PP/ABS合金的制备及不同阻燃剂对其性能的影响研究

通过将DCP作为交联剂、TAIC为助交联剂,利用密炼机通过熔融共混进行PP/ABS的制备。通过对性能的测试,当DCP添加的质量分数是0.2%时,TAIC添加质量分数为4%时,制备的PP/ABS合金性能最佳。在此基础上只加入阻燃剂BT-93W以及BT-93W与DMDPB进行混合添加,并对得到的材料进行性能测定。     

高性能丁腈橡胶/聚氯乙烯汽车油管胶料的研制

采用过氧化二异丙苯(DCP)作主交联剂、三烯丙基异氰脲酸酯(TAIC)作助交联剂硫化丁腈橡胶/聚氯乙烯(NBR/PVC)共混胶以制备汽车油管胶料,研究了TAIC用量对胶料的硫化特性、压缩永久变形、力学性能、耐溶剂性能、耐热老化性能以及耐臭氧老化性能的影响。结果表明,随着TAIC用量的增加,共混胶料的正硫化时间逐渐缩短,硫化速率逐渐加快,交联效率提高,最大转矩增加;同时共混胶的硬度和拉伸强度逐渐增大,扯断伸长率减小,其压缩永久变形、耐溶剂、耐热老化以及耐臭氧老化性能则呈现不同的变化。当DCP用量为3.5份、TAIC用量为3份时,NBR/PVC共混硫化胶的综合性能最好。     

化学改性高熔体聚丙烯的制备及其挤出发泡特性研究

以过氧化二异丙苯(DCP)为交联剂、三烯丙基异三聚氰酸酯(TAIC)为助交联剂,通过平行双螺杆挤出机制备了高熔体强度聚丙烯(HMSPP),研究了DCP用量对PP的流变性能、材料的热性能及发泡特性的影响。结果表明:DCP与TAIC配合使用能有效控制PP交联,从而制得有一定凝胶含量的HMSPP,同时材料的耐热性也得以提高,当DCP用量为0.8份,TAIC为3份时,制备的HMSPP,挤出发泡特性最佳。     

助交联剂松香酯对聚丙烯交联性能的研究

以过氧化二异丙苯(DCP)为主交联剂,松香酯为助交联剂,采用化学交联法对聚丙烯进行交联改性。分别测试DCP和DCP/松香酯交联体系下,PP的熔体质量流动速率-凝胶含量-抗熔断能力以及力学性能。结果表明,与单独使用DCP相比,DCP/松香酯交联体系使PP抗熔断能力延长了12 min,当DCP为2 phr时,PP的熔体质量流动速率减少了0.1 g/10min,凝胶含量提高了15%,冲击强度和拉伸强度分别增加了0.73 k J/m2、1.97 MPa。     

汽车用PVC/热塑性聚氨酯交联电缆料的研制

以汽车用电缆料为试验目标,研究了增塑剂、引发剂、助交联剂、热塑性聚氨酯(TPU)的用量对PVC/TPU体系硬度、力学性能、热延伸率的影响,并考察了其耐磨性能和耐老化性能。结果表明:①在助交联剂TAIC存在下,引发剂DCP可引发PVC/TPU体系的交联反应,并且随着DCP、TPU用量的增加,交联度增大。②PVC/TPU交联电缆料的优化配方为:PVC 100份,钙锌稳定剂8份,TO TM 50份,TAIC 3份,DCP 0.2份,TPU 30份,抗氧剂0.8份,其他助剂适量;采用该配方能生产出合格的汽车用电缆料。     

不同硫化体系对动态硫化POE/PP性能的影响

采用动态硫化法制备POE／PP共混型热塑性弹性体，研究了交联剂过氧化二异丙苯（DCP）用量对POE／PP体系熔体流动速率和力学性能的影响．并用配方优化系统（RCAD）对DCP和助交联剂做了变量分析，考察DCP／S和DCP／TAIC不同配比对体系物理性能的影响。结果表明，DCP的加入使体系中PP降解，体系熔体流动速率单调上升、力学性能下降。DCP用量在一定范围内。助交联剂硫黄S对POE／PP体系才有较好的补强作用，固定DCP用量为2-4份，S用量范围为0．1～0-46份时，体系拉伸强度可达13．9MPa。当DCP用量超过2．0份，TAIC对强度的影响不大，DCP用量为1．72份，TAIC用量在2．44～3．0份时．体系的拉伸强度较好。     

WABS/WPP共混合金的研究

采用原位增容技术．以氯化聚乙烯（CPE）、交联剂过氧化二异丙苯（DCP）和三烯丙基异氰脲酸酯（TAIC）改性废旧ABS（WABS）／废旧PP（WPP）共混物，制备了综合性能较好的WABS／WPP共混合金。结果表明，CPE与交联剂DCP和TAlC协同作用，可以对WABS／WPP起到良好的增容作用，共混合金在不降低拉伸强度的同时，冲击强度可获得较大的提高。采用6份CPE与适量交联剂DCP和TAIC并用改性的WABS／WPP（90／10）共混合金的冲击强度比改性前提高了127％。WABS／WPP共混合金改性后的耐热性能也有所提高，改性后WABS／WPP两相的相容性得到了改善。     

