Highest Limiting Oxygen Index Value Research Articles

Synthesis of novel liquid crystalline and fire retardant molecules based on six-armed cyclotriphosphazene core containing Schiff base and amide linking units.

Nucleophilic substitution reaction between 4-hydroxybenzaldehyde and hexachlorocyclotriphosphazene, HCCP formed hexakis(4-formlyphenoxy)cyclotriphosphazene, 1. Intermediates 2a–e was formed from the alkylation reaction of methyl 4-hydroxybenzoate with alkyl bromide which further reduced to form benzoic acid intermediates. Further reaction of 2a–e and other substituted benzoic acid formed 3a–h, which then reduced to give subsequent amines, 4a–h. Other similar reaction was used to synthesis 4i. Condensation reaction between 1 and 4a–i yielded hexasubstituted cyclotriphosphazene compounds, 5a–i having Schiff base and amide linking units, and these compounds consist of different terminal substituents such as heptyl, nonyl, decyl, dodecyl, tetradecyl, hydroxy, carboxy, chloro, and nitro groups, respectively. Compound 5j with amino substituent at terminal end was formed from the reduction of 5i. All the intermediates and compounds were characterized using Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR) and CHN elemental analysis. Mesophase texture of these compounds were determined using Polarized Optical Microscope (POM) and their mesophase transition were further confirmed using Differential Scanning Calorimetry (DSC). Only compounds 5a–e with alkoxy chains exhibited smectic A phase while other intermediates (1, 2a–e, 3a–h, and 4a–i) and final compounds (5f–j) are found to be non-mesogenic with no liquid crystal behaviour. The confirmation of the identity of the SmA phase was determined using XRD analysis. The study on the structure–properties relationship was conducted in order to determine the effect of the terminal group, length of the chains and linking units to the mesophase behaviour of the compounds. Moreover, the fire retardant properties of these compounds were determined using Limiting Oxygen Index (LOI) testing. Polyester resin with LOI value of 22.53% was used as matrix for moulding in the study. The LOI value increased to 24.71% when this polyester resin incorporated with 1 wt% of HCCP. Generally, all the final compounds showed a positive results with LOI value above 27% and the highest LOI value was belonged to compound 5i with 28.53%. The high thermal stability of the Schiff base molecules and the electron withdrawing group of the amide bonds and nitro group enhanced the fire retardant properties of this compound.

Preparation of piperazine cyanurate by hydrogen‐bonding self‐assembly reaction and its application in intumescent flame‐retardant polypropylene composites

Piperazine cyanurate (PCA) is designed and synthesized via hydrogen‐bonding self‐assembly reactions between piperazine and cyanuric acid. Chemical structure and morphology of PCA are investigated by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The prepared PCA is combined with ammonium polyphosphate (APP) to prepare flame‐retardant polypropylene (PP) composites. Thermostability, flammability, and combustion characteristics of PP composites are analyzed. The maximum thermal decomposition rate of flame‐retarded PP composites has an apparent reduction compared with that of pure PP, and obvious char is left for this intumescent flame retardant (IFR) system of APP and PCA. A high limiting oxygen index value and UL‐94 V‐0 rating are achieved with addition of APP and PCA. In cone calorimetry test, heat and smoke releases of PP are significantly decreased by this IFR system. Gaseous decomposition products during the thermal decomposition of flame‐retardant composites are studied. Chemical structure and morphology of char residues are analyzed. The results illustrate that APP and PCA have a superb synergistic action in the aspect of improvement in fire safety of PP. A possible flame‐retardant mechanism is concluded to reveal the synergism between APP and PCA.

