Synthesis and properties of novel phosphorus‐containing bismaleimide/epoxy resins

A novel soluble phosphorus‐containing bismaleimide (BMI) monomer, bis(3‐maleimidophenyl)phenylphosphine oxide (BMIPO), was synthesized by the imidization of bis(3‐aminophenyl) phenylphosphine oxide, in which its structural characterization was identified with ¹H‐NMR, ¹³C‐NMR, and Fourier transform infrared spectra. The BMIPO resin, with five‐membered imide rings and high phenyl density, was an excellent flame retardant with a high glass‐transition temperature (T_g), onset decomposition temperature, and limited oxygen index. In phosphorus‐containing BMI/epoxy/4,4′‐methylene dianiline (DDM)‐cured resins, homogeneous products were obtained from all proportions without phase separation. Because of the higher reactivity of BMIPO/DDM relative to that of 4,4′‐bismaleimidodiphenylmethane (BMIM)/DDM, the increase in the BMIPO/BMIM ratio in this blending resin increased the recrosslinking hazards of the postcuring stage and so lowered the T_g value and thermal stability. The thermal stability of the BMI/epoxy‐cured system was lower than that of the epoxy‐cured system because of the introduction of a phosphide group into BMIPO, whereas for the T_g value and flame retardancy, the former was significantly higher than the latter: the higher the BMIPO content in the blend, the higher the flame retardancy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2080–2089, 2002; DOI 10.1002/app.10607     

Synthesis and properties of novel phosphorus‐containing hardener for epoxy resins

A novel phosphorus‐containing curing agent, 2‐(6‐oxid‐6H‐dibenz〈c,e〉〈1,2〉oxa‐phosphorin‐6‐yl) phenol formaldehyde novolac [OD‐PN], was prepared from phenol formaldehyde novolac resin (PN) and a reactive 2‐(6‐oxid‐6H‐dibenz〈c,e〉〈1,2〉oxa‐phosphorin‐6‐yl)chloride (ODC) while ODC was synthesized through reaction between o‐phenylphenol and phosphoryl trichloride. The compound (OD‐PN) was used as a reactive flame‐retardant in o‐cresol formaldehyde novolac epoxy resin (CNE) for electronic application. Owing to the rigid structure of ODC and pendant P group, the resulted phosphorus containing epoxy resin exhibited better flame retardancy, higher glass transition temperature, and thermal stability than the noncyclic P‐containing curing agent or the bromine containing flame‐retardant epoxy resin. UL 94‐VO rating could be achieved with a phosphorus content of as low as 1.21% (comparable to bromine content of 6%) in the cured resin, and no fumes and toxic gas emission were observed. The relationship between the structure and flammability for both phosphorus containing curing agents OD‐PN and TP‐PN (triphenyl phosphate‐phenol formaldehyde novolac reaction product) are also examined. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1636–1644, 2000     

Synthesis and properties of phosphorus‐containing advanced epoxy resins. II

Two phosphorus‐containing diacids were synthesized from 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) and either maleic acid or itaconic acid and then reacted with diglycidyl ether of bisphenol A (DGEBA) to form two series of advanced epoxy resins. Reaction conditions, such as reaction time, temperature and catalyst, are discussed in this article. After curing with 4,4'‐diaminodiphenyl sulfone (DDS), thermal properties of cured epoxy resins were studied using dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA). The flame retardancy of cured epoxy resins was evaluated using a UL‐94 measurement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 228–235, 2000     

Flame‐retardant properties and mechanisms of epoxy thermosets modified with two phosphorus‐containing phenolic amines

