基于乙烯-乙酸乙烯共聚物/丁腈橡胶热塑性硫化橡胶超亲水材料的制备与性能

采用动态硫化法制备了基于乙烯–乙酸乙烯酯共聚物/丁腈橡胶的热塑性硫化橡胶（EVA/NBR TPV）,以不同型号金相砂纸为模板,通过模压法在其表面构建具有微纳米结构的表面,研究了橡塑质量比对EVA/NBR TPV粗糙表面超亲水行为的影响及EVA/NBR TPV超亲水表面的微观结构和超亲水性能,并初步探讨了EVA/NBR TPV表面的亲水机制。结果表明,当EVA/NBR TPV的橡塑质量比为20/80时,采用模板法且以耐水砂纸为模板制得的EVA/NBR TPV表面亲水性较好。其中,当橡塑质量比为20/80时,以NO 1000砂纸为模板,模压温度为165 ℃,经过预热10 min、热压3 min、冷压5 min后制得的EVA/NER TPV薄膜表面的亲水性最佳。     

可膨胀石墨对氯化聚乙烯/乙烯-乙酸乙烯共聚物热塑性硫化胶力学性能及阻燃性能的影响

研究了可膨胀石墨（EG）的粒径及用量、EG/聚磷酸铵（APP）对氯化聚乙烯（CM）/乙烯-乙酸乙烯共聚物（EVA）热塑性硫化胶（TPV）力学性能及阻燃性能的影响。结果表明,随着EG粒径的增加,CM/EVA TPV的拉伸强度及扯断伸长率呈下降趋势,极限氧指数（LOI）增大,垂直燃烧测试均能达到V-0级别,800℃残炭量（CR800）增加;当EG的粒径为48μm时,CM/EVA TPV的综合性能较佳。随着EG用量的增加,CM/EVA TPV的拉伸强度呈下降趋势,而100%定伸应力呈增加趋势,LOI增大,CR800增加。当EG/APP（质量比）为3/1时,CM/EVA TPV的拉伸强度为11.82 MPa,LOI为31.8%,垂直燃烧测试达到V-0级别,综合性能最佳。     

高抗冲聚苯乙烯/乙烯-乙酸乙烯共聚物/丁苯橡胶热塑性硫化胶的黏弹行为

采用动态硫化法制备了高抗冲聚苯乙烯/乙烯-乙酸乙烯共聚物(EVA)/丁苯橡胶热塑性硫化胶(TPV),考察了EVA用量对TPV的动态硫化操作性、微观相态、力学性能、熔体表观黏度、动态黏弹行为及应力弛豫的影响。结果表明,在基质树脂相中加入EVA,可改善TPV动态硫化的操作性及制品的外观质量,且TPV的形变回复能力得到增强,但对TPV力学性能和表观黏度的影响不明显。随着TPV中EVA用量的增加,在频率扫描模式下,TPV的储能模量和损耗模量下降,损耗因子出现一定程度的波动;在温度扫描模式下,储能模量、损耗模量及损耗因子均下降。随着EVA用量的增加,TPV应力弛豫测试的残留应力降低。     

BR/EVA TPV的制备及性能研究

采用动态硫化法制备BR/乙烯-乙酸乙烯酯共聚物(EVA)热塑性硫化胶(TPV),并对其性能进行研究.结果表明:当BR/EVA共混比大于50/50时,TPV呈现出典型弹性体的应力-应变行为;当BR/EVA共混比为50/50～65/35时,TPV的硬度较低,综合物理性能良好;当BR/EVA共混比为60/40时,微米级的BR粒状物均匀分散在EVA基体中,两相界面结合良好.     

BR/EVA/HIPS TPV的制备和性能研究

采用苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改善BR/乙烯-乙酸乙烯酯共聚物(EVA)/高抗冲聚苯乙烯(HIPS)共混物的界面相容性,通过动态硫化法制备BR/EVA/HIPS TPV,并对其性能进行研究.结果表明:未加入SBS的BR/EVA/HIPS共混物未表现出橡胶类弹性体特征,而加入适量SBS的共混物表现出典型橡胶类弹性体特征;当SBS用量为8～12份时,BR/EVA/HIPS TPV的综合物理性能较好,拉伸断面平滑,界面相容性良好.     

