Phase controlled surface reaction — reaction of a monolayer at the gas-water interface

A new technique for esterification of an acid monolayer at the gas-water interface has been introduced. This novel process termed phase controlled surface reaction (PCSR), utilizes Gibbs' surface energies to ensure reaction in an environment that would normally inhibit it. Because surface energies are important in numerous environments, PCSR should work with many condensation reactions. The addition of a benzyl alcohol subphase to water leads to a concentration of excess benzyl alcohol at all water interfaces including the gas-water interface. This surface enriched benzyl alcohol zone reacts with a polymerized monolayer present at the gas-water interface. FT-IR characterization of the deposited reacted monolayer shows that up to 70% of the monolayer molecules have been reacted. Further experiments indicate that the degree of conversion is dependent on the pH of the water subphase. Preliminary studies of electron lithographic patterning of the deposited product indicates that it is more electron sensitive than the original monolayer. PCSR may thus be a method by which chemical changes can be made in an existing monolayer, without altering its structure.     

Surface properties of a long-chain 10:12 diynoic acid monolayer at air-liquid and solid-liquid interfaces

Monolayer stabilities of two long-chain diacetylene monocarboxylic acids at fluid interfaces have been studied and are compared with those of a conventional n-alkanoic acid. The diacetylene derivatives form highly incompressible solid monolayers at the air-liquid interface. Their surface pressure-area isotherms are shown to depend on the mode of monolayer compression, indicating the necessity of a cautious approach to experimental protocol. The coherence of deposited monolayers on hydrophobic glass surfaces was characterized by interference reflection microscopy. Birefringent crystals were obtained with UV polymerized pentacosanoyl 10:12 diynoic acid in sharp contrast to the well-defined deposition behaviour observed for monolayers of eicosanoic acid.     

Molecular switching in nano-structured photochromic films of biopolymers

This paper reports the investigation of the photochromic and conformational behaviour of a poly (l-glutamic acid) (PSG) chemically modified with 85% spiropyran units in the side chains, PSG. We preliminary studied the behaviour of PSG in solution and then we performed a characterisation of the polymer in bidimensional systems. PSG monolayer at the water–air interface was characterised by means of surface pressure–molecular area isotherms and UV–Vis Spectroscopy and the photochromic behaviour was illustrated. Moreover, we transferred, by means of the Langmuir–Blodgett (LB) technique, polypeptide monolayers onto solid support in order to obtain ordered and nano-organized systems whose spectroscopic properties were investigated.     

酰胺链硅烷界面结合剂对尼龙66/玻纤复合材料性能的影响

采用熔融挤出共混制备了尼龙66(PA66)/玻璃纤维(GF)复合材料,比较了常用硅烷偶联剂KH550与不同有机酸封端的酰胺链硅烷界面结合剂(ASI)对复合材料的力学性能、动态力学性能及界面层结构的影响,探究了复合材料中界面层形成的机理。结果表明,ASI与玻纤表面反应发生了化学反应,ASI添加量为1.5%时,对PA66/GF复合材料的力学性能改善效果最明显,其中,以对苯二甲酸封端,相对分子质量为2000左右的PTA-ASI使PA66/GF复合材料的界面能力提升最高,拉伸强度提高了54.8%,复合材料的综合性能提高最为显著。     

Rehydroxylation of dehydrated silica surfaces by water vapor adsorption

The rehydroxylation reaction of siloxane bridges was studied for silica gel particles dehydrated by preheating. Adsorption isotherms of water vapor at 298 K were measured for the samples which were preheated at different temperatures. The amounts of total adsorption and irreversible adsorption were examined against the preheating temperature and vapor pressure. The number of the hydroxyl groups produced by the rehydroxylation of siloxane was measured by thermogravimetrican alysis to determine the adsorption isotherms for chemisorption of water. For the surface preheated at 673 K, the siloxane bridges were fully rehydroxylated for about 3 h at a relative pressure of 0.3. The surface preheatedat 873 K was gradually rehydroxylated with increasing pressure and the rehydroxylation was not complete even for 90 h at a relative pressure lower than 0.7. In the high-pressure region, the rehydroxylation was promoted by condensed water. The number of surface hydroxyls after rehydroxylation became greater than that on the original surface. The possibility of the generation of the geminal hydroxyls was suggested from the degree of rehydroxylation on the surface.     

Cellulose fiber/poly(ethylene-co-methacrylic acid) composites with ionic interphase

Cellulose fiber/thermoplastic composites with ionic interphase were prepared from modified cellulose fibers and poly(ethylene-co-methacrylic acid) (PE-co-MA). The cellulose fiber was treated by using coupling agent or sodium hydroxide followed by introduction of ionic quaternary ammonium groups on the fiber surface, which was then compounded with the polymer having anionic groups. The effect of the ionic interface on the composite physical and thermal dynamic properties was investigated. An obvious improvement in mechanical strength of the ionic-interface composites was observed due to acid–base interactions. The improved adhesion could be ascribed to the interaction between cationic grafted groups at the cellulose fiber surface and the anionic groups in the PE-co-MA.     

