碳纳米管的表面修饰对PA6的影响

利用多巴胺(DOPA)对多壁碳纳米管(MWNTs)进行表面改性后得到MWNTs-PDA,通过熔融共混的方法制备MWNTs-PDA/DBDPE/Sb_2O_3/PA6复合材料。通过傅里叶红外变化光谱(FTIR)和极限氧指数(LOI)、垂直燃烧(UL-94)、热失重分析(TGA)和力学性能测试等方法分别研究了MWNTs的表面修饰情况和不同浓度多巴胺修饰的MWNTs对MWNTs-PDA/DBDPE/Sb_2O_3/PA6复合材料阻燃性能、热稳定性能及力学性能的影响。结果表明:随着多巴胺浓度的增加,复合材料的阻燃性能随之逐渐增大,热稳定性能变化不大,力学性能则呈先增大后减小的趋势。当多巴胺浓度为3 g/L时,复合材料的力学性能最佳,拉伸强度、弯曲强度和冲击强度分别为73.84、89.96 MPa、9.23 k J/m~2。     

不同转速下制备的疏松型纳米氢氧化镁对LLDPE性能的影响

采用气泡液膜法得到了不同搅拌器转动速度下制备的疏松型纳米氢氧化镁（LNMH）,用激光散射粒径分析仪研究了转速对LNMH粒径及粒径分布的影响,通过常规力学性能测试、极限氧指数测试（LOI）和锥形量热仪测试（CONE）研究了不同转速下制备的LNMH对线型低密度聚乙烯（LL-DPE）性能的影响。结果表明：在实验条件下,转速为10000r/min时LNMH的平均粒径最小,粒径分布最窄;不同转速下制备的LNMH对LLDPE拉伸强度、氧指数、平均热释放速率、点燃时间的影响不大,但对LLDPE的弯曲强度、弯曲模量、冲击强度、最大热释放速率和燃烧质量损失率有较大影响;实验条件下,以2000r/min制备的LNMH可使LLDPE的拉伸强度、冲击强度及阻燃性能均达到较优值。     

氢氧化镁/红磷填充LLDPE的阻燃性及力学性能研究

以氢氧化镁(MH)为主阻燃剂、红磷为辅助阻燃剂,制备了一种无卤、低烟线型低密度聚乙烯(LLDPE)阻燃材料,利用氧指数(OI)和力学性能测试探讨了阻燃剂复配对该阻燃LLDPE力学性能及阻燃性能的影响,并通过热重(TG)和差示扫描量热分析(DSC)考察了材料的结构和性能。结果表明:随着红磷用量的增大,阻燃LLDPE的阻燃性能和拉伸强度明显提高,但缺口冲击强度和断裂伸长率有所下降;同时材料的结晶度下降、热稳定性提高。     

PP/IFR/水滑石阻燃复合材料的研究

通过极限氧指数(LOI)测定、垂直燃烧试验和锥型量热分析,研究了结晶性聚磷酸铵(APP)和三嗪成炭剂组成的膨胀型阻燃剂(IFR)对聚丙烯(PP)的阻燃作用,并考察了复合水滑石和对IFR的表面处理对阻燃PP的阻燃性能、热稳定性和力学性能的影响。结果表明:该IFR对PP具有良好的阻燃作用,当APP与三嗪成炭的质量比为3∶1,IFR质量分数为20%时,阻燃PP的LOI就达28.0%,阻燃等级达V-0,复合少量水滑石并对IFR进行表面处理不影响复合材料阻燃性能,但改善了阻燃PP的热稳定性和力学性能。     

多聚芳基磷酸酯与乙烯基硅树脂复合改性聚乳酸研究

将多聚芳基磷酸酯(PX-220)和微米级乙烯基硅树脂微球(VSR)加入到聚乳酸(PLA)中,通过红外测式、扫描电镜、氧指数、垂直燃烧测试、热重分析和力学性能测试等研究方法研究了PX-220与VSR对PLA阻燃性能、热稳定性及力学性能的影响。结果表明,只添加15%PX-220能使材料的极限氧指数(LOI)提高至33%,但力学性能下降明显;当9%PX-220与6%VSR并用时,材料的(LOI)为30.5%,初始分解温度提高了10℃,且拉伸强度达到最大值,材料的综合性能达到最佳。     

聚丙烯的高性能化研究

研究了玻璃纤维、线型低密度聚乙烯(LLDPE)、三元乙丙橡胶(EPDM)对聚丙烯(PP)流变性能、力学性能、热性能和硬度的影响。结果表明:玻璃纤维的加入使PP的硬度及拉伸强度增大,热变形温度提高;LLDPE与EPDM使PP的冲击强度提高;玻璃纤维、LLDPE、EPDM复配可综合提高PP的力学性能、硬度及热变形温度。     

