Increase In Limiting Oxygen Index Value Research Articles

Novel Hybrid Organic–Inorganic Polymeric Coatings Containing Phosphonium or Acidic Groups for Improving Flame Retardancy of Wood

Flame-retardant polymeric coatings with high limiting oxygen index (LOI) were prepared by combining inorganic mineral huntite (H5) and polymeric additives synthesized in the present work into a polymeric formulation. In order to improve the dispersion of the Mg- (and Ca)-based H5 particles, additives containing phosphonium and acidic groups were employed to homogenize the inorganic fillers into the polymer matrix. Specific blend combinations of the commercial matrix Ecrovin® LV 340 eco with huntite and the additives poly(benzyltriphenylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSBTPB60) and poly(hexadecyltributylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSTBHDPB80), combining acidic and phosphonium groups, led to LOI values of 34.5% and 33.5%, respectively. The novel flame-retardant polymeric coatings inhibited the combustion of the coated wood substrates, which is attributed to the combination of acidic groups that promote the dispersion of inorganic filler in the polymer matrix and phosphonium groups that support the increase in LOI values.

Flame-Retardant Properties and Mechanism of Polylactic Acid-Conjugated Flame-Retardant Composites.

The DOPO derivative-conjugated flame retardant 4, 4'-{1'', 4'' - phenylene - bis [amino - (10‴ - oxy -10‴-hydro-9‴-hydrogen-10‴ λ5 -phosphaphenanthrene-10''-yl)-methyl]}-diphenol (P-PPD-Ph) with two hydroxyl groups was synthesized. Polylactic acid conjugated flame-retardant composites with P-PPD-Ph were papered by using a twin-screw extruder. The flame-retardant properties of polylactic acid-conjugated flame-retardant composites were investigated. The flame-retardant properties of PLA-conjugated flame-retardant composites were characterized by the limiting oxygen index (LOI) and the vertical burning test (UL94). The results showed that the PLA-conjugated flame-retardant composites achieved a V-0 rating (UL-94, 3.2 mm) when the conjugated flame retardant was added at 5 wt%, and increase in LOI value from 22.5% to 31.4% relative to composites without added conjugated flame retardant. The flame-retardant mechanism of PLA-conjugated flame-retardant composites were further studied by TG-FTIR, the results showed that the P-PPD-Ph promoted the PLA-conjugated flame-retardant composites to decompose and also released fragments with quenching and dilution, which suggests that P-PPD-Ph for PLA-conjugated flame-retardant composites mainly play a role of the gas-phase flame retardant.

Investigation on the thermal-flammability and mechanical performance of coir fiber reinforced biocomposites

In this study coir fiber reinforced high density polyethylene (HDPE) composites containing varying amount of raw and alkali treated coir fiber were investigated. The thermal stability of the raw and treated fiber and its corresponding composites were evaluated by Thermo gravimetric analysis (TGA). Alkali treated fiber exhibited single-step degradation due to removal of lignin with remarkable amount of residual char. Incorporation of both raw and alkali treated fiber in composites resulted in early-stage decomposition process. The treated fiber composites (HDPE-ACF) showed improved thermal stability with considerable amount of residual char which can be correlated to the limiting oxygen index (LOI) studied. The 30% fiber loaded composites recorded 14%, 12% and 10% increase in LOI value compared to pristine HDPE, 10% and 20% fiber loaded composites respectively. A comparative analysis of experimental and theoretical LOI value were done and correlated to the TGA results. Composites of treated fibers exhibited better impact strength compared to its corresponding untreated ones. The hardness of the composites increased with increase in fiber dosage for both type of composites.