Silylation of epoxidized soybean oil with triethoxysilanes, synthesis and characterization of their polyurethanes

Silylation of epoxidized soybean oil (ESBO) was carried out by epoxy ring opening reaction of methoxy and ethoxy silane compounds. $^{1}$H NMR and FTIR spectra confirmed that two novel bio-based polyols, PSiTh and PSiAm, were obtained through the ring opening of epoxy by the mercapto and amino moieties of MPTMS and APTES, respectively. Polyurethanes of these polyols were prepared using 4,4'- methylene-bis(phenyl isocyanate) (MDI) to incorporate silanol groups into polymer network and were labeled as PUSiTh and PUSiAm, respectively. To see the impact of silanol and phosphorous groups on flame retardant properties, the chain extended polyurethanes, PUSiThCE and PUSiAmCE were also prepared with bisphenol-A bis (hydroxy phenyl phosphonate) (BABHPP). Polyurethanes bearing thio-ether bonds besides alkoxy silane groups were characterized using FTIR spectroscopy. Prepared foams exhibited significant thermal stability and flame retardant properties with a limiting oxygen index (LOI) of 22-24%. Chain extended polyurethanes had 11-13% higher LOI value than the corresponding non-chain extended polyurethanes.

Synthesis of a novel phosphorus-nitrogen flame retardant and its application in epoxy resin

A novel phosphorus-nitrogen flame retardant named as melamine phenyl phosphate (MAPPO) was synthesized successfully via the neutralization reaction between phenylphosphonic acid (PPOA) and melamine (MA). The chemical structure of MAPPO was characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (NMR) and element analysis (EA). MAPPO was introduced into epoxy resin by blending to improve the flame retardancy. Flame retardancy and combustion behavior of EP/MAPPO were investigated by limiting oxygen index (LOI) test, vertical burning (UL-94) test and cone calorimeter test. UL-94 and LOI tests results showed EP containing 18 wt% MAPPO passed the UL-94 V-0 rating and got a high LOI value of 33%. In the cone calorimeter test, compared with that of EP, the values of peak of heat release rate (HRR), total heat release (THR), peak of smoke production rate (PSPR) and total smoke production (TSP) of modified EP were reduced by 58.7%, 40%, 49% and 61.6%, respectively. By analyzing the volatile pyrolysis products of MAPPO, it was known that MAPPO mainly produced CO2, NH3, H2O and other nitrogen-containing compounds, which diluted the concentration of fuel gases and oxygen during combustion. Meanwhile, the char residue of EP/MAPPO system after combustion was also analyzed by scanning electron microscope (SEM), FT-IR and Raman tests, and the results showed MAPPO was able to promote the crosslinking of EP leading to the formation of compact char layer containing P–O–C, PO and CC, etc. In a word, the enhancement in flame retardancy was attributed to both dilution effect of non-combustible gases and barrier effect of compact char.

Effects of Carbon Nanotube-Phosphorus Based Flame Retardant Combinations on Flammability of Polypropylene

The effects of multi-walled carbon nanotubes (MWCNTs) on fire behavior of phosphorus-based flame retardant (PBFR)/polypropylene (PP) were investigated. Two different type phosphorus-based flame retardant that commercially available; ammonium polyphosphate-based (Exolit AP 760) and organic phosphorous-based (Aflammit PCO 900) powders were studied to enhance the flammability of polypropylene. Phosphorus-based flame retardant content was fixed at 8 wt% of total flame retardant (FR) formulation. MWCNTs was incorporated into FR formulation at four different concentrations (0.5 wt%, 1.0 wt%, 1.5 wt% and 2.0 wt%). All composites were prepared by melt compounding in a twin-screw extruder followed by injection molding technique. Thermal properties and flammability of the prepared samples were determined by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and micro combustion calorimetry (MCC). Incorporation of organic phosphorous-based powder into PP matrix showed a better fire performance compared to ammonium polyphosphate-based flame retardant by resulting in an 11.6% higher LOI value. The LOI values decreased with the incorporation of MWCNTs into PP/ PBFR combinations; however, they still increased the thermal stability of each respective system. The addition of 2.0 wt% MWCNTs decreased the LOI value of PP/organic phosphorous-based FR system 5.2% higher than PP/ammonium polyphosphate-based FR system. The heat release rate of PP reduced in the presence of both PBFRs, but; increased with the introduction of MWCNTs

