Xufu Cai

Effects of common synergistic agents on intumescent flame retardant polypropylene with a novel charring agent

In this article, the laboratory-made poly (p-ethylene terephthalamide) (PETA) was used as a novel charring agent and it combined with ammonium polyphosphate (APP) to prepare the intumescent flame retardant (IFR). For improving the flame-retardant efficiency of IFRs on polypropylene (PP), several general synergistic agents, such as common zinc oxide (Com-ZnO), nanometer structural zinc oxide (Nano-ZnO), zeolite 4A, and aluminum hypophosphite(Al(H2PO2)3), were added in composites of PP/IFR, and the synergistic effect was investigated by the limited oxygen index (LOI), the UL-94 (vertical flame) test, thermogravimetric analysis (TG), thermogravimetry-fourier transform infraredspectroscopy (TG-IR) test, and scanning electron microscopy (SEM). It indicated that the flame retardancy was significantly enhanced in terms of prompting the char formation of PETA and interaction between APP and synergistic agents. Overall, Al(H2PO2)3 was the most effective synergistic agent among them. TG-IR analysis showed that the addition of Al(H2PO2)3 could delay the release of NH3, and make the release of NH3 more smooth, which was useful to form a dense char. SEM presented that compact, continuous and good intumescent charring layers were observed in all PP/IFR systems with synergistic agent.

Effect of a novel flame retardant containing silicon and nitrogen on the thermal stability and flame retardancy of polycarbonate

A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and diphenylsilanediol through solution polycondensation and it was added to polycarbonate (PC). The structure and thermal properties of PSiN were characterized by fourier transform infrared spectroscopy and thermogravimetric analysis (TG) tests. The effect of PSiN on the flame retardancy and thermal behaviors of PC was investigated by limited oxygen index (LOI), vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and the thermal stability of PC are improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% diphenylsulfone sulfonate (KSS) are incorporated, the LOI value of PC is found to be 46, and class V-0 of UL-94 test is passed. The char structure observed by scanning electron microscopy indicated that the surface of the char for PC/KSS/PSiN system holds a firmer and denser char structure when compared with neat PC and PC/KSS system.

Synergistic effect of methyl phenyl silicone resin and DOPO on the flame retardancy of epoxy resins

A series of flame-retarded epoxy resins (EPN) loaded with methyl phenyl silicone resin (Si603) and DOPO (9, 10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) have been prepared. The morphology of these EPN composites were characterized by differential scanning calorimentry (DSC). The mixed epoxy systems all exhibit single glass transition temperature which indicates a homogeneous morphology of these mixed epoxy systems. The thermal stability and flammability of these EPN composites were investigated with limiting oxygen index, UL 94 vertical burning, and themogravimetric analysis tests (TG). The results showed that the DOPO and Si603 system had excellent flame retardancy and antidripping properties for EPN. The TG curves suggested that there was a distinct synergistic effect of DOPO and Si603, and this effect greatly promoted the char formation of the EPN composites and hence improved the flame retardancy. Additionally, the structure and morphology of char residues were studied with Fourier transform infrared and scanning electron microscopy.

The synergistic effect of adjuvant on the intumescent flame-retardant ABS with a novel charring agent

A laboratory-made poly-N,N′-ethyleneterephthalamide (PETA) was used as a novel charring agent and it was combined with ammonium polyphosphate (APP) to prepare the intumescent flame retardant (IFR). For improving the flame retardant efficiency of IFR on acrylonitrile–butadiene–styrene copolymer (ABS), several adjuvant (Adj), such as zeolite 4A (4A), aluminum phosphinate (AlPi), organic montmorillonite, and 2,2′-bis(2-oxazoline), was added, and the synergistic effect was investigated by the limiting oxygen index (LOI), the UL-94 (vertical flame) test, the thermogravimetric analysis (TG), and the scanning electron microscopy (SEM). The results showed that the LOI values of ABS/IFR/Adj (70/30/2) system exceeded 30, and they passed the V-0 rating in the UL-94 test. The TG data demonstrated that the thermal stability and the mass residue of ABS/IFR/Adj were effectively enhanced. Besides, the SEM indicated that adjuvant promoted the formation of the compact, uniform, dense, and intumescent charred layer after burning. After that, the synergistic effect of AlPi and 4A on APP/PETA was investigated by Thermogravimetry-Fourier transform infrared spectroscopy.

Antagonistic flame retardancy between hexakis(4-nitrophenoxy) cyclotriphosphazene and potassium diphenylsulfone sulfonate in the PC system

Hexakis(4-nitrophenoxy) cyclotriphosphazene (HNTP) was added to polycarbonate (PC) as intumescent flame retardant. In order to get high-flame-retardant PC composite with a small quantity of addition, potassium diphenylsulfone sulfonate (KSS) was added to PC as synergetic flame retardant. The flame retardancy and thermal degradation behavior of composites was investigated with limiting oxygen index (LOI), UL-94 vertical burning test, microscale combustion calorimeter (MCC), and thermogravimetric analysis (TG). TG coupled with FTIR (TG/FTIR) was used to research their gaseous products. Scanning electron microscopy analyses and FTIR spectrophotometer were used to study the structure of residual char. But the flammability properties of PC systems indicated the synergistic was instead of antagonistic effects. The antagonistic behaviors between HNTP and KSS were further researched by MCC, TG, and FTIR. The antagonism of KSS was quantified by Lewin M’s synergistic effectiveness parameter, calculated from sample LOI data.

