EPDM-g-MAH对PA6/ABS合金性能的影响

通过熔融共混法制备了马来酸酐接枝(乙烯/丙烯/二烯)共聚物(EPDM-g-MAH)增容的尼龙6/(丙烯腈/丁二烯/苯乙烯)共聚物(PA6/ABS)合金,考察了PA6/ABS配比和EPDM-g-MAH用量对PA6/ABS合金力学性能、热学性能及吸湿状态的影响;观察了PA6/ABS合金表面微观结构。结果表明,EPDM-g-MAH是PA6/ABS合金的有效增容剂,当PA6/ABS/EPDM-g-MAH质量比为90/10/10时合金综合性能最好,尤其能显著地改善材料的冲击韧性、耐热性,降低吸水率。     

PA610/PC合金的制备及其力学性能研究

分别选用环氧树脂(EP)及(乙烯/马来酸酐/甲基丙烯酸缩水甘油酯)三元共聚物(EMG)为增容剂,采用熔融挤出法制备了PA610/PC/EP合金和PA610/PC/EMG合金,并研究了这两种合金的力学性能。结果表明,在保持合金其它力学性能基本不变的情况下,当PA610/PC/EP的质量比为75/25/2时,合金的缺口冲击强度比未加入EP时提高了83.7%,比纯PA610提高了84.1%;而且在PA610/PC(75/25)体系中加入EMG增容时,合金的缺口冲击强度也随其含量的增加而明显提高;在加入9份EMC的PA610/PC/EMG体系中再加入2份EP协同增容时,合金的缺口冲击强度比未增容时提高了142.0%。     

共混工艺对SMAH增容ABS/PA6共混物形态和力学性能的影响

以(苯乙烯/马来酸酐)共聚物(SMAH)为增容剂,研究了共混工艺对(丙烯腈/丁二烯/苯乙烯)共聚物/尼龙6(ABS/PA6)共混物聚集态结构和力学性能的影响。结果表明,ABS与PA6直接共混时相容性差;加入增容剂SMAH后,分散相尺寸变小且易均匀分散,显著改善了ABS/PA6共混物的力学性能。当ABS为连续相、PA6为分散相时,共混物的聚集态结构强烈地受共混工艺的影响,(ABS/SMAH)/PA6共混物的分散相尺寸最小、力学性能最优;当PA6为连续相、ABS为分散相时,共混物的聚集态结构基本不受共混工艺的影响。     

组分对PA6/ABS合金力学性能的影响

通过双螺杆挤出制备了尼龙6(PA6)/丙烯腈-丁二烯-苯乙烯共聚物(ABS)合金,考察了PA6、ABS和相容剂的种类及含量对PA6/ABS合金力学性能的影响。结果表明,通过中黏度(2.4~2.7 Pa·s)的尼龙6与聚丁烯(PB)质量分数达到16%的ABS制备的PA6/ABS合金有优异的力学性能;随着PA6含量增加,PA6/ABS合金的拉伸和弯曲强度增加,冲击强度下降,ABS含量增加使PA6/ABS冲击强度上升,拉伸和弯曲强度反而下降;相容剂马来酸酐(MAH)接枝ABS(ABS-g-MAH)对PA6/ABS合金增容效果优于苯乙烯接枝马来酸酐共聚物(SMA);当ABSg-MAH质量分数为3%,PA6与ABS质量比为62/35时,制备出的PA6/ABS合金具有最佳的力学性能,缺口冲击强度可达28 kJ/m2。     

马来酸酐接枝ABS的增容改性研究

研究了增容剂马来酸酐接枝ABS对PC／ABS合金、PA6／ABS合金及ABS／GF复合材料力学性能的影响。结果表明，该增容剂的加入明显提高了PC／ABS合金的冲击强度和断裂伸长率，使PA6／ABS合金的各项力学性能均明显提高，使ABS／GF复合材料的拉伸强度和断裂伸长率也有较大提高。     

ABS-g-MAH对PA6/ABS合金性能的影响研究

以马来酸酐(MAH)接枝丙烯腈-丁二烯-苯乙烯共聚物(ABS)作为相容剂,研究了相容剂ABS-g-MAH对PA6/ABS合金凝聚态结构和力学性能的影响。结果表明,当ABS-g-MAH质量分数为20%时,合金的冲击强度比未加相容剂的提高了41%。动态力学性能(DMA)和偏光显微镜也很好地说明了加入相容剂的合金,其相容性得到了很好的改善。ABS和ABS-g-MAH的加入明显改善了PA6的吸水性能,当ABS-g-MAH质量分数为10%时,合金吸水率较纯PA6降低了50%。     

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。     

有机蒙脱石改性PA6/ABS合金材料的制备和性能

利用环氧化合物(EP)表面处理蒙脱石(MMT),制备的有机蒙脱石(OMMT)层片间距增加到5.13 nm,热降解温度高达380.3℃。研究了苯乙烯与马来酸酐(MAH)的共聚物(SMA)对PA6/ABS合金的增容效果,当增容剂用量为4%,合金的综合性能最好。制备了PA6/ABS/OMMT复合材料,随着SMA含量的增加,PA6/ABS/OMMT复合材料力学性能和耐热温度都有较大幅度的提高。     

PA6/ABS/PC合金的研制

以PA6，ABS，PC为基础树脂，ABS-g-MAH为增容剂，二叔丁基过氧化物为引发剂，并加入改性剂等助剂，制备了PA6／ABS／PC合金，研究了增容剂的种类及含量，引发剂的种类，PA6的粘度，ABS的牌号及改性剂的含量对PA6／ABS／PC合金性能的影响。结果表明，采用1．0％－1．2％的ABS-g-MAH,30%的相对粘度2．8－3．0的PA6，40％的1300型PC，28％的ABS及0．5％的改性剂制得的PA6／ABS／PC合金优于日本孟山都公司的PA6／ABS合金。     

阻燃PC/ABS合金的研制及其在电器上的应用

通过对3种增容剂增容PC／ABS合金性能的测试对比,选用了1种效果最佳的增容剂制备PC／ABS合金．用十溴联苯醚和三氧化二锑作为阻燃体系,对阻燃PC／ABS合金的力学性能、热性能、阻燃性能进行了检测。结果表明,当PC：ABS：增容剂：阻燃体系为70：30：8：15时,阻燃PC／ABS合金的综合力学性能最好,阻燃性能达到UL 94V-0级．该合金已用于生产防火电器开关、插座面板系列产品。     

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.     

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.     

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.     

(Bi1/2Na1/2)TiO3–Ba(Cu1/2W1/2)O3 Lead-Free Piezoelectric Ceramics

(Bi_1/2Na_1/2)TiO₃ with 0–6 mol% Ba(Cu_1/2W_1/2)O₃ (BNT-BCW), a new member of the BNT-based group, has been prepared following the conventional mixed oxide route. The compacted bodies were sintered at 1130°C for 2 h to get dense ceramics. The addition of BCW into BNT ceramics facilitated the poling process because of a reduction in leakage current. 0.995BNT·0.005BCW ceramics exhibit a relatively high piezoelectric constant ( d ₃₃= 80 × 10⁻¹² C/N) and a relatively low dielectric loss (tan δ= 1.5%). Increased amount of BCW was found to increase the dielectric constant and loss of BNT-BCW ceramics and to suppress the grain growth. During sintering, some BCW diffuses into the lattice of BNT to form a solid solution and some remains on the grain boundaries.     

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.