Combustion characteristics of halogen‐free flame‐retarded polyethylene containing magnesium hydroxide and some synergists

Halogen‐free flame‐retarded polyethylene materials have been prepared by using magnesium hydroxide (MH) as a flame retardant combined with red phosphorous (RP) and expandable graphite (EG) as synergists. The effects of these additives on the combustion behavior of the filled linear low density polyethylene (LLDPE), such as a limiting oxygen index (LOI), the rate of heat release (RHR), the specific extinction area (SEA), etc., have been studied by the LOI determination and the cone calorimeter test. The results show that RP and EG are good synergists for improving the flame retardancy of LLDPE/MH formulations. In addition, a suitable amount of ethylene and vinyl acetate copolymer (EVA) added in the formulations can increase the LOI values while promoting the char formation and showing almost no effect on the RHR and SEA values. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 206–214, 2001     

Expandable graphite systems for halogen‐free flame‐retarding of polyolefins. I. Flammability characterization and synergistic effect

The use of some types of expandable graphite (EG) as an intumescent flame‐retardant additive in polyolefins was studied using the cone calorimeter test (CCT), thermogravimetric analysis (TGA), the limiting oxygen index (LOI), and the‐UL 94 test and through measurement of EG's mechanical and electrical properties. The present study has shown that some suitable EG systems combined with other organic and inorganic halogen‐free flame‐retardant (HFFR) additives apparently can improve the flame‐retardant capacity with good mechanical properties of polyolefin blends. For linear low‐density polyethylene and/or ethylene vinyl acetate/EG/HFFR blends the limiting oxygen index can reach a rating above 29, and the UL‐94 test can produce a value of V–0. The CCT and TGA data show that the EG and EG/HFFR additives not only promoted the formation of carbonaceous char but also greatly decreased the heat release rate and the effective heat of combustion and increased the residues after burning. The synergistic effect of EG with other HFFR additives, such as zinc borate, the phosphorus–nitrogen compound NP28, and microcapsulated red phosphorus is examined and discussed in detail in this article. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1181–1189, 2001     

线性低密度聚乙烯/有机蒙脱土纳米复合材料的制备及性能研究

通过熔融共混法制备了线性低密度聚乙烯／有机蒙脱土（LLDPEtOMMT）纳米复合材料,采用X-射线衍射分析（XRD）和透射电镜（TEM）对材料的结构进行表征,研究了OMMT的用量对LLDPE／OMMT纳米复合材料力学性能及阻燃性能的影响。结果表明,当OMMT的用量为30％（重量百分比）8寸,材料的极限氧指数（LOI）从180％提高到23．8％,热释放速率峰值（PHRR）从LLDPE的771．9kW／m2下降到5113kW／m2,下降幅度高达33．8％,表现出较好的阻燃性能;同时材料也呈现出良好的力学性能。     

OMMT和EG/MH协同阻燃LLDPE的研究

采用氢氧化镁(MH)、膨胀石墨(EG)和有机蒙脱土(OMMT)为阻燃剂制备了无卤阻燃线性低密度聚乙烯(LLDPE),研究了OMMT对LLDPE/EG/MH阻燃性能和力学性能的影响。结果表明:少量OMMT的加入,可以有效改善LLDPE/EG/MH的力学性能、阻燃性能和热稳定性。当OMMT质量分数为3.0%时,LLDPE/EG/MH/OMMT的拉伸强度和冲击强度分别为1.4 MPa和26.5 kJ/m~2;极限氧指数为35.0%,符合UL-94 V-0级;其热释放速率峰值、平均热释放速度、生烟速率和总生烟量比LLDPE/EG/MH的低。     

Influence of nano silica hybrid expandable graphite on flammability,thermal stability,and mechanical property of polypropylene/polyamide 6 blends

Silica (SiO₂) nanohybrid expandable graphite (nEG) particles fabricated through one-step method are used as an efficient flame retardant for polypropylene (PP)/polyamide 6 (PA6) blends. The effect of nEG on the flammability, thermal stability, crystallization behaviors, and mechanical properties of PP/PA6 composites is investigated by using limit oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared, scanning electron microscopy, and mechanical tests. Compared with pure expandable graphite (EG), nEG improves the flame retardancy of composites. The results of LOI show that LOI of PP/PA6/nEG10 and PP/PA6/nEG15 composites are 26.0% and 27.2%, respectively. But the LOI values of PP/PA6/EG10 and PP/PA6/EG15 composites are 25.7% and 26.9%, respectively. The UL-94 test results show that PP/PA6/nEG10 composites reach V-1 level when the nEG content is only 10%. However, the PP/PA6 composites with 10% EG does not pass the UL-94 test. In addition, PP/PA6 composites with 15% nEG can reach V-0 level. The CCT results further show that nEG has a higher flame-retardant efficiency than pure EG for PP/PA6 blends. The thermal stability of PP/PA6/nEG composites is better than that of PP/PA6/EG composites. The mechanical property tests indicate that nEG is more conducive to maintain the tensile and impact strengths of PP/PA6 blends than EG due to the enhanced compatibility and interfacial adhesion.     

