PA6/SMA/N-PMI复合材料的热性能和力学性能研究

采用熔融共混法制备了聚酰胺6/苯乙烯-马来酸酐共聚物/N-苯基马来酰亚胺复合材料(PA6/SMA/N-PMI),利用差示扫描量热法(DSC)、热重分析(TGA)及力学性能测试等手段研究了N-PMI用量对PA6/SMA/N-PMI复合材料熔融结晶行为、热性能以及力学性能的影响。结果表明:复合材料的最大分解温度较纯PA6有所提高;随着N-PMI用量的增加,复合材料的结晶温度、结晶度以及熔融焓均逐渐降低;当N-PMI用量为15份时,复合材料的弯曲强度、弯曲模量、拉伸强度以及热变形温度均达到最大值,分别为101.0、2 892、71.6 MPa以及56.6℃,较纯PA6分别提高了11.0%、21.3%、3.1%和10.0%。     

PA6/SMA共混物的热性能及力学性能

采用熔融共挤制备了尼龙6(PA6)/苯乙烯-马来酸酐共聚物(SMA)共混物,利用差示扫描量热法、热重分析、热变形温度测试及力学测试等手段研究了SMA含量对PA6/SMA共混物熔融结晶行为、热性能及力学性能的影响。结果表明,SMA的加入使共混物的熔融温度、结晶温度及结晶度降低;当SMA用量为5份时,共混物最大分解温度较纯PA6提高了33.5℃;共混物的弯曲强度和弯曲模量在SMA用量为2.5份时达到最大,分别为115.0、3 227 MPa,比纯PA6提高了26.4%、37.0%,拉伸强度在SMA用量为5份时达到最大87.5 MPa,比纯PA6提高了25.9%。     

PA6/SMA/N-PMI共混物的制备及其性能研究

采用熔融共混法制备了尼龙6/苯乙烯-马来酸酐共聚物/N-苯基马来酰亚胺共混物(PA6/SMA/N-PMI),并利用DSC、TGA及力学性能测试等手段研究了SMA用量对PA6/SMA/N-PMI共混物熔融结晶行为、热学性能以及力学性能的影响。结果表明,共混物的最大分解温度较纯PA6有较大提高;SMA用量的增加,共混物的结晶温度、结晶度以及熔融焓均先降低再升高;当SMA用量为5份时,共混物的弯曲强度、弯曲模量以及热变形温度均达到最大值,分别为113.8、3 053 MPa及61.3℃,较纯PA6分别提高了25.1%、28.0%及19.0%;拉伸强度在SMA用量为7.5份时达到最大值81.4 MPa,较纯PA6提高了17.1%。     

新型烷基次膦酸铝对PA6/LGF复合材料性能影响

通过热重分析、极限氧指数及力学性能测试分析不同含量的二异丁基次膦酸铝(APBu)对PA6/LGF复合材料热性能、阻燃性能、力学性能的影响。结果表明,随着二异丁基次膦酸铝含量的增加,PA6/LGF/APBu复合材料的初始分解温度、最大分解温度均较PA6/LGF复合材料逐渐降低,而最大分解速率逐渐降低,复合材料成炭率略有增加。而且,PA6/LGF/APBu复合材料随着二异丁基次膦酸铝含量的增加其阻燃性能逐渐增强,但拉伸强度和弯曲强度呈逐渐降低趋势,而冲击性能保持超韧状态。     

PA6/长玻纤/氯化钙复合材料结构与性能研究

采用熔融挤出工艺制备了尼龙(PA)6/长玻璃纤维(LGF)/氯化钙复合材料;研究了LGF含量对复合材料力学性能、维卡软化点、结晶性能的影响.结果表明,LGF的加入可以提高PA6的结晶速率和结晶度;当LGF质量分数为30％时结晶度最大,达到33.1％.随着LGF含量的增加,复合材料的力学性能及维卡软化点温度均大幅提高,当...     

PA 6/NMA/nano-OMMT复合材料的制备

采用自制耐热改性剂N-苯基马来酰亚胺-马来酸酐二元共聚物(NMA)与纳米有机蒙脱土(nanoOMMT)复配对聚酰胺(PA)6进行共混改性,研究了不同m(NMA)∶m(nano-OMMT)对PA 6熔融结晶行为、热性能及力学性能的影响。结果表明:nano-OMMT剥离分散在PA 6基体中;随着nano-OMMT含量增加,PA 6/NMA/nano-OMMT复合材料的熔融温度、结晶温度、结晶度及熔融焓均先升后降;m(NMA)∶m(nano-OMMT)为8∶2时,复合材料弯曲强度、弯曲模量、拉伸强度和负荷变形温度均达最大,分别为117.1,3 301,80.5 MPa及82.7℃,较不加nano-OMMT分别提高21.2%,25.0%,12.9%,27.8%。     

