高抗冲聚苯乙烯/蒙脱土复合材料的阻燃性研究

用经十六烷基三甲基溴化铵有机化改性的蒙脱土 (OMMT)与高抗冲聚苯乙烯 (HIPS)通过熔融插层法制备了HIPS OMMT复合材料 ,用X ray衍射技术对材料结构进行了表征 ,发现钠基蒙脱土 (Na+ MMT)和有机蒙脱土的层间距分别为 1 5 1nm和 2 18nm ,HIPS OMMT(5phr)复合材料中蒙脱土的层间距因聚合物大分子的插入扩大为 3 4 4nm ;而HIPS与Na+ MMT形成的复合材料的层间距与Na+ MMT的层间距相比却没有变化 ,表明未有机化处理土没有形成插层结构 .锥形量热仪的研究结果表明HIPS OMMT复合材料的热释放速率、质量损失速率以及生烟速率等燃烧特性参数均显著降低 ,具有较明显的阻燃性和抑烟性 ,而HIPS Na+ MMT非插层型复合材料只有在Na+ MMT很高填充量下 (>2 0phr)才有一定阻燃效果 .比较了铵盐对HIPS阻燃性的影响 ,结果表明铵盐自身的阻燃作用很小 ,主要是插层复合结构起阻燃作用 .     

Properties of poly(vinyl chloride)/wood flour/montmorillonite composites: Effects of coupling agents and layered silicate

Organomodified montmorillonite (OMMT) was prepared using cetylalkyl trimethyl amine bromide. OMMT and wood flour (WF) were surface-modified by silane coupling agent. They were melt-blended with polyvinyl chloride (PVC) and extruded into wood-plastic composite samples using one conical twin screw extruder. The effects of their contents on the composite mechanical properties were investigated. X-ray diffraction, transmission electron microscopy and scanning electron microscopy observed intercalation and dispersion of the OMMT. FTIR and X-ray photoelectron spectroscopy were used to analyze the silane-modification effects. The possible reaction mechanisms were proposed. After wood flour was modified by 1.5 phr silane, the impact strength and the tensile strength of wood flour-PVC composite were increased by 14.8% and 18.5%, respectively. Mechanical tests showed that the addition of OMMT did not enhance the untreated wood flour-PVC composites. However, adding 0.5% OMMT did improve the mechanical properties of the treated ones. The grafting improved the interfacial compatibility between components producing higher properties of the composites. Further addition of OMMT reinforced the composites. Too higher contents of silane and OMMT impaired some properties because of weak interfacial layer and higher concentrated stress. Cone calorimetry showed that the fire flame retardancy and smoke suppression of composites were strongly improved with the addition of OMMT.     

Preparation of urea formaldehyde microsphere and its effect on flame retardant ethylene vinyl acetate composites

Urea formaldehyde microsphere (UFM) was prepared and used with organic montmorillonite (OMMT) to modify the flame retardant efficiency of ethylene vinyl acetate copolymer (EVA)/intumescent flame retardant (IFR) composites. The results show that single IFR may modify the flame retardancy of EVA, but its efficiency is not good enough. The EVA composite containing 21 wt% IFR is just classified the UL_94 V2 and has a limiting oxygen index (LOI) 24.7 vol%. Combining UFM with IFR does not improve the flame retardancy of EVA/IFR composites, and blending OMMT with IFR only improves its LOI. Adding 2 wt% UFM, 2 wt% OMMT, and 17 wt% IFR into EVA, it obtains the UL_94 V0 without melt dripping and a LOI 29.0 vol%. Also, the peak heat release rate and total heat release decrease a lot. Good synergistic effects among IFR, UFM, and OMMT improve the char residues and modify the char micromorphology of EVA composites, which provide better protect for the underlying resin.     

