刚性聚合物改性PVC/CPE/CaCO_3共混体的研究

本文研究刚性聚合物(PS、PMMA)对CaCO_2填充的PVC/CPE共混体力学性能和流变性能的影响。结果表明,刚性聚合物的填入提高了共混体的冲击强度,其中,对PVC/CPE/CaCO_3=100/15/10体系的增韧效果较好。PMMA使共混体的拉伸强度有所提高而PS使共混体拉伸强度下降。流变性的测定显示,Ca-CO_2使共混体的表观粘度和粘流活化能增加,牛顿的流动性增强,而在PVC/CPE/CaCO_3共混体中加入4.5份PS能明显降低共混体的表观粘度和粘流活化能,牛顿的流动性降低,但仍有良好的挤出物外观和较低的挤出膨胀率。     

PVC/PE共混体系的研究—CPE对PVC/LDPE共混物的增容作用

采用氯化聚乙烯(CPE)作为聚氯乙烯(PVC)/低密度聚乙烯(LDPE)共混物的增容剂,用机械共混法制样,研究了共混条件及共混物组成对共混物的力学性能、加工性能、相态结构的影响。研究表明,在120℃下 LDPE 与 CPE 先预混5分钟,再于155℃下将 LDPE、CPE 与 PVC 共混15～20分钟所得到的共混物性能较好。PVC 为主的 PVC/LDPE 共混物中 CPE 较佳用量为5份(相对于100份 PVC)。DTA、扫描电子显微镜(SEM)研究证实了 CPE 的增容作用。此外,熔融指数测定结果表明,共混物中 LDPE 含量增高,共混物的熔融指数增大。     

磁性塑料流动性能的研究

通过对 PVC/CPE 共混体系作为粘结剂的磁性塑料的流动性能及力学性能的研究,得出 PVC/CPE 的最佳配比为80/20。为改善此体系的流动性,加入第三组份LDPE 或 ACR,研究其不向含量对体系流动性能的影响.结果表明,第三组份的加入能明显改善体系的流动性,当 LDPE 或 ACR 为3份左右时,其扭矩最小。但体系的拉伸强度稍有下降。     

CPVC／PVC／CPE三元共混改性的应用

研究了CPVC/PVC/CPE三元共混物的物理力学性能和流变性能。结果表明 :共混物的维卡软化温度、拉伸屈服强度和熔体粘度随CPVC用量的增加而明显增加 ;CPE的用量为 4～ 8份时可明显改善共混物的冲击强度     

活化CaCO3填充PVC／P—65共混材料的研究

研究了用硬脂酸活化处理过的轻质CaCO_3填充PVC/P-65(一种具有包藏结构的粉末丁腈橡胶)共混材料的力学性能和流变性能。结果显示:活化CaCO_3有明显的补强作用,综合考虑20份为其最佳加入量;含有活化CaCO_3的PVC/P-65体系流动性较好,可能是因为外覆硬脂酸的CaCO_3在熔化时受硬脂酸的影响而具有润滑作用。     

LDPE／NR共混物的力学性能的研究

研究了低密度聚乙烯(LDPE)与天然橡胶(NR)共混物基本力学性能,考察了LDPE/NR共混比、填充剂、硫化体系、共混温度对共混物性能的影响。实验结果表明:LDPE/NR并用比为30/70,并用温度为110～120℃时制得共混物性能优异;填充剂的补强效果:炭黑>白炭黑>陶土>碳酸钙。     

CPE对PVC／PP共混体系的增容作用

在单螺杆挤出机上用一次投料直接共混方法制样,通过差热分析(DSC),透射电镜(TEM),图象分析和力学性能试验等法研究表明,PVC 和 PP 不相容,CPE对 PVC/PP 共混体系具有较好的增容作用。5份 CPE 使得 PVC/PP 体系分散相(PP)粒径变小,粒径分布均匀性提高,并且使得 PVC 和 PP 两相界面变得比较模糊。在 PVC/PP 体系中加入 CPE 后,共混物的拉伸性能和冲击性能都有较大提高。     

