus containing polyimides

Phosphorus containing polyimides were prepared via phosphorylation of organosoluble polyimides. This was achieved by phenoxaphosphine oxide ring formation reaction or esterification with diethylchlorophosphate. The phosphorylation was confirmed by infrared, 31P nuclear magnetic resonance, and elemental analysis for phosphorus. Polyimides containing phosphorus of 8.3 and 5.4% by weight were found. Thermal characteristics and decomposition behavior of the resulting polyimides were investigated by differential scanning calorimetry and thermogravimetric analysis. Introduction of phosphorus into polyimides slightly reduced their initial weight loss temperatures and led to high char yields at temperatures higher than 800°C. Limiting oxygen index values higher than 48 were found for the phosphorylated polyimides. Such properties make these polymers useful in flame retardant applications.

Benzophenone-sensitized photodegradation of polystyrene films under atmospheric conditions

Abstract Benzophenone-sensitized photodegradation reactions of polystyrene films were studied under atmospheric conditions. Polymer hydroperoxide is observed to be the major product, and the minor product is a polymeric acetophenone compound. The relative yields of these two products were measured as a function of irradiation time. Calculations have been made based on a suggested reaction mechanism and the calculated results are in good agreement with the experimental data.