Preparation and thermal properties of expanded graphite/paraffin/organic montmorillonite composite phase change material

Expanded graphite (EG)/paraffin/organic montmorillonite (OMMT) composite phase change material (PCM) was prepared by using melt intercalation method. The microstructure of EG/paraffin/OMMT is observed by scanning electron microscope (SEM). The thermal properties are investigated by differential scanning calorimetry (DSC). The mass loss of EG/paraffin/OMMT after 50 heating cycles was measured for investigating the influence of EG and OMMT on the thermal properties of paraffin. The results show that EG and OMMT have the ability of adsorption and shape-stability. The melting point EG/paraffin/OMMT is decreased slightly with an addition of paraffin and the latent heat of EG/paraffin/OMMT is determined by the mass ratio of paraffin. The heat transfer efficiency of EG/paraffin/OMMT is strengthened and the heating time is decreased to one-sixth of that of paraffin by addition of EG and OMMT. The thermal stability of EG/paraffin/OMMT is improved by addition of OMMT.     

Gas permeation and mechanical properties of polypropylene nanocomposites with thermally-stable imidazolium modified clay

Dialkyl imidazolium salt with better thermal stability than the commonly used dimethyldioctadecyl ammonium salt was synthesized and ion exchanged on the montmorillonite surface. Polypropylene nanocomposites with different volume fractions of the obtained organo-montmorillonite (OMMT) were prepared and the effect of the modified clay on the gas barrier and mechanical properties was studied. Wide angle X-ray diffraction (WAXRD) and transmission electron microscopy (TEM) were used to investigate the microstructure obtained. Thermal behavior of the composites analyzed by thermogravimetric analysis was observed to enhance significantly with the filler volume fraction. The gas permeation through the nanocomposite films markedly decreased with augmenting the filler volume fraction. The decrease in the gas permeation was even more significant than through the composites with ammonium treated montmorillonite. Better thermal behavior of the organic modification owing to the delayed onset of degradation hindered the interface degradation along with detrimental side reactions with polymer itself. Transmission electron microscopic studies indicated the presence of mixed morphology i.e., single layers and the tactoids of varying thicknesses in the composites. The crystallization behavior of polypropylene remained unaffected with OMMT addition. A linear increase in the tensile modulus was observed with filler volume fraction owing to partial exfoliation of the clay.     

Synergistic flame‐retardant effect of DOPO‐based derivative and organo‐montmorillonite on glass‐fiber‐reinforced polyamide 6 T

Herein, a bridged 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) derivative (PN‐DOPO) in combination with organ‐montmorillonite (OMMT) was used to improve the flame retardancy and mechanical properties of glass‐fiber‐reinforced polyamide 6 T (GFPA6T). The flame retardancy and thermal stabilities of the cured GFPA6T composites were investigated using limiting oxygen index, vertical burning (UL‐94) test, cone calorimeter test, and thermogravimetric analysis (TGA). The morphological analysis and chemical composition of the char residues after cone calorimeter tests were characterized via scanning electron microscopy and energy dispersive spectrometry. The results indicate that 2 wt% OMMT combined with 13 wt% PN‐DOPO in GFPA6T achieved a V‐0 rating in UL‐94 test. The peak heat release rate and total smoke release remarkably decreased with the incorporation of OMMT as compared to those of GFPA6T/15 wt% PN‐DOPO. The TGA results show that the thermal stability and residual mass of the samples effectively increased with the increase in OMMT content. The morphological analysis and composition structure of the residues demonstrate that a small amount of OMMT could help form a more thermally stable and compact char layer during combustion. Also, with the incorporation of OMMT, the layers consisted of more carbon‐silicon and aluminum phosphate char in the condensed phase. Furthermore, GFPA6T/PN‐DOPO/OMMT composites exhibited excellent mechanical properties in terms of flexural modulus, flexural strength, and impact strength than the GFPA6T/PN‐DOPO system. The combination of PN‐DOPO and OMMT has improved the flame retardancy and smoke suppression of GFPA6T without compromising the mechanical properties.     

