膨胀阻燃LLDPE/EVA复合材料的制备及其改性

将预先配制好的膨胀阻燃剂[IFR,聚磷酸铵(APP)/季戊四醇(PER)/硼酸锌(ZB)]与线性低密度聚乙烯(LLDPE)/乙烯-醋酸乙烯共聚物(EVA)进行混和,采用双螺杆挤出机,制备阻燃LLDPE/EVA复合材料。用氧化钙(CaO)、天然石墨(NG)、膨胀石墨(EG)对阻燃LLDPE/EVA复合材料进行改性。结果表明:APP/PER/ZB具有明显的膨胀阻燃作用,同时,发现CaO,NG,EG与IFR有协同作用,提高了膨胀炭层的热稳定性和阻燃效率。     

可膨胀石墨阻燃EVA燃烧性能及热失重行为的研究

用粒径为37、48及75μm的可膨胀石墨(EG)阻燃EVA,用锥形量热仪探讨了不同粒径的EG对EVA的阻燃作用,利用热失重分析仪研究了EVA/EG体系的热稳定性。结果表明:经过锥形量热仪测试表明,EVA/EG的热释放速率曲线呈现前单峰型,体现了典型的凝聚相阻燃机理;30 g EG的加入可以明显降低热释放速率,且粒径越大,阻燃效果越好;通过TG考察EG/EVA阻燃体系的热降解行为,在空气气氛下,EG膨胀炭层负载催化EVA交联成炭;相比于75μm EG,48μmEG形成炭层紧密,成炭量超过2.2%,形成的炭层稳定,在850℃也不会分解。     

用锥形量热法研究EVA/EG复合材料的阻燃性能

采用哈克转矩流变仪将阻燃剂可膨胀石墨(EG)、乙烯-乙酸乙烯酯共聚物(EVA)树脂和其它助剂进行熔融混和均匀,制备阻燃EVA/EG复合材料,并通过锥形量热仪研究其阻燃性能。研究结果表明:经膨胀石墨阻燃的EVA/EG复合材料的热释放速率峰值(PHRR)、总热释放速率(THR)、烟发生速率(SPR)、总释烟速率(TSR)逐渐降低,火灾性能指数(FPI)、点燃时间(TTI)及燃烧残渣逐渐增加,表现出明显的阻燃性和抑烟性特点。阻燃EVA/EG复合材料燃烧时,其EG片层受热膨胀形成保护层,有效延缓了热、氧传递,降低了材料的热分解和扩散速率,促进了成炭,是阻燃性提高的关键因素。     

EG与IFR复合阻燃EVA的动态燃烧性能和协同效应

将可膨胀石墨(EG)与P-N膨胀阻燃剂(IFR)复合阻燃EVA树脂,通过氧指数(OI)、垂直燃烧测试(UL94)、锥形量热仪(CONE)研究了EG与IFR复合阻燃EVA的协同效应。结果表明:阻燃剂总添加量为30 phr,随着其中EG含量的增加,OI呈先增加后下降趋势,确定EG:IFR=1:1为最佳配比,OI达到36.6%,UL94为V-0级;EG与IFR复合阻燃EVA,热释放速率曲线呈现"前单峰型",为凝聚相阻燃机理;燃烧后形成的炭层结构较致密,表现出一定的协同作用。     

不同粒径EG阻燃ABS体系燃烧性能和阻燃机理

采用不同粒径可膨胀石墨(EG)作为阻燃剂,添加量为20%,制备了阻燃ABS;研究EG粒径对ABS燃烧性能的影响,并通过CONE、TG对阻燃机理进行研究.结果表明:EG对ABS具有很好的阻燃作用,EG粒径越大.膨胀体积(EV)越大,阻燃效果越好,EG粒径大于48μm时就可有效抑制火焰传播;EG膨胀炭层具有良好耐热性,可保护ABS成炭产物,增加ABS成炭量,EG阻燃ABS具有典型的凝聚相阻燃特征.     

