Synergistic effect of expandable graphite and melamine phosphate on flame‐retardant polystyrene

The halogen‐free flame‐retardant polystyrene (PS) composites containing expandable graphite (EG) and melamine phosphate (MP) were prepared successfully, and the thermal degradation behavior and fire performance were investigated by various measurements. The experimental results show that EG and MP have a synergistic effect on flame‐retardant PS, which can catalyze the char formation from PS. PS/MP/EG_(1:2) composite achieves limited oxygen index value of 28.0% and UL‐94V‐0 (1.6 mm) rate. The mass retention at high temperature (800 °C) under air atmosphere of PS composites have a large increase by the introduction of EG and MP. Microscale combustion calorimeter (MCC) and cone calorimetric analysis indicate that the heat release rate and total heat release of PS/MP/EG_(1:2) composite are reduced significantly, because the formed thick char layer has a notable barrier property. The study on the char residue of PS/MP/EG_(1:2) composite by X‐ray photoelectron spectroscopy (XPS) analysis confirms the formation of the stable structures containing P? O? C. Furthermore, the mechanical properties of PS composites were also investigated; compared with neat PS, the addition of flame retardants leads to the decrease of tensile strength and flexural strength, but the impact strength of PS/MP/EG_(1:2) has increased by 44.2%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45474.     

Ab initio reversible addition–fragmentation chain transfer emulsion polymerization of styrene/butyl acrylate mediated by poly(acrylic acid)‐block‐polystyrene trithiocarbonate

Ab initio reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of styrene/butyl acrylate was investigated with the trithiocarbonate macro‐RAFT agent poly(acrylic acid)‐block‐polystyrene (PAA‐b‐PS) as a stabilizer and a RAFT agent. Influences of the amount of ammonium persulfate (APS), the amount of PAA‐b‐PS and the mass ratio of monomers on emulsion polymerization and film properties are discussed. The particle morphology exhibited spherical‐like structure with particles of about 90 nm in diameter and relatively narrow particle size distribution characterized using transmission electron microscopy and dynamic laser scattering. Fourier transform infrared and ¹H NMR spectra showed that the styrene/butyl acrylate emulsion was successfully synthesized. The monomer conversion increased initially with increasing amount of APS, from 0.4 up to 0.8 wt%, and then decreased. The particle size increased and its distribution decreased gradually with increasing amount of APS. The monomer conversion increased from 76.83 to 94.21% as the amount of PAA‐b‐PS increased from 3 to 4 wt%, and then decreased with further increase of PAA‐b‐PS. The particle size decreased and its distribution increased with increasing amount of PAA‐b‐PS. The water resistance and solvent resistance of the polymer films initially increased and then decreased with decreasing mass ratio of butyl acrylate to styrene. © 2014 Society of Chemical Industry     

Preparation of poly(styrene‐co‐butyl acrylate)/montmorillonite nanocomposite by emulsion polymerization: Characterization and nanoscratch behavior

Organic–inorganic hybrid poly(styrene‐co‐butyl acrylate)/organically modified montmorillonite (PSBA/organo‐MMT) latex particles have been prepared by in situ emulsion polymerization. The effects of modifier variety and the level of organo‐MMT have been investigated on the basis of the characteristics and mechanical properties of the resulting hybrid emulsion polymers. Although the more hydrophilic intercalated organic modifiers increased the latex particle size, the hydrophobic ones decreased the particle size. A more heterogeneous copolymer chain intercalation was seen by widespread XRD reflection as the organo‐MMT (organoclay) level increases. The tapping mode atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to determine the dispersion state of organoclay particles inside the nanocomposite copolymer films. Dynamic mechanical thermal analysis (DMTA) showed that adding the organoclay to the copolymer decreased the maximum loss tangent (tanδ) value and caused the shift to a lower temperature. Interestingly, the incorporation of organoclay decreased the glass storage modulus of the copolymer, while increased the rubbery storage modulus to some extent. In addition, a standard indenter for the nanoscratching of copolymer nanocomposite films was used under low applied loads of 150 and 250 μN. The nanoscratch results showed that incorporation of a 3 wt % hydrophobic organoclay, e.g., Closite15A, in the copolymer matrix enhanced considerably the near‐surface hardness and grooving resistance of the nanocomposite film at room temperature. In fact, copolymer nanocomposite films with higher near‐surface hardness and tanδ curve broadening exhibited more nanoscratch resistance through a specific variety of viscoelastic deformation, which did not create a bigger groove. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synergistic effect of nickel formate on the thermal and flame‐retardant properties of polypropylene