High pressure squeeze casting of stainless steel wire reinforced aluminium matrix composites

Stainless steel wire-reinforced aluminium matrix composites with a fibre volume fraction up to 40% were fabricated by high pressure squeeze casting. The mechanical properties of these composites were investigated and it was found that their tensile strength was somewhat lower than that predicted by the rule-of-mixtures; failure occurred predominantly by fibre pull-out. Details of the optical microscopic studies and the microhardness data are presented. This reveals that the fibre-to-matrix bonding is relatively weak as a result of the more-than-desirable interfacial reaction. Several inter-metallic compounds have been identified at the interface. Growth kinetics of these interface intermetallic compounds are discussed.     

Properties of mixed chlorophyll a-glycolipid monolayers

Surface pressure, ellipsometric and surface potential-area isotherms have been measured to investigate the properties of chlorophyll a-digalactosyldiacyglycerol (Chl a-DGDG) and Chl a-sulfoquinovosyldiacylglycerol (SQDG) monolayers at the nitrogen-water interface. The surface pressure-area isotherms of Chla-DGDG exhibit a pronounced negative deviation with respect to ideality, whereas ellipsometric and surface potential isotherms of the mixed monolayers fall between those of the pure components. Hydrophilic interactions have been ruled out on the basis of the additivity law followed by the surface dipole moment of the mixed monolayers. The observed deviation exhibited by the π-A isotherms is interpreted in terms of an intermolecular cavity effect.     

Atmospheric pressure glow discharge plasma polymerization for surface treatment on sized basalt fiber/polylactic acid composites

This study evaluates the effects of atmospheric pressure glow discharge plasma polymerization on basalt fiber to the properties of basalt fiber/polylactic acid composite. Plasma exposure time was the object of interest so the basalt fiber was exposed to the glow for 0.5, 1.5, 3, 4.5, and 6 min, respectively. Characterization was conducted on the plasma polymerized fibers by identifying the molecular bonds and surface morphology. Properties (mechanical and thermal) and water absorption behavior of the fabricated composites were tested. Plasma exposure time on BF affected mechanical properties of its BF/PLA composite, showing a decline in mechanical properties until the BF was plasma polymerized beyond 1.5 min. Optimum plasma polymerization on BF was for 4.5 min of plasma exposure time where the composite’s strength and modulus were 45% and 18% higher, respectively, compared to those of untreated one.     

高体积分数SiC_p/Al复合材料中界面现象研究

利用 XRD及 TEM方法测定了真空气压渗流法制备的四种基体复合材料及其界面区域的相组成。结果表明 ,复合材料中界面处出现了新相 ,认为新相的出现是界面反应的结果。应用热力学及动力学方法分析讨论了界面反应及其产物的形成过程。指出 ,通过控制基体中的添加元素含量便可控制复合材料中界面反应及出现的相 ,界面反应对材料的制备过程及其性能有重要的影响。     

碳纤维/乙烯基酯树脂拉挤复合材料界面性能研究

对PAN基碳纤维在线热氧化表面处理,分析了处理前后碳纤维的表面形貌,通过拉挤成型工艺制备出碳纤维/乙烯基酯树脂复合材料。对拉挤复合材料的微观结构观察以及力学性能测试表明:碳纤维经表面处理后表面粗糙度增加,与乙烯基酯树脂的界面粘结性明显改善,复合材料的力学性能尤其是层间剪切强度得到显著提高。对不同界面性能的碳纤维复合材料进行动态热机械分析(DMTA),认为界面性能的改善可降低损耗模量,提高复合材料的耐疲劳性能。     

Improving the interfacial property of carbon fiber/vinyl ester resin composite by grafting modification of sizing agent on carbon fiber surface

The poor interfacial adhesion between carbon fibers (CFs) and vinyl ester resin (VE) has seriously hampered the application of CFs/VE composites. In this work, the interfacial adhesion was efficiently enhanced by grafting acrylamide with epoxy sizing agent on CFs surface. The grafting reaction was feasible according to the thermodynamic calculation. The optimal grafting condition was 80 °C for 10 min based on the kinetic investigation by differential scanning calorimeter. Surface morphology and surface composition of modified carbon fibers (MCFs) were characterized, which indicated that acrylamide was grafted successfully on CFs surface and the surface roughness was increased slightly. After grafting, the interface shear strength of MCFs/VE composites was significantly improved by 86.96% and the interlaminar shear strength was enhanced by 55.61% due to the covalent bonds in interphase and the toughening effect of sizing gent. Moreover, the static and dynamic mechanical properties of composites with different interfacial adhesion were measured, which further confirmed the effect of the grafting modification.     