不同膨胀机理制备低烟无卤阻燃热收缩模缩套性能的研究

分别采用两种不同的磷-氮(P-N)膨胀型阻燃剂(IFR-A,IFR-B)、聚磷酸铵(APP)及红磷(RP)协同可膨胀石墨(EG)阻燃乙烯-醋酸乙烯酯共聚物(EVA),经辐照交联得到模缩套制品,对合成材料阻燃性能、力学性能进行测试分析,观察燃烧后残炭形貌,进而探讨阻燃体系的阻燃机理,同时研究了可膨胀石墨粒径对材料力学性能的影响。结果表明,EG与不同P-N阻燃剂间存在不同程度的协同效应,模缩套产品性能优异,低害环保,可应用于电线电缆及其附件领域。     

EG/IFR对长玻璃纤维增强PP的协同阻燃作用

将可膨胀石墨(EG)作为协效剂,与膨胀型阻燃剂(IFR)协同阻燃玻璃纤维增强聚丙烯(PP)复合材料,研究了EG与IFR对长玻璃纤维增强PP的协同阻燃作用。采用氧指数(OI)和热失重(TG)进行分析,结果表明:EG与IFR的协同阻燃作用存在佳协同比例;在佳协同比例下,长玻璃纤维增强PP的阻燃性和热稳定性佳。     

ABS的协同阻燃及热降解动力学

将可膨胀石墨(EG)和十溴二苯乙烷(DBDPE)/Sb2O3协同并用阻燃ABS树脂,探讨了EG和DBDPE/Sb2O3的协同阻燃作用,研究了阻燃丙烯腈-丁二烯-苯乙烯共聚物(ABS)体系的热失重行为,采用Kissinger法研究了阻燃ABS体系热降解动力学。结果表明,EG与DBDPE/Sb2O3协同并用可以同时发挥气相阻燃作用和凝聚相阻燃作用,具有更好的阻燃效果。     

可膨胀石墨阻燃ABS分解成炭性能研究

通过观测可膨胀石(墨EG)的宏观和微观结构,探讨了EG的分解成炭性能,利用热失重分析仪研究了EG与EG阻燃ABS的热失重行为,并采用扫描电镜观察了EG阻燃ABS膨胀炭层的微观结构。结果表明:EG自身膨胀后具有独特的"蠕虫"状结构,使EG炭层具有尺寸效应和负载作用;EG阻燃ABS形成了致密、耐高温的膨胀炭层,发挥隔氧、隔热作用,并且炭层呈现多孔的发泡堆砌结构,结构稳定性提高;EG膨胀炭层的负载催化作用促进了ABS的热氧降解反应和交联成炭反应同,时EG炭层能够保护ABS成炭产物提,高实际残炭量。     

可膨胀石墨/聚磷酸铵协同阻燃聚乙烯的研究

本文进行了可膨胀石墨(EG)/聚磷酸铵(APP)协同阻燃聚乙烯的研究。采用氧指数(LOI)、扫描电镜(SEM)和热重分析(TG)等技术手段对EG/APP阻燃聚乙烯体系进行表征。结果表明,加入APP后,体系氧指数明显提高,热降解速率降低,热稳定性增强。说明EG/APP发挥了协同阻燃作用,形成了致密稳定的膨胀炭层。     

Combustion characteristics and synergistic effects of red phosphorus masterbatch with expandable graphite in the flame retardant HDPE/EVA composites

In this work, the flammability behaviors and synergistic effects of red phosphorus masterbatch (RPM) with expandable graphite (EG) in flame‐retardant high‐density polyethylene/ethylene vinyl‐acetate copolymer (HDPE/EVA) composites have been investigated by limiting oxygen index (LOI), UL‐94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR) and scanning electron microscopy (SEM). The data obtained from LOI, UL‐94 test and CCT showed that suitable amount of RPM had synergistic effects with EG in the HDPE/EVA/EG/RPM composites. The addition of RPM greatly increased the LOI values by 3.4%, obtained UL‐94 V‐0 rating, decreased the heat release rates and total heat release, and prolongated the ignition time when 6.7 phr RPM substituted for EG in the HDPE/EVA/EG/RPM composites. The data from TGA and FTIR spectra also indicated the synergistic effects of RPM with EG considerably enhanced the thermal degradation temperatures. The morphological observations after UL‐94, CCT, and SEM images presented positive evidences that the synergistic effects took place for RPM with EG, and the flame‐retardant mechanism has been changed in flame‐retardant HDPE/EVA/EG/RPM composites. The formation of stable and compact charred residues promoted by RPM acted as effective heat barriers and thermal insulations, which improved the flame‐retardant performances and prevented the underlying polymer materials from burning. POLYM. ENG. SCI., 55:2884–2892, 2015. © 2015 Society of Plastics Engineers     

