Reactive,intumescent, halogen‐free flame retardant for polypropylene

A reactive, intumescent, halogen‐free flame retardant, 2‐({9‐[(4,6‐diamino‐1,3,5‐triazin‐2‐yl)amino]‐3,9‐dioxido‐2,4,8,10‐tetraoxa‐3,9‐diphosphaspiro[5.5]undecan‐3‐yl}oxy)ethyl methacrylate (EADP), was synthesized through a simple three‐step reaction from phosphorus oxychloride, pentaerythritol, hydroxyethyl methacrylate, and melamine. EADP exhibited excellent thermal stability and char‐forming ability, as revealed by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The TGA results show that the temperature at 5% weight loss was 297.8°C and the char yield at 700°C was 51.75%. SEM observation revealed that the char showed a continuous and compact surface and a cellular inner structure with different sizes. Composite of polypropylene (PP) with a 25 wt % addition of EADP (PP/EADP25) passed the UL‐94 V‐0 rating and showed a limiting oxygen index value of 31.5. Compared with those of neat PP, the flexural strength and modulus values of PP/EADP25 were somewhat improved, the tensile strength was basically unchanged, and the notched Izod impact strength was slightly decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40054.     

Thermal degradation behavior and gas phase flame‐retardant mechanism of polylactide/PCPP blends

The thermal degradation behavior of the blend based on polylactide (PLA) and poly(1,2‐propanediol 2‐carboxyethyl phenyl phosphinate) (PCPP) was investigated by the thermogravimetric analysis (TGA). Thermal degradation activation energies (E_a) of neat PLA and PLA/15% PCPP blend were calculated via the Flynn–Wall–Ozawa method. The E_a of the blends increased with the addition of PCPP increasing when the conversion was higher than 10%. In addition, the appropriate conversion models for the thermal degradation process of PLA and PLA/15% PCPP were studied via the Criado method. At the same time, the main gaseous decomposition products of PLA and its blend were identified by TGA/infrared spectrometry (TGA–FTIR) analysis. And it revealed that the PCPP improved the flame‐retardant property of PLA via altering the release of the flammable gas and nonflammable gas. Moreover, the PCPP improved the flame‐retardant property of PLA by inhibiting exothermic oxidation reactions in the combustion, which was further proved by pyrolysis–gas chromatography–mass spectrometry analysis. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40480.     

Flame‐retarding mechanism of organically modified montmorillonite and phosphorous‐Nitrogen flame retardants for the preparation of a halogen‐free,flame‐retarding thermoplastic poly(ester ether) elastomer

In this study, thermoplastic poly(ester ether) elastomer (TPEE) nanocomposites with phosphorus–nitrogen (P–N) flame retardants and montmorillonite (MMT) were prepared by melt blending. The fire resistance of the nanocomposites was analyzed by limiting oxygen index (LOI) and vertical burning (UL 94) tests. The results show that the addition of the P–N flame retardants increased the LOI of the material from 17.3 to 27%. However, TPEE containing P–N flame retardants only obtained a UL 94 V‐2 ranking; this resulted in a flame dripping phenomenon. On the other hand, TPEE containing the P–N flame retardant and organically modified montmorillonite (o‐MMT) achieved better thermal stability and good flame retardancy; this was ascribed to its partially intercalated structure. The synergistic effect and synergism were investigated by Fourier transform infrared spectroscopy and thermogravimetry. The introduction of o‐MMT decreased the inhibition action of the P–N flame retardant and increased the amount of residues. The catalytic decomposition effect of MMT and the barrier effect of the layer silicates are discussed in this article. The residues after heating in the muffle furnace were analyzed by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and laser Raman spectroscopy. It was shown that the intercalated layer silicate structure facilitated the crosslinking interaction and promoted the formation of additional carbonaceous char residues in the formation of the compact, dense, folded‐structure surface char. The combination of the P–N flame retardant and o‐MMT in TPEE resulted in a better thermal stability and fire resistance because of the synergistic effect of the mixture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41094.     