Syntheses of intrinsically flame‐retardant polyamide 6 fibers and fabrics

ABSTRACTIn this study, flame‐retarded polyamide 6 (FR‐PA6) was prepared via the direct co‐condensation of ε‐caprolactam with two different organophosphorus compounds in a typical melt‐polymerization process. Polymer microstructures, especially the incorporation of the phosphorus‐containing comonomers, as well as the thermal and physical properties of the resulting copolyamides have been studied in detail. The phosphorus‐modified PAs have a P‐content of 0.10–0.30 wt %, possess high relative viscosities of 2.2–2.4 and good thermal stability. FR‐PA6 multifilaments were prepared by melt spinning and show tensile strengths up to 40 cN/tex and tenacities up to 0.5 GPa. Knitted fabrics of FR‐PA6 exhibit high limiting oxygen index values around 35%. Due to the very low phosphorus content, there is no impairment of the material properties of PA6. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47829.

Flame retardant effect of aluminum hypophosphite in heteroatom-containing polymers

In the present study, the effect of the aluminum hypophosphite (AlHP) concentration on the flame retardant properties of the four different polymers [polyamide 6 (PA6), poly(lactic acid) PLA, thermoplastic polyurethane (TPU) and poly(methyl methacrylate) (PMMA)] was investigated through mass loss calorimeter tests (MLC), thermogravimetric analysis, limiting oxygen index (LOI) and vertical burning test (UL-94). Test results from UL-94 test revealed that 20 wt% AlHP was needed to reach V0 rating in the PA6, TPU and PMMA and 10 wt% was required for PLA. LOI values and the char yields of all composites were increased with increasing AlHP amount. However, peak heat release (pHRR) and total heat evolved values decreased as the added amount of AlHP increased. The highest LOI value (31) and the lowest pHRR value (134 kW/m2) were obtained in TPU/30 AlHP composites. In brief, the comprehensive test results showed that the incorporation of the AlHP improved the flame retardant properties of the PA6, PLA, TPU and PMMA via the formation of the char in the condensed phase and radical trapping and dilution effect in the gas phase.

Polyurethane foams with functionalized graphene towards high fire-resistance, low smoke release, superior thermal insulation

To overcome the contradiction among flame retardancy, smoke suppression and thermal insulation for polyurethane foams (PUFs), in this manuscript, a novel functionalized graphene (FGN) is designed and prepared from expandable graphite (EG) and phosphorus-containing compounds. This FGN decorated with phosphorus-containing epoxy shows excellent compatibility with polyurethane matrix, leading to an improved compressive strength and decreased thermal conductivity as low as 0.02975 W/(m∙K). Notably, the resultant PUFs with FGNs exhibit great fire resistance and smoke suppression performance. With only 50 pphp FGNs (6.1 wt%) incorporated, the composite foam can pass the UL-94V-0 rating with a high limiting oxygen index value of 27. More importantly, the incorparation of FGNs not only effectively reduces the heat release rate (HRR) and total release rate (THR) of PUFs, but also significantly suppresses smoke release of materials during combustion. The mean specific extinction area (mSEA) and total smoke production (TSP) values of the composite foam can be reduced to 208.52 m2/s (−70.0%) and 2.08 m2/m2 (−66.0%), respectively. These characteristics with high fire resistance, excellent smoke suppression and low thermal conductivity very beneficial for polyurethane foams used as thermal isolation materials.