助交联剂并用对动态硫化POE/PP弹性体的影响

为了选择合适的交联剂,研究了两种不同的过氧化物双叔丁基过氧化异丙苯(BIPB)和过氧化二异丙苯(DCP)对动态硫化乙烯-辛烯共聚物/聚丙烯(POE/PP)弹性体的影响,同时,固定助交联剂的总用量,研究了不同比例的N,N'-间苯撑双马来酰亚胺(HVA-2)和三烯丙基异氰脲酸酯(TAIC)对POE/PP弹性体的影响。相对于40%DCP(DCP有效含量40%,其余为载体)而言,40%BIPB(BIPB有效含量40%,其余为载体)作为交联剂得到的硫化胶具有较好的撕裂强度。从拉伸断面的扫描电子显微镜(SEM)图上可以看到:过氧化物用量同为2份时,以BIPB作为交联剂的POE在PP中分散得更均匀,粒径更小。不同比例的HVA-2和TAIC并用时,当HVA-2和TAIC的并用比为4:1时,总体力学性能最好。SEM图表明:与HVA-2用量为1.5份时相比,1.2份HVA-2和0.3份TAIC并用时胶料的拉伸断面更粗糙,分散相更小。从差示扫描量热仪(DSC)上可以看到:与HVA-2用量为1.5份时相比,1.2份HVA-2和0.3份TAIC并用时,POE的玻璃化转变温度(Tg)、熔融温度(Tm)和熔融焓(ΔHf)都降低,PP的ΔHf也降低。     

助交联剂TAIC对聚丙烯发泡性能影响的研究

在过氧化二异丙苯（DCP）引发下,研究三烯丙基异氰脲酸酯（TAIC）对聚丙烯（PP）的交联程度、熔体强度及其发泡性能的影响。在TAIC加入前后,分别测定PP的抗流淌能力和熔体流动速率及PP发泡材料的凝胶率和力学性能。结果表明,DCP／TAIC交联体系使PP的抗流淌时间平均延长了6-7min;当DCP为1．4份时,PP发泡材料的最大凝胶率提高14％,拉伸强度和撕裂强度分别提高了24．5％和55．8％。偏光显微镜观察结果显示,在DCP/TAIC交联体系作用下,PP发泡材料表面光滑,泡孔细密且均匀一致。     

以助交联剂为第二单体的聚丙烯熔融接枝反应

以助交联剂三烯丙基异氰尿酸酯(TAIC)或三聚氰酸三烯丙酯(TAC)作为聚丙烯(PP)熔融接枝马来酸酐(MAH)过程中的第二单体制备PP-g-MAH,与苯乙烯、丙烯酸、甲基丙烯酸甲酯等常用的第二单体进行了对比,对其反应机理进行了探讨;以TAIC为例,研究了其用量对PP-g-MAH接枝率、熔体流动速率(MFR)等性能的影响。结果表明,与苯乙烯等第二单体相比,以助交联剂TAIC或TAC为第二单体,制备的PP-g-MAH接枝率更高,MFR更低,且未产生刺激性气味;在MAH用量不变的条件下,当TAIC用量(占PP-g-MAH中PP质量的百分数)由0%增加至0.5%时,接枝率由0.36%增至0.85%,MFR由95.7 g/10 min降至38.2 g/10 min。将制备的PP-g-MAH应用于PP/玻璃纤维(GF)复合材料和PP/尼龙(PA)6合金中,结果表明,随TAIC用量增加,两种材料的力学性能整体提高,TAIC用量以0.5%为宜。在PP/GF/PP-g-MAH质量比为70/30/0.7或PP/PA6/PP-g-MAH质量比为20/70/10时,与未加TAIC的相比,PP/GF复合材料的冲击强度、弯曲强度和弯曲弹性模量分别提升了10.9%,20.8%和17.7%,PP/PA6合金的断裂伸长率、冲击强度、弯曲强度和弯曲弹性模量分别提升了42.9%,8%,12.9%和8.8%。     

Polymorphism of LiGa5O8 and of LiGa5O8-MgGa2O4Solid Solutions

High-temperature X-ray diffraction and differential thermal analyses showed that LiGa₅O₈ exists in two polymorphs related by the first-order transition at 1138°±3°C of the low-temperature simple-cubic form, space group (probably) O⁷, to the high-temperature spinel (fcc) form, space group O _h ⁷. The transition is rapid, and the high-temperature form in pure LiGa₅O₈ could not be quenched to room temperature under the conditions used. However, the high-temperature polymorph can be quenched under equilibrium conditions when 40 mol% or more MgGa₂O₄ is present. The subsolidus equilibrium relations in the system MgGa₂O₄-LiGa₅O₈ are discussed.     

