Three in one: β‐cyclodextrin,nanohydroxyapatite, and a nitrogen‐rich polymer integrated into a new flame retardant for poly (lactic acid)

A new halogen‐free flame retardant was developed by integrating β‐cyclodextrin, triazin ring, and nanohydroxyapatite (BSDH) into a hybrid system. A β‐cyclodextrin was grafted to a commercially available SABO®STAB UV94 via an aromatic deanhydrate. The BSDH was prepared in situ in the presence of β‐cyclodextrin‐grafted nitrogen‐rich precursor. The resulting hybrid was applied as a flame retardant for poly(lactic acid) (PLA) and compared for performance with ammonium polyphosphate (APP). PLA composites containing BSDH and APP, individually or simultaneously, were examined for thermal degradation and flammability by TGA, cone calorimeter, and pyrolysis‐combustion flow calorimetry. TGA results confirmed enhancement of thermal stability of PLA with assistance of BSDH compared to APP. The gases evolved during thermal degradation were assessed by a thermogravimetric analysis and Fourier infrared spectroscopy device. APP revealed catalytic effect to initiate PLA degradation, while BSDH continued to release some gases at elevated temperatures. The flame retardancy of PLA/APP/BSDH blend containing only 10 wt.% of additives was significantly improved. In cone calorimetric tests, a significant fall in peak of heat release rate was observed for this sample, 49% more than that of neat PLA, which was indicative of more gas and condensed phase reflected in more char residue. The corresponding PLA/APP sample, however, showed 17% improvement, as compared to neat PLA. Also, total heat release rate of PLA/APP/BSDH was 45 MJ.m^?2, whereas those of PLA and PLA/APP were 89 and 65 MJ.m^?2, respectively. BSDH and APP showed a synergistic effect on improving the flame retardancy of PLA composites.     

Durable flame‐retardant finished cotton fabrics characterized by thermal degradation behaviors

After a series of investigations on the durable flame‐retardant finishes, it was thought to be important to study these durable flame‐retardant finished materials from the thermal analytical standpoint. Accordingly, cotton fabric was finished with N‐methylol dialkyl phosphonopropionamide (Pyrovatex C) by thermofixation and tetrakis (hydroxymethyl) phosphonium sulfate (THPS) precondensate by ammonia cure (Proban), as well as with THPS monomer by heat cure under various conditions, and subjected to the thermogravimetry (TG) to observe thermal degradation behaviors and obtain apparent activation energy (E_a). TG curves of Proban‐finished samples showed the largest shift to lower temperatures with a steep slope; thermofixed THPS‐finished sample gave a smaller shift with similar steep slope, whereas Pyrovatex‐finished samples exhibited a similar shift but with a gradual slope. E_a versus residual ratio curves led us to conclude that C N bond‐rich Proban polymer requires the highest E_a and decomposes with considerable rapidity, whereas ethylene‐bond‐rich Pyrovatex‐finished samples with melamine crosslinking decompose gradually with the lowest E_a. As for the relationship between flame retardance and E_a distribution in the process of thermal degradation, typical differences among the above three kinds of finished samples were found, which are compared and discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 975–987, 1999     

Flexible and flame resistant poly(lactic acid)/organomontmorillonite nanocomposites

The PLA/OMMT nanocomposites were produced using a melt compounding technique with isopropylated triaryl phosphate ester flame retardant (FR; 10–30 parts per 100 resin). The flammability of the PLA/OMMT composites was evaluated with an Underwriter Laboratory (UL‐94) vertical burning test, and their char morphology was studied using scanning electron microscopy (SEM). The thermal properties of the PLA/OMMT were characterized with a thermogravimetric analyzer (TGA) and a differential scanning calorimeter (DSC). The thermal analyses showed that adding FR reduced the decomposition onset temperature (T_o) of PLA/OMMT. Both PLA/OMMT/FR20 and PLA/OMMT/FR30 showed excellent flame retardant abilities, earning a V‐0 rating during the UL‐94 vertical burning test. A compact, coherent and continuous protective char layer was formed in the PLA/OMMT/FR nanocomposites. Additionally, the DSC results indicated that the flexibility of the PLA/OMMT composites increased after adding FR due to the FR‐induced plasticization. The impact strength of PLA/OMMT was greatly increased by the addition of FR. Flexible PLA nanocomposites with high flame resistance were successfully produced. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41253.     

