MWCNTs/PS复合材料导电性能及导电行为研究

多壁碳纳米管(MWCNTs)与聚苯乙烯(PS)熔融共混,制备试样,部分试样进行热处理。通过导电性能的测试研究了不同测试温度对MWCNTs/PS非结晶复合材料电性能及其导电行为的影响;通过SEM观察了该复合材料的表面形貌。研究结果表明:随着MWCNTs加入量的增加,MWCNTs/PS的体积电阻率(ρ)呈现下降趋势;当MWCNTs加入量达到8.0%,复合材料的ρ降到102数量级;120℃热处理后MWCNTs(10.0%)/PS复合材料的ρ比未经热处理的ρ下降近1个数量级;MWCNTs(10.0%)/PS 1-3型复合材料的PTC行为不明显,但5.0%MWCNTs/PS1-3型复合材料的PTC效应明显,在150℃以后,出现NTC效应。     

多壁碳纳米管表面羧基化及其阻燃ABS的性能

采用硝酸氧化/低温等离子处理两步法,将多壁碳纳米管(MWCNTs)羧基化(MWCNTs-COOH),以改善其在ABS基体中的分散性。通过熔融共混的方法制备不同组分ABS/MWCNTs-COOH复合材料。利用红外、拉曼分析、扫描电镜对改性修饰后MWCNTs结构进行研究;利用扫描电镜、热重分析、极限氧指数、残炭分析、力学性能测试对ABS/MWCNTs-COOH复合材料分散性、热性能、阻燃性能、力学性能进行研究。实验结果表明,MWCNTs羧基化改性后提高了在ABS基体材料中的分散性;当MWCNTs-COOH含量为1%时,复合材料初始分解温度和最大分解温度分别提高了22.69℃和27.90℃,热稳定性提高,同时复合材料力学性能也得到改善,拉伸强度提高了18.3%;极限氧指数和残炭测试表明,MWCNTs-COOH加入提高了复合材料的极限氧指数,MWCNTs-COOH在复合材料燃烧过程中,会在材料表面形成网络状炭层,提高复合材料的阻燃性能。     

基于TPP/E618体系的PS阻燃性能研究

TPP(芳香族磷酸酯)/环氧树脂在PS(聚苯乙烯)燃烧过程中具有催化成碳作用,并可减少可燃蒸汽的产生和释放,达到PS阻燃的目的.相对于PS、TPP/E618(环氧树脂)的协同比例为30/5(质量比)时阻燃效果最好,PS的氧指数可达到39.4%;TPP/E618协同比例为20/5时得到PS最佳的力学性能和阻燃性能.试样燃烧符合UL 94 V-1评价标准.     

PS/MCA复合材料的阻燃性能研究

将聚苯乙烯(PS)树脂与氰脲酸三聚氰胺(MCA)直接进行熔融复合制备PS/MCA复合材料,通过X射线衍射对复合材料微观结构进行了分析,用水平燃烧试验、垂直燃烧试验、氧指数试验和高温处理试验研究了复合材料的燃烧性能.结果表明:复合材料在制备和加工过程中MCA微观结构并没有发生变化,因此复合材料中MCA的阻燃机理不变;MCA的引入使PS的阻燃性能得到明显改善,随着MCA含量增加,复合材料的发烟和滴落减少,氧指数增大,水平燃烧级别提高;MCA用量为20份时复合材料能够自熄,40份时,复合材料的氧指数从17.5%增加至20.8%,水平燃烧斌验可达到FH-1级.研究发现,MCA的引入并不能够使PS基体成炭,其对PS的阻燃机理主要是气相稀释和对PS基体的冷却效应.     

PS/PP/Nano-TiO_2复合材料的制备及性能研究

采用熔融共混法制备了聚苯乙烯/聚丙烯/纳米二氧化钛(PS/PP/nano-TiO2)复合材料,并对该复合材料的力学性能、热稳定性和微观结构进行了研究。结果表明:随着nano-TiO2用量的增加,PS/PP/nano-TiO2复合材料的亲水性和热稳定性明显提高,冲击和拉伸强度均先增大后减小,其中当nano-TiO2用量为2%时,复合材料的力学性能均达到峰值;此外微观分析结果显示,nano-TiO2的引入改善了PS与PP的相容性。     