Synergistic effect of aluminum hydroxide and expandable graphite on the flame retardancy of polyisocyanurate–polyurethane foams

For the first time, expandable graphite (EG) and aluminum hydroxide (ATH) was combined to improve the flame retardancy of polyisocyanurate–polyurethane (PIR–PUR) foam. The limited oxygen index increased from 26.5 for the PIR–PUR matrix to an incredible value of 92.8 when 24 phr (parts per 100 of matrix) EG and 60 phr ATH were incorporated into the matrix. Based on morphology observation and thermogravimetric analysis, it was speculated that two factors contributed to the improvement of flame retardancy primarily. First, ATH could effectively induce “villi” like particles, which was useful to form a dense char. The compact char layer could effectively impede the transport of bubbles and heat. Second, ATH and EG accelerated the initial degradation and fluffy char was quickly generated on the surface of the composites. Thus, the degradation of the composite was slowed down and the diffusion of volatile combustible fragments to flame zone was delayed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39936.     

Preparation of a chitosan‐based flame‐retardant synergist and its application in flame‐retardant polypropylene

A novel flame‐retardant synergist, chitosan/urea compound based phosphonic acid melamine salt (HUMCS), was synthesized and characterized by Fourier transform infrared spectroscopy and ³¹P‐NMR. Subsequently, HUMCS was added to a fire‐retardant polypropylene (PP) compound containing an intumescent flame‐retardant (IFR) system to improve its flame‐retardant properties. The PP/IFR/HUMCS composites were characterized by limiting oxygen index (LOI) tests, vertical burning tests (UL‐94 tests), microscale combustion calorimetry tests, and thermogravimetric analysis to study the combustion behavior and thermal stability. The addition of 3 wt % HUMCS increased the LOI from 31.4 to 33.0. The addition of HUMCS at a low additive amount reduced the peak heat‐release rate, total heat release, and heat‐release capacity obviously. Furthermore, scanning electron micrographs of char residues revealed that HUMCS could prevent the IFR–PP composites from forming a dense and compact multicell char, which could effectively protect the substrate material from combusting. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40845.     

Component ratio effects of hyperbranched triazine compound and ammonium polyphosphate in flame‐retardant polypropylene composites

A hyperbranched derivative of triazine group (EA) was synthesized by elimination reaction between ethylenediamine and cyanuric chloride. The different‐mass‐ratio EA and ammonium polyphosphate (APP) were mixed and blended with polypropylene (PP) in a constant amount (25%) to prepare a series of EA/APP/PP composites. The component ratio effect of EA/APP on the flame‐retardant property of the EA/APP/PP composites was investigated using the limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimetry tests. Results indicated that the EA/APP/PP (7.50/17.50/75.00) composite with the appropriate EA/APP mass ratio had the highest LOI, UL94 V‐0 rating, lowest heat release rate, and highest residue yield. These results implied that the appropriate EA/APP mass ratio formed a better intumescent flame‐retardant system and adequately exerted their synergistic effects. Furthermore, average effective combustion heat values revealed that EA/APP flame retardant possessed the gaseous‐phase flame‐retardant effect on PP. Residues of the EA/APP/PP composites were also investigated by scanning electron microscopy, Fourier‐transform infrared, and X‐ray photoelectron spectroscopy. Results demonstrated that the appropriate EA/APP mass ratio can fully interact and lock more chemical constituents containing carbon and nitrogen in the residue, thereby resulting in the formation of a dense, compact, and intumescent char layer. This char layer exerted a condensed‐phase flame‐retardant effect on EA/APP/PP composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41006.     