Preparation of expandable graphite with silicate assistant intercalation and its effect on flame retardancy of ethylene vinyl acetate composite

A halogen‐free intumescent flame retardant expandable graphite composite (EG), with an initial expansion temperature of 202°C and expansion volume of 517 mL g⁻¹, was successfully prepared via a facile two‐step intercalation method, i.e. using KMnO₄ as oxidant and H₂SO₄, Na₂SiO₃·9H₂O as intercalators. The prepared EG flame retardant was characterized by field emission scanning electron microscope, X‐ray diffraction spectroscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Furthermore, flame retardancy and thermal property of various ethylene vinyl acetate copolymer (EVA) composites, including EVA/EG and EVA/EG/APP (ammonium polyphosphate) specimens, were studied through limiting oxygen index instrument (LOI), vertical combustion UL‐94 rating, thermal gravimetric and differential thermal analysis. The results indicate that the EVA/EG and EVA/EG/APP composites exhibit a better flame retardancy. Addition of EG at a mass fraction of 30% leads LOI of 70EVA/30EG composite improved to 28.7%. Even more, the synergistic effect between EG and APP improves the LOI of 70EVA/10APP /20EG composite to 30.7%. This synergistic efficiency is attributed to the formation of compact and stable layer‐structure, and the prepared EG can make EVA composite reach the UL‐94 level of V‐0. POLYM. COMPOS., 36:1407–1416, 2015. © 2014 Society of Plastics Engineers     

Thermal behavior and electrical conductivity of ethylene vinyl acetate copolymer/expanded graphite nanocomposites: Effects of nanofiller size and loading

Nanocomposites based on ethylene‐vinyl acetate (EVA) copolymer and expanded graphite (EG) were prepared using direct and two‐step melt‐mixing processes. The effect of elongational flow on the dispersion of EG nanoparticles in the polymeric matrix was investigated by thermal analysis and electrical conductivity measurements. Two types of EG having different aspect ratio were applied to prepare the nanocomposites. The nanocomposites containing higher aspect ratio nanofiller have shown higher values of transition temperature (Tg) and a stronger reinforcing effect of EG. The evaluation of EVA crystallization behavior has clarified that both the EG loading and particle size have noticeably influenced the crystallization characteristics of EVA. The restrictions imposed by nanoparticles on molecular motion and, correspondingly, the crystal growth stage have been the most notable effect of EG nanopartciles on the EVA crystallization behavior. Moreover, the presence of EG nanofiller has intensified the formation of a second‐type of EVA crystals during long annealing time. Furthermore, chemically crosslinking of EVA chains has led to the formation of smaller crystals with more uniform size. J. VINYL ADDIT. TECHNOL., 22:51–60, 2016. © 2014 Society of Plastics Engineers     

A facile method for preparation of PGS@ZB‐N and gas‐sol alternating synergistic effect for fire resistance of EVA

Through the simple precipitation of palygorskite (PGS) by zinc borate (ZB) (to make PGS@ZB) and the decoration of PGS@ZB by dodecylamine (N), a novel organic‐inorganic@inorganic hybrid flame retardant of PGS@ZB‐N was prepared and was incorporated with ethylene vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@ZB‐N were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM), and it was confirmed that the PGS@ZB‐N hybrid had been successfully prepared. The flame retardancy and burning behavior of EVA/PGS@ZB‐N/EG (EG = expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 (by the vertical burning test), and cone calorimeter test (CCT) characterizations. The prepared EVA/PGS@ZB‐N/EG composite obtained an LOI value of 41.2% with the addition of 30 wt% PGS@ZB‐N/EG. It was found that EVA/PGS@ZB‐N/EG was protected through a gas phase and condensed phase alternating synergistic effect mechanism.     