VC／BA共混物增容PVC／HDPE共混体系的研究

采用氯乙烯—丙烯酸丁酯(VC/BA)共混物作为聚氯乙烯(PVC)/高密度聚乙烯(HDPE)共混物的增容剂,通过冲击实验、拉仲实验、动态力学分析,系统地研究了共混体系性能与其结构之间的关系。通过Brabender流变仪测定了VC/BA共混物增容PVC/HDPE共混体系的流变性能。结果表明,VC/BA共混物是PVC/HDPE共混体系的良好增容剂。在一定范围内,VC/BA共混物与HDPE对PVC有协同增韧效应。vC/BA和HDPE的加入改善了PVC的塑化和流变性能     

固相法氯化聚乙烯与聚氯乙烯共混物的形态与性能

研究了聚氯乙烯(PVC)与固相法氯化聚乙烯(CPE)共混物的应力-应变行为和冲击强度对CPE用量和氯含量的依赖关系,考察了共混物形态与性能的关系。动态力学性能和透射电子显微镜的研究结果表明,PVC/CPE为部分相容体系,两相间存在着一定的相互作用,当CPE氯含量为36％～42％,用量为7～15份时,CPE在PVC/CPE共混物中形成比较完整的网络结构、共混物具有更好的抗冲击性能。Brabender流变仪研究表明,CPE能促进PVC的塑化,共混物的加工性优于纯PVC。     

TPU／CPE及TPU／CPE／PVC的性能研究

采用机械共混的方法，将CPE、PVC与TPU熔融共混。研究了TPU／CPE及TPU／CPE／PVC共混体系。对其力学性能、流变性能及耐油性能进行了测试及分析。结果表明：CPE及CPE／PVC的加入可改善TPU的加工性能并降低其成本。     

EVA/EPDM/IR/IR共混发泡材料的性能研究

研究了乙烯醋酸乙烯酯共聚物（ＥＶＡ）／ＥＰＤＭ／ＩＲ三元共混和ＥＶＡ／ＥＰＤＭ／ＩＲ／ＩＲ四元共混发泡材料的性能。在ＥＶＡ中混入ＥＰＤＭ可使发泡材料的拉伸强度、撕裂强度和粘合强度提高,而收缩率和压缩永久变形降低;在ＥＶＡ中混入ＩＲ除具备混入ＥＰＤＭ同样的优点外,还可提高发泡材料的柔性;ＩＲ的混入可改善发泡材料二次热压成型制品的表面清晰度。     

SO42-/MxOy型固体超强酸研究进展

SO₄^2-/M_xO_y固体超强酸具有不腐蚀设备、污染小、耐高温、对水稳定性好和可重复使用等优点。综述了SO₄^2-/M_xO_y型固体超强酸的催化机理、失活原因、改性及表征方法,并对今后SO₄^2-/M_xO_y型固体超强酸的研究方向进行了展望。     

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.     

Effect of V2O5 Doping on the Sintering and Dielectric Properties of M-Phase Li1+x−yNb1−x−3yTix+4yO3 Ceramics

The effect of the addition of V₂O₅ on the structure, sintering and dielectric properties of M -phase (Li_{1+ x − y} Nb_{1− x −3 y} Ti _x +4 _y )O₃ ceramics has been investigated. Homogeneous substitution of V⁵⁺ for Nb⁵⁺ was obtained in LiNb_{0.6(1− x )}V_{0.6 x} Ti_0.5O₃ for x ≤ 0.02. The addition of V₂O₅ led to a large reduction in the sintering temperature and samples with x = 0.02 could be fully densified at 900°C. The substitution of vanadia had a relatively minor adverse effect on the microwave dielectric properties of the M -phase system and the x = 0.02 ceramics had [alt epsilon]_r= 66, Q × f = 3800 at 5.6 GHz, and τ_f= 11 ppm/°C. Preliminary investigations suggest that silver metallization does not diffuse into the V₂O₅-doped M -phase ceramics at 900°C, making these materials potential candidates for low-temperature cofired ceramic (LTCC) applications.     

Ferromagnetism and Magnetoresistance in La0.67Sr0.33Fe0.07Mn0.93O3

A bulk ceramic sample La_0.67Sr_0.33Fe_0.07Mn_0.93O₃ (LSFMO) with a rhombohedral structure has been prepared from a coprecipitated carbonate precursor in this study. Ferromagnetism and a negative, isotropic magnetoresistance (MR) as large as 11% have been observed in a ceramic sample of LSFMO. There are two resistivity transition peaks on the resistivity versus temperature curves. The resistivity peak and MR have been related to the ferromagnetic state in LSFMO.     

