Phase transition in polyamide-66/montmorillonite nanocomposites on annealing

The crystalline-phase transition in polyamide-66/montmorillonite nanocomposites before melting was investigated by in situ X-ray diffraction and is reported for the first time in this work. The phase-transition temperature in the nanocomposites was 170 degreesC, 20 degreesC lower than that in polyamide-66. The lower phase-transition temperature of the nanocomposites could be attributed to the gamma-phase-favorable environment caused by silicate layers. Meanwhile, the addition of silicate layers changed the crystal structure of the polyamide-66 matrix and influenced the phase-transition behavior.

Microstructure analysis of nylon 66 by WAXD and SAXS

The analysis of the small angle X-ray scattering (SAXS) data was based upon particle characteristic function, one-dimensional electron-density correlation function and particle distribution function. The microstructure of nylon 66 with different degrees of crystallinity was studied by means of X-ray scattering method. The radius of gyration R-g, the Porod radius R-p, the thickness of crystalline region L-c the thickness of non-crystalline region L-n, the thickness of interphase region d(tr), the long period L, the semiaxises of particles (a, a, b), the distribution of the particle sizes and the scattering invariant were calculated. The results indicate that there was a significant interphase region between the crystalline region and the non-crystalline region. and its content (W-t,W-x) should not be neglected in comparison with that of crystalline region W-c,W-x. The morphology of nylon 66 prepared by isothermal crystallization at a high temperature was mainly a lamellar structure, while the spherical crystals dominated in the quenched sample. The size of the particles in the quenched sample was smaller than that of those in the isothermally crystallized sample. and the distribution of the particle sizes in the isothermally crystallized sample was wider.

Melting crystallization behavior of nylon 66

Analysis of isothermal and nonisothermal crystallization kinetics of nylon 66 was carried out using differential scanning calorimetry (DSC). The commonly used Avrami equation and that modified by Jeziorny were used, respectively, to fit the primary stage of isothermal and nonisothermal crystallizations of nylon 66. In the isothermal crystallization process, mechanisms of spherulitic nucleation and growth were discussed. The lateral and folding surface free energies determined from the Lauritzen-Hoffman treatment are sigma = 9.77 erg/cm(2) and sigma (e) = 155.48 erg/cm(2), respectively; and the work of chain folding is q = 33.14 kJ/mol. The nonisothermal crystallization kinetics of nylon 66 was analyzed by using the Mo method combined with the Avrami and Ozawa equations. The average Avrami exponent (n) over bar was determined to be 3.45. The activation energies (DeltaE) were determined to be -485.45 kJ/mol and -331.27 kJ/mol, respectively, for the isothermal and nonisothermal crystallization processes by the Arrhenius and the Kissinger methods.

PA1010/66共聚物红外光谱研究

用红外光谱法研究了Pa1010/66共聚物氢键含量、N-H键伸缩振动力常数分布与组成的关系，发现66盐重量含量为40%时氢键含量最低，N-H伸缩振动力常数分布最宽，解释了PA1010/66共聚物热力学、结晶、机械等性能随组成改变而变化的原因.

尼龙1010/6及尼龙1010/66基本物理性能与组成的关系

尼龙1010/6 和尼龙1010/66 的基本物理性能随着组成的改变而改变,尼龙1010 含量高时,共聚物密度大于计算值;含量低时,共聚物密度小于计算值.尼龙1010 含量20%左右时,共聚物具有较大吸水率

Crystallization and melting behavior of nylon 66 poly(ether imide) blends

Isothermal crystallization and melting behavior of nylon 66 and its blends with poly(ether imide) (PEI) were investigated by differential scanning calorimetry. Crystallization kinetics such as overall rate constant Z and index n were calculated according to Avrami approach. Crystallization in the blend was retarded with respect to that of pure nylon 66 by incorporation of PEI with high glass transition temperature (T-g). The lowest growth rate of the spherulites was observed in the blends containing 10 and 15 wt% fraction of PEI. A transition temperature where positively birefringent spherulites disappear and negative birefringent spherulites develop was measured by thermal analysis. The transition temperature increased with content of PEI in the blends. A suitable range of isothermally crystallization temperatures, 238.5-246 degrees C, is suggested For determining the equilibrium melting points by means of Hoffman-Weeks approach.

Tremolite-reinforced nylon 66 composites: Mechanical and rheological properties

The reinforcement effect of an acicular inorganic filler, tremolite, on nylon 66 was studied. The mechanical properties of tremolite-filled nylon 66 composites and the effect of the filler particle size on them were obtained. The dynamic mechanical properties and rheological properties of the composites were measured. Two treatments, silane and unsaturated polyester, were used to improve the interface between tremolite and the nylon matrix. The morphologies of the composites were investigated using SEM. (C) 1998 John Wiley & Sons, Inc.