Thermal stability of styrene–(ethylene butylene)–styrene-based elastomer composites modified by liquid crystalline polymer, clay, and carbon nanotube

The thermal decomposition behaviors of styrene?C(ethylene butylene)?Cstyrene (SEBS) thermoplastic elastomer filled with liquid crystalline polymer (LCP), organomontmorillonite (OMMT), and carbon nanotube (CNT) as a heat stabilizing filler, were comparatively investigated using nonisothermal- and isothermal-thermogravimetric analyses in air. The isoconversional method was employed to evaluate the kinetic parameters (E _a, lnA, and n) under dynamic heating. For neat samples, OMMT and CNT exhibited their respective lowest and highest thermal stabilities as revealed from the lowest and the highest T _onset values, respectively. The decomposition rates of the composites containing OMMT at the temperature >250?°C were higher than those containing CNT and LCP, respectively, whereas the elastomer matrix degraded with the highest rate. The obtained TG profiles and calculated kinetic parameters indicated that the incorporation of LCP, OMMT, and CNT into elastomer matrix improved the thermal stability. Especially, the CNT- and OMMT-containing composites significantly improved the thermal stability compared with the neat matrix polymer. Simultaneously recorded DSC thermograms revealed that the degradation processes for the neat polymers and their composites were exothermic in air. From the simultaneously recorded DSC data, the enthalpy of thermal decomposition for each composite system was found to be lower than that of the neat matrix and mostly decreasing with increasing filler loading. The isothermal decomposition stabilities of the neat SEBS and its composites containing the different fillers were in agreement with those of the nonisothermal investigation.     

Preparation and characterization of an asphalt-modifying agent with waste packaging polyethylene and organic montmorillonite

In this paper, waste packaging polyethylene (WPE)/organic montmorillonite (OMMT) nanocomposites were prepared and used as an asphalt-modifying agent. The structure and morphology of the nanocomposites and the effects of OMMT on the thermal properties of WPE were investigated. The influence of the microcosmic effects and physical properties of the composite agents on the base asphalt were also studied. The results show that the WPE/OMMT asphalt-modifying agents are exfoliated nanocomposites. When compared with WPE, the melting range of the composites decreases and the thermal stability is improved. In addition, the composite agents not only promote good dispersion of WPE in asphalt, but also improve the low temperature properties of WPE-modified asphalt without adversely affecting its excellent high temperature properties. Therefore, from an environmental and economic standpoint, it is a novel and significant attempt at dealing with waste plastics packaging.     

Effect of polyphenylsilsesquioxane on the ablative and flame-retardation properties of ethylene propylene diene monomer (EPDM) composite

Polyphenylsilsesquioxane (PPSQ) microspheres with ladder structure synthesized in the laboratory have been incorporated into ethylene propylene diene monomer (EPDM) composite in order to study the effect of PPSQ on the ablative and flame-retardation properties of EPDM composites. The results showed that PPSQ microspheres serve as an effective ablative additive and flame retardant for EPDM composites. Thus, PPSQ greatly improved the ablative properties of EPDM composites, with a 4.8 wt% loading leading to a remarkable reduction in the linear ablation rate of EPDM by about 50%. Moreover, this loading of PPSQ improved the flame retardancy and smoke suppression, and significantly reduced the PHRR of EPDM composite from 504 kW/m² to 278 kW/m². Moderate tensile strength could be obtained and the breaking elongation was improved for the EPDM/PPSQ composites. TGA results showed that PPSQ had little influence on the thermal decomposition of EPDM. SEM, CONE, and TG-FTIR tests showed that the char structure of EPDM composites was the primary factor through which PPSQ affected the ablative and flame-retardation properties of EPDM. The chars formed during the ablation of EPDM composites containing PPSQ had better structural stability and thermal stability, owing to the fact that they were denser, remained intact, and had an ordered arrangement of holes.     