聚烯烃塑料用胶粘剂SBS／MMA／BA／MAA的合成与性能研究

以甲基丙烯酸（MAA）为功能单体,与SBS和甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）进行四元接枝共聚,合成了聚烯烃塑料用胶粘剂,探讨了不同溶剂、MMA／BA配比、MAA和BPO用量以及固化时间对粘接性能的影响,并对该四元接枝胶的性能与三元胶和SBS／MMA／BA／AA四元接枝胶进行了比较。结果发现：四元接枝胶性能优于三元胶,特别是与异氰酸酯配合时,剪切强度、固化速度明显提高,四元胶的优化配方是120＃汽油：甲苯：乙酸乙酯为8：1：1,MMA：BA配比3：1,MAA加入量7份,BPO用量1．5－2份（以100份SBS计）。     

BA／VAc／AN／AA共聚乳液胶粘剂的研制

介绍了一种丙烯酸丁酯／醋酸乙烯酯／丙烯腈／丙烯酸四元共聚乳液胶粘剂的制备方法,该胶具有良好的耐黄变性,可替代天然橡胶胶乳应用于EVA低发泡体与腈纶绒面布的复合。     

Electronic Structure and Bonding in Crystalline Y10[SiO4]6N2

The electronic structure and bonding of the complex ceramic crystal Y₁₀[SiO₄]₆N₂ is studied by a first-principles method. It is shown that this crystal is an insulator with a direct band gap of 1.3 eV. It has some unique properties related to the one-dimensional chain structure in the c -direction and the planar N-Y bonding in the x - y plane.     

Relaxor Behavior of the 0.9BaTiO3–0.1La(Mg1/2Ti1/2)O3 Solid Solution

Low-frequency dielectric response of air- and oxygen-sintered ceramics with the composition 0.9BaTiO₃–0.1La(Mg_1/2Ti_1/2) O₃ (0.9BT–0.1LMT) has been studied in the temperature range of 12–550 K. In comparison with pure BT, in 0.9BT–0.1LMT the dielectric permittivity maximum is shifted by almost 300 K toward lower temperatures. Both real and imaginary parts of dielectric permittivity of the solid solution, in the range 12–150 K, show a strong frequency-dependent behavior, which is typical of relaxors. On the basis of the model of exponential cluster size distribution and the Cole–Cole equation, the degree of interaction between the polar clusters was estimated. It was shown that the oxygen vacancies arising during sintering at high temperatures did not affect noticeably the relaxor properties of the material. The role of heterovalent La³⁺/Ba²⁺ and Mg²⁺/Ti⁴⁺ substitutions in the relaxor behavior formation is discussed.     

A- and B Site Cosubstituted Ba6−3xSm8+2xTi18O54Microwave Dielectric Ceramics

Tin (Sn) substitution into the B-site and Nd/Sn cosubstitution into the A- and B-sites were investigated in a Ba _{6−3 x} Sm_{8+2 x} Ti₁₈O₅₄solid solution ( x = 2/3). A small amount of tin substitution for titanium improved the temperature coefficient of resonant frequency (τ_f) but led to a decrease of the relative dielectric constant (ɛ) and the quality factor ( Qf ). The Ba_{6−3 x} Sm_{8+2 x} (Ti_{1− z} Sn_z)₁₈O₅₄-based tungsten-bronze phase became unstable for compositions with a tin content of ≥10 mol%, where BaSm₂O₄and Sm₂(Sn,Ti)₂O₇appeared, and finally, these phases became the major phases. On the other hand, Nd/Sn cosubstitution led to a good combination of high ɛ, high Qf , and near-zero τ_f. Excellent microwave dielectric properties were achieved in Ba_{6−3 x} (Sm_{1− y} Nd _y )_{8+2 x} (Ti_{1− z} Sn _z )₁₈O₅₄ceramics with y = 0.8 and z = 0.05 sintered at 1360°C for 3 h: ɛ= 82, Qf = 10 000 GHz, and calculated τ_f=+17 ppm/°C. The tolerance factor and electronegativity difference exhibited important effects on the microwave dielectric properties, especially the Qf value. A large tolerance factor and high electronegativity difference generally led to a higher Qf value.