Synthesis and characterization of novel fluorinated poly(ether imide)s containing pyridine and/or phenylphosphine oxide moieties

4-(4-Trifluoromethylphenyl)-2,6-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]pyridine (9FPBAPP), as a new aromatic diamine, was prepared by a modified Chichibabin reaction of 4-(4-nitro-2-trifluoromethylphenoxy)acetophenone with 4-triflouromethylbenzaldehyde, followed by a catalytic reduction. A series of fluorinated poly(ether imide)s containing pyridine and/or phenylphosphine oxide moieties were prepared from bis(3-aminophenyl)phenylphosphine oxide (BAPPO), 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), and 9FPBAPP via a conventional two-step thermal imidization procedure with various mole ratios of BAPPO and 9FPBAPP. All the polymers were amorphous and soluble in common organic solvents such as N, N-dimethylacetamide and N-methyl-2-pyrrolidone and had Tg’s of 277–285°C, 5% weight loss temperature of 521–550°C in nitrogen. Furthermore, high char yields and good limited oxygen index values indicated that these polymers exhibited good thermal stability and flame-retardant property. Tough and flexible polymer films also had good mechanical properties with tensile strengths of 75–99 MPa, tensile moduli of 1.1–1.6 GPa, and elongations at break of 12%–24% and low dielectric constants of 2.81–3.53 (1 MHz), as well as high optical transparency with the ultraviolet cutoff wavelength in the range of 350–384 nm.

Enhanced flame retardancy of polyethylene/magnesium hydroxide with polycarbosilane

Polycarbosilane (PCS) was used for surface modification of magnesium hydroxide (MNH) to enhance the flame retardant effectiveness by forming cohesive binding between MgO particles with ceramic adhesive. Chemical interaction and ceramic reaction were revealed between PCS and MNH, which made for a compact, thermal stable and ceramic-like barrier during the combustion of polyethylene (PE). The flame retardancy of PE/MNH/PCS composites was greatly enhanced and a limiting oxygen index (LOI) of 35.0 was achieved at the PCS/MNH ratio of 4/26 in the composite with 30 wt.% PCS modified MNH. Such results were superior in terms of high LOI value at low global content of MNH. Thanks to the better shielding effect of the integrated and self-supporting ceramic char, the peak heat release rate (p-HRR) and the total heat release (THR) of PE/MNH/PCS composites with 50 wt.% PCS modified MNH were remarkably decreased by 36% and 25% in comparison with PE/MNH with 50 wt.% MNH, respectively. The ceramic reaction between PCS and MNH, the superior thermal stability due to crosslinked PCS and the good barrier function of cohesive ceramic layer play important roles in the effective flame retardant mechanism.

Crystallization, flame‐retardant, and mechanical behaviors of poly(lactic acid)\9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide–calcium montmorillonite nanocomposite

ABSTRACTPoly(lactic acid) (PLA) nanocomposite with 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) intercalated calcium montmorillonite (Ca‐MMT) nanocompound was prepared, and the properties were compared with those of PLA/Ca‐MMT, PLA/DOPO, and PLA/DOPO+Ca‐MMT nanocomposites (where DOPO+Ca‐MMT indicates a physical mixture of DOPO and Ca‐MMT). The structures and properties of the four PLA nanocomposites were investigated by X‐ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry, thermogravimetric analysis, limiting oxygen index (LOI) testing, UL‐94 vertical testing, and cone calorimetry measurements. The XRD and TEM tests showed that the DOPO–Ca‐MMT nanocompound existed in both intercalated and exfoliated montmorillonite morphologies in the PLA matrix, a better dispersion state than the Ca‐MMT added alone and DOPO+Ca‐MMT in PLA; this benefited improvements in the crystallinity, thermal stability, and flame retardancy for the PLA/DOPO–Ca‐MMT nanocomposite, as seen in the higher degree of crystallinity, higher LOI values, and lower peak heat‐release rate. A loading of only 5 wt % DOPO–Ca‐MMT increased the LOI value of PLA from 20.0 to 28.3% and made the PLA pass the UL‐94 vertical test V‐0 rating at a 3.2 mm thickness. The nanocomposites based on DOPO–Ca‐MMT could be used as very efficient systems for flame‐retardant PLA. The PLA/DOPO–Ca‐MMT also had better tensile mechanical properties than the pure PLA and PLA/DOPO+Ca‐MMT. The annealing specimens of the four nanocomposites were also characterized to study the relationship between the PLA crystallization and flame retardancy or mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46982.