Nickel formate was used as a catalyst to improve the flame‐retardancy of intumescent systems based on ammonium polyphosphate (APP) and pentaerythritol (petol) in polypropylene (PP). Limited oxygen index (LOI), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to characterize the fire‐retardancy and thermal stability of the PP system and the microstructure of the burned residue. The catalytic effect was shown in an increase in LOI, and a change in the residue microstructure and the thermal stability of the PP system. LOI increased with the concentration of the catalyst in the range 0.1–5 wt% of the composition until a maximum was reached. At higher concentration of the catalyst a decrease in the LOI was observed. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of chlorine‐containing flame‐retardant polyurethane nanocomposites via in situ polymerization

We have developed flame‐retardant polyurethanes (FRPUs) and polyurethane (PU) nanocomposites via in situ polymerization. Three series of thermoplastic elastomeric PUs were synthesized to investigate the effect of incorporating 3‐chloro‐1,2‐propanediol (CPD) and nanoclay on mechanical, thermal properties, and also resistance to burning. PU soft segments were based on poly(propylene glycol). Hard segments were based on either CPD or 1,4‐buthane diol (BDO) in combination with methyl phenyl di‐isocyanate named PU or FRPU, respectively. In the third series, CPD was used as chain extender also nanoclay (1% wt) and incorporated and named as flame‐retardant polyurethane nanocomposites (FRPUN). Mechanical properties and LOI of PUs and nanocomposites have been evaluated. Results showed that increasing the hard segment (chlorine content) leads to the increase in flame retardancy and burning time. Addition of nanoclay to CPD‐containing PUs leads to obtain self‐extinguish PUs using lower CPD contents, higher Young's modulus, and strength without any noticeable decrease in elongation at break. Investigation of the TGA results showed that copresence of nanoclay and chlorine structure in the PU backbone can change thermal degradation pattern and improve nanocomposite thermal stability. X‐ray diffraction and transmission electron microscopy studies confirmed that exfoliation and intercalation have been well done. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate (BA) without added initiator has been studied. The experimental results show that high conversion of BA can be reached in a short time by employing an ultrasonic irradiation technique with a high purge rate of N₂. The viscosity average molecular weight of poly(n‐butyl acrylate) (PBA) obtained reaches 5.24 × 10⁶ g mol^?1. The ultrasonically initiated emulsion polymerization is dynamic and complicated, with polymerization of monomer and degradation of polymer occurring simultaneously. An increase in ultrasound intensity leads to an increase in polymerization rate in the range of cavitation threshold and cavitation peak values. Lower monomer concentration favours enhancement of the polymerization rate. ¹H NMR, ¹³C NMR and FTIR spectroscopies reveal that there are some branches and slight crosslinking, and also carboxyl groups in PBA. Ultrasonically initiated emulsion polymerization offers a new route for the preparation of nanosized latex particles; the particle size of PBA prepared is around 50–200 nm as measured by transmission electron microscopy. © 2001 Society of Chemical Industry     

Bio‐based Mg(OH)2@M‐Phyt: improving the flame‐retardant and mechanical properties of flexible poly(vinyl chloride)

Two novelty bio‐based multifunctional metallic phytate coated (M‐Phyt, M ≡ Cu, Zn) Mg(OH)₂ (MH@M‐Phyt) were designed and incorporated into flexible poly(vinyl chloride) (PVC). MH@M‐Phyt was incorporated into PVC materials in a powder form. The morphology of the interface between MH and M‐Phyt and their binding states were characterized by TEM and X‐ray photoelectron spectroscopy (XPS), respectively. The TEM images of MH@M‐Phyt indicated that M‐Phyt was successfully coated on the MH surface. Additionally, from the XPS spectra M‐Phyt and MH were connected by Mg–O–P bonds. The flame retardancy and mechanical properties of the PVC composites were investigated through the limiting oxygen index, cone calorimetry and mechanical tests. The char residues were analyzed by SEM. The results revealed that the MH@M‐Phyt powder functioned well in PVC, with a flame retardancy, smoke density, tensile strength and elongation at break better than those of PVC/MH. With 10 phr loading, the peak heat release rate of PVC/MH@Zn‐Phyt and PVC/MH@Cu‐Phyt decreased by 33.5% and 24.6%, respectively, benefitting from the formation of firmer and denser char layers on the char residues. © 2019 Society of Chemical Industry     