Mechanical Properties and Degrading Behaviors of Aluminum Hypophosphite-Poly(Lactic Acid) (PLA) Nanocomposites

The flame retardancy of poly(lactic acid) (PLA)/aluminum hypophosphite (AHP, phosphorous content = 41.87 wt.%) nanocomposites (PLA/(AHP-x), x = 15%, 20%, 25%; and x denotes the weight percentage content of AHP) was greatly enhanced by melt blending of AHP into PLA through twin-screw extruder and injection-molding process. The UL 94 V-0 flammability rating can be reached for PLA/(AHP-20%) with the LOI value over 28.8. The well dispersion of the AHP in PLA/(AHP-x) was investigated by FT-IR spectra under the line mapping model. Based on TGA results under a non-isothermal condition, the thermal degradation kinetics of PLA/(AHP-x) composites were studied by Kissinger’s, Ozawa’s and Flynn-Wall-Ozawa’s (FWO’s) methods. And those thermal degradation dynamic analyses showed lower activation energy (E_K or E_O) (from 155 to 122 kJ·mol^–1) corresponded to higher content of AHP (from 15 to 25 wt.%) for PLA/(AHP-x) nanocomposites. Kissinger’s, FWO’s and Coast-Redfern’s methods were used to discriminate the kinetic models and kinetic parameters for the thermal degradation of PLA/(AHP-x), which suggested conversion function G (α) = [-ln(1-α)]^2/3 or G (α) = α for the investigated process. The flame retardant PLA nanocomposites obtained in this study will become safety environment-friendly potential candidates in household and automobile engineering with high performance.     

Functionalized N‐(4‐hydroxy phenyl) maleimide monomers: Kinetics of thermal polymerization and degradation using model‐free approach

N‐(4‐Hydroxy phenyl) maleimide (HPMI) is prepared and is functionalized with acryloyl, methacryloyl, allyl, propargyl, and cyanate groups. The structural and thermal characterizations of the materials are done using FTIR, NMR, DSC, and TGA. Curing and degradation kinetics are performed using Flynn–Wall–Ozawa, Vyazovkin, and Friedman methods. Activation energies (E_a) for the polymerization of the synthesized monomers varied and are dependent on the nature of the functional group present in HPMI. The propargyl functionalized monomer shows the highest E_a values whereas the methacryloyl functionalized monomer shows the lowest E_a values. In the case of thermal degradation of the polymerized materials, the apparent E_a values for acryloyl, methacryloyl and cyanate functionalized materials are slightly higher than that of poly‐HPMI (PHPMI). The thermally cured allyl and propargyl functionalized materials show a different trend and may be attributed to the complications arising due to Claisen rearrangement reaction during the thermal curing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39935.     

The flame retardant group‐synergistic‐effect of a phosphaphenanthrene and triazine double‐group compound in epoxy resin

A flame retardant tri‐(phosphaphenanthrene‐(hydroxyl‐methylene)‐phenoxyl)‐1, 3, 5‐triazine (Trif‐DOPO) and its control samples are incorporated into diglycidyl ether of bisphenol‐A (DGEBA) and 4, 4′‐diamino‐diphenyl sulfone (DDS) to prepare flame retardant thermosets, respectively. According to the results of limited oxygen index (LOI), UL94 vertical burning test and cone calorimeter test, the Trif‐DOPO/DGEBA/DDS thermoset with 1.2 wt % phosphorus possesses the LOI value of 36% and UL94 V‐0 flammability rating, and Trif‐DOPO can decrease the peak of heat release rate (pk‐HRR) and reduce the total heat release (THR) of thermosets. All these prove better flame retardant performance of Trif‐DOPO than that of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide(DOPO). The residue photos of thermosets after cone calorimetry test disclose that Trif‐DOPO can promote the formation of thick and tough melting char layer for combined action of the flame retardant groups of Trif‐DOPO. The results from thermo gravimetric analysis (TGA) and pyrolysis‐gas chromatography‐mass spectrometry(Py‐GC/MS) show that the groups in Trif‐DOPO can be decomposed and produce PO₂ fragments, phosphaphenanthrene and phenoxy fragments, which can jointly quench the free radical chain reaction during combustion. Therefore, the excellent flame retardancy of Trif‐DOPO is attributed to its flame retardant group‐synergic‐effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39709.     