A study on carbon fiber reinforced poly(lactic acid)/polycarbonate composites

ABSTRACTIn this study, the properties of carbon fiber (CF) reinforced poly(lactic acid)/polycarbonate (PLA/PC) composites was investigated. Two compositions of PLA/PC (90/10 and 50/50) blends were used as matrix. Characterization of composites was carried out by differential scanning calorimetry, thermal gravimetric analysis, tensile test, dynamic mechanical analysis, limiting oxygen index (LOI), scanning electron microscope, and heat release rate (HRR). The tensile strength values of 90PLA/10PC and 50PLA/50PC blends were improved by the addition of CF. The highest tensile strength value was observed at 50PLA50PC30CF composite as 114.6 MPa. Storage modulus values of CF reinforced PLA/PC composites enhanced with increasing CF loading. The highest LOI value was obtained for 50PLA50PC30CF composite. It was observed that there is a significant decrease in peak of HRR (pHRR) and total heat release value for all of the composites with increasing CF loading. It was concluded that CF reinforced 50PLA/50PC composite has better mechanical and thermal properties than 90PLA/10PC composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46881.

Mechanical, thermal and fire performance of an inorganic-organic insulation material composed of hollow glass microspheres and phenolic resin

HypothesisOrganic foamy materials possess good thermal insulation properties and inorganic materials are non-combustible. Hence, it is possible to develop a kind of organic-inorganic lightweight thermal insulation materials with excellent fire safety. ExperimentsHollow glass microsphere (HGM), as one kind of lightweight noncombustible inorganic material, was chosen as the filling material. Phenolic resin (PR), as the flame retardant polymeric material, was used as binding material. A series of HGM/PR composites with various PR/HGM mass ratio were prepared. Properties, such as apparent density, microstructure, mechanical strength, thermal conductivity, burning behavior and flame retardancy of the specimens were determined, respectively. FindingsThe results show that the surface of HGM particles is coated by a layer of cured PR and the HGM powder is glued together firmly from the scanning electron microscope (SEM) images. With the increase of PR/HGM mass ratio, both of apparent density and mechanical strength of HGM/PR composites increase, but thermal conductivity and limiting oxygen index (LOI) values decrease, all of the specimens still possess high LOI value (>50%). What’s more, no flaming combustion (merely partial carbonization) and hardly any smoke can be observed during the burning process, which indicates the HGM/PR composites possess excellent flame retardant property and fire safety.

Rational design and preparation of flame retardant silk fabrics coated with reduced graphene oxide

Environmentally-friendly flame retardant silk fabrics were successfully fabricated by an industrialized surface modification method. The coating-reduction process was rationally designed and repeated several cycles to deposit more amounts of reduced graphene oxide (rGO) sheets on silk fabric surface for better flame retardant performance of the prepared fabric. The prepared rGO-coated silk fabric (rGOSF), especially the silk fabric after 9 cycles of coating-reduction process showed improved flame retardant performance compared with pristine silk fabric, as evidenced by higher limiting oxygen index value, better thermal stability and shorter damaged length in vertical flame test. Moreover, smoke density test demonstrated the prepared rGOSF also had excellent smoke suppression property. In addition, the UPF value of rGOSF can also be increased to 55.19 (50+). Mechanical properties tests indicated the used surface modification method had no effect on the tensile strength of rGOSF. Moreover, washing durability test showed the prepared rGOSF had good fastness to washing.