Flame retardant treatments for polyamide 66 textiles: Analysis the role of phosphorus compounds

Three different phosphorus (P) compounds, namely phytic acid (PA), graphene phosphonic acid (GPA) and a DOPO derivative [3-H-P-DOPOHQ (DOH)] having a diverse origin, structure and chemical activity were used along with some naturally derived polyelectrolytes like chitosan (CS), sodium alginate (SA) and montmorillonite (MMT) in a layer-by-layer (LbL) fashion to enhance the flame retardant performance of polyamide 66 (PA66) textiles. Obtained results showed that these P-compounds, irrespective of their varied action surely played a positive role in improving the flame retardancy; though a typical P-compound was effective in modifying a specific type of flame retardant parameter. The formulation containing phytic acid particularly brought a considerable reduction in the peak heat release rate (pHRR) and a handsome increase in residue% due to its dominant activity in the condensed phase flame retardant mechanism. Meanwhile, the application of GPA further modified this condensed phase activity via providing added thermal stability to these residues and thus, a sharp increase in limiting oxygen index (LOI) value up to 27.5% and a maximum reduction in pHRR by 45% was handed. In contrast, the DOPO derivative (DOH) was quite effective in the gas phase mechanism through its radical quenching effect and offered a moderate increase in LOI values (i.e., 24.5%). Finally, it was realized that the formulation containing an engineered structure of a P-compound with graphene, basically worked in the condensed phase mechanism and well supported by thermal insulation effect available from graphene nanosheets and MMT platelets seemed to be an effective solution in escalating the fire performance of PA66 textiles.

Studying the effect of organo-modified nanoclay loading on the thermal stability, flame retardant, anti-corrosive and mechanical properties of polyurethane nanocomposite for surface coating

Abstract Clay polyurethane nanocomposite (CPN) coating films were fabricated by uniformly dispersing nanoclay, organically modified with 25–30 wt.% octadecylamine in varying concentrations up to 5 wt.%, in a commercial two component, glossy, acrylic aliphatic polyurethane using ultrasonication. Organo-modified nanoclay was characterized by X-ray diffraction (XRD). The dispersion of the nanoclay into the matrix was investigated by scanning electron microscopy (SEM). CPN coating films were characterized by thermogravimetric analysis (TGA), and flame retardant, corrosion resistance and mechanical properties were also investigated. The XRD measurement indicated that, the organo-modified nanoclay particles were mainly constituted of montmorillonite with traces of quartz and calcite also found to be present. The SEM analysis showed that the nanoclay layers were dispersed and intercalated into the polyurethane coating. Thermogravimetric analysis showed that incorporating 5 wt.% organo-nanoclay into polyurethane considerably enhanced the thermal stability and increased the char residue to 14.11 wt.% relative to 4.58 for the sample without organo-nanoclay (blank polyurethane). The limiting oxygen index (LOI) test revealed that incorporation of organo-nanoclay led to a further increase in LOI values, which indicate an improvement in flame retardancy properties. The corrosion resistance also improved and this improvement increases with increase nanoclay wt.%. The mechanical resistance measurements demonstrated that the gloss of the CPN coating films slightly decreased, although hardness, adhesion and impact resistance of the CPN coating films improved with the incorporation of the organo-nanoclay.

Effect of phosphorus‐containing flame retardants on flame retardancy and thermal stability of tetrafunctional epoxy resin

Hexaphenoxycyclotriphosphazene (HPCTP) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) were used to flame retard N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane epoxy resins. The curing behaviors and glass transition temperature were investigated by differential scanning calorimetry. The limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests were used to assess the flame retardancy of the cured epoxy resins. The increase in LOI value and UL‐94 rating was strongly dependent on the phosphorus content. The reduction in peak of heat release rate and total heat release showed that the incorporation of flame retardants could improve the flame retardancy of epoxy resin. The higher smoke release and CO yield of the flame‐retardant epoxy resins indicated that both DOPO and HPCTP showed a gas phase flame retardancy action. Thermogravimetric analysis of the flame‐retardant epoxy resins indicated that the incorporation of the flame retardants reduced the initial decomposition temperature of epoxy resin. Copyright © 2015 John Wiley & Sons, Ltd.