Morphology and thermal degradation studies of melt‐mixed PLA/PHBV biodegradable polymer blend nanocomposites with TiO2 as filler

The morphology and thermal stability of melt‐mixed poly(lactic acid) (PLA)/poly(hydroxybutyrate‐co‐valerate) (PHBV) blends and nanocomposites with small amounts of TiO₂ nanoparticles were investigated. PLA/PHBV at 50/50 w/w formed a co‐continuous structure, and most of the TiO₂ nanoparticles were well dispersed in the PLA phase and on the interface between PLA and PHBV, with a small number of large agglomerates in the PHBV phase. Thermogravimetric analysis (TGA) and TGA–Fourier‐transform infrared spectroscopy was used to study the thermal stability and degradation behavior of the two polymers, their blends, and nanocomposites. The thermal stability of PHBV was improved through blending with PLA, whereas that of the PLA was reduced through blending with PHBV, and the presence of TiO₂ nanoparticles seemingly improved the thermal stability of both polymers in the blend. However, the degradation kinetics results revealed that the nanoparticles could catalyze the degradation process and/or retard the volatilization of the degradation products, depending on their localization and their interaction with the polymer in question. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42138.     

Thermal properties of extruded injection‐molded poly(lactic acid) and milkweed composites: Degradation kinetics and enthalpic relaxation

To determine the degree of compatibility between poly(lactic acid) (PLA) and different biomaterials, PLA was compounded with milkweed fiber, a new crop oil seed. After oil extraction, milkweed remaining cake retained approximately 10% residual oil, 47% protein, and 10% moisture. The fiber (300 μm) was added at 85 : 15 and 70 : 30 PLA : Fiber and blended by extrusion (EX) followed by injection molding (IM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used for testing the composites. After melting in the DSC sealed pans, composites were cooled by immersion in liquid nitrogen and aged (stored) at room temperature for 0, 7, 15, and 30 days. After storage, samples were heated from room temperature to 180°C at 10°C/min. The pure PLA showed a glass transition (T_g) at 60.3°C and the corresponding ΔCp was 0.464 J/g/°C followed by crystallization and melting transitions. The enthalpic relaxation (ER) of neat PLA and composites steadily increased as a function of storage time. Although the presence of fiber had little effect on ER, IM reduced it. The percentage crystallinity of neat unprocessed PLA dropped by 95 and 80% for the EX and IM, respectively. The degradation activation energy (E_a) of neat PLA exhibited a significant drop in nitrogen environment, whereas increased in air, indicating PLA resistant to heat degradation in the presence of oxygen. Overall, IM appeared to decrease E_a of the composites, whereas milkweed significantly reduced E_a values in nitrogen environment. Enzymatic degradation of the composites revealed higher degradation rate for the EX samples versus IM, whereas 30% milkweed exhibited higher weight loss compared to the 15%. The degradation mechanism was observed by looking at the percent conversion as a function of E_a from the TGA data, where multisteps degradation occurred mostly in air. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The pyrolysis behaviors of ternary copolyimide derived from aromatic dianhydride and aromatic diisocyanates

A polyimide (PI) based on benzophenone‐3,3′,4,4′‐tetracarboxylic acid dianhydride, toluene diisocyanate (TDI), and 4,4′‐methylenebis (phenyl isocyanate) (MDI) has been synthesized via a one‐step polycondensation procedure. The resulting PI possessed excellent thermal stability with the glass transition temperature (T_g) 316°C, the 5% weight loss temperature (T_5%) in air and nitrogen 440.4°C and 448.0°C, respectively. The pyrolysis behaviors were investigated with dynamic thermogravimetric analysis (TGA), TGA coupled with Fourier transform infrared spectrometry (TGA–FTIR) and TGA coupled with mass spectrometry (TGA–MS) under air atmosphere. The results of TGA–FTIR and TGA–MS indicated that the main decomposition products were carbon dioxide (CO₂), carbonic oxide (CO), water (H₂O), ammonia (NH₃), nitric oxide (NO), hydrogen cyanide (HCN), benzene (C₆H₆), and compounds containing NH₂, C?N, N?C?O or phenyl groups. The activation energy (E_a) of the solid‐state process was estimated using Ozawa–Flynn–Wall (OFW) method which resulted to be 143.8 and 87.8 kJ/mol for the first and second stage. The pre‐exponential factor (A) and empirical order of decomposition (n) were determined by Friedman method. The activation energies of different mechanism models were calculated from Coats–Redfern method. Compared with the activation energy values obtained from the OFW method, the actual reaction followed a random nucleation mechanism with the integral form g(α) = ?ln(1 ? α). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40163.     

