PA6/ABS的结构与力学性能研究

采用熔融共混法制备了苯乙烯-马来酸酐共聚物(SMA)增容的聚酰胺6/丙烯腈-丁二烯-苯乙烯共聚物(PA6/ABS)共混物,用扫描电镜(SEM)对PA6/ABS共混物结构进行了表征.结果表明,随着SMA含量的增加,PA6/ABS共混体系的橡胶相粒径减小.橡胶颗粒的多分散系数保持不变,基体层厚度逐渐减小;PA6/ABS共混体系的脆韧转变温度随SMA含量的增加先减小后增加.     

ABS/PET合金的组成配比及SMA的增容化研究

以苯乙烯接枝马来酸酐共聚物(SMA)为增容剂对丙烯睛-丁二烯-苯乙烯共聚物(ABS)/聚对苯二甲酸乙二醇酯(PET)共混物进行研究,探讨了SMA用量对合金的力学性能和热稳定性的影响;并进一步研究了无增容剂下ABS与PET之间配比对合金性能的影响.研究表明:增容剂SMA用量为10 phr时,合金的冲击强度和断裂伸长率分别提高20%和50%;随着PET用量的增加,合金的弯曲强度、拉伸强度和维卡软化温度不断提高,当PET用量接近50%时发生相转变;断裂伸长率在PET的质量分数为30%时达到最低(32%).通过示差扫描量热法(DSC)测试,发现ABS破坏了PET的结晶行为,且合金中两者的玻璃化转变温度存在重合现象.通过扫描电子显微镜(SEM)和偏光显微镜观察发现,SMA增容的ABS/PET合金中PET颗粒尺寸较小且分散较好;PET晶粒在ABS中可以形成"岛"相和连续相.     

ABS/HIPS相容性的研究

采用苯乙烯-马来酸酐共聚物(SMA)作为丙烯腈-丁二烯-苯乙烯共聚物/高抗冲聚苯乙烯(ABS/HIPS)的相容剂,研究了SMA对ABS/HIPS共混体系力学性能的影响,并用扫描电子显微镜对共混物的亚微观形态结构进行了分析。结果表明,SMA的加入起到了很好的增容作用。随着HIPS/SMA用量的增加,共混物的冲击性能先增大后减小,当HIPS/SMA=8.5/1.5(质量比),且HIPS/SMA质量分数为10%时,共混物的缺口冲击强度达到97.1J/m,同时拉伸强度和弯曲强度最大。     

ABS/PET合金的相容性研究

选用甲基丙烯酸甲酯-丁二烯-苯乙烯接枝共聚物(MBS)、KT-18和KT-5A作为丙烯腈-丁二烯-苯乙烯共聚物(ABS)/聚对苯二甲酸乙二醇酯(PET)的增容剂,通过双螺杆挤出机共混制得综合性能优良的合金,探讨了ABS和PET的配比、增容剂用量、增容剂种类对合金性能的影响。结果表明,PET在合金中的比例为20%~30%(质量分数,下同)时,合金的力学性能较好;选用KT-18的增容效果最好,使ABS/PET合金的冲击强度可达到8.79kJ/m2;增容剂KT-18的最佳用量为3%~5%。     

ABS高胶粉增韧PA6的结构与性能研究

采用熔融共混法制备了苯乙烯-马来酸酐共聚物（SMA）增容的PA6/ABS共混物,用透射电子显微镜对PA6/ABS共混物结构进行了表征,研究了增容剂含量对PA6/ABS共混体系结构、性能以及脆-韧转变温度的影响。结果表明,随着SMA含量的增加,PA6/ABS共混体系的橡胶相粒径先逐渐减小,后趋于平缓;橡胶颗粒的多分散系数逐渐增加;基体层厚度不断减小;PA6/ABS共混体系的拉伸强度逐渐增加;PA6/ABS共混体系的脆-韧转变温度先减小,后上升。     

不同增容剂对PET/ABS合金性能的影响

研究了不同增容剂对PET/ABS合金的增容效果,采用苯乙烯-马来酸酐共聚物(SMA)、苯乙烯-丙烯腈-甲基丙烯酸缩水甘油酯共聚物(SAG)、乙烯-丙烯酸正丁酯-缩水甘油酯共聚物(PTW)为增容剂,考察了其增容效果,结果表明,SMA对PET/ABS的增容效果最好,SAG对PET/ABS的增容效果次之,PTW对PET/ABS的增容效果不好。考察了增韧剂对PET/ABS合金性能的影响。结果表明,具有核壳结构的甲基丙烯酸甲酯-丁二烯-苯乙烯(MBS)对PET/ABS合金具有优异的增韧效果,为实现PET/ABS合金的产业化打下了基础。     

相容剂种类对PA6/ABS合金性能的影响

采用苯乙烯-马来酸酐(SMA)、苯乙烯-丙烯腈-马来酸酐(SAMAH)和苯乙烯-丙烯腈-甲基丙烯酸(SAMAA)三种共聚物增容尼龙6/丙烯腈-丁二烯-苯乙烯共聚物(PA6/ABS)共混物,利用双螺杆挤出机制备出PA6/ABS合金,对其结构及其性能进行了表征和探讨。结果表明,三种相容剂均可有效地增容PA6/ABS合金,改善ABS在PA6中的分散,大幅度提高了缺口冲击强度;通过差示扫描量热(DSC)分析发现PA6/ABS的结晶度降低,结晶速率变慢;同时通过流变实验发现PA6/ABS共混物为假塑性流体,三种相容剂均提高了其表观黏度。     