Enhanced polyimide proportion effects on fire behavior of isocyanate-based polyimide foams by refilled aromatic dianhydride method

Lightweight and fire-resistant isocyanate-based polyimide foams (PIFs) were rapidly formed via a simple one-pot process; polymethylene polyphenylene isocyanate (PAPI) was added into a solution containing refilled aromatic dianhydride. The obtained Fourier transform infrared spectra (FT-IR) showed that the refilled 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) reacted with isocyanate and amino groups in PIFs during the forming and postcuring process. These reactions increased the percentage of polyimide in the foams. Meanwhile, the reaction between refilled BTDA which has a higher reactivity than its derivatives and amino groups, reduced the reaction between isocyanate and amino groups. Subsequently, the generation of ureido was restrained. Thermal gravimetric analysis (TGA) and differential thermogravimetry (DTG) results presented that when the refilled BTDA dosage was increased, the percentage of polyimide and ureido were increased and reduced, respectively. However, the proportion of different ingredients in the PIFs prepared by different formulations was basically the same when the refilled BTDA dosage exceeded 50%. As such, the refilled dosage of BTDA between 50% and 60% was sufficient for this system, the refilled BTDA had extreme effects on enhancing polyimide proportion and reducing the generation of ureido. Fire resistance was characterized by limiting oxygen index (LOI) and cone calorimeter (CCT). Results showed that with the gradual increasing in polyimide proportion of the PIFs resulting from the increase in refilled BTDA dosage, their fire resistance was remarkably improved, which was mainly reflected by the following: gradual increase in LOI value, decrease in heat release rate (HRR), decrease in the peak of HRR (PHRR), decrease in total smoke production (TSP), and decrease in average specific extinction area (ASEA). Compared with the foam prepared without refilled BTDA, the foam prepared with 60% BTDA refilled dosage exhibited increased LOI value from 20.8% to 30.1%, PHRR reduction from 181.91 kW/m2 to 41.54 kW/m2, and significant reduction of HRR. The reduction in TSP and ASEA reached up to 78.2% and 83.1%, respectively. Meanwhile, when the refilled dosage of BTDA exceeded 60%, the LOI value also showed a slower increase. This change was possibly due to the residual BTDA in foams, which acted as a retardant packing role. The density of foams also increased when the post-additive dosage of BTDA was increased. Possible chemical reactions involved in this preparation method of isocyanate-based PIFs were also discussed in this paper.

Influence of morphology on the flame retardancy of polystyrene/nylon-6/ammonium polyphosphate/clay blends

Ammonium polyphosphate (APP) and clay were utilized to flame retard polystyrene/nylon 6 (PS/PA6) blends. X-ray diffraction and transmission electron microscopy (TEM) results showed that clay formed exfoliated structures in PS/PA6/APP/clay. The results of Fourier transform infrared spectra and TEM indicated that APP and clay were exclusively dispersed in the PA6 phase. The influences of the distribution of APP and clay in PS/PA6 blends and the continuity of the (PA6 + APP) phase on flame retardancy were investigated. The flame-retardant properties were evaluated by limiting oxygen index (LOI), vertical flammability test, and cone calorimeter tests. For blends with a continuous PA6 + APP phase, the decrease of PA6 content caused an increase in LOI values from 26 to 34% and a remarkable reduction of the heat release rate. Results of thermogravimetric analysis indicated that the localization of APP and clay in the PA6 phase caused an increase in APP concentration in the PA6 phase with decreasing PA6 content, resulting in the rapid formation of intumescent charred layer, which augmented the flame retardancy. The transformation of (PA6 + APP) phase morphology from a continuous state to a discontinuous state at a PA6 content of below 40% (w/w) was observed. Meanwhile, the flame-retardant properties were decreased as the PA6 content decreases. The discontinuous intumescent charred layer thus formed and the inhibiting action of clay on the residue char from expanding could be responsible for the deterioration of flame-retardant properties, which were also confirmed by scanning electron microscopy and the aspect of intumescent charred layer.