Preparation and characterization of flame‐retardant melamine cyanurate/polyamide 6 nanocomposites by in situ polymerization

This article focuses on an improved method, i.e., improved in situ polymerization of ε‐caprolactam in the presence of melamine derivatives to prepare flame‐retardant melamine cyanurate/polyamide 6 (MCA/PA6) nanocomposites. The chemical structures of these synthetic flame retardant composites are characterized by Fourier‐transform infrared spectroscopy and X‐ray diffraction. Morphologies, mechanical properties, and thermal properties also are investigated by the use of transmission electron microscopy, mechanical testing apparatus, differential scanning calorimetry, and thermogravimetric analysis, respectively. Through transmission electron microscopy photographs, it can be found that the in situ‐formed MCA nanoparticles with diametric size of less than 50 nm are nanoscaled, highly uniformly dispersed in the PA6 matrix. These nanocomposites, which have good mechanical properties, can reach UL‐94 V‐0 rating at 1.6‐mm thickness even at a relatively low MCA loading level. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synergistic effect of amino silane functional montmorillonite on intumescent flame‐retarded SEBS and its mechanism

A functional modified montmorillonite (F‐OMMT) was prepared by intercalating pristine montmorillonite using phosphonium salt and subsequent grafting through alkyl amino silane coupling. The synergistic effect of F‐OMMT on the flame retardancy and char‐forming mechanism of intumescent flame‐retarded polystyrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) composite (SEBS/IFR) was investigated. When 2 wt % F‐OMMT was introduced to the SEBS/IFR composite, the limited oxygen index (LOI) value of the composite increased from 24.9% to 26.9%, and the peak heat release rate significantly reduced according to microscale combustion calorimeter (MCC) test. The outer char demonstrated that F‐OMMT produced dense and intact nanoparticles with a stabilised graphite structure. Meanwhile, F‐OMMT helped form a crosslinking network containing large amounts of P, O, N, and Si in the char layer. Along with IFR, the amino functional group on the clay released nonflammable ammonia in the gaseous phase, the enhanced blowing effect can overcome the high‐viscosity resistance of SEBS, more intumescent coating with strengthened clay platelets was then produced. In addition, the tensile properties of SEBS/IFR/F‐OMMT composite increased evidently for the good dispersion effect. F‐OMMT can serve as an effective and environmentally friendly additive for SEBS/IFR composite. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44953.     

Environmentally friendly flame‐retardant materials produced by atmospheric pressure plasma modifications

The objective of this work was to investigate plasma modification of viscose for environmentally friendly flame‐retardant cellulosic materials. Sodium silicate layers were predeposited onto viscose and cotton flannel substrates and grafted/crosslinked using atmospheric pressure plasma. The modified cellulosic fabrics tested with the automated 45° angle test chamber showed significant improvement in their flame‐retardant properties. Analysis conducted by TGA and DSC exhibited enhanced thermal stability of the treated fabrics. Furthermore, the surface analysis (XPS and SEM) confirmed the presence of the SiO₂ network attached to the substrate even after intense ultrasound washes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Intumescent char structures and flame‐retardant mechanism of expandable graphite‐based halogen‐free flame‐retardant linear low density polyethylene blends

The structures of the intumescent charred layers formed from expandable graphite (EG)‐based intumescent halogen‐free flame retardant (HFFR) linear low‐density polyethylene (LLDPE) blends and their flame‐retardant mechanism in the condensed phase have been studied by dynamic Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), scanning electron microscopy (SEM), differential thermal analysis (DTA) and thermal conductivity (TC) measurements. The dynamic FTIR, XPS and LRS data show that the carbonaceous structures of intumescent charred layers consist of EG and various numbers of condensed benzene rings and/or phosphocarbonaceous complexes attached by the P? O? C and P? N bonds or quaternary nitrogen products. The addition of EG can hasten the formation of these phosphocarbonaceous structures. The above results show that the flame‐retardant mechanism in the condensed phase is that the compact char structures, as observed by SEM, slow down heat and mass transfer between the gas and condensed phase and prevent the underlying polymeric substrate from further attack by heat flux in a flame. The DTA and TC data show that carbonaceous charred layers are good heat‐insulating materials, the TC value of which is only about one‐tenth of that of the corresponding blend and that they increase the oxidization temperature and decrease thermal oxidization heat of the LLDPE/EG/HFFR systems. © 2003 Society of Chemical Industry     

Synergistic effect of mesoporous silica SBA‐15 on intumescent flame‐retardant polypropylene