无卤膨胀阻燃长玻纤增强聚丙烯性能研究*

利用无卤膨胀阻燃剂(IFR)阻燃长玻纤增强聚丙烯(LGFPP)复合材料,研究IFR的添加量对复合材料阻燃性能、热稳定性能、燃烧性能和力学性能的影响。结果表明,加入IFR使复合材料燃烧后生成了具有阻燃作用的炭层,显著提高了复合材料的阻燃性能。随IFR添加量的增加,复合材料的极限氧指数(LOI)逐渐提高,热释放速率峰值及其平均值、总热释放速率和生烟速率逐渐降低,力学性能略有下降。当IFR质量分数为20%时,复合材料的LOI和垂直燃烧等级分别达到了24.4%和UL 94 V-0级。     

尼龙增强无卤阻燃聚丙烯复合材料的研究

研究了尼龙6(PA6)对红磷、氢氧化镁复配阻燃聚丙烯(PP)复合材料力学性能的影响.采用氧指数(LOI)和热失重法(TGA)分析了PA6对该无卤阻燃PP体系的燃烧及热降解行为的影响.结果表明:PA6的加入提高了该体系的力学性能和热稳定性,并对该无卤阻燃体系具有良好的协效作用.PA6的用量为12份时,该体系的拉伸强度提高了20.5%,分解温度提高了15℃,同时获得了良好的阻燃性.     

不同氢氧化镁对LLDPE性能的影响

采用气泡液膜法制备了疏松型纳米氢氧化镁（LN-MH）,将其和不同氢氧化镁分别填充到线型低密度聚乙烯（LLDPE）中制得复合材料。通过常规力学性能测试、TG、极限氧指数（LOI）和锥形量热仪（CONE）研究了疏松型氢氧化镁（LN-MH）和普通氢氧化镁（C-MH）对LI。DPE性能的影响。结果表明：LN-MH／LLDPE复合材料的拉伸强度、弯曲强度和氧指数均比C-MH／LLDPE有显著的提高;与C-MH相比,LN-MH对LLDPE有更好的阻燃效果和成炭作用,但热稳定性稍差。     

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%。     

The water resistance of surface-modified APP with melamine-TDI in LLDPE

Ammonium polyphosphate (APP) which was surface-modified with melamine (MA) and 2,4-toluene diisocyanate(TDI) in turn was used as flame-retardant in linear low density polyethylene (LLDPE). Its water resistance in LLDPE was respectively evaluated with its water-solubility, the limited oxygen index(LOI) changes and P content changes of the LLDPE which being immersed in water 180 h at room temperature. Its compatibility with LLDPE was observed with scanning electron microscope (SEM). As a result, the water-solubility of the surface-modified APP reduced. When the LLDPE was treated with surface-modified APP, its LOI and P content changes were less than that treated with unmodified-APP after being immersed in water. The surface-modified APP was better compatible with LLDPE than unmodified APP.     

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     

Thermal Properties and Flammability of Ethylene-Vinyl Acetate Copolymer/Montmorillonite/Polyethylene Nanocomposites with Flame Retardants

Ethylene-vinyl acetate copolymer (EVA)/montmorillonite (MMT) composite was blended with a linear low density polyethylene (LLDPE). X-ray diffraction and transmission electron microscopy (TEM) image of the EVA/MMT composite are in support of an intercalated with partially delaminated nanocomposite. The tensile strength of the nanocomposite is about 20% higher than that without layered silicates, MMT. Furthermore, the incorporation of MMT into polymer blend delays the main thermo-oxidative degradation. Cone calorimeter test points out that the addition of layered silicates into the pristine EVA/LLDPE blend or the blend with a low smoke non-halogen (LSNH) fire retardants, aluminum trihydroxide, and antimony trioxide, can reduce the maximum heat release rate by 30–40%. The smoke suppressing effect of layered silicates is only observed in the nanocomposite containing flame retardants. According to the limiting oxygen index (LOI) data and cone calorimeter test, the addition of the nanodispersed layered silicate and LSNH flame retardants to the EVA/LLDPE exhibits a synergistic effect on the flame retardancy and smoke suppression.     