Estimation of interphase thickness and properties in PP/layered silicate nanocomposites

Nanocomposites were prepared from sodium montmorillonite (NaMMT) and organoclays (OMMT) with different particle sizes as a function of silicate content. Composite structure was characterized by various methods including X-ray diffraction (XRD), scanning electron microscopy (SEM) and rheology. Model calculations were carried out to estimate the thickness and yield stress of the interphase forming in the composites. The results proved the formation of an interphase, but the determination of interphase properties was hampered by several factors. First of all, the particle size of the filler changed quite considerably in PP/OMMT composites in spite of earlier observations and expectations. Particle characteristics changed even further when a relatively small amount (5 vol.%) of functionalized polymer (MAPP) was added to the composite. As a consequence, the estimation of the contact surface between the silicate and the polymer became extremely difficult. In spite of the uncertainties overall values of interphase properties were obtained using the results of all composites prepared. The prediction for the average thickness of the interphase is 0.23 μm and we obtained 51.2 MPa for interphase yield stress, but this estimate neglects the different interactions developing in composites containing the uncoated and the modified silicate, respectively.     

Effect of Different Organic Modifiers on the Tensile Properties of PVC／EVA／Montmorillonite Composites

Poly (vinyl chloride)/ethylene-vinyl acetate/montmorillonite (PVC/EVA/OMMT) composites were prepared by melt blending method. Two kinds of montmorillonites were organically modified by trimethyloctadecyl ammonium and dimethyl bis (hydrogenated tallow) ammonium, respectively. The morphology and tensile properties of the resultant composites were discussed in terms of the modifier type and OMMT content. The PVC/EVA/OMMT composites have intercalated structure, which is independent of the polarity of the modifiers, while the tensile properties show strong dependence on the modifier type. The OMMT modified by polar modifier gives higher tensile ductile and strength of PVC/EVA/OMMT composites.     

Evaluation of activation energy conformity derived from model-free non-isothermal predictions and Arrhenius isothermal results

Organically modified montmorillonite (OMMT) was used as synergist to enhance the flame-retardant and mechanical properties of poly(butylene succinate)/intumescent flame retardant (PBS/IFR) composites. The flame-retardant, thermal degradation and combustion properties of PBS and its flame-retardant composites were characterized by limiting oxygen index (LOI) test, vertical burning (UL-94) test, thermogravimetric analysis, cone calorimeter and scanning electron microscopy, respectively. The results indicate that PBS/IFR composites exhibit excellent flame retardance when OMMT is at an appropriate content. PBS/IFR composite with 20 wt% IFR and 1.5 wt% OMMT has an LOI of 40.1% and can pass the UL-94 V0 rating. The synergistic effect between OMMT and IFR on the flame-retardant properties of PBS depends on the content of OMMT, and excessive OMMT diminish this synergistic effect. The possible flame-retardant mechanism of OMMT on PBS/IFR composite is proposed. The results of mechanical test also indicate that OMMT can effectively increase the notched impact strength of PBS/IFR composites.     

Synergistic effect of decabromodiphenyl ethane and montmorillonite on flame retardancy of polypropylene

Polypropylene (PP) is melt-compounded in a twin-screw extruder with surface-modified decabromodiphenyl ethane/antimony trioxide (DBDPE/Sb₂O₃) and organically modified montmorillonite (OMMT). The intercalation and dispersion microstructure of OMMT in the nanocomposites are investigated by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermal stability and char residue are characterized by thermogravimetric and differential thermal analysis (TGA–DTA). Flame retardant properties are evaluated by limited oxygen index (LOI) and UL-94 vertical burning test.The results indicate that better flame retardancy can be achieved for the composite containing a modified mixture DBDPE/Sb₂O₃. The presence of DBDPE/Sb₂O₃ could improve the dispersion of OMMT in polypropylene, leading to higher thermal stability and more char residue. A synergistic effect between OMMT and DBDPE/Sb₂O₃ has been observed and discussed.     