MWCNTs对LGFPP/红磷阻燃体系性能的影响

用熔融共混法制备了长玻纤增强聚丙烯/红磷/多壁碳纳米管(LGFPP/RP/MWCNTs)复合材料。氧指数(OI)测试结果表明:MWCNTs的加入提高了LGFPP/RP阻燃体系的阻燃性能。在LGFPP/RP阻燃体系中添加1%的MWCNTs后,LGFPP/RP/MWCNTs复合材料的OI提高到23.4%。热失重分析(TGA)研究表明:在氮气气氛下MWCNTs提高了LGFPP/RP阻燃体系的热稳定性。1%的MWNTs可使LGFPP/RP阻燃体系的热分解起始温度提高12.4℃。力学性能测试结果表明:MWCNTs的加入提高了LGFPP/RP阻燃体系的力学性能。在LGFPP/RP阻燃体系中添加1%的MWNTs后,LGFPP/RP/MWCNTs复合材料的拉伸强度、弯曲强度和冲击强度分别提高了3.2%、12.3%和7.7%。     

含磷阻燃剂与硼酸锌协效阻燃聚酰胺11的研究

以二乙基次磷酸铝(DEAP),三聚氰胺磷酸盐(MP)和硼酸锌(ZB)为阻燃体系对聚酰胺11(PA11)进行阻燃改性。通过极限氧指数、垂直燃烧测试(UL 94)和锥形量热仪以及热失重分析研究了阻燃体系构成对复合材料阻燃性能与热稳定性的影响,采用红外光谱对残炭成分进行分析。结果表明,添加20 % DEAP时,复合材料的极限氧指数达到28 %,UL 94 测试达到V-2级, 添加13 %DEAP/7 %MP和12.5 %DEAP/7 %MP/0.5 %ZB时,复合材料的极限氧指数可达到29 %,UL 94测试达到V-1级;DEAP对PA11的热释放速率及总热释放量有显著的控制作用,MP和ZB的加入进一步提升其阻燃性能;DEAP/MP/ZB协同使用时残炭的膨胀性、强度及致密性最好;ZB的加入使残炭中的羟基含量增加,应该是ZB的分解所致。     

聚苯乙烯/次磷酸铝复合材料的制备及阻燃性能

采用熔融共混的方法制备了聚苯乙烯/次磷酸铝(PS/AHP)复合材料。采用热重分析测试研究了复合材料的热稳定性,通过极限氧指数、垂直燃烧和微型量热测试研究了复合材料的阻燃性能。研究表明:次磷酸铝(AHP)有效提高了PS/AHP复合材料的阻燃性能,当次磷酸铝添加量为20%时,复合材料可以达到UL-94 V-0级别,极限氧指数为24.0%;热重分析研究表明次磷酸铝的加入可以延缓聚苯乙烯分子链的降解,提高复合材料高温成炭率;微型量热(MCC)测试表明PS/AHP30与纯PS相比,其热释放速率峰值和总热释放分别下降40.5%和18.9%。     

偏硼酸钡在红磷阻燃增强尼龙中的应用研究

采用熔融共混法制备了尼龙(PA6、 PA66)/红磷母粒/玻纤/偏硼酸钡复合材料。通过力学性能测试、 UL94垂直燃烧法、灼热丝试验、氧指数(LOI)等研究了偏硼酸钡对复合材料力学性能和阻燃性能的影响。力学性能测试结果表明,加入偏硼酸钡不影响复合材料的强度,但会降低缺口冲击强度;阻燃测试结果表明,偏硼酸钡在红磷阻燃尼龙中有良好的协效作用,可使复合材料阻燃性能达到UL94 V-0 (1.6 mm)等级,且灼热丝起燃温度(GWIT)可达750℃;氧指数测试结果表明,加入偏硼酸钡能有效提高复合材料的氧指数。     

阻燃型氢氧化镁表面改性及与PS复合效果研究

采用硬脂酸对氢氧化镁[ Mg(OH)2]施行湿法有机化表面改性,将改性后的氢氧化镁加入到聚苯乙烯(PS)中混炼制备无机阻燃型PS - Mg(OH)2复合功能材料.通过X射线衍射(XRD)、红外光谱(FT-IR)、热分析(TG- DSC)和扫描电镜(SEM)等测试手段对氢氧化镁的表面改性机理进行综合分析,通过SEM以及氧指数、拉伸强度等测试方法对PS-Mg(OH)2复合材料的复合效果及性能进行测定.研究结果表明:硬脂酸对氢氧化镁的表面改性本质上是一个化学吸附过程;改性后的氢氧化镁颗粒与PS基体的相容性得到显著改善,复合材料的氧指数(OI)显著提高.当氢氧化镁添加量为PS质量的40％～ 60％时,OI达到25％左右,且材料的力学性能变化不大.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.