Kinetic analysis of nonisothermal degradation of acrylonitrile–butadiene/ethylene–propylene–diene rubber blends reinforced with carbon black filler

The nonisothermal degradation process of acrylonitrile–butadiene/ethylene–propylene–diene rubber blends reinforced with carbon black filler was investigated with thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG), using the different calculation procedures. Using different isoconversional methods, it was found that the degradation of the 50 phr loaded carbon black in NBR/EPDM (80/20) blend represents the complex process, where exists the conversion region with a constant value of the apparent activation energy (E_a). It was found that the degradation process of the carbon black‐loaded polymer blend under nitrogen atmosphere, can be described by the three‐(D3) dimensional diffusion mechanism. Good agreement was observed between the experimental and calculated differential (rate) conversion curves, for the investigated degradation process. It was established that the considered polymer blend which have high contents of the carbon black (50 phr carbon black), shows very strong self‐protective behavior (i.e., in the formation of a protective barrier). POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Thermal and biodegradation properties of poly(lactic acid)/fertilizer/oil palm fibers blends biocomposites

Poly(lactic acid) (PLA) and NPK fertilizer with empty fruit bunch (EFB) fibers were blends to produced bioplastic fertlizer (BpF) composites for slow release fertilizer. Thermal properties of BpF composites were investigated by thermogavimteric analysis (TGA), differential scanning calorimetry (DSC), and morphological and degradation properties were anlayzed by scanning electron microscopy (SEM), soil burial test, respectively. TGA themogram display that neat PLA, PLA/NPK, and BpF composites degradate at different temperatures. DSC curves of PLA and other composites exhibited same glass transition temperature (T_g) value indicating that both major blend components are miscible. The T_g, crystallization temperature (T_c), melting temperature (T_m) values also decreased with increased amount of fertilizer and fibers. The T_m of BpF composites did not change with an increase in fertilizer content because thermal stability of PLA and PLA/NPK composites was not affected. Soil burial and fungal degradation test of PLA, PLA/NPK, and BpF composites were also carried out. Soil burial studies indicated that BpF composites display better biodegradation as compared with neat NPK. Fungal degradation study indicated that fungi exposure times of BpF composites show higher value of degradation as compared with PLA/NPK. We attribute that developed BpF composites will help oil palm plantation industry to use it as slow release fertilizer. POLYM. COMPOS. 36:576–583, 2015. © 2014 Society of Plastics Engineers     

Phosphazene cyclomatrix network polymers: Some aspects of the synthesis,characterization, and flame‐retardant mechanisms of polymer

Novel phosphazene cyclomatrix network polymers were synthesized via nucleophilic displacement of activated nitro groups of tri(4‐nitrophenoxy)tri(phenoxy)cyclotriphosphazene and hexa(p‐nitrophenoxy)cyclotriphosphazene with the hydroxyls of bisphenol A. Both the monomers and polymers were characterized by Fourier transform infrared (FTIR) and ¹H‐NMR spectroscopy, and their structures were identified. The thermal and flame‐retardant properties of the polymers were investigated with thermogravimetric analysis in air, pyrolysis, and combustion experiments. Both solid and gaseous degradation products were collected in a pyrolysis process and analyzed with FTIR spectroscopy, gas chromatography/mass spectrometry, and scanning electron microscopy. The results demonstrated that the cyclomatrix phosphazene polymer would have excellent thermal stability and flame‐retardant properties if it could form a crosslinked phosphorous oxynitride structure during pyrolysis or combustion. A flame‐retardant mechanism of “intumescent” was proposed to elucidate the pyrolysis and combustion process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 880–889, 2005     

Kinetics and crystal structure of isothermal crystallization of poly(lactic acid) plasticized with triphenyl phosphate

In this article, the spherulitic growth rate of neat and plasticized poly(lactic acid) (PLA) with triphenyl phosphate (TPP) was measured and analyzed in the temperature range of 104–142°C by polarizing optical microscopy. Neat PLA had the maximum value of 0.28 μm/s at 132°C, whereas plasticized PLA had higher value than that of neat PLA, but the temperature corresponding to the maximum value was shifted toward lower one with increasing TPP content. The isothermal crystallization kinetics of neat and plasticized PLA was also analyzed by differential scanning calorimetry and described by the Avrami equation. The results showed for neat PLA and its blends with various TPP contents, the average value of Avrami exponents n were close to around 2.5 at two crystallization temperatures of 113 and 128°C, the crystallization rate constant k was decreased, and the half‐life crystallization time t_1/2 was increased with TPP content. For neat PLA and its blend with 15 wt % TPP content, the average value of n was 2.0 and 2.3, respectively, the value of k was decreased, and the value of t_1/2 was increased with crystallization temperature (T_c). Further investigation into crystallization activation energy ΔE_a of neat PLA and its blend with 15 wt % TPP showed that ΔE_a of plasticized PLA was increased compared to neat PLA. It was verified by wide‐angle X‐ray diffraction that neat PLA and its blends containing various TPP contents crystallized isothermally in the temperature range of 113–128°C all form the α‐form crystal. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synergistic effect of THEIC‐Based charring agent on flame retardant properties of polylactide