Synergistic effect of different nanoparticles on flame retardant poly(lactic acid) with bridged DOPO derivative

This study aimed to examine synergistic effect of nanoparticles including nano silica (SiO2), organic montmorillonite (OMMT) and zinc borate (ZnB) on flame retardant poly(lactic acid) (PLA) composites containing a phenethyl‐bridged 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide derivative (DiDOPO). 2% was the optimal addition content for these nanoparticles in PLA/DiDOPO composites, and nano SiO2 showed higher limiting oxygen index value (27.0%) than OMMT (25.8%) and ZnB (26.5%) at the same content. When compared with that of PLA/DiDOPO, the peak heat release rate was decreased dramatically after introducing nanoparticles, and the smoke was significant suppressed by adding SiO2. Among these nanoparticles, SiO2 had an obvious enhancement in the thermal stabilities of PLA composites both under nitrogen and air conditions resulting from its barrier effect. Moreover, a compact char was formed after combustion for PLA/DiDOPO/SiO2. In addition, high‐resolution electron microscope and rheology results showed that SiO2 had a well dispersive quality in PLA/DiDOPO composites. Consequently, SiO2 shows the best synergistic effect with DiDOPO toward improving the flame retardancy of PLA. POLYM. COMPOS., 40:1043–1052, 2019. © 2018 Society of Plastics Engineers

Halogen‐free intumescent flame‐retardant ethylene‐vinyl acetate copolymer system based on organic montmorillonite and graphene nanosheets

ABSTRACTHalogen‐containing flame retardants are not preferred for environmental reasons. Herein, a halogen‐free intumescent flame‐retardant ethylene‐vinyl acetate copolymer (EVA/IFR) system containing organic montmorillonite (OMMT) and graphene nanosheets (GNSs) is fabricated with well dispersion structure, enhanced thermal‐oxidative resistance at high temperature. Interestingly, the amount of residual chars from thermogravimetric analysis is increased to 12.7 wt % at 700 °C, the EVA/IFR composite containing both OMMT and GNSs exhibits the best flame retardancy with the lowest peak heat release rate value of 529.58 kW m−2, and the highest limited oxygen index value of 24.8%. The excellent flame retardancy is attributed to the formation of complete and compact protective char layer. Furthermore, the decreases of the mechanical properties caused by the addition of IFR are relieved and a high volume resistivity is maintained when combining OMMT and GNSs in the EVA/IFR system together. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46361.

Synergistic effect between ammonium polyphosphate and expandable graphite on flame-retarded poly(butylene terephthalate)

In this paper, the synergistic effect of ammonium polyphosphate (APP) and expandable graphite (EG) on flame-retarded poly(butylene terephthalate) (PBT) was systermically investigated using limiting oxygen index (LOI), UL-94 testing, microscale combustion calorimetry (MCC), thermal-gravimetric analysis (TGA) and scanning electronic microscopy (SEM). PBT composites containing 20 wt% of APP: EG (1:3) combinations exhibits a high LOI value of 29.8 and reaches V-0 rating in UL-94 testing, indicating that the flame retardant property is greatly enhanced compared to the composites solely with APP or EG. SEM images show that the combination of APP and EG could promote the formation of a compact char layer. The compact char layer protects the PBT resin efficiently by preventing penetration of heat flux inside the matrix and retards the decomposition of PBT, consequently improves the thermal stability of PBT materials as revealed by TGA. All of the results demonstrate that APP and EG are high efficiency synergists for improving the flame retardation of PBT materials.