Effect of surfactant and electron treatment on the electrical and thermal conductivity as well as thermal and mechanical properties of ethylene vinyl acetate/expanded graphite composites

This study presents an investigation of the electrical and thermal conductivities of composites based on an ethylene vinyl acetate (EVA) copolymer matrix and nanostructured expanded graphite (EG). To improve the EG dispersion in EVA, EG sheets were modified by treating them with the anionic surfactant sodium dodecyl sulphate (SDS) in water. The modified SDS‐EG platelets, after being filtered and dried, were melt‐mixed with EVA to prepare the composites. Finally, both EVA/EG and EVA/SDS‐EG composites were subjected to 50 kGy electron beam (EB) irradiation. SEM images confirm that the irradiated EVA/EG samples had improved interfacial adhesion, while the irradiated EVA/SDS‐EG samples showed even better interfacial adhesion. The gel contents of the irradiated samples without and with SDS treatment increased with increase in EG loading. The EVA/EG composites exhibited a sharp transition from an insulator to a conductor at an electrical percolation threshold of 8 wt %, but with SDS‐EG the electrical conductivity was extremely low, showing no percolation up to 10 wt % of filler. The EB irradiation had no influence on electrical conductivity. The thermal conductivity linearly increased with EG content, and this increase was more pronounced in the case of SDS‐EG, but decreased after EB irradiation. The thermal properties were little influenced by EB irradiation, while better polymer–filler interaction and better filler dispersion as a result of SDS treatment, and the EB irradiation initiated formation of a cross‐linked network, had a positive effect on the tensile properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42396.     

The effect of expanded graphite on the physical properties of conductive EVA/wax phase change blends for thermal energy storage

A study of the morphology, dynamic mechanical, impact, and tensile properties of ethylene vinyl acetate copolymer (EVA)/expanded graphite (EG) and EVA/wax/EG composites is presented. The composites were prepared by melt blending. The EVA/EG composites showed ductile behavior, while brittle behavior was observed in the presence of wax. A finer dispersion of EG was observed in the matrix when wax was present. The storage modulus of the EVA/wax/EG composite was higher than that of the EVA/EG composite, which is ascribed to a better interaction between the EVA and the wax‐covered EG that significantly reduced the EVA chain mobility. The composites showed a decrease in impact strength with increasing EG and wax contents. There was a significant difference in the elongation at break between the EVA/EG and EVA/wax/EG composites, and little change in Young's modulus of EVA in the presence of EG and with increasing EG content. However, Young's modulus of the EVA/wax blends increased in the presence of and with increasing EG content. In all the investigated samples containing EVA and wax, irrespective of the EG content, the stress at break decreased with an increase in wax content. POLYM. COMPOS., 37:3025–3032, 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     

The effect of expanded graphite on the thermal stability,latent heat,and flammability properties of EVA/wax phase change blends

This article reports on the morphology, melting and crystallization behavior, thermal stability, flammability and thermal conductivity of shape‐stabilized phase‐change materials (PCM) for thermal energy storage, based on a soft Fischer–Tropsch paraffin wax, the PCM, blended with ethylene vinyl acetate (EVA). These immiscible blends were melt‐mixed with expanded graphite (EG) (up to 9 wt%) to improve the thermal conductivity and flame resistance of the material. It was observed that the EG particles agglomerate in the absence of wax, but disperse much better in the EVA/wax blend, probably because the wax penetrates in between the EG layers (there seems to be a better interaction between wax and EG than between EVA and EG) and separates the layers, giving rise to smaller and better dispersed EG particles. This gives rise to better thermal conductivity and flame resistance. There were no significant changes in the melting temperature of EVA in the EVA/EG composites, while the crystallinities of EVA were observably lower in the presence of EG. The thermal stability and flammability results show an increase in thermal stability and flame resistance of EVA, which further improved in the presence of wax because of the smaller and better dispersed EG particles in these systems. POLYM. ENG. SCI., 55:1255–1262, 2015. © 2015 Society of Plastics Engineers