Morphology and physical properties of polyethylene/silicate nanocomposite prepared by melt intercalation

Maleated polyethylene (PEMA)/silicate nanocomposites with a different aspect ratio of silicate and maleated PEMA/SiO₂ composite were prepared by melt intercalation. The nanocomposites with a high aspect ratio silicate (montmorillonite) showed a faster decrease in the terminal slope of the storage modulus and a steeper increase in complex viscosity than those with a low aspect ratio silicate (laponite) and SiO₂. The addition of montmorillonite increases the crystallization and the melting temperature of PEMA but decreases above 3 vol % of the silicate content because of the increased viscosity. The nanocomposite with montmorillonite showed the highest yield strength and secant modulus among the composites because of the highest aspect ratio of the filler. It also revealed strong interfacial adhesion with the matrix and orientation during tensile deformation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1454–1463, 2002     

Synthesis and characterization of exfoliated MEH-PPV/clay nanocomposites by in situ polymerization

In this article, we demonstrate the synthesis of a conjugated polymer, poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) in the presence of organophilic montmorillonite (OMMT) and the properties of the MEH-PPV/OMMT composites produced herefrom. By controlling the reaction conditions, such as the ratio of monomeric precursors to montmorillonite, exfoliated MEH-PPV/OMMT nanocomposites were synthesized via in situ polymerization. These materials exhibit higher electroluminescent properties and enhanced performance of thermal stability than that of the pure polymer. Additionally, based on the solid-state ¹³C NMR measurement results, the possible origin of the optoelectronic property improvement is discussed from the point of view of segmental mobility.     

Effect of surface modification of montmorillonite on the properties of rigid polyurethane foam composites

<正>This study investigated the influence of various organically modified montmorillonites(organoclays) on the structure and properties of rigid polyurethane foam(RPUF) nanocomposites.The organoclays were modified with cetyltrimethyl ammonium bromide(CTAB),methyl tallow bis(2-hydroxyethyl) quaternary ammonium chloride (MT2ETOH) and tris(hydroxymethyl)aminomethane(THMA) and denoted as CMMT,Cloisite 30B and OMMT, respectively.MT2ETOH and THMA contain hydroxyl groups,while THMA does not have long aliphatic tail in its molecule. X-ray diffraction and transmission electron microscopy show that OMMT and Cloisite 30B can be partially exfoliated in the RPUF nanocomposites because their intercalating agents MT2ETOH and THMA can react with isocyanate.However, CMMT modified with nonreactive CTAB is mainly intercalated in the RPUF matrices.At a relatively low filler content,the RPUF/CMMT composite foam has a higher specific compressive strength(the ratio of compressive strength against the apparent density of the foams),while at relatively high filler contents,RPUF/Cloisite 30B and RPUF/OMMT composites have higher specific compressive strengths,higher modulus and more uniform pore size than the RPUF/CMMT composite.     

Rice Husk‐derived Hierarchical Micro/Mesoporous Carbon–Silica Nanocomposite as Superior Filler for Green Electronic Packaging Material

In this study, a carbon‐controllable hierarchical micro/mesoporous carbon–silica material derived from agricultural waste rice husk was easily synthesized and utilized as filler in an epoxy matrix for electronic packaging applications. Scanning electron microscopy, thermogravimetric analysis, and N₂ adsorption/desorption isotherms were used to characterize the morphology, thermal stability, carbon content, and porous structural properties, respectively, of the as‐obtained carbon–silica material, namely rice husk char (RHC ). As a filler material, the uniformly dispersed RHC filler in the epoxy/RHC composite was easily prepared through hydrogen bonding of the silanol group of silica with the epoxy matrix. For electronic packaging applications, the thermal conductivity and thermomechanical properties (storage modulus and coefficient of thermal expansion) of the epoxy/RHC composites improved with increasing carbon content. Moreover, loading of the 40% RHC filler substantially enhanced the storage modulus of the epoxy/RHC composite (5735 MPa ) compared to the epoxy with 40% commercial silica filler (3681 MPa ). Considerable commercial potential is expected for the carbon–silica composite because of the simple synthesis process and outstanding performance of the prepared packaging material.     