Effects of the processing conditions and blending with linear low-density polyethylene on the properties of low-density polyethylene films

Effects of blending low-density polyethylene (LDPE) with linear low-density polyethylene (LLDPE) were studied on extrusion blown films. The tensile strength, the tear strength, the elongation at break, as well as haze showed more or less additivity between the properties of LDPE and LLDPE except in the range of 20–40% where synergistic effects were observed. The LLDPE had higher tensile strength and elongation at break than did the LDPE in both test directions, as well as higher tear strength in the transverse direction. The impact energies of the LLDPE and the LDPE were approximately the same, but the tear strength of the LLDPE was lower than that of LDPE in the machine direction. The comparative mechanical properties strongly depend on the processing conditions and structural parameters such as the molecular weight and the molecular weight distribution of both classes of materials. The LLDPE in this study had a higher molecular weight in comparison to the LDPE of the study, as implied from its lower melt flow index (MFI) in comparison to that of the LDPE. The effects of processing conditions such as the blow-up ratio (BUR) and the draw-down ratio (DDR) were also studied at 20/80 (LLDPE/LDPE) ratio. Tensile strength, elongation at break, and tear strength in both directions became equalized, and the impact energy decreased as the BUR and the DDR approached each other.     

Interface modification and characterization in linear low-density polyethylene highly loaded with aluminium hydroxide

Fire-retardant linear low-density polyethylene (LLDPE) composites were prepared by combining this polymer with uncoated and surface treated forms of aluminum hydroxide (Al(OH)₃). The poor toughness and ductility of polyethylene highly filled with Al(OH)₃ can be significantly improved by addition of a small amount of silicon oil. It is found that silicon oil improves elongation at break of the composite remarkably, but this is accompanied by the deterioration of tensile strength. Silane crosslinked polyethylene substituting for polyethylene as the matrix in Al(OH)₃-filled polyethylene improves the tensile strength of the composite. Fractured surface analysis and limiting oxygen index (LOI) of the composites were also studied. Possible mechanisms accounting for these effects are discussed.     

Synergistic effect of intumescent flame retardant and zinc borate on linear low-density polyethylene

A series of novel intumescent flame retardant (IFR) based on melamine, neopentyl glycol, and aluminum diethylphosphinate were prepared and tested. In addition, the synergistic effect of the novel IFR and zinc borate (ZB) on the flame retardancy of LLDPE composites was investigated. The structures of novel IFR and ZB were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The limiting oxygen index (LOI) increased from 19.3% for the pure LLDPE to 27% for the 25 wt% IFR/5 wt% ZB composites and the composites achieved the desired V-0 rating in the UL-94 test. Thermogravimetric analysis showed that the addition of IFR/ZB reduced the pyrolysis rate of the LLDPE composites at high temperatures and increased the amount of the char residues, and the char residue of LLDPE-5 reached 12.1 wt% at 700°C. Cone calorimetry (CCT) data showed that the peak of total heat release, heat release rate, and fire growth index were comparatively reduced, indicating that the addition of IFR/ZB decreased the fire hazard of LLDPE composites. The formation of a compact and thermally stable char layer on the surfaces of LLDPE composites was revealed from the scanning electrone microscopy images and digital photographs of the char residue after the CCT tests.     

The use of Isocyanate as a Bonding Agent to Improve the Mechanical Properties of Polyethylene-Wood Fiber Composites

Abstract

Chemithermomechanical pulp (CTMP) of aspen was used as a filler in high density (HDPE) and linear low density (LLDPE) polyethylenes. To improve the bonding between the fiber and polymer, different chemical treatments of the fiber a) treatment with different isocyanates b) coating with maleic anhydride was carried out. Composites with isocyanate treated wood fibers produced higher tensile strength compared to untreated fiber composites. But when compared to diisocyanate, the polyisocyanate treated fibers produced higher gain in strength. HDPE or LLDPE filled with maleic anhydride coated CTMP aspen fibers showed a slight decrease in strength with the increase in filler concentration. Tensile modulus generally increased with filler loading and was not much affected by fiber treatment.     

Influence of modified polyethylene compatibilizer on filler dispersion and flammability characteristics of linear low density polyethylene/cyclo olefin copolymer blends containing flame retardant combinations

In this study, the combination of organomodified montmorillonite (MMT), magnesium hydroxide (MDH), graphene oxide (GO) and expandable graphite (EG) as intumescent flame retardant for Linear Low-Density Polyethylene-Cyclo-Olefin Copolymer (LLDPE/COC) blends has been investigated. An amine-alcohol modified polyethylene (PEgDMAE) was used as compatibilizer. Limiting oxygen index (LOI), cone calorimeter determinations and flammability test (Underwriters Laboratory – UL-94) were used to evaluate the flame retardant properties. The structural characterization was measured by FTIR and scanning electron microscopy (SEM). The mechanical properties were also evaluated by Dynamic-mechanical analysis (DMA). The PEgDMAE compatibilizer enhanced the filler dispersion and increased the LOI to 22% for clay, 23% for GO and 26.5% for EG composites. The results indicated that the combination of each additive makes it possible to reduce the total Magnesium hydroxide filler content from 55 to 20% to achieve the flame retardant requirements. The flame retardant and mechanical properties of LLDPE/COC blends increased to a higher extent when using the combination of these additive fillers.