A novel charring agent tris(2‐hydrooxyethyl) isocyanurate terephthalic acid ester, tetramer (TT4) was synthesized using tris(2‐hydrooxyethyl) isocyanurate and terephthalic acid as raw materials, and it was characterized by Fourier transformed infrared spectrometry and ¹H‐NMR spectrum. It was combined with ammonium polyphosphate (APP) to form intumescent flame retardants for polylactide (PLA). The combustion properties and thermal stability of PLA/APP/TT4 composites were evaluated by UL‐94 burning tests, limiting oxygen index (LOI), and thermogravimetric analyses (TGA). It was found PLA with 30 wt % of APP/TT4 (5 : 1) achieved UL‐94 V‐0 rating and a 40.6 LOI value. Results from TGA demonstrated that APP/TT4 composites could retard the degradation of PLA above 410°C. The char residue at 500°C is higher than 24%, showing a good char forming ability. Moreover, the continuous and expansionary char layer observed from the SEM images proved good charring forming ability of TT4. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41218.     

Synthesis of bio-based reactive N/P flame retardant and its curing and flame retarding behavior in epoxy resins

In this study, a pioneering bio-based nitrogen–phosphorus flame retardant and curing accelerator named oxime-phosphazene hexakis [(4-(hydroxyimino) 2-methoxy) phenoxy] cyclotriphosphazene (HAPV) was successfully synthesized using hexachlorocyclotriphosphazene and vanillin. When 5 wt % HAPV was added into epoxy, the limiting oxygen index increased from 22% to 27% and passed UL-94 V-0 (UL is defined as Underwriters Laboratories) rating. Meanwhile, with the addition 5 wt% HAPV, the apparent activation energy (E_a) of HAPV/EP decreased from 20.22 to 67.15 kJ/mol, and the pHRR value was suppressed from 581.21 to 330.18 kW/m². It was due to that the HAPV quenched the combustion chain reaction through the gas phase and condensed phase, forming a dense char layer for blocking the heat transfer. Overall, the study provides an environmentally friendly epoxy flame retardant curing accelerator that shows great potential in epoxy flame retardant applications.     

Preparation and study of intumescent flame retardant poly(butylene succinate) using MgAlZnFe‐CO3 layered double hydroxide as a synergistic agent

Intumescent flame retardant consisting of ammonium polyphosphate and melamine, and MgAlZnFe‐CO₃ layered double hydroxides (LDHs) prepared by the constant pH coprecipitation method, were added to poly(butylene succinate) (PBS) via melt blending to obtain novel intumescent flame retardant poly(butylene succinate) (IFR‐PBS) composites. A study on the effect of MgAlZnFe‐CO₃ LDHs on the mechanical, thermal, and flame retardancy properties of IFR‐PBS composites was investigated. It was revealed that IFR‐PBS composites exhibited both excellent flame retardancy and antidripping properties when the content of MgAlZnFe‐CO₃ LDHs was 1% (the total loading of flame retardant was 20%), for a goal of vertical flammability (UL‐94) V‐0 rate and a limiting oxygen index value of 35. The results showed that a suitable amount of MgAlZnFe‐CO₃ LDHs had a noticeable synergistic effect on IFR‐PBS composites. Importantly, tensile strength and flexural strength were improved by the presence of MgAlZnFe‐CO₃ LDHs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40736.     