Activation and characterization of Fe---Mn---SO4/ZrO2 catalysts

Changes in Fe---Mn---SO₄²⁻/ZrO₂ catalyst formulations during activation have been observed. In air or an inert gas, the added salt, such as iron and/or manganese nitrate, decomposes over a temperature range of about 200–400°C to produce nitric oxide, oxygen and iron and/or manganese oxide. The crystallization of zirconia occurs at 450°C; when the sample contains sulfate the exothermic event occurs at a temperature that is about 200°C higher. Heating in the presence of hydrogen causes the evolution of nitric oxide to occur over a narrow temperature range and at a lower temperature than when the sample is heated in helium or air. It appears that the nitrate ions associated with Fe, Mn and Zr decompose to produce nitric oxide, and presumably water, at different temperatures when the sample is heated in the presence of hydrogen. Heating samples of sulfated zirconia containing iron and/or manganese in hydrogen causes sulfur evolution at a lower temperature, and a significant fraction of it in the form of H₂S.     

The structures of VOx/MOx and alkali-VOx/MOx catalysts and their catalytic performances for soot combustion

Vanadium oxides supported on γ-Al₂O₃, SiO₂, TiO₂, and ZrO₂ were studied on their molecular structures and reactive performances for soot combustion. To investigate the effect of different alkali metals on the structures and reactivities of supported-vanadium oxide catalysts, they were doped into the V₄/TiO₂ catalyst which had the best intrinsic activity for soot combustion in the selected supported vanadium oxide catalysts. The experimental results demonstrated that the catalytic properties of these catalysts depended on the vanadium loading amount, support nature, and the presence or the absence of alkali metals. The spectroscopic analysis (FT-IR and UV–vis) and H₂-TPR results revealed that the higher activity of alkali-promoted vanadium oxide catalysts could be related to the ability of alkali metal promoting the redox cycle of the active vanadyl species. TG results showed that adding alkali to V_m/TiO₂ catalyst was beneficial to lowering their melting points. Low melting points could ensure the good surface atom migration ability, which would improve the contact between the catalyst and soot. Due to the alkali metal components promoting the redox ability and the mobility of the catalysts, alkali-modified vanadium oxide catalysts could remarkably improve their catalytic activities for soot combustion. The catalytic activity order for soot combustion followed Li > Na > K > Rb > Cs in the catalyst system of alkali-V₄/TiO₂, and the reason why it followed this sequence was discussed.     

Magnetoresistance of CuxCo1-xFe2O4 Ferrites

Magnetoresistance measurements (Δ/R) were carried out on Cu _x Co_{1- x} Fe₂O₄ samples with x =1, 0.75, 0.50, 0.25 and cobalt ferrite in the range of magnetic intensity (H) from 1.0 to 4.5 kG. Linear plots were obtained between log (Δ/R) and log H for all compositions except that of cobalt ferrite. The values of n at x =0.5 do not agree with the results of some authors. The discrepancy may be attributed to the value of magnetic field intensity at which such measurements were carried out. The similarity of features of n and μ_D with composition leads us to believe that the magnetoresistance may arise from the scattering of conduction electrons by localized electrons involving the s-d exchange interaction.     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.     

Preparation of the High-Quality Superconductor La1Ba2Cu3Oy

The relationship between the preparation procedure and superconducting properties of La₁Ba₂Cu₃O_y was studied. A series of samples was sintered in an N₂-gas atmosphere for various lengths of time ranging from 1 to 40 h, followed by a fixed annealing procedure in O₂. It was found that the shorter the sintering period, the higher was the oxygen content. The samples sintered for a period of less than 15 h contained excess oxygen compared with La₁Ba₂Cu₃O₇ and exhibited poor superconducting properties. The sample sintered for 40 h had an oxygen content y equal to 6.95, and had excellent superconducting properties. The mechanism for preparing high-quality La₁Ba₂Cu₃O_y is discussed.     

Microwave Dielectric Properties of CaTiO3-CaAl1/2Nb1/2O3 Ceramics Doped with Li3NbO4

The microwave dielectric properties of CaTi_{1− x} (Al_1/2Nb_1/2) _x O₃ solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO₃. The substitution of Ti⁴⁺ by Al³⁺/Nb⁵⁺ improved the quality factor Q of the sintered specimens. A small addition of Li₃NbO₄ (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛ_r) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τ_f) of −2 ppm/K. Li₃NbO₄ as a sintering additive had no harmful influence on τ_f of ceramics.     

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.     

Expansive properties of the mixture C4ASH12 − 2CS III. Effects of temperature and restraint

The effects of temperature and restraint upon the hydration and the expansion of $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}\text{? 2}\text{C}\text{S}$ mixture compacts in different contact solutions have been investigated. Temperatures above 20°C do apparently hinder the formation of an impervious felt-like layer of ettringite around the $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}$ particles, thus greatly reducing the retarding effect of the lime. An uniaxial restraint of 1 Kg/cm² is enough to reduce sensibly the expansions which remain however high (about 100%). The results can be satisfactorily interpreted by the reaction and expansion mechanism hypothesized in our previous papers.