聚碳酸1,2-丙二酯/蒙脱土复合材料的制备与性能

利用阳离子交换法,以十六烷基三甲基溴化铵(HTAB)改性钠基蒙脱土制备了有机改性蒙脱土(OMMT),OMMT的层间距达到了2nm,比普通的钠基蒙脱土增加了0.74nm.采用熔融插层法制备了插层-絮凝型PPC/OMMT复合材料,当复合材料中OMMT含量为5wt%时,复合材料的杨氏模量较纯PPC树脂大幅度提高了61.8%,同时玻璃化温度(Tg)提高了2.4℃,热分解温度提高了32.3℃.因此,OMMT对大幅度提高PPC的杨氏模量具有很大的潜力.     

Preparation of thermosetting polyurethane nanocomposites by montmorillonite modified with a novel intercalation agent

A novel thermosetting polyurethane (TSPU)/organic montmorillonite (OMMT) nanocomposite has been synthesized. N‐diamino octadecyl trimethyl ammonium chloride (DODTMAC) was used as an intercalation agent to treat Na⁺‐montmorillonite (MMT) and form a novel kind of OMMT. Fourier transform infrared spectroscopy (FT‐IR), wide angle X‐ray diffraction (WAXD), and thermogravimetric analysis (TGA) data indicated that the MMT was successfully intercalated by this intercalation agent, as evidenced by the fact that the basal spacing of MMT galleries was expanded from 1.5 to 3.2 nm. This OMMT was used to prepare the TSPU nanocomposites. Both the reinforcing and compatibilizing performance of the filler were investigated. Tensile tests showed that the tensile strength of TSPU/OMMT‐4 was the highest, and was about 3.62 times higher than that of the pure TSPU, and also the elongation at break showed an enhancement. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) measurements illustrated that the glass transition temperature of the TSPU/OMMT‐4 nanocomposite was improved from 0.5 to 6.5 °C, which corresponded to the restriction of the soft segments of TSPU. The highest initial and center temperatures of TSPU/OMMT‐4 obtained from TGA were due to the highest retard effect of the TSPU molecular chains. WAXD studies showed that the formation of the nanocomposites in all the cases with the almost disappearance of the peaks corresponding to the basal spacing of MMT. SEM and TEM were used to investigate the morphologies of the TSPU/OMMT‐4 nanocomposite, and demonstrated that the nanocomposite was comprised of a well dispersion of a mixture of intercalated and exfoliated silicate layers throughout the matrix. It was proposed that the nano‐reinforcing effect caused by the well‐dispersed silicate layers might reduce the amount and size of voids and increase the length of the crack‐spreading path during tensile drawing. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 519–531, 2007.     

本质阻燃聚苯乙烯/蒙脱土纳米复合物的制备及性能

通过原位聚合法制备了本质阻燃聚苯乙烯[P(St-co-AEPPA)]/有机改性蒙脱土(OMMT)纳米复合物[P(St-co-AEPPA)/OMMT], 并用普通聚苯乙烯/有机改性蒙脱土(PS/OMMT)复合物作为对比实验, 研究了含磷、氮单体丙烯酸羟乙基-苯氧基-二乙基磷酰胺(AEPPA)和OMMT等添加物对本质阻燃聚苯乙烯性能的影响.用X射线衍射仪(XRD)和透射电子显微镜(TEM)分析了复合材料的结构与形貌, 并对OMMT在基体中的分散机理进行了讨论.用差示扫描量热仪(DSC)、热重分析(TGA)和微型量热仪(MCC)研究了材料的热性能和燃烧性能.结果表明, AEPPA和OMMT能够显著提高基体的热稳定性和阻燃性.