A comparison between the SBR vulcanizates reinforced by magnesium methacrylate added directly or prepared in situ

The styrene-butadiene rubber (SBR) cured by dicumyl peroxide was reinforced by magnesium methacrylate [Mg(MAA)₂], which was added into SBR directly or prepared in situ in SBR through the neutralization of magnesium oxide (MgO) and methacrylic acid (MAA). The experimental results show that the SBR vulcanizates reinforced by Mg(MAA)₂ prepared in situ have better mechanical properties than those reinforced by Mg(MAA)₂ added directly. The SBR vulcanizates with Mg(MAA)₂ prepared in situ are semi-transparent, but those with Mg(MAA)₂ added directly are opaque. The Fourier transform infrared analysis shows that the polymerization conversion of Mg(MAA)₂ in the SBR vulcanizates with Mg(MAA)₂ prepared in situ is much higher than that in the SBR vulcanizates with Mg(MAA)₂ added directly. The scan probe microscopy photographs show that the particles in the SBR vulcanizates with Mg(MAA)₂ prepared in situ are much finer and disperse more evenly than that in the SBR vulcanizates with Mg(MAA)₂ added directly.     

淫羊藿根与叶活性成分的分析和比较

采用细胞膜色谱法（ＣＭＣ）筛选，并结合离体药理实验确定主要活性成分，利用高效液相色谱法分析比较了淫羊藿根与叶中的活性成分及其差异性．色谱条件为Ｋｒｏｍａｓｉｌ ＯＤＳ 柱（１５０ ｍｍ× ４．６ ｍｍ．Ｉ．Ｄ ）流动相甲醇－水（７０：３０，Ｖ：Ｖ）；检测波长２７０ｎｍ。筛选发现淫羊藿根中的两个有效成分ＹＹＨ－２１４和ＹＹＨ－２１６对血管有较强的舒张作用，表明活性成分在ＣＭＣ模型体系中的保留特性与药理作用之间存在良好的相关性。在此色谱条件下淫羊藿叶未检测到这两种活性成分．     

Instantaneous strain recovery elasticity and endothermic heat change in nylon-6 monofilaments and silicone rubbers

The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,E _c ,E _s andE _e , respectively. It was found that during strain recoveryE _s (>E _e ) andE _e increase monotonically with increasing load,m ₁, on the sample. The extrapolated value of E_s atm ₁=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofE _c also increased with increasingm ₁, and atm ₁=600 g (1.93 t cm^–2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,E _s ,E _c andQ were also investigated for silicone rubber. It was found thatE _s (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,E _s was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol^–1 (atD=1.2) to 56 J mol^–1 (atD=1.9). FurthermoreE _c (5.58 MPa atm ₁=133.8 g (429.4 kg cm^–2)) increased gradually with increasing m₁ and attained 16.6 MPa atm ₁=548.4 g (1.76 t cm^–2). In the case of creep,Q was in the range of 0–11.5 J mol^–1 and larger when larger loads,m ₂ were removed during the later stages of creep.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe author wishes to thank Mr. Keizi Igarashi and Mr. Tetsuya Yasui for helping in the experiments.     

带甲基侧基的环氧树脂增容剂对炭黑在丁苯橡胶中分散度的影响

用自制的带甲基侧基的环氧树脂(TMBP)作为界面增容剂, 从拉伸性能、键合胶含量、动态性能、扫描电镜和流变性能等方面, 研究了TMBP对炭黑在丁苯橡胶中分散度的影响, 并与市售通用双酚A型环氧树脂(E-51)和橡胶工业常用软化剂邻苯二甲酸二辛酯(DOP)进行了比较. 结果表明, 带甲基侧基的环氧树脂TMBP在提高炭黑分散性方面的效果远比E-51好， 其作用模式具有典型的增容特性.     

Thermal behaviour of styrene butadiene rubber/poly(ethylene-co-vinyl acetate) blends

The thermal behaviour of styrene butadiene rubber (SBR)/poly (ethylene-co-vinyl acetate) (EVA) blends was studied by using thermogravimetry (TG) and differential scanning calorimetry (DSC). The effects of blend ratio, cross-linking systems and compatibilization on the thermal stability and phase transition of the blends were analyzed. It was found that the mass loss of the blends at any temperature was lower than that of the components, highlighting the advantage of blending SBR and EVA. The addition of compatibilizer was also found to improve the thermal stability. DSC studies indicated the thermodynamic immiscibility of SBR/EVA system even in the presence of the compatibilizer. This is evident from the presence of two different glass transition temperatures, corresponding to SBR and EVA phases in both compatibilized and uncompatibilized blends.     