ABS接枝物的制备及其对r-PET/ABS的增容作用

通过反应挤出法制备马来酸酐(MAH)接枝丙烯腈-丁二烯-苯乙烯三元共聚物(ABS)(ABS-g-MAH)和甲基丙烯酸缩水甘油酯(GMA)接枝ABS(ABS-g-GMA),将其用于增容回收聚对苯二甲酸乙二酯(PET)瓶片(r-PET)/ABS共混物,发现能显著提高共混物的冲击强度。ABS-g-MAH的增容效果优于ABS-g-GMA;ABS-g-MAH的接枝率为1.35%,w(ABS-g-MAH)为5%时对r-PET/ABS的增容作用最佳,此时r-PET/ABS/ABS-g-MAH的简支梁缺口冲击强度和无缺口冲击强度比r-PET/ABS分别提高了42%和23%。扫描电子显微镜观察表明,加入ABS接枝物能使ABS在r-PET连续相中的分散更均匀,粒径尺寸更均一。     

超韧PA6/ABS合金的制备

以苯乙烯-马来酸酐（SMA）共聚物为增容剂，考察了ABS及SMA的含量对PA6／ABS共混体系的力学性能的影响；并利用SEM研究了PA6／ABS冲击断面的相结构。研究表明：SMA是PA6／ABS共混体系的有效增容剂。随着其含量的增加，分散相ABS粒子的尺寸减小，分散更加均匀，能显著地改善PA6／ABS共混物的冲击、拉伸和弯曲性能。在该共混体系中，ABS含量的增加能够大幅度地提高PA6／ABS共混物的冲击韧性；但当ABS含量超过10％时，将使PA6／ABS共混物的拉伸和弯曲性能明显下降。SMA的添加量为0．5％，且质量比为90／10的PA6／ABS共混体系能保持较好的加工性能，制备的PA6／ABS合金具有最佳的综合力学性能和超高韧性．Izod缺口冲击强度高达1200J／m。     

SMA增容PA1012/ABS共混物的研究

采用熔融共混方法制备一系列尼龙1012(PA1012)/丙烯腈-丁二烯-苯乙烯共聚物(ABS)/苯乙烯-马来酸酐共聚物(SMA)共混物,利用冲击试验仪、示差扫描量热仪(DSC)和扫描电子显微镜(SEM)等手段,探究增容剂SMA和ABS的添加量对PA1012/ABS共混物性能的影响。结果表明,当SMA含量为5%且ABS含量为50%时,PA1012/ABS/SMA共混物的缺口冲击强度最优,为669 J/m;随着SMA含量增加,结晶温度有先增大后减小趋势,并且与纯PA1012相比,PA1012/ABS/SMA共混物结晶温度升高了10℃,促进PA1012结晶;SMA加入后,ABS分散相粒子尺寸减小,PA1012和ABS间界面黏结作用增强,证实SMA对PA1012/ABS有明显增容作用。     

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.     

Synthetic routes to nanoscale BxCyNz architectures

B_xC_yN_z nanoscale materials, hybrids of h-BN and graphite, have been recently synthesised using various techniques. Here, we present the latest advances in the synthesis and characterisation of B-C-N nanotubes and nanofibres. In particular, we focus on layered BC₂N, BN, BC and CN_x systems, reviewing their production methods as well as their structural and electronic properties. These materials may find important applications in the fabrication of nanotransistors, robust nanocomposites, conducting polymers, storage components and field emission sources.     

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.     

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.     

Structure Evolution from Pb(Mg1/3Nb2/3)O3 to La(Mg2/3Nb1/3)O3

The crystal structure of lanthanum-modified lead magnesium niobates having composition (Pb_{1− x} La _x ) (Mg_{(1+ x )/3}-Nb_{(2− x )/3})O₃ with X = 0 to 1 was investigated by X-ray powder diffraction. It was found that the fundamental reflections from perovskite structure remain in the whole range of composition. The superlattice reflections from the A(B'_1/2-B"_1/2)O₃ ordered structure are also well preserved for La content greater than 50 at.%; however, a series of extra peaks of mixing indices appears, with intensities gradually enhanced with the increase of La content. For the complete substitution of Pb by La, a splitting of some reflections can be observed in the diffraction pattern. The results indicate that the crystal structure evolves continuously with the La content, from disordered cubic perovskite of space group Pm 3 m for X = 0, to ordered cubic perovskite of space group Fm 3 m for X = 0.5, distorted cubic perovskite of space group Pa 3 for 0.5 < X < 0.9, and finally to a rhombohedral perovskite, possibly belonging to the space group R 3 , for X ≥ 0.9. In the evolution of structure, a linear reduction of the lattice constant of the perovskite cell from 4.048 to 3.964 Å was observed.     

Characteristic Spherulitic Microstructure in Partial-Melt-Processed YBa2Cu3Ox/HfO2

The microstructure of partial-melt-processed YBa₂Cu₃O _x /HfO₂ has been studied by transmission electron microscopy. A characteristic spherulitic microstructure is formed in the system. A model for the growth mechanism has been proposed. The critical heterogeneous nucleation of the YBa₂Cu₃O _x phase appears to occur from the melt in an epitaxially controlled manner on CuO particles. Subsequent growth of YBa₂Cu₃O _x platelets from the nucleus region is repeatedly interrupted by the nucleation of hafnium-rich phases in the liquid at the solid/liquid interface in a manner that again appears to be epitaxially controlled and that promotes the splay of the c orientation of the YBaCuO grain.