A novel curing agent based on diphenylphosphine oxide for flame-retardant epoxy resin

A phosphorous/nitrogen-containing diphenylphosphine oxide (DPO) derivative (DPO-SS) was designed and synthesized via a two-step reaction of 4,4′-diaminodiphenylsulfone, 2-hydroxy-benzaldehyde, and DPO. The structure of DPO-SS was confirmed by Fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS). DPO-SS was used as a flame retardant and curing agent for copolymerizing with diglycidyl ether of bisphenol-A. Thermal and flame-retardant properties of the obtained flame-retardant epoxy resin (F-EP) were investigated by thermogravimetric analysis, dynamic thermomechanical analysis, limited oxygen index (LOI) measurement, vertical burning test (UL-94), and cone calorimeter test. Results indicated that all F-EP samples exhibited excellent thermal stability and flame-retardant property. Especially for F-EP with P content of 0.7 wt% (denoted as EP/P-0.7), it achieved high LOI values (32.4%) and UL-94 V-0 rating. Compared with pure EP, all F-EP samples showed lower heat release rate, total heat release, total smoke produce, and little Tg fluctuation. In order to study the flame-retardant mechanism, the char residues were investigated by FTIR, scanning electron microscopy, and energy-dispersive spectrometer analysis. The results manifested that DPO-SS acted as flame retardant in both gas phase and condensed phase. Water absorption properties of pure EP and F-EP were also compared through immersion experiments. Results showed that EP/P-0.7 sample had apparently lower water absorptivity than pure EP.

INVESTIGATION OF THE EFFECTS OF CARBONIC AGENT AND NANOCLAY ON THE PROPERTIES OF THE POLYLACTIC ACID BASED NANOCOMPOSITES

The objective of this study is an investigation of the effects of carbonic agent and nanoclay loading level on the properties of the added flame retardant and plasticized polylactic acid (PLA) composites. Pentaerythritol (PER) was used as a carbonic agent in the composites. The flammability behaviour of these composites was investigated with the increasing nanoclay loading level. Flame retardant properties of plasticized PLA composites which are consisting of PER and nanoclay as a synergistic agent were evaluated. While the nanoclay loading levels were changed between 1-5 wt% of these samples, PER loading levels were fixed at 2 wt%. Besides, effects of increased PER loading level were also investigated with 3 wt% clay loading. Samples were produced by using extrusion and injection molding techniques. The morphological, thermal and mechanical properties were studied. The flammability was evaluated by using limiting oxygen index (LOI) and vertical burning test (UL-94). The results showed increased PER level didn’t significantly change LOI values of the PLA based nanocomposites. In addition, the highest LOI value was observed as 32 for 1 wt% nanoclay including sample. While adding PER to the PLA/PEG/TPP increased the elongation at break value, adding of the nanoclay decreased this value for nanocomposites.

Intumescent flame-retardant poly(1, 4-butylene terephthalate) with ammonium polyphosphate and a hyperbranched triazine charring-foaming agent: Flame retardancy performance and mechanisms

Intumescent flame-retardant poly(1, 4-butylene terephthalate) composites with ammonium polyphosphate and a hyperbranched triazine charring-foaming agent were prepared through melt blending. The flame retardancy, pyrolysis behavior, and flame-retardant mechanism of flame-retardant poly(1, 4-butylene terephthalate) were investigated using flammability tests, cone calorimeter measurements, thermogravimetric analysis including evolved gas analysis, and residue analysis (Fourier transform infrared and scanning electron microscopy). The results showed that the intumescent flame retardant with the appropriate ammonium polyphosphate/hyperbranched triazine charring-foaming agent mass ratio (4/1) could significantly improve the flame retardancy of poly(1, 4-butylene terephthalate), and the highest Limiting Oxygen Index value and UL-94 V-0 rating was reached. The peak heat release rate and total heat evolved remarkably decreased, respectively, by 84% and 76% corresponding to poly(1, 4-butylene terephthalate). Thermogravimetric analysis results showed the synergistic effect between ammonium polyphosphate and hyperbranched triazine charring-foaming agent could enhance the char formation ability of composites. The results of gaseous products and residue char structure analysis indicated intumescent flame retardant influenced the decomposition behavior and promoted the formation and accumulation of phosphorous/azotic and polyaromatic char possessing high graphitization degree, which exerted a condensed-phase flame-retardant effect on the flame-retardant composites.