接枝和交联对纳米Si02改性NR／PP共混型热塑弹性体的影响

动态硫化制备纳米二氧化硅（SiO2）改性天然橡胶，聚丙烯共混型热塑性弹性体（NR/PPTPE）．研究了马来酸酐，苯乙烯，过氧化二异丙苯（MAH／St／DCP）多单体“就地”熔融接枝、交联对TPE力学性能、耐溶剂性能和耐热变形性能的影响，并用SEM分析了TPE的断面形貌．结果表明：纳米SiO2和MAH／St／DCP的最佳质量分数分别为0．03和0．0375／0．0188／0．00375时，MAH／St／DCP接枝、交联改性NR／PP／纳米SiO：TPE的力学性能、耐溶剂性能和耐热变形性能最佳．MAH／St／DCP“就地”接枝、交联通过细化交联NR分散相、改善交联NR分散的均匀性和增加两相之间的共交联，使NR与PP两相界面结合强度明显提高，NR／PPTPE的综合性能得到明显的改善．     

高硅ZSM—5沸石填充硅橡胶膜的醇—水渗透蒸发分离性质

高硅ZSM－5沸石填充疏水性硅橡胶蓦地低浓度醇－水体度醇－水体的渗透蒸发性质的研究有明，提高沸石硅铝比，增加填充量以及进行酸处理皆有利于改善膜对醇－水的分离系数和通量。料液的成，浓度以及温度对膜的分离性质也有显著影响。     

聚氯乙烯—丁腈橡胶—氯丁橡胶三元共混物的研究

测定了聚氯乙烯（ＰＶＣ）－丁脯橡胶（ＮＢＲ－２９）－氯丁橡胶（ＣＲ）三元共混物的冲击性能和应力－应变行为，用动态力分析、扫描电和透射电镜研究了共混物的相容性和形态结构。结果表明，ＮＢＲ－２９对ＰＶＣ，ＣＲ有良好的增容作用，三元共混物是部分相容的二相体系，具有良好的抗冲击性能。     

Influence of two grinding methods on the uncertainty of determinations of heavy metals in atomic absorption spectrometry/electrothermal atomisation of plant samples

 Chemical analyses of trace elements are affected by relatively high analytical errors due to the different steps of the laboratory procedures: samples grinding, mineralisation and instrumental measurements. In the present communication, the influence of the grinding phase on the global uncertainty of Pb, Cd, Ni and Cr determinations in plant samples by the classical method of atomic absorption spectrometry/electrothermal atomisation (AAS-ETA) after dry ashing is quantified. Two grinding machines, a planetary mill with balls and jars of agate versus a stainless steel grinder were compared by analysing leaf samples of cucumber, strawberry, kiwivines, apple trees and grapevines from agricultural experimental plots under controlled conditions. Variance components due to the difference between grinding methods and experimental plots were estimated. Further, the simultaneous effects of the grinding methods on all considered metals have been evaluated by analysis of variance. With the stainless steel grinder, on average, higher levels of the considered heavy metals were obtained (up to 67% of the mean values). On average, the increments were similar for metals contained in steel (Ni and Cr) and those not contained (Pb and Cd). The true causes of these differences need further investigation to determine whether the higher metal detection is due to possible contamination, to a different grinding quality or to other reasons. Finally, the grinding methods did not seem to affect the combined uncertainty of the analyses. Received: 3 November 1997 · Accepted: 29 November 1997     

Advances in two-dimensional GC with glass capillary columns

A versatile two-dimensional gas chromatograph is described, consisting of 2 separate ovens, one intermediate trap, an auxiliary inlet, and the necessary hardware to effect off-line switching according to the principle of Deans. The unit has been designed for use with high resolution glass capillary columns. The performance of individual instrumental components was critically evaluated. Results showed that low dead volume glass to metal connections were required in the manifold and detector lines to minimize extra-column effects. The mass of the intermediate trap must be low to allow rapid heating. Operational parameters are discussed and examples of some applications are shown.