Structural characterization of LDPE/EVA blends containing nanoclay‐flame retardant combinations

The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d₀₀₁ signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

EG阻燃热固性聚苯乙烯泡沫保温板的性能

以可发性聚苯乙烯(EPS)为基材,利用酚醛树脂(PF)作为包覆剂,可膨胀石墨(EG)作为阻燃剂,利用包覆法,制备了一种无卤环保、阻燃性能好、力学性能优良的热固性PS外墙泡沫保温板。研究了PF与EG对EPS保温板阻燃及力学性能的影响,探究了阻燃机理。结果表明,使用PF作为包覆剂制得的EPS/PF泡沫保温板力学性能尤其是压缩强度明显提高,当PF用量为90份时,LOI值可由18%提升至27.9%;阻燃剂EG的加入,使得保温板的阻燃性能及压缩性能进一步提高,当添加4份的EG时,保温板的压缩强度最高,LOI值达到了29.4%,垂直燃烧等级达到V–0级,残炭率由纯EPS的10%提高到50%。     

PGS@P-N阻燃剂的制备及增强EVA复合材料的 阻燃性能的研究

利用坡缕石表面的羟基，采用化学方法首先将坡缕石（PGS）用磷酸进行了改性，随后通过酸碱中和的方法，将十二胺接枝到磷酸分子上，得到改性的含P、N型复合阻燃剂PGS@P-N。通过SEM、 XRD、 FTIR等方法对所合成阻燃剂PGS@P-N的形貌和结构进行了表征，利用氧指数法(LOI)、垂直燃烧法(UL-94)和锥形量热法(CCT)对复合材料的阻燃性能进行了测试，并对复合材料的力学性能和相容性进行了考察。结果表明：当向EVA中加入质量分数为30%的PGS@P-N/EG后，EVA/PGS@P-N/EG(可膨胀石墨)复合材料的氧指数达到了36.3%，与EVA/PGS/EG比较，接入烷基链后，EVA/PGS@P-N/EG复合材料的断裂伸长率提高了40%。     

Flame retardancy of hollow glass microsphere/rigid polyurethane foams in the presence of expandable graphite

Rigid polyurethane foams (RPUF) filled with various loadings of expandable graphite (EG) or/and hollow glass microspheres (HGM) were prepared by cast molding. The flame retardant properties of these composites were investigated by limiting oxygen index (LOI), horizontal and vertical burning tests. The composite with 10 wt % HGM and 20 wt % EG had the best flame retardant properties, and its LOI value reached 30 vol %. The addition of an appropriate loading of HGM improved the compressive strength and modulus of RPUF and EG/RPUF. When the HGM content arrived at 10 wt %, the compressive strength and modulus of the composites reached the maximum value. The dynamical mechanical analysis (DMA) showed that the addition of EG and HGM made the glass transition temperature shift to a higher temperature, and 10 wt % EG and 10 wt % HGM filled RPUF had the highest storage modulus. The scanning electronic microscope (SEM) observation indicates that the additives led to the decrease in the cell size. In addition, the flame retardant mechanism, the thermal properties, the burned surfaces and the interface surfaces were elucidated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Physical and mechanical properties of linear low‐density polyethylene/cycloolefin copolymer/layered silicate nanocomposite

Nanocomposites based on cyclic olefin copolymer/linear low density polyethylene blends (COC/LLDPE) with various contents of three different modified organoclays (20A, 10A, and I28E) compatibilized with polyethylene grafted maleic anhydride (PEgMA) were prepared by met mixing. The influence of content and type of organoclay and compatibilizer on nanocomposite morphology, thermal, and mechanical properties as well as on oxygen and water vapour barrier properties was determined. X‐ray diffraction (XRD) and transmission microscopy (TEM) were used to investigate the clay dispersion, which showed a strong dependence on compatibilizer and type of organoclay. An exfoliated–intercalated morphology was obtained for compatibilized samples of C20A and I28E organoclays at 5 wt%. A less intercalated structure was obtained for samples with C10A. The exfoliated–intercalated structure was influenced both by the compatibilizer and the increase on the nanocomposite viscosity due to the COC incorporation as was determined by Rheological measurements. Mechanical analysis gave an evidence of increasing stiffness after nanoclay was added into COC/LLDPE blend matrix observing higher Young modulus for the compatibilized samples. A notorious decrease of Oxygen and Water vapour permeation rate was observed for COC/LLDPE blend films nanocomposites only when using C20A and I28E clays. These results can be useful in the design of sustainable flexible films for the packaging requirements of specific types of food. POLYM. COMPOS., 37:3167–3174, 2016. © 2015 Society of Plastics Engineers     