Preparation and characterization of a water resistance flame retardant and its enhancement on charring–forming for polycarbonate

Hexakis(4-nitrophenoxy) cyclotriphosphazene (HNTP) was synthesized and was added into polycarbonate (PC) functioned as intumescent flame retardant and charring agent. The chemical structure of HNTP was confirmed by hydrogen and phosphorus nuclear magnetic resonance (1H-NMR, 31P-NMR), energy-dispersive spectroscopy and Fourier transform infrared (FTIR). Flame retardancy and charring–forming behaviors of HNTP- and PC-based composites were extensively investigated with the limiting oxygen index, UL-94 vertical burning test, microscale combustion calorimeter (MCC) and thermogravimetric analysis. The water resistance of PC-based composites was studied by stationary water contact angle measurements. Furthermore, TG/FTIR was used to research their gaseous products and their releasing intensity during the decomposition. The morphology and chemical structure of residual char were used to study scanning electron microscopy (SEM) analyses and FTIR spectroscopy. The mechanical properties of samples were compared by tensile and impact tests.

Synergistic flame-retardant behavior and mechanism of tris(3-nitrophenyl) phosphine and DOPO in epoxy resins

A novel flame-retarded epoxy resins system is prepared by copolymerizing diglycidyl ether of bisphenol A (EP) with tris(3-nitrophenyl) phosphine (NPPh3), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and 4,4-diaminodiphenylmethane (DDM). The thermogravimetric curves suggest that there is an obvious synergistic effect between NPPh3 and DOPO. Flame-retardant properties of the cured products are evaluated using limited oxygen index (LOI) and vertical burning tests (UL-94). The results indicate that the flame retardancy of NPPh3/DOPO/EP thermosets is enhanced. 2%NPPh3/4%DOPO/EP achieves a LOI value of 33.8% and V-0 rating in UL-94 test. The thermal stability of the EP composites is detected by thermogravimetric analysis (TG) and differential scanning calorimetry. The results demonstrate that the thermal stability of NPPh3/DOPO cured epoxy resins displays an improvement in the high-temperature region and the glass transition temperature decreases slightly compared with pure EP. The pyrolytic gases are characterized using thermogravimetric analysis/infrared spectrometry (TG-FTIR) in an air atmosphere. The gaseous species produced by the flame-retarded EP composites are the same as those from EP. Additionally, the morphology and the structure of char residues are studied by scanning electron microscopy and Fourier transform infrared spectra (FTIR). The morphology of the residual char for flame-retarded EP composites shows a compact, smooth, and tight structure. These outstanding integrated properties will make EP composites attractive for practical applications.

Gas–condensed phase flame-retardant mechanisms of tris(3-nitrophenyl) phosphine/triphenyl phosphate/ABS

Tris(3-nitrophenyl) phosphine (NPPh3), a flame retardant containing phosphorus and nitro group, is synthesized. And a novel flame retardant loading with NPPh3 and triphenyl phosphate (TPP) is prepared to flame-retardant acrylonitrile–butadiene–styrene (ABS). The effects of NPPh3 and TPP on the flammability of ABS are studied by various methods. The flame retardation of ABS/NPPh3/TPP composite is characterized by limiting oxygen index method and vertical and horizontal burning tests (UL-94). Compared with the systems with ABS/NPPh3 and ABS/TPP alone, ABS/NPPh3/TPP obtains a higher limiting oxygen index. Additionally, the flame-retardant effect of ABS/NPPh3/TPP in condensed phase is studied by thermogravimetric analysis (TG), scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). The gases evolved during thermal degradation process in nitrogen are studied by means of thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR). The results show that ABS/NPPh3/TPP exerts gas-condensed phase flame-retardant effect.

Toughening and Compatibilization of Acrylonitrile–Butadiene–Styrene/Poly (Ethylene Terephthalate) Blends Using an Oxazoline-Functionalized Impact Modifier

An oxazoline-functionalized core–shell impact modifier was synthesized between aminoethanol and acrylonitrile/butadiene/styrene high rubber powder. According to the Fourier transform infrared spectroscopy test, the nitrile groups were partially converted into oxazoline groups successfully. The oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was used as an impact modifier for acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends. The differential scanning calorimeter and rheological tests demonstrated that poly(ethylene terephthalate) was partially miscible with acrylonitrile–butadiene–styrene, because the oxazoline groups of oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder reacted with the end groups of poly(ethylene terephthalate). The results of scanning electron microscopy indicated that the morphology of acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends with proper oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder content was improved significantly. The best mechanical properties were achieved, When 6 wt% oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was added into acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends. GRAPHICAL ABSTRACT

The enhancement on thermal stability and charring–forming capability of nitration group

To obtain a novel charring agent, hexaphenoxy-cyclotriphosphazene (HCTP) was designed to be nitrified hexaphenoxy-cyclotriphosphazene (N-HCTP) by one step of nitration. Then the charring capability and thermal degradation behaviors of HCTP and N-HCTP were extensively investigated with the thermogravimetric analysis (TG) under pure nitrogen and air, respectively. TG results showed that nitration made the char residue yield of N-HCTP increase from 0 to 40% under nitrogen. And the effects of nitration made the char residue yield of N-HCTP increase from 0 to 2.3% under air. Meanwhile, TG was used to show the effect of nitration in inducing charring of acrylonitrile–butadiene–styrene under nitrogen. With 30% addition of N-HCTP, the char residual yield increased from 0.9 to 22%. Then TG/FTIR was used to research their gaseous products and their releasing intensity during decomposition. The TG/FTIR showed that the nitration made the decomposition of N-HCTP completely different from that of HCTP.