Two phosphorus‐containing phenolic amines, a 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO)‐based derivative (DAP) by covalently bonding DOPO and imine (SB) obtained from the condensation of p‐phenylenediamine with salicylaldehyde, and its analog (AP) via the addition reaction between diethyl phosphite and SB, were used to prepare flame‐retardant epoxy resins. The burning behaviors and dynamic mechanical properties of epoxy thermosets were studied by limited oxygen index (LOI) measurement, UL‐94 test, and dynamic mechanical analysis. The flame‐retardant mechanisms of modified thermosets were investigated by thermogravimetric analysis, Py‐GC/MS, Fourier transform infrared, SEM, elemental analysis, and laser Raman spectroscopy. The results revealed that epoxy thermoset modified with DAP displayed the blowing‐out effect during UL‐94 test. With the incorporation of 10 wt % DAP, the modified thermoset showed an LOI value of 36.1% and V‐0 rating in UL‐94 test. The flame‐retardant mechanism was ascribed to the quenching and diluting effect in the gas phase and the formation of phosphorus‐rich char layers in the condensed phase. However, the thermoset modified with 10 wt % AP only showed an LOI value of 25.7% and no rating in UL‐94 test, which was possibly ascribed to the mismatching of charring process with gas emission process during combustion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43953.     

Flame‐retarded polystyrene with phosphorus‐ and nitrogen‐containing oligomer: Preparation and thermal properties

A phosphorus‐ and nitrogen‐containing compound (2‐dimethylamino ethyl phenyl hydroxyethyl acrylate phosphate) and its oligomer (poly(2‐dimethylamino ethyl phenyl hydroxyethyl acrylate phosphate), PDPHP) were synthesized and characterized. The polystyrene (PS) composites with various amounts of PDPHP were prepared by melt blending. The thermal stability of the PDPHP and PS composites was investigated by thermogravimetric analysis. The flame retardancy of the composites was evaluated using microscale combustion calorimeter and limiting oxygen index test. A Fourier transform infrared (FTIR) spectroscopy coupled with a thermogravimetric analyzer was also used to study the gas phase from the degradation of PS composites. The char residues of the PS composites containing 30 wt % PDPHP were analyzed by FTIR and scanning electron microscopy. The results suggest that the incorporation of PDPHP into PS can evidently enhance the char formation and improve the flame retardancy of virgin PS. The compact and coherent char formed during degradation was attributed to the enhancement of char quality and flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel flame retardant thermosets from nitrogen‐containing and phosphorus‐containing epoxy resins cured with dicyandiamide

A novel phosphorus‐containing epoxy resin (EPN‐D) was prepared by addition reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) and epoxy phenol‐ formaldehyde novolac resin (EPN). The reaction was monitored by epoxide equivalent weight (EEW) titration, and its structure was confirmed by FTIR and NMR spectra. Halogen‐free epoxy resins containing EPN‐D resin and a nitrogen‐containing epoxy resin (XT resin) were cured with dicyandiamide (DICY) to give new halogen‐free epoxy thermosets. Thermal properties of these thermosets were studied by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), thermal mechanical analyzer (TMA) and thermal‐gravimetric analysis (TGA). They exhibited very high glass transition temperatures (T_gs, 139–175°C from DSC, 138–155°C from TMA and 159–193°C from DMA), high thermal stability with T_{d,5 wt %} over 300°C when the weight ratio of XT/EPN‐D is ≥1. The flame‐retardancy of these thermosets was evaluated by limiting oxygen index (LOI) and UL‐94 vertical test. The thermosets containing isocyanurate and DOPO moieties showed high LOI (32.7–43.7) and could achieve UL‐94 V‐0/V‐1 grade. Isocyanurate and DOPO moieties had an obvious synergistic effect on the improvement of the flame retardancy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis,characterization, and properties of a novel epoxy resin containing both binaphthyl and biphenyl moieties

A new epoxy resin containing both binaphthyl and biphenyl moieties in the skeleton (BLBPE) was synthesized and confirmed by electrospray ionization mass spectroscopy, ¹H‐nuclear magnetic resonance spectroscopy, and infrared spectroscopy. To evaluate the combined influence of two moieties, one epoxy resin containing binaphthyl moiety and another containing biphenyl moiety were also synthesized, and a commercial biphenyl‐type epoxy resin (CER3000L) was introduced. Thermal properties of their cured polymers with phenol p‐xylene resins were characterized by differential scanning calorimetry, dynamic mechanical, and thermogravimetric analyses. The cured polymer obtained from BLBPE showed remarkably higher glass transition temperature and lower moisture absorption, as well as comprehensively excellent thermal stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Flammability and thermal degradation of epoxy acrylate modified with phosphorus‐containing compounds