辐射交联型PA－66机械物理性能研究

本文讨论了进口与国产ＰＡ—６６经钴源辐射交联后，对机械物理性能产生的影响。发现适量经辐射的ＰＡ—６６球压硬度、拉伸强度、Ｉｚｏｄ冲击强度都有较大幅度提高，并在１００，０００Ｇｙ剂量对达最大值，而断裂伸长率在１００，０００Ｇｙ剂量以下变化不大。国产ＰＡ—６６辐射后在乙二醇中，在２５０℃时，２小时不起层，性能变化不大，可替代进口材料。

MORPHOLOGY AND DYNAMIC-MECHANICAL PROPERTIES OF NYLON 66/POLY(ETHER IMIDE) BLENDS

The morphology and dynamic mechanical properties of blends of poly(ether imide) (PEI) and nylon 66 over the full composition range have been investigated. Torque changes during mixing were also measured. Lower torque values than those calculated by the log-additivity rule were obtained, resulting from the slip at the interface due to low interaction between the components. The particle size of the dispersed phase and morphology of the blends were examined by scanning electron microscopy. The composition of each phase was calculated. The blends of PEI and nylon 66 showed phase-separated structures with small spherical domains of 0.3 similar to 0.7 mu m. The glass transition temperatures (T(g)s) of the blends were shifted inward, compared with those of the homopolymers, which implied that the blends were partially miscible over a range of compositions. T-g1, corresponding to PEI-rich phase, was less affected by composition than T-g2, corresponding to nylon 66-rich phase. This indicated that the fraction of PEI mixed into nylon 66-rich phase increased with decreasing PEI content and that nylon 66 was rarely mixed into the PEI-rich phase. The effect of composition on the secondary relaxations was examined. Both T-beta, corresponding to the motion of amide groups in nylon 66, and T-gamma, corresponding to that of ether groups in PEI, were shifted to higher temperature, probably because of the formation of intermolecular interactions between the components.

硅灰石填充尼龙66的力学性能

硅灰石填充尼龙６６的力学性能王雪芹，李滨耀（中国科学院长春应用化学研究所长春１３００２２）关键词硅灰石，尼龙６６，填充改性，力学性能硅灰石是一种工业矿物，具有完整的短纤维针状结构，在塑料的填充改性中，能够与石棉、滑石、云母等相媲美，在欧美占无机填料市...

Transfer and transport of phosphorus and silica in the turbidity maximum zone of the Changjiang estuary

The concentration of suspended particulate matter (SPM), sedimentation flux, and various forms of phosphorus and silica in turbidity maximum zone (TMZ) in the Changjiang (Yangtze) estuary was studied. Based on the budget of P and Si, their mass balances in the TMZ were calculated. Results show that the variation in concentration of dissolved inorganic silicon (DISi) was mainly controlled by seawater dilution, while that of dissolved inorganic phosphor-us (DIP) was considerably affected by the buffering of suspended matter and sediment. Our experiments showed that the sedimentation fluxes of SPM and particulate inorganic phosphorus (PIP), total particulate phosphorus (TPP), particulate inorganic silicon (PISi), and biological silicon (BSi) in the TMZ were 238.4 g m(-2) d(-1) and 28.3, 43.1, 79.0, 63.0 mg m(-2) d(-1), respectively. In addition, a simple method to estimate the ratio of resuspension of sediment in the TMZ was established, with which the rate in surface and bottom waters of the TMZ accounted for 55.7 and 66.1% of the total SPM, respectively, indicating that the sediment resuspension in the TMZ influenced significantly the mass balances of P and Si. Particulate adsorbed P (60.8%) and 35.5% of total particulate P discharged from the river were filtered and then deposited in the TMZ. The input flux of PIP from the river mouth was 55.9% of that of DIP, being important as biologically available P, while that of PISi was only 3.5% of DISi, showing that particulate adsorbed Si was much less important than particulate adsorbed P. (c) 2008 Elsevier Ltd. All rights reserved.

Xanthoria parietina as a biomonitor of airborne heavy metal pollution in forest sites in the North East of Morocco

Xanthoria parietina, common foliose lichen, growing in its natural habitat, was analysed for the concentration of five heavy metals (Fe, Cr, Zn, Pb and Cu) from different forest sites of North East of Morocco (Kenitra, Sidi Boughaba, Mkhinza, Ceinture Verte near Temara city, Skhirate, Bouznika and Mohammedia). The quantification was carried out by inductively coupled plasma - atomic emission spectrometry (ICP-AES). Results were highly significant p<0,001. The concentration of metals is correlated with the vehicular activity and urbanization. The total metal concentration is highest at the Kenitra area, followed by Ceinture Verte site near Temara city, which experience heavy traffic throughout the year. Scanning electron microscopy (SEM) of particulate matter on lichen of Xanthoria parietina was assessed as a complementary technique to wet chemical analysis for source apportionment of airborne contaminant. Analysis revealed high level of Cu, Cr, Zn and Pb in samples near roads.  

Influence of service loading and the resulting micro-cracks on chloride resistance of concrete

Chloride-induced corrosion of steel in reinforced concrete structures is one of the main problems affecting their durability, but most previous research projects and case studies have focused on concretes without cracks or not subjected to any structural load. Although it has been recognised that structural cracks do influence the chloride transport and chloride induced corrosion in reinforced concrete structures, there is little published work on the influence of micro-cracks due to service loads on these properties. Therefore the effect of micro-cracks caused by loading on chloride transport into concrete was studied. Four different stress levels (0%, 25%, 50% and 75% of the stress at ultimate load – fu) were applied to 100 mm diameter concrete discs and chloride migration was measured using a bespoke test setup based on the NT BUILD 492 test. The effects of replacing Portland cement CEMI by ground granulated blast-furnace slag (GGBS), pulverised fuel ash (PFA) and silica fume (SF) on chloride transport in concrete under sustained loading were studied. The results have indicated that chloride migration coefficients changed little when the stress level was below 50% of the fu; however, it is desirable to keep concrete stress less than 25% fu if this is practical. The effect of removing the load on the change of chloride migration coefficient was also studied. A recovery of around 50% of the increased chloride migration coefficient was found in the case of concretes subjected to 75% of the fu when the load was removed.