新型膨胀阻燃聚丙烯结构与性能研究

采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了具有良好阻燃性能的膨胀阻燃聚丙烯(PP).研究了MPP/PEPA质量比和Cr2O3用量对PP阻燃和力学性能的影响.结果表明,MPP/PEPA质量比为3:2时,复配效果最好;添加少量的Cr2O3即可显著提高材料的阻燃性能.当MPP,PEPA,Cr2O3添加质量分数分别为12%,8%和2%时,阻燃PP的氧指数高达31.5%,且具有较好的力学性能.热失重(TGA)、扫描电镜(SEM)和Kissinger动力学分析表明添加Cr2O3可催化MPP/PEPA间的酯化反应,促进材料成炭,减缓材料的热降解速率,提高材料隔热、隔氧能力.     

ZnO对MPP/PEPA阻燃PP性能的影响

采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备具有良好阻燃性能的无卤阻燃PP.研究MPP/PEPA质量比和ZnO添加量对PP阻燃性能的影响.结果表明:MPP/PEPA质量比为3:2时,复配效果最好;添加少量的ZnO可以显著提高材料的阻燃性能;当MPP/PEPA/znO添加量分别为12%、8%和1%时,阻燃PP的极限氧指数达29.5%.TGA结果表明:添加ZnO可以起催化MPP/PEPA酯化,促进成炭的作用.SEM分析表明:ZnO可以起到稳定炭层.增加炭层厚度的作用.     

Cr2O3增效阻燃PP的制备及其热降解性能的研究

以Cr2O3为阻燃协效剂,采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了具有良好阻燃性能的无卤阻燃PP.研究了Cr2O3添加量对PP阻燃性能和协效作用的影响.结果表明:添加少量的Cr2O3可显著提高PP的阻燃性能.当MPP/PEPA/Cr2O3添加量分别为12%、8%和2%时,阻燃PP的氧指数高达31.5%.TGA、FTIR和Flynn-Wall法热降解活化能分析结果表明:添加Cr2O3可以起催化MPP/PEPA酯化,促进成炭的作用,使PP的活化能提高.     

TiO2对MPP／PEPA阻燃PP性能的影响

采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了无卤阻燃聚丙烯(PP).研究了MPP/PEPA质量比和TiO2添加量对PP阻燃性能的影响.结果表明:MPP/PEPA质量比为3∶2时,复配效果好;添加少量的TiO2可以显著提高PP的阻燃性能.当MPP/PEPA/TiO2添加质量分数分别为12%,8%和1%时,阻燃PP的氧指数高达31.5%.热失重分析结果表明:添加TiO2可以起催化MPP/PEPA酯化,促进成炭的作用.扫描电镜形貌观察表明,TiO2可以起到稳定炭层,增加炭层厚度作用.     

ZnO对PP/MPP/PEPA膨胀阻燃体系的协同作用

以ZnO为阻燃协效剂,采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了具有良好阻燃性能的无卤阻燃PP。研究了ZnO用量对PP阻燃性能和协效作用的影响。结果表明:添加少量的ZnO即可显著提高PP的阻燃性能。当MPP、PEPA和ZnO添加量分别为12%、8%和1%时,阻燃PP的氧指数高达29.5%。TGA、FTIR分析和体式显微镜观测结果表明:添加ZnO可以催化MPP/PEPA间的酯化反应,促进体系成炭,形成更致密的炭层,从而提高材料的阻燃性能。     

MnO2对MPP/PEPA阻燃PP性能的影响

采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂以及MnO2为阻燃增效剂,制备了具有良好阻燃性能的无卤阻燃聚丙烯(PP),研究了MnO2用量对PP阻燃和力学性能的影响.结果表明,添加少量的MnO2即可显著提高材料的阻燃性能;当MPP,PEPA,MnO2添加质量分数分别为12%,8%和2%时,材料的氧指数(LOI)高达32.0%,并具有较好的力学性能.Kissinger动力学分析结果表明,添加MnO2可以催化MPP/PEPA问的酯化反应,改变材料的热降解途径.扫描电子显微镜(SEM)和热重分析(TGA)表明,MnO2可以起到稳定炭层,促进成炭、增加炭层厚度作用.     

MPP/PEPA阻燃PP的制备及其性能研究

采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了具有良好阻燃性能的无卤阻燃PP.研究了各组分质量比及用量对PP阻燃性能的影响.结果表明:MPP/PEPA质量比为3∶2.且总量为20%时,可以制备氧指数为27%的阻燃PP,垂直燃烧等级为V-O.TGA结果表明:MPP/PEPA的复配可以延缓PP的分解,且提高成炭率.     

纳米SiO2对PP/MPP/PEPA膨胀阻燃体系的协同作用

以纳米SiO,为阻燃协效剂,采用多聚磷酸蜜胺(MPP)和茏状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备具有良好阻燃性能的无卤阻燃聚丙烯(PP).研究纳米SiO2用量对PP阻燃性能和协效作用的影响.结果表明:添加少量的纳米SiO2可提高PP的阻燃性能;当纳米SiO2添加量为1%时,阻燃PP的氧指数达28.5%.TGA和FTIR分析及SEM和体式显微镜观测结果表明:添加少量的纳米SiO2可促进体系成炭,稳定炭层,从而提高材料的阻燃性能.     

纳米SiO_2对MPP/PEPA阻燃PP性能的影响

采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)为复配阻燃剂,制备了无卤阻燃聚丙烯(PP)。研究了MPP/PEPA质量比和纳米SiO2用量对PP复合材料阻燃性能和力学性能的影响。结果表明:当MPP:PEPA=3:2时,协效阻燃效果最好,添加少量的纳米SiO2即可提高PP复合材料的阻燃和力学性能;当MPP、PEPA、纳米SiO2添加量分别为12%、8%和1%时,阻燃PP的氧指数达28.5%,并具有较好的力学性能。TGA和EDX结果表明:添加少量纳米SiO2可以催化MPP/PEPA间的酯化反应,促进PP复合材料成炭,保留更多的磷。SEM分析表明:添加少量的纳米SiO2可稳定炭层和加固泡孔,增强炭层隔热隔氧的能力。     

KH550改性PEPA对PP/IFR体系阻燃、耐水和力学性能的影响

利用硅烷偶联剂KH550对季戊四醇磷酸酯(PEPA)进行表面改性,得到Si-PEPA,将其与三聚氰胺聚磷酸盐(MPP)复配成膨胀型阻燃剂(IFR)对聚丙烯(PP)进行阻燃改性。研究了KH550改性PEPA对PP/IFR体系阻燃、耐水和力学性能的影响。利用极限氧指数(LOI)仪、垂直燃烧(UL94)仪、锥形量热(CONE)仪对阻燃PP的燃烧性能进行测试,结果表明,当IFR的添加量为20%时,PP/MPP/Si-PEPA体系可以达到UL94 V-0级,氧指数达到32.5%,最大热释放速率(PHRR)和总热释放量(THR)都较PP/MPP/PEPA体系有明显降低。热重分析(TGA)显示,经KH550处理后,PP/IFR材料的热稳定性显著提高。经70℃热水浸泡72 h后,PP/MPP/Si-PEPA材料仍然可以通过UL94 V-1级。同时,KH550对PEPA的表面处理也提高了PP/IFR材料的力学强度。     

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.