A series of UV‐curable flame‐retardant resins was obtained by blending phosphate acrylate (BTP) in different ratios with epoxy acrylate resin (EA). The flammability was characterized by limiting oxygen index (LOI), UL 94 flammability rating and cone calorimeter, and the thermal degradation of the flame‐retardant resins was studied using thermo gravimetric analysis (TGA), and real‐time Fourier transform infrared (RTFTIR). The results indicated that the flame‐retardant efficiency increases with the addition of BTP. The heat release rate with the addition of BTP decreases greatly. The TGA data showed that EA/BTP blends have lower initial decomposition temperatures and higher char residues than pure EA, whereas BTP has the lowest initial decomposition temperature and the highest char residue. The RTFTIR study indicates that the EA/BTP blends have lower thermal oxidative stability than the pure EA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of novel epoxy composites containing electrospun PA6/F‐MWNTs fibers

The Nylon 6 (PA6)/the functionalized multiwalled carbon nanotubes (F‐MWNTs) fibrous membranes were fabricated by electrospinning, and then incorporated into an epoxy matrix. Their morphology, thermal stability, mechanical properties, thermal conductivities, and electrical resistivity were investigated. The electrospun PA6/F‐MWNTs fibers performed as a skeleton in the epoxy matrix, and the well interfacial adhesion between the epoxy matrix and the PA6/F‐MWNTs fibers leads to high mechanical properties of composites. The PA6 serves as an intermediate layer and alleviates the modulus mismatch between the stiff MWNTs and the soft epoxy matrix. The thermal conductivities of the epoxy composites increase by 27.3, 35.0, and 36.1%, respectively, with 0.5, 1 and 1.5 wt% F‐MWNTs loading in the PA6/F‐MWNTs fibers. At the same time, the PA6 simultaneously retains the high electrical resistivity of these epoxy composites. POLYM. ENG. SCI., 56:1259–1266, 2016. © 2016 Society of Plastics Engineers     

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

A novel phosphorus‐ and silica‐containing hybrid (DPS) was synthesized by the reaction between diethyl phosphate (DEP) and polyhedral oligomeric siloxanes (POS) formed by hydrolysis condensation of 3‐glycidoxypropyltrimethoxysilane (GPTMS). The novel phosphorus‐ and silica‐containing hybrid was characterized by the flourier transform infrared spectroscope (FT‐IR), silicon nuclear magnetic resonance, and gel permeation chromatography (GPC). Then, the determination of the activation of the reaction between epoxy resin and phosphorus‐, and silica‐containing hybrids was studied by differential scanning calorimeter (DSC). In the presence of catalyst, the activation energies of the curing reaction were 63.3 and 66.7 kJ/mol calculated by Kissinger model and Ozawa model respectively. The thermal and flame retardant properties of the cured epoxy modified by DPS were determined by differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA), and limited oxygen index (LOI). The results revealed that those properties were improved in comparison with unmodified epoxy resin. In addition, scanning electron microscopy (SEM) was used to investigate the morphology of the cured epoxy resin modified by DPS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of novel phosphorus‐containing poly(ether ether ketone ketone)s

A novel monomer, bis[4‐(4‐fluorobenzoyl)phenyl]phenylphosphine oxide, was synthesized through the reaction of bis(4‐chloroformylphenyl) phenyl phosphine oxide with fluorobenzene. Three poly(ether ether ketone ketone)s derived from bis[4‐(4‐fluorobenzoyl)phenyl]phenylphosphine oxide and different aromatic bisphenols were prepared by aromatic nucleophilic substitution reactions. The resulting polymers had inherent viscosities in the range of 0.55–0.73 dL/g. The structures of the poly(ether ether ketone ketone)s were characterized with Fourier transform infrared and ¹H‐NMR. Thermal analysis indicated that the glass‐transition temperatures of the poly(ether ether ketone ketone)s were higher than 200°C, and the 5% weight loss temperatures in nitrogen were higher than 463°C. All the polymers showed excellent solubility in polar solvents such as N‐methyl‐2‐pyrrolidone, dimethylformamide, and dimethylacetamide and could also be dissolved in chlorinated methane. The polymers afforded transparent and flexible films by solvent casting. Organic phosphorous moieties also imparted good flame‐retardancy to the polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel phosphorus‐containing hardeners with tailored chemical structures for epoxy resins: Synthesis and cured resin properties