Influence of nanozirconia on the thermal stability of poly(methyl methacrylate) prepared by in situ bulk polymerization

Nanozirconia (nano‐ZrO₂) was prepared by the sol–gel method and incorporated into poly(methyl methacrylate) (PMMA) by the in situ bulk polymerization of methyl methacrylate. The structure of the nano‐ZrO₂ was confirmed by X‐ray diffraction (XRD), transmission electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The structure of the nano‐ZrO₂ nanocomposites were studied by differential scanning calorimetry, FTIR spectroscopy, XRD, and scanning electron microscopy, and the results show that there were interactions between the nanoparticles and the polymer. The influence of the nano‐ZrO₂ on the thermal stability of PMMA was investigated by thermogravimetric analysis (TGA). The results indicate that nano‐ZrO₂ enhanced the thermal stability of the PMMA/nano‐ZrO₂ nanocomposites. The effects of the heating rate in dynamic measurements (5–30°C/min) on kinetic parameters such as apparent activation energy (E_a) in TGA both in nitrogen and air were investigated. The Kissinger method was used to determine E_a for the degradation of pure PMMA and the PMMA/nano‐ZrO₂ nanocomposites. The kinetic results show that the values of E_a for the degradation of the nanocomposites were higher than that of pure PMMA in air. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The flame retardant behaviors and synergistic effect of expandable graphite and dimethyl methylphosphonate in rigid polyurethane foams

A series of flame‐retardant rigid polyurethane foams (RPUFs) containing dimethyl methylphosphonate (DMMP) and expandable graphite (EG) were prepared by box‐foaming. The RPUFs were characterized by thermogravimetric analysis (TGA), the limiting oxygen index (LOI), cone calorimeter, and scanning electron microscope (SEM). The decomposition process of DMMP was investigated by Pyrolysis‐Gas Chromatography/Mass Spectroscopy (Py‐GC/MS). Accordingly, their flame retardant behaviors and mechanism were also discussed. The results show that the DMMP/EG system can linearly enhance the LOI value from 19.2% of the pure RPUF to 33.0% of RPUFs containing 16 wt% flame retardant. In addition, the DMMP/EG system also remarkably increases yields of the residual char and drastically decreases the peak value of heat release rate (PHRR), heat release rate (HRR), total heat release (THR), total smoke release (TSR), and the yields of CO (COY). In the flame retardant RPUFs, when the matrix is ignited, the flame retardant DMMP should be decomposed to gaseous PO₂ fragments, which can inhibit free radical chain reaction of flammable alkyl free radical from the decomposed matrix; whereas the flame retardant EG can rapidly expand and form loose and worm‐like expanding graphite char layer accordingly, which can hinder the heat transmission to the inner matrix and reduce decomposing velocity of matrix. After the combination of the two flame retardant effects, the DMMP/EG flame retardant system provides the matrix with better flame retardant effects than one of them does. Namely, it shows excellent gas‐condensed bi‐phase synergistic effect. POLYM. COMPOS., 35:301–309, 2014. © 2013 Society of Plastics Engineers     

The flame‐retardant effect of calcium hypophosphite in various thermoplastic polymers

The flame‐retardant behavior of calcium hypophosphite (CaHP) was investigated in different thermoplastic polymers including polyamide 6 (PA), poly (lactic acid) (PLA), thermoplastic polyurethane (TPU), and poly methyl metacrylate (PMMA). CaHP was used at three different amounts of 10, 20, and 30 wt%. The characterization of the composites was performed using limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis (TGA), and mass loss calorimeter test. According to the test results, CaHP enhances the fire‐retardant properties in different levels depending on the polymer type. The CaHP exhibits its flame‐retardant effect via the formation of foamed char structure in the condensed phase and via the dilution and radical scavenging effect in the gas phase.     

Effects of ammonium polyphosphate and triphenyl phosphate on the flame retardancy,thermal, and mechanical properties of glass fiber–reinforced PLA/PC composites

The purpose of this study is to increase of the flammability properties of the glass fiber (GF)–reinforced poly (lactic acid)/polycarbonate (PLA/PC) composites. Ammonium polyphosphate (APP) and triphenyl phosphate (TPP) were used as flame retardants that are including the organic phosphor to increase flame retardancy of GF‐reinforced composites. APP, TPP, and APP‐TPP mixture flame retardant including composites were prepared by using extrusion and injection molding methods. The properties of the composites were determined by the tensile test, limiting oxygen index (LOI), differential scanning calorimetry (DSC), and heat release rate (HRR) test. The minimum T_g value was observed for the TPP including PLA/PC composites in DSC analysis. The highest tensile strength was observed in GF‐reinforced PLA/PC composites. In the LOI test, GF including composite was burned with the lowest concentration of oxygen, and burning time was the longest of this composite. However, the shortest burning time was obtained by using the mixture flame retardant system. The flame retardancy properties of GF‐reinforced PLA/PC composite was improved by using mixture flame retardant. When analyzed the results of HRR, time to ignition (TTI), and mass loss rate together, the best value was obtained for the composite including APP.