Influence of morphology and ammonium polyphosphate dispersion on the flame retardancy of polystyrene/nylon‐6 blends

SUMMARYThe influences of the distribution of ammonium polyphosphate (APP) in polystyrene/nylon‐6 [PS/polyamide‐6 (PA6)] blends and the continuity of the (PA6 + APP) phase on flame retardancy were investigated. The flame retardant properties were evaluated by limiting oxygen index (LOI), vertical flammability test and cone calorimeter tests. The results showed that APP is exclusively dispersed in the PA6 phase, and (PA6 + APP) phase formed a continuous state when the content of PA6 in PS/PA6 blends was higher than 32% (w/w). For blends with a continuous (PA6 + APP) phase, the decrease of PA6 content caused an increase in LOI values from 26% to 33% and a reduction of peak heat release rate. The improvement of flame retardancy was attributed to the increase of APP concentration in the PA6 phase, which benefited the fast formation of a continuous intumescent charred layer. The transformation of (PA6 + APP) phase morphology from a continuous state to a discontinuous state at a PA6 content of below 32% (w/w) caused a decrease in LOI. Results of thermo‐gravimetric and cone calorimeter tests indicated that the discontinuous intumescent charred layer thus formed could be responsible for the deterioration of flame retardant properties, which was also confirmed by scanning electron microscopy. Copyright © 2013 John Wiley & Sons, Ltd.

Synergism between Intumescent Flame Retardant and Organo-Montmorillonite in Polypropylene Nanocomposites

A simple method of melt blending was used to prepare PP, PP/IFR and PP/IFR/OMMT composites. The Flammability and mechanical property of the composites were investigated. Limiting oxygen index (LOI) tests and cone calorimetry results indicate that there are synergisms between IFR and OMMT. Incorporation of OMMT led to a further increase in LOI value of intumescent retarded PP samples when the addition amounts of OMMT are less than 2%. Cone calorimeter measurements demonstrate that the peak heat release rate (PHRR), average mass loss rates (AMLR) and fire growth rate index (FIGRA) of PP/IFR/OMMT composites are all less than that of PP/IFR30 when OMMT contents are less than 1.5% (including 1.5%).Char residues after cone calorimeter tests were investigated. Unlike the expansion char residue of PP/IFR, the char residues of PP/IFR/OMMT display a lower height and compact morphology, which are due to the barrier effect of OMMT. The presence of less than 1.5% OMMT can somewhat enhance the tensile strength and Izod impact strength of PP/IFR/OMMT composites. Larger OMMT amounts decrease the above mechanical properties.

Influence of red phosphorus on the flame-retardant properties of ethylene vinyl acetate/layered double hydroxides composites

Mg–Al–Fe ternary layered double hydroxides (LDHs) were synthesized based on Bayer red mud by a calcination–rehydration method, and characterized using powder X-ray diffraction and thermogravimetric analysis techniques. The synergistic flame-retardant effects of red phosphorus (RP) in ethylene vinyl acetate (EVA)/LDHs composites were studied with the limiting oxygen index (LOI), the UL 94 test, the cone calorimeter test (CCT), and the smoke density test (SDT). And, the thermal degradation behavior of the composites was examined by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) analysis. Results showed that the LOI values of the composites with RP were basically higher than those of the pure EVA sample and composites containing LDHs only. And the addition of a suitable amount of RP in EVA/LDHs/RP composites can apparently favor UL 94 test. In the UL 94 test there was a V-1 rating and dripping phenomena for the composites containing 50 % LDHs. However, the composites containing 47.5 % LDHs and 2.5 % red phosphorus did not drip. The CCT results indicated that the heat release rate (HRR) of the EVA/LDHs/RP composites with a suitable amount of RP decreased in comparison with that of the EVA/LDHs composites. The SDT showed that RP was helpful to smoke suppression. TG-FTIR data showed that the EVA/LDHs/RP composites show a higher thermal stability than the EVA/LDHs composites. A suitable amount of RP in EVA/LDHs/RP composites resulted in an increase in LOI values, a decrease in the HRR, the achievement of the UL 94 V-1 rating with no dripping phenomenon, a good smoke suppression character, and a high thermal stability.