A comparative evaluation of systematically tailored chemical structures of various phosphorus‐containing aminic hardeners for epoxy resins was carried out. In particular, the effect of the oxidation state of the phosphorus in the hardener molecule on the curing behavior, the mechanical, thermomechanical, and hot‐wet properties of a cured bifunctional bisphenol‐A based thermoset is discussed. Particular attention is paid to the comparative pyrolysis of neat cured epoxy resins containing phosphine oxide, phosphinate, phosphonate, and phosphate (with a phosphorus content of about 2.6 wt %) and of the fire behavior of their corresponding carbon fiber‐reinforced composites. Comparatively faster curing thermosetting system with an enhanced flame retardancy and adequate processing behavior can be formulated by taking advantage of the higher reactivity of the phosphorus‐modified hardeners. For example, a combination of the high reactivity and of induced secondary crosslinking reactions leads to a comparatively high T_g when curing the epoxy using a substoichiometric amount of the phosphinate‐based hardener. The overall mechanical performance of the materials cured with the phosphorus‐containing hardeners is comparable to that of a 4,4′‐DDS‐cured reference system. While the various phosphorus‐containing hardeners in general provide the epoxy‐based matrix with enhanced flame retardancy properties, it is the flame inhibition in the gas phase especially that determines the improvement in fire retardancy of carbon fiber‐reinforced composites. In summary, the present study provides an important contribution towards developing a better understanding of the potential use of such phosphorus‐containing compounds to provide the composite matrix with sufficient flame retardancy while simultaneously maintaining its overall mechanical performance on a suitable level. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Flame retardant epoxy polymers using phosphorus‐containing polyalkylene amines as curing agents

Two series of novel phosphorus‐containing poly(alkylene) amines with or without aromatic groups were synthesized via reacting phosphoryl chloride derivatives with commercially available polyetheramines, ethylenediamine and N‐phenyl‐1,4‐phenylenediamine, respectively. Chemical structures of the amines were characterized with FTIR, NMR, P (phosphorus) content measurement, and amine content titration. These amines were then utilized as curing agents to react with diglycidyl ether of bisphenol A for preparing phosphorus containing epoxy polymers. The introduction of soft ? P? O? linkage, polyalkyene, and hard aromatic group into the backbones of the synthesized phosphorus‐containing amine (PCA) provides epoxy resins with tunable flexibility. Thermal analysis of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveals that these resulted epoxy resins possess moderate T_g's and thermal stability. Furthermore, high char yields in TGA and high limited oxygen index (LOI) values indicate that these phosphorus‐containing epoxy (PCE) resins are capable of exhibiting excellent flame retardant properties. These polymers can be potentially utilized in flame retardant epoxy coatings and other applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3526–3538, 2001     

Preparation and properties of high performance phthalide‐containing bismaleimide modified epoxy matrices

A series of intercrosslinked networks formed by diglycidyl ether of bisphenol A epoxy resin (DGEBA) and novel bismaleimide containing phthalide cardo structure (BMIPP), with 4,4′‐diamino diphenyl sulfone (DDS) as hardener, have been investigated in detail. The curing behavior, thermal, mechanical and physical properties and compatibility of the blends were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), notched Izod impact test, scanning electron microscopy (SEM) and water absorption test. DSC investigations showed that the exothermic transition temperature (T_p) of the blend systems shifted slightly to the higher temperature with increasing BMIPP content and there appeared a shoulder on the high‐temperature side of the exothermic peak when BMIPP content was above 15 wt %. TGA and DMA results indicated that the introduction of BMIPP into epoxy resin improved the thermal stability and the storage modulus (G′) in the glassy region while glass transition temperature (T_g) decreased. Compared with the unmodified epoxy resin, there was a moderate increase in the fracture toughness for modified resins and the blend containing 5 wt % of BMIPP had the maximum of impact strength. SEM suggested the formation of homogeneous networks and rougher fracture surface with an increase in BMIPP content. In addition, the equilibrium water uptake of the modified resins was reduced as BMIPP content increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and studies of new phosphorus‐containing diols as potential flame retardants