CaCl_2对PA6/OMMT/POE-g-MAH复合材料结构与性能的影响

通过挤出机熔融共混法制备了PA6/POE-g-MAH/OMMT/CaCl_2复合材料,研究了CaCl_2含量对PA6/POE-gMAH/OMMT/CaCl_2复合材料结晶行为及其力学性能的影响。结果表明:随着CaCl_2含量的增加,PA6/POE-g-MAH/OMMT/CaCl_2复合材料的弯曲强度呈现出逐渐增大的趋势。当CaCl_2为9%时,复合材料的弯曲强度达到最大值76.6 MPa。另外,随CaCl_2含量的增加,复合材料拉伸强度和冲击强度都呈现出先增大后减小的趋势。当CaCl_2为5%时,复合材料的拉伸强度(70.8 MPa)和冲击强度(11.8 k J/m2)分别达到最大值,与纯PA6相比拉伸强度(65.5 MPa)和冲击强度(5.5 k J/m2)分别提高了8%和114%。结晶性能研究表明:随着CaCl_2含量的增加,复合材料的成核温度、增长温度及熔融温度向低温方向移动。     

PA6/NMA共混物的制备及其性能研究

以聚酰胺6(PA6)为基体、自制N-苯基马来酰亚胺-马来酸酐二元共聚物(NMA)为耐热改性剂,通过熔融共混法制备了PA6//NMA共混材料。并采用差示扫描量热法(DSC)、热重分析(TGA)、热变形温度及力学性能测试等手段研究了NMA用量对PA6/NMA共混物熔融结晶行为、热性能及力学性能的影响。结果表明:随着NMA用量的增加,PA6/NMA共混物的熔融温度、结晶温度、结晶度以及熔融焓均逐渐降低,而且共混物的最大分解温度较纯PA6显著提高;随着NMA用量的增加,PA6/NMA共混物的力学性能及热性能均明显改善,其中当NMA用量为10份时,共混物的弯曲强度、弯曲模量、拉伸强度及热变形温度分别增至113.8 MPa、3 146 MPa、80.4 MPa以及71.5℃,较纯PA6提高了25.1%、31.9%、15.7%和27.5%;另外,随着NMA用量的增加,共混物的熔体流动速率(MFR)大幅下降,其中当NMA用量增至10份时,共混物的MFR降至5.3 g/10min。     

NMA与纳米SiO2复配对PA6热性能及力学性能的影响

N-苯基马来酰亚胺与马来酸酐的共聚物(NMA)对尼龙(PA)6具有良好的耐热改性作用,纳米Si O2能够较好地改善PA6的力学性能。采用自制的NMA与纳米Si O2以不同质量配比复配,对PA6进行共混改性,利用差示扫描量热法、热重分析、热变形温度和力学性能等表征方法研究了不同复配比例对PA6热性能及力学性能的影响。结果表明,随着纳米Si O2含量增加,PA6/NMA/纳米Si O2复合材料的熔融温度、结晶温度、结晶度及熔融焓均呈现先上升后下降的趋势;当NMA与纳米Si O2的质量比为10∶0时,复合材料的热稳定性最好;当NMA与纳米Si O2的质量比为8∶2时,复合材料的弯曲强度、弯曲弹性模量、拉伸强度和热变形温度均达到最大值,分别为108.3,2 989,77.6 MPa以及68.4℃,较纯PA6分别提高了19.0%,25.3%,11.7%和19.2%。随着纳米Si O2含量的增加,复合材料的熔体流动速率呈现先增加后减小的趋势。     

尼龙6/环氧树脂/氯化锂共混体系的结构与性能

采用易规模化生产的熔融挤出法制备了尼龙6(PA6)/环氧树脂(E51)/氯化锂(Li Cl)复合材料,研究了Li Cl的含量对PA6/E51/Li Cl复合材料的结晶、力学、光学及加工性能的影响。研究表明:随着Li Cl含量的增加,PA6/E51/Li Cl复合材料的熔融温度和结晶温度均向低温方向移动,结晶速率减小,结晶不完善程度增大,结晶度降低,PA6的结晶受限。另外,随着Li Cl含量的增加,PA6/E51/Li Cl复合材料的冲击强度和弯曲强度逐渐增大,当Li Cl用量为6份时,复合材料的拉伸强度、弯曲强度和透过率达到最大值分别为7.5 k J/m2、121.9 MPa和79.3%,PA6/E51/Li Cl复合材料的MFR呈现先增大后减小的趋势。综合得知,当添加Li Cl用量为6份时,可以得到熔点较低、力学性能、加工性能和透过率较好的PA6/E51/Li Cl复合材料。     

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.