Mesoporous silica SBA‐15 synthesized from Pluronic P123 and tetraethoxysilane was used as a synergistic agent on the flame retardancy of polypropylene (PP)/intumescent flame‐retardant (IFR) system. Limiting oxygen index (LOI), UL‐94 rating and thermogravimetric analysis were used to evaluate the synergistic effect of SBA‐15 on PP/IFR system. It showed that PP/IFR system could reach V‐0 with loading of SBA‐15 ranging from 0.5 to 3 wt%, while without SBA‐15 it had no rating at UL‐94 test. The LOI value increased from 25.5 to 32.2 when the loading of SBA‐15 was 1 wt%. The thermal stability of PP/IFR was improved in the presence of SBA‐15 and the amount of the char residue at 600° C was increased from 8.96 to 16.42 wt% when loading of SBA‐15 varied from 0.5 to 5 wt%. Laser Raman spectroscopy (LRS) and scanning electron microscopy were employed to study the morphology of the char residue of PP/IFR system with and without SBA‐15. Copyright © 2010 John Wiley & Sons, Ltd.     

A novel intumescent flame‐retardant system for flame‐retarded LLDPE/EVA composites

A new intumescent flame retardant (IFR) system consisting of ammonium polyphosphate (APP) and charing‐foaming agent (CFA) and a little organic montmorillonite (OMMT) was used in low‐density polyethylene (LLDPE)/ethylene‐vinyl acetate (EVA) composite. According to limiting oxygen index (LOI) value and UL‐94 rating obtained from this work, the reasonable mass ratio of APP to CFA was 3 : 1, and OMMT could obviously enhance the flame retardancy of the composites. Cone calorimeter (CONE) and thermogravimetric analysis (TGA) were applied to evaluate the burning behavior and thermal stability of IFR‐LLDPE/EVA (LLDPE/EVA) composites. The results of cone calorimeter showed that heat release rate peak (HRR‐peak) and smoke production rate peak (SPR‐peak) and time to ignition (TTI) of IFR‐LLDPE/EVA composites decreased clearly compared with the pure blend. TGA data showed that IFR could enhance the thermal stability of the composites at high temperature and effectively increase the char residue. The morphological structures of the composites observed by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) demonstrated that OMMT could well disperse in the composites without exfoliation, and obviously improve the compatibility of components of IFR in LLDPE/EVA blend. The morphological structures of char layer obtained from Cone indicated that OMMT make the char layer structure be more homogenous and more stable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

浓乳液双相聚合制备聚丙烯酸丁酯粒子及其对聚氯乙烯的改性研究

用浓乳液双相法合成PBA，通过在合成过程中添加不同用量的DVB交联剂和MMA硬单体调节PBA粒子的硬度及性能，研究了不同DVB及MMA加入量的PBA对PVC力学性能的影响。并通过复合材料断面微观形态分析验证了实验结果。结果表明：在BA单体中加入硬单体MMA和交联剂DVB均可提高PBA粒子的硬度，当MMA和DVB用量较大时，会导致粒子呈现刚性，不利于PBA对PVC改性；PBA粒子与硬质PVC共混后能较好地分散在PVC中，并能在提高材料冲击强度的同时，拉伸强度也有所改善；DVB和MMA的用量均为2mL时，PBA异形粒子对硬质PVC的改性效果最好。此配方PBA粒子与PVC相容性好、界面结合力强。     

Preparation of poly(tert‐butyl acrylate)‐poly(acrylic acid) amphiphilic copolymers via radiation‐induced reversible addition–fragmentation chain transfer mediated polymerization of tert‐butyl acrylate

Poly(tert‐butyl acrylate) (PtBA) is a versatile hydrophobic macromolecule usually preferred in the development of new materials for a host of applications. PtBA homopolymers with well‐defined structure and controlled molecular weight in a wide range were successfully synthesized via radiation‐induced reversible addition–fragmentation chain transfer (RAFT) polymerization in the presence of a trithiocarbonate type RAFT agent. The polymerization of tBA was performed under ⁶⁰Co γ‐irradiation in the presence of 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid (DDMAT) as the RAFT agent in toluene at room temperature with three [tBA]/[DDMAT] ratios (400, 600 and 1000) and different irradiation times. Radiation‐induced polymerization of tBA displayed controlled free radical polymerization characteristics: a narrow molecular weight distribution (M_w/M_n ~ 1.1), pseudo first order kinetics and controlled molecular weights. The system followed the RAFT polymerization mechanism even at very low amounts of RAFT agent ([tBA]/[DDMAT] = 1000), and molecular weights up to 113 900 with narrow dispersity (Ð =1.06) were obtained. PtBA was further hydrolysed into different amphiphilic PtBA‐co‐poly(acrylic acid) (PAA) copolymers by low (27.5%) and high (77.3%) degrees of hydrolysis. The pH sensitivity of the two copolymers was investigated by dynamic light scattering at pH 2 and pH 9 (above and below the pK_a value of PAA) and their hydrodynamic diameters and zeta potential values were determined. © 2020 Society of Chemical Industry     