Several new phosphorus‐containing potential flame retardants (FRs) were prepared and evaluated for heat release reduction potential, by incorporation of the molecules into polyurethane samples, generated from methylene diphenyl diisocyanate and 1,3‐propane diol. The potential FRs were all prepared from commercial diisocyanates, with the phosphorus‐containing substructure introduced as a semicarbazone. All of the target structures were diols, to facilitate their incorporation into a polyurethane main chain. The polyurethane samples were prepared via copolymerization, and analysis clearly demonstrated that the potential FRs were chemically incorporated, prior to heat release testing. The heat‐release reduction potential of these substances was evaluated using the microcombustion calorimeter. Results demonstrated that both heat release reduction potential and char formation were structure dependent. Some of the compounds containing an aromatic core had more effect on char formation (higher char yields) and peak heat‐release rate (lowered heat release) than just phosphorus content alone.     

Synthesis and properties of a novel phosphorous‐containing flame‐retardant hardener for epoxy resin

An aryl phosphinate dianhydride 1,4‐bis(phthalic anhydride‐4‐carbonyl)‐2‐(6‐oxido‐6H‐dibenz[c,e][1,2]‐oxaphosphorin‐6‐yl)‐phenylene ester (BPAODOPE) was synthesized and its structure was identified by FTIR and ¹H‐NMR. BPAODOPE was used as hardener and flame retardant for preparing halogen‐free flame‐retarded epoxy resins when coupled with another curing agent. Thermal stability, morphologies of char layer, flame resistance and mechanical properties of flame‐retarded epoxy resins were investigated by thermogravimetric analysis, SEM, limiting oxygen index (LOI), UL‐94 test, tensile, and charpy impact test. The results showed that the novel BPAODOPE had a better flame resistance, the flame resistance and char yield of flame‐retarded epoxy resins increased with an increase of phosphorus content, tensile strength and impact strength of samples gradually decreased with the addition of BPAODOPE. The flame‐retarded sample with phosphorus contents of 1.75% showed best combination properties, LOI value was 29.3, and the vertical burning test reached UL‐94 V‐0 level, tensile strength and impact strength were 30.78 MPa and 3.53 kJ/m², respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of phosphorus‐containing polysulfone

Chemical modification of a chloromethylated polysulfone (CMPS) was performed by reacting the chlorometyl group with P? H bond of 9,10‐dihydro‐oxa‐10‐phosphophenanthrene‐10‐oxide (DOPO). A kinetic study of phosphorylation of CMPS with different chlorine content was reported. The obtained polymers bearing cyclic bulky groups containing phosphorus were characterized by analytical methods; Fourier transforms spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR). The thermal stability of phosphorus‐modified polysulfone was evaluated by dynamic thermogravimetric analysis in nitrogen gas. The polymers were readily soluble in polar organic solvent, such as N‐methylpyr‐rolidone (NMP), N,N‐dimethylacetamide (DMAc), and N,N‐dimethylformamide (DMF). Differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA) proved an amorphous morphology of these polymers. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Synthesis and characterization of phosphorus‐containing polystyrene

Poly(o‐toluidine) ( POT) has been electrodeposited on brass from an aqueous salicylate solution by using cyclic voltammetry, and its corrosion protection performance has been evaluated by potentiodynamic polarization technique and electrochemical impedance spectroscopy in aqueous 3% NaCl solution. The corrosion potential was about 0.115 V vs. SCE more positive for the POT‐coated brass than that of uncoated brass and reduces the corrosion rate of brass almost by a factor of 800. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010