剪切速率对乙烯-丙烯酸酯橡胶/聚偏氟乙烯热塑性硫化胶性能的影响

采用动态硫化法制备了乙烯-丙烯酸酯橡胶（AEM）/聚偏氟乙烯（PVDF）热塑性硫化胶（TPV）,考察了动态硫化过程中转子剪切速率对TPV微观相态结构及性能的影响。结果表明,动态硫化过程中转子的剪切速率越快,AEM和PVDF更易发生相转变,微观相态结构更加精细,形成具有“海-岛”结构的TPV。随转子的剪切速率加快,TPV的拉伸强度和扯断伸长率均先增大后减少。当剪切速率为75 r/min时,AEM/PVDF TPV具有较好的力学性能,拉伸强度达到14.84 MPa,扯断伸长率为246%,TPV具有更加优异的耐热油和热空气老化性能。     

撕裂模式下乙烯-乙酸乙烯酯共聚物/氯丁橡胶热塑性硫化胶的Mullins效应及其可逆回复

采用动态硫化法制备了乙烯-乙酸乙烯酯共聚物（EVA）/氯丁橡胶（CR）热塑性硫化胶（TPV）,对其微观形貌、撕裂强度、撕裂模式下的Mullins效应、热处理后的可逆回复行为及其机制进行了研究。结果表明,EVA/CR TPV橡塑质量比为30/70时其撕裂模式下的应变和撕裂强度较高,橡胶相与树脂相呈“海-岛”结构;撕裂模式下EVA/CR TPV的单轴循环测试中表现出明显的Mullins效应,增大应变时,其最大撕裂强度、瞬时残余应变、内耗值和阻尼因子均增加,但应力软化因子趋于下降;随着热处理温度的上升,Mullins效应的可逆回复效果获得改善,且温度为70℃时其可逆回复行为最好。     

丁腈橡胶/乙烯-乙酸乙烯共聚物热塑性硫化胶的Mullins效应形成机制及可逆回复

采用动态硫化法制备了丁腈橡胶(NBR)/乙烯-乙酸乙烯共聚物(EVA)热塑性硫化胶(TPV),考察了其压缩Mullins效应及其在不同温度下的可逆回复行为,并与EVA及NBR静态硫化胶进行了对比。结果表明,在单轴循环压缩过程中NBR/EVA TPV及EVA均存在明显的Mullins效应,在一定压缩应变下,第1次加载-卸载的最大压缩应力和内耗出现最大值,第2次循环压缩时则显著降低,之后下降趋势减缓。升高热处理温度,第2次单轴循环压缩时压缩Mullins效应的回复程度增大。在NBR静态硫化胶的单轴循环压缩过程中未观察到明显的Mullins效应。     

低硬度乙烯-乙酸乙烯酯共聚物/聚烯烃弹性体/充油丁苯橡胶热塑性硫化胶的性能

采用动态硫化法制备了乙烯-乙酸乙烯酯共聚物/充油丁苯橡胶热塑性硫化胶(EVA/SBR TPV),在此基础上以聚烯烃弹性体(POE)替代部分EVA制备出低硬度TPV,并对其力学性能、Mullins效应和微观形貌进行了研究。结果表明,当EVA/SBR(质量比)为30/70时,TPV的综合性能良好;当EVA/POE/SBR(质量比)为25/5/70~20/10/70时,TPV的扯断伸长率超过1 000%,邵尔A硬度在50左右。EVA/POE/SBR TPV存在明显的Mullins效应,拉伸比一定时,最大应力和内耗随循环拉伸次数的增加而下降,瞬时残留变形则逐渐增大;拉伸比增大时,最大应力、瞬时残留变形和内耗均增加。基体中POE的存在赋予TPV更强的弹性回复能力。     

交联剂用量对BR/EVA热塑性硫化胶性能的影响

采用动态硫化法制备了BR/EVA热塑性硫化胶(TPV),考查了硫化体系中硫黄用量对混炼胶的硫化行为、静态硫化胶的溶出物含量及性能的影响,并对BR/EVA型TPV的力学性能及微观结构进行了研究。结果表明,随着硫黄用量的提高,混炼胶硫化历程中的平坦期较长,但t90趋于明显降低,静态硫化胶溶出物含量及力学性能均呈下降趋势;当硫黄用量为0.5份时,静态硫化胶及BR/EVA TPV表现出良好的综合性能。显微镜照片表明,BR硫化胶的粒状物平均尺寸为5～10μm左右,较均匀地分散在EVA树脂基体中;FE-SEM的测试表明,TPV的断面平滑,TPV具有良好的形变回复性。     

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.