Study on flame‐retardancy and thermal degradation behaviors of intumescent flame‐retardant polylactide systems

Two intumescent flame‐retardant (IFR) additives, IFR‐I and IFR‐II, were synthesized and their structure was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Polylactide (PLA) was modified by the two IFRs to obtain flame‐retardant composites. The flammability of the PLA/IFR composites was characterized by the vertical burning test UL‐94 and limiting oxygen index. The limiting oxygen index values of the PLA composites increased with increase of IFR content. The PLA composite with 20 wt% IFR‐I could pass the UL‐94 V0 rating, while the composite with 30 wt% IFR‐II could not. The results of pyrolysis combustion flow calorimetry showed that the heat release capacity of PLA composites with 30 wt% IFR‐I decreased 43.1% compared with that of pure PLA. The thermal degradation and gas products of PLA/IFR‐I systems were monitored by thermogravimetric analysis and thermogravimetric analysis infrared spectrometry. Scanning electron microscopy was used to investigate the surface morphology of the char residue. Copyright © 2011 Society of Chemical Industry     

Development of halogen‐free flame‐retardant thermoplastic elastomer polymer blend

Ethylene‐propylene diene rubber (EPDM) and isotactic polypropylene (iPP) blends have widest industrial applications that require a degree of flame retardancy. Halogen‐free intumescent technology based on phosphorous salt is a significantly advanced approach to make the polymer flame‐retardant. Both ammonium polyphosphate and ethylenediamine phosphate are important intumescent compounds. Their combination with carbonific and spumific agents were studied in binary blends of EPDM/PP. The polymer system was vulcanized online during melt mixing. Intumescent flame‐retardant polymer systems exhibit good flame‐retardancy with optimum comparable physiomechanical, electrical, and fluid resistance properties, including lower smoke emission, which is essential to protect people because the visibility remains unaffected in the event of fire. Pronounced charring and intumescent effect appear to enhance the flame‐retardancy of the polymers. Possible expected intumescent mechanism is proposed based on the nonpyrolysis mechanism for the flame‐retarded polymer and the intumescent components. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 407–415, 2004     

The effect of morphology on the flame‐retardant behaviors of melamine cyanurate in PA6 composites

Three types of melamine cyanurate (MCA) with micrometer‐size sphere‐like, micrometer‐scale rod‐like, and nanometer‐scale flake‐like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X‐ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame‐retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer‐scale flake‐like MCA obtained an LOI value of 29.5% and a UL94 V‐0 rating, which were higher than those with micrometer‐size sphere‐like and rod‐like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame‐retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA‐Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer‐scale flake‐like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame‐retardant effect. The nanometer‐scale flake‐like MCA had a better performance compared with the other samples because of the delaying and even release of flame‐retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40558.     

Linking the flame‐retardant mechanisms of an ethylene‐acrylate copolymer,chalk and silicone elastomer system with its intumescent behaviour

In this paper the flame‐retardant mechanisms of a flame‐retardant system consisting of ethylene‐acrylate copolymer, chalk and silicone elastomer are linked to its foaming process and to its formation of a final intumescent structure. Thermocouples were placed inside and at the surface of cone calorimeter test specimens in order to measure the temperature at different depths during the formation of the intumescent structure. The temperature and visual observations of the foaming process were then linked to chemical reactions seen with thermogravimetric analysis and also coupled with earlier knowledge of the flame‐retardant mechanism. A correlation is seen between the chemical reactions, the temperature (inside and at the surface of a cone calorimeter test specimen) as measured by thermocouples and visual observations in the intumescent process. Further, the outcome of this study provides useful information for achieving a deeper understanding of the flame‐retardant mechanisms of the ethylene‐acrylate copolymer, chalk and silicone elastomer system. Copyright © 2005 John Wiley & Sons, Ltd.