Flame retardant mechanism of organo-bentonite in polypropylene

Effects of organo-bentonite on the flame retardancy, mechanical and rheological properties of intumescent flame retardant (IFR) polypropylene (PP) were investigated. The X-ray diffraction and transmission electron microscopy measurements indicated that the organo-clay particles were partially exfoliated. Thermogravimetric analysis showed that incorporating 1.8 mass% organo-clay into PP/IFR considerably enhanced the thermal stability and increased the char residue by ca. 7 mass% relative to the sample without organo-clay. Limiting oxygen index (LOI) tests revealed that incorporation of organo-clay led to a further increase in LOI value of intumescent retarded PP samples. The cone calorimeter measurements demonstrated that the organo-clay cannot only further reduce the first peak heat release rate (PHRR 1), especially for the reduction in smoke level, but delay the time to the secondary combustion (PHRR 2) of intumescent flame retardant PP samples relative to PP/IFR. Unlike the plainland-like structure of residue of PP/IFR, the char residue of PP/IFR/organo-bentonite displayed a folded structure or mountain terrain-like morphology which was due to the deposition of char residue generated by IFR on the surface of clay mineral layers. This interesting morphology of residue was responsible for the enhanced thermal stability, improved flame retardancy, and higher char yields. The rheological behavior of the flame retarded PP samples suggested that the organo-clay can strengthen the three-dimensional network structure formed by the IFR particles in the flame retarded samples. The presence of organo-clay can somewhat enhance the tensile strength and Izod impact strength of PP/IFR composites. Larger organo-clay amounts decreased the above mechanical properties.

4485234 Method of preparing polyamide acid for processing of semiconductors

Lightweight and fire-resistant isocyanate-based polyimide foams (PIFs) were rapidly formed via a simple one-pot process; polymethylene polyphenylene isocyanate (PAPI) was added into a solution containing refilled aromatic dianhydride. The obtained Fourier transform infrared spectra (FT-IR) showed that the refilled 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) reacted with isocyanate and amino groups in PIFs during the forming and postcuring process. These reactions increased the percentage of polyimide in the foams. Meanwhile, the reaction between refilled BTDA which has a higher reactivity than its derivatives and amino groups, reduced the reaction between isocyanate and amino groups. Subsequently, the generation of ureido was restrained. Thermal gravimetric analysis (TGA) and differential thermogravimetry (DTG) results presented that when the refilled BTDA dosage was increased, the percentage of polyimide and ureido were increased and reduced, respectively. However, the proportion of different ingredients in the PIFs prepared by different formulations was basically the same when the refilled BTDA dosage exceeded 50%. As such, the refilled dosage of BTDA between 50% and 60% was sufficient for this system, the refilled BTDA had extreme effects on enhancing polyimide proportion and reducing the generation of ureido. Fire resistance was characterized by limiting oxygen index (LOI) and cone calorimeter (CCT). Results showed that with the gradual increasing in polyimide proportion of the PIFs resulting from the increase in refilled BTDA dosage, their fire resistance was remarkably improved, which was mainly reflected by the following: gradual increase in LOI value, decrease in heat release rate (HRR), decrease in the peak of HRR (PHRR), decrease in total smoke production (TSP), and decrease in average specific extinction area (ASEA). Compared with the foam prepared without refilled BTDA, the foam prepared with 60% BTDA refilled dosage exhibited increased LOI value from 20.8% to 30.1%, PHRR reduction from 181.91 kW/m2 to 41.54 kW/m2, and significant reduction of HRR. The reduction in TSP and ASEA reached up to 78.2% and 83.1%, respectively. Meanwhile, when the refilled dosage of BTDA exceeded 60%, the LOI value also showed a slower increase. This change was possibly due to the residual BTDA in foams, which acted as a retardant packing role. The density of foams also increased when the post-additive dosage of BTDA was increased. Possible chemical reactions involved in this preparation method of isocyanate-based PIFs were also discussed in this paper.