Synergistic effects of exfoliated LDH with some halogen‐free flame retardants in LDPE/EVA/HFMH/LDH nanocomposites

The synergistic effects of exfoliated layered double hydroxides (LDH) with some halogen‐free flame retardant (HFFR) additives, such as hyperfine magnesium hydroxide (HFMH), microencapsulated red phosphorus (MRP), and expandable graphite (EG), in the low‐density polyethylene/ethylene vinyl acetate copolymer/LDH (LDPE/EVA/LDH) nanocomposites have been studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermal analysis (TGA and DTG), mechanical properties, limiting oxygen index (LOI), and UL‐94 tests. The XRD results show that EVA as an excellent compatilizer can promote the exfoliation of LDH and homogeneous dispersion of HFMH in the LDPE/EVA/HFMH/LDH nanocomposites prepared by melt‐intercalation method. The TEM images demonstrate that the exfoliated LDH layers can act as synergistic compatilizer and dispersant to make the HFMH particles dispersed homogeneously in the LDPE matrix. The results from the mechanical, LOI, and UL‐94 tests show that the exfoliated LDH layers can also act as the nano‐enhanced and flame retardant synergistic agents and thus increase the tensile strength, LOI values, and UL‐94 rating of the nanocomposites. The morphological structures of charred residues observed by SEM give the positive evidence that the compact charred layers formed from the LDPE/EVA/HFMH/LDH nanocomposites with the exfoliated LDH layers play an important role in the enhancement of flame retardant and mechanical properties. The TGA and DTG data show that the exfoliated LDH layers as excellent flame retardant synergist of MRP or EG can apparently increase the thermal degradation temperature and the charred residues after burning. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Flame‐retardant and mechanical properties of high‐density rigid polyurethane foams filled with decabrominated dipheny ethane and expandable graphite

The article reported the flame‐retardant and the mechanical properties of expandable graphite (EG), an intumescent type, and decabrominated dipheny ethane (DBDPE), a gas‐phase type of flame‐retardant‐containing high‐density rigid polyurethane foams (RPUF) with a constant density of 0.5g/cm³. The results indicated that both EG and DBDPE could effectively interdict the burning of RPUF, besides, the EG exhibited more effective flame retardancy than the DBDPE. When the flame‐retardant loadings were 20 wt %, the LOI value of DBDPE‐filled RPUF increased to 33 vol %, while, surprisingly, the EG‐filled RPUF reached 41 vol %. Unfortunately, when they were both simultaneously added into RPUF, there was not any flame‐retardant synergistic effect. Although EG had outstanding flame retardancy, the compressive strength and modulus of 20 wt % EG‐filled RPUF dropped to only 9.1MPa and 229.7MPa respectively, which were lower than those of DBDPE (12.4 MPa and 246.8 MPa). The phenomena were ascribed to the different flame‐retardant mechanisms of EG and DBDPE, which were verified by scanning electronic microscope (SEM) observation of the burned surfaces. Besides, the dynamical mechanical analysis (DMA) demonstrated that the additions of EG and DBDPE made the glass transition temperature shift to the high temperatures, and the EG‐filled RPUF had the higher storage modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

不同表面活性剂包覆的LMH对LLDPE性能影响

采用气泡液膜法制备了不同表面活性剂包覆的疏松型氢氧化镁(LMH),通过对常规力学性能和极限氧指数(LOI)的测试、燃烧实验和热重分析,研究了不同表面活性剂包覆的LMH对线型低密度聚乙烯(LLDPE)性能的影响.结果表明:不同表面活性剂包覆的LMH对LLDPE拉伸强度、弯曲强度和LOI的影响不大,但会显著影响材料的冲击强度、热释放速率、燃烧质量损失率及热稳定性;以聚乙二醇6000包覆的LMH可使LLDPE的力学性能、阻燃性能及热稳定性能较优.     

氢氧化铝无卤阻燃乙烯醋酸乙烯共聚物的结构与性能

以表面修饰的氢氧化铝（ATH）作为无卤阻燃剂,以线形低密度聚乙烯接枝物为相容剂制备了阻燃性能和力学性能优良的无卤阻燃乙烯醋酸乙烯（EVA）复合材料。通过扫描电子显微镜、力学性能测试、动态热力学分析、极限氧指数、垂直燃烧测试表征了AHT阻燃EVA复合材料的结构与性能。研究了表面处理及相容剂的引入对ATH在EVA中的分散性和界面相容性的影响,以及AHT粒径大小、添加量对EVA阻燃性能和力学性能的影响。结果表明,界面相容剂和表面处理剂同时使用,能显著提高ATH与基体之间的界面相容性,从而提高了EVA的力学性能和阻燃效果,ATH尺寸越小,阻燃性能越好。     