Thermal and flammability performance of polypropylene composites containing melamine and melamine phosphate‐modified α‐type zirconium phosphates

In this article, melamine (MA) and melamine phosphate (MP) have been intercalated into α‐type zirconium phosphate (α‐ZrP) interlayer spaces. The structure and thermal properties of the corresponding powders, MA‐ZrP and MP‐ZrP, were ascertained by X‐ray diffraction, Fourier transform infrared spectra, X‐ray photoelectron spectroscopy measurement, and thermogravimetric analyses (TGA). Furthermore, polypropylene (PP) and its intumescent flame retardant (IFR) composites containing the two organically modified α‐ZrP powders using maleic anhydride‐grafted PP (JPP) as compatibilizer were fabricated by melt blending. The results from TGA and cone calorimetry demonstrated that PP/JPP and PP/JPP/IFR composites containing MA‐ZrP and MP‐ZrP exhibited better thermal stability and burning behavior in comparison with their corresponding counterparts, PP/JPP and PP/JPP/IFR, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40254.     

Expanding the application field of post‐consumer poly(ethylene terephthalate) through structural modification by reactive blending

With the aim of up‐grading the material properties of post‐consumer PET, making them suitable for extrusion of thermoformable thick sheets, a series of polyepoxy chain extenders have been comparatively evaluated as melt viscosity modifiers for a toughened compatibilized blend containing up to 80 wt % of bottle‐grade post‐consumer recycled poly(ethylene terephtalate) (r‐PET). Combinations of a commercial modifier with pentaerythritol were also successfully employed to cause simultaneous hyperbranching and controlled chain scission, thereby modifying the melt rheology of the material without excessively increasing the molecular weight, as highlighted by common technological melt viscosity measurements such as online torque and off‐line melt flow rate (MFR). Since the high melt fluidity of PET plays a critical role on its flame resistance, the combined effect of chain extenders and halogen‐free phosphorated additives on the fire resistance of the modified toughened blends was also investigated. Preliminary results indicate that the chemical reactions among polymer and additives must be taken into careful account to prevent unfavorable effects on the ultimate melt rheology and mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40881.     

Char barrier effect of graphene nanoplatelets on the flame retardancy and thermal stability of high‐density polyethylene flame‐retarded by brominated polystyrene

Graphene nanoplatelets (GNPs) with the char barrier effect were combined with brominated polystyrene (BPS) and antimony trioxide (Sb₂O₃) to improve the flame retardancy and thermal stability of high‐density polyethylene. Thermogravimetric analysis, limited oxygen index (LOI) testing, and vertical burning testing (UL‐94) showed that the presence of GNPs led to enhanced thermal oxidation stability and significantly reduced the flammability. The addition of 1 wt % GNPs to polyethylene/BPS–Sb (mass ratio = 92/6/2) led to UL‐94 grades from NG (first burning time > 30 s) to V‐2 (total burning time = 14 s), and the LOI value increased from 23.4 to 24.1%. The results of the pyrolysis products provided evidence that the GNPs restricted volatilization. The morphology of the chars also proved the formation of the char layer, which could act as a barrier to isolate the material from the flame and retard the vaporization of flammable gases via a tortuous pathway. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40520.     

Flame retardancy and thermal property of novel UV-curable epoxy acrylate coatings modified by melamine-based hyperbranched polyphosphonate acrylate

A novel melamine-based hyperbranched polyphosphonate acrylate (MHPA), successfully synthesized via the Michael addition polymerization of 2-(2-amino-ethylamino)-4,6-bisethylamino-1,3,5-triazine with tri(acryloyloxyethyl) phosphate, was blended with the epoxy acrylate (EA) to prepare UV-cured flame retardant coatings. The study of their flammability revealed that MHPA can improve the flame retardancy and the sample with 45 wt% MHPA (EA3) showed a good intumescent behavior when combusted. The results of their thermal degradation displayed that MHPA had a dual effect on the thermal stability of EA: leading to its earlier degradation catalyzed by acidic species from the relatively weak phosphorus-bearing parts, but improving the thermal stability of the char layer at high temperature due to the formed intumescent phosphorus–carbon compounds. Besides, the total release amount of gas products of EA3 was much lower than that of pure EA and various flammable gases like hydrocarbons and highly toxic CO were also reduced