无卤阻燃LLDPE/PDMS共混物的研究

采用高乙烯基含量硅橡胶(PDMS)与线性低密度聚乙烯(LLDPE)进行熔融共混,并添加阻燃母料,制得LLDPE/PDMS阻燃共混物;研究了无机阻燃剂和PDMS用量对共混物力学性能、阻燃性能的影响以及无机阻燃剂与PDMS的协同阻燃性;同时初步探讨了两者的协同阻燃机理。结果表明:采用添加母料和添加PDMS的方法,提高了无机阻燃剂在基体树脂中的分散性,降低了无机阻燃剂对材料力学性能的破坏,同时提高了无机阻燃剂的阻燃效果;同时添加2 0 %无机阻燃剂与1 0 %PDMS ,共混物的氧指数达到2 8% ,拉伸强度约1 3MPa ,断裂伸长率约4 70 % ;PDMS与无机阻燃剂具有较好的协同阻燃性。     

Mechanical properties and morphology of polylactide,linear low‐density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer‐grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882‐91. On the basis of this, LLDPE 80 [80 wt % LLDPE and 20 wt % poly(L ‐lactic acid) (PLLA)] and MA‐g‐low‐density polyethylene 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) were found to be an optimum composition. The blends were characterized according to their mechanical, thermal, and morphological behavior. Fourier transform infrared spectroscopy revealed that the presence of compatibilizer enhanced the blend compatibility to some extent. The morphological characteristics of the blends with and without compatibilizer were examined by scanning electron microscopy. The dispersion of PLLA in the LLDPE matrix increased with the addition of compatibilizer. This blend may be used for packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A novel phytic acid based flame retardant to improve flame retardancy,hydrophobicity and mechanical properties of linear low-density polyethylene

Exploiting high phosphorus content of phytic acid, it was grafted onto magnesium hydroxide (MH) by neutralization reaction to obtain MGPA, a flame retardant. A current study investigated the effect of MGPA on hydrophobicity, flame retardancy, and mechanical properties of MGPA-linear low-density polyethylene (LLDPE) composites. The LLDPE composite with 50 parts of MGPA has the better flame retardancy and thermal stability with a limiting oxygen index of 23.3%, which is higher than that of neat LLDPE (17%). In addition, MGPA could effectively promoted LLDPE to form a continuous and compact char residue during combustion, which reduce the peak of heat release rate and total smoke production value of LLDPE composite by 70% and 36%, respectively, and the char residue rate increase to 67.5%. Furthermore, the maximum of loss-rate showed by LLDPE composite with MGPA reduce to 1.25%/min while the value of LLDPE composite with MH is 1.8%/min. Meanwhile, the LLDPE composite with MGPA show remarkable elongation at break and hydrophobicity, which are 398% and 99°, respectively. In addition, this study presents a substantial flame retardancy and interfacial compatibility of MGPA for extending the applications of flame-retardant LLDPE composites.     

Effect of hydrated fillers and red phosphorus on the limiting oxygen index of poly(ethylene‐co‐vinyl actate)‐poly(vinyl butyral) and low density polyethylene‐poly(ethylene‐co‐vinyl alcohol) blends

The limiting oxygen index (LOI) values of EVA‐PVB and low density polyethylene (LDPE)‐poly(ethylene‐co‐vinyl alcohol) (EVOH) polymer blends containing hydrated filler‐type flame retardants and red phosphorus were measured. When used as the sole flame retardant, magnesium hydroxide [Mg(OH)₂] and alumina trihydrate (ATH) performed best in EVA and PVB, respectively. Magnesium hydroxide addition had a limited effect on the LOI of plasticized PVB, and addition of red phosphorus made little difference. This result is attributed to a mismatch between the decomposition temperature of Mg(OH)₂ and the temperature at which the PVB plasticizer vaporizes. Otherwise, low‐level addition of red phosphorus significantly improved LOI values. The presence of hydroxyl groups on the polymer backbone had a beneficial effect with respect to LOI values in ATH‐filled blends. An LOI value of 30 was achieved in EVOH with as little as 32% of ATH and 3% of red phosphorus. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

A study on PVC/LLDPE blends with solid-state-chlorinated polyethylene as compatibilizer

Chlorinated polyethylene (CPE) prepared by solid-state chlorination was used as compatibilizer for poly(vinyl chloride) (PVC)/linear low-density polyethylene (LLDPE) blends. Effects of CPE molecular structure on stress-strain behaviors, dynamic mechanical properties, and morphologies of PVC/LLDPE blends were studied by using SEM, TEM, DMA, and testing mechanical properties. The results showed that the compatibility of PVC/LLDPE blends was improved with the addition of CPE. Also, adhesion strength between the two phases and mechanical properties of the blends were increased. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2535–2541, 1997