pH值对合成聚苯丙炔酸的影响

苯丙炔酸上的羧基起到终止剂的作用,限制了苯丙炔酸的聚合。加入NaOH将单体转化成钠盐,聚合后用HCl酸化成聚苯丙炔酸。单体由肉桂酸和液溴通过先加成后消去反应制得。利用红外光谱、紫外光谱、荧光光谱、凝胶渗透色谱和TGA对单体及聚合物的结构和性能进行了表征,2212cm-1处C≡C键伸缩振动特征吸收峰消失形成1602cm-1C—C键伸缩振动特征峰,表明了聚合物的合成。荧光光谱显示聚苯丙炔酸在375nm激发波长下发蓝光,于465nm处有特征荧光发射峰,与没有加NaOH聚合的聚合物相比较,紫外吸收波长范围更大,加碱聚合的聚苯丙炔酸分子量能达到10552,TGA测试结果表明聚苯丙炔酸具有一定的热稳定性。     

T800碳纤维/9518氰酸酯复合材料的性能

通过差示扫描量热（DSC）法研究了9518氰酸酯的固化反应,制定了9518氰酸酯的固化工艺;通过动态热机械分析（DMA）测试、力学性能测试、金相显微镜和SEM等方法研究了T800碳纤维/9518氰酸酯复合材料的受热行为、力学性能、纤维微观形貌和界面特性。结果表明：9518氰酸酯的固化反应只有一个固化反应放热峰,其比较合理的固化工艺为130℃/0.5 h+160℃/0.5 h（加压合模）+200℃/2 h+230℃/2 h。T800碳纤维/9518氰酸酯复合材料的玻璃化转变温度为255℃,其各项力学性能比T700碳纤维/9518氰酸酯复合材料提高均大于10%,室温-湿态力学性能保持率大于83%,200℃的力学性能保持率大于60%。T800碳纤维不规则的截面和表面沿长度方向的沟槽有利于树脂与纤维间形成良好的结合界面。     

PMDA对废旧HIPS的修复作用

采用均苯四甲酸二酐(PMDA)为扩链剂,通过双螺杆挤出机将废旧高抗冲聚苯乙烯塑料(rHIPS)与PMDA进行熔融共混,成功实现了rHIPS的分子结构以及相界面的修复。研究了PMDA含量对rHIPS的相对分子质量、力学性能、动态力学性能、熔体流动性和断面形貌特征的影响。结果表明:PMDA与rHIPS发生了扩链反应,相对分子质量也得到了明显提升;当PMDA含量为0.9%(质量分数,下同)时,rHIPS/PMDA共混物的冲击强度达到10.8kJ/m2,提高了57%;随PMDA含量的增加熔融指数先减小后趋于平缓,储能模量和损耗模量升高,试样的冲断面形貌变得粗糙,相界面模糊。     

浓乳液法PS/PBMA及PS/PBA基团反应自增容合金的制备

首先通过苯乙烯与丙烯酸本体预聚、甲基丙烯酸丁酯（丙烯酸丁酯）与甲基丙烯酸党费水甘油酯浓乳液预聚,在聚苯乙烯（PS）链与聚甲基丙烯酸丁酯（PBMA）链（聚丙烯酸丁酯（PBA)链）中分别引入羧基与环氧基团,然后将两种体系的浓乳液混合并完成聚合,利用聚合过程中浓乳液乳胶粒间的界面反应特性,使羧基与环氧基团反应,生成接枝共聚物,改善了聚苯乙烯与聚甲基丙烯酸丁酯（聚丙烯酸丁酯）间的相容性,最终获得自增容的聚苯乙烯与聚甲基丙烯酸丁酯（聚丙烯酸丁酯）合金。红外谱图证实了所得合金中基团间发生了反应,并且聚合过程中基团间的反应是充分的,。随着基团含量的增加,合金的冲击强度提高,即两相间的相容性也随之提高。     

Preparation of polymeric biosurfactant containing sugar and fatty acid esters

 Vinyl sugar ester, 6-O-vinyladipoyl-d-glucose (VAG), was polymerized with vinyl fatty acid esters in dimethylformamide (DMF) with azobisisobutyronitrile (AIBN) to produce new amphiphilic polymers having branches of sugar and fatty acid esters. The influence of structural variations by changing the length of the alkyl chain of fatty acid moiety was examined by measurements of the surface tension and biodegradability. Received: 16 August 1999 / Accepted: 13 December 1999     

The geometry of vacuum assisted interface adhesion: Resistance to axial moment

Many engineering applications require joining two surfaces by temporary methods that do not harm either surface. The need for non-destructive surface bonding includes the need to resist axial moments. Suction cups in two different arrangements, in pairs at 180° apart and in fours at 90° apart, were pressed onto a polymerized thermoset polyester surface and then subjected to an axial moment. Defining failure as either sliding or complete loss of adhesion, the maximum torque applied before adhesive failure at the cup-plate interface was quantified using an MTS materials testing system. A linear relationship existed between the distance from the centroid of the cups and the applied torque at failure; also a linear relationship existed between the contact area of the cups and the tangential reaction force. Experiment verified that the applied load is distributed among the cups such that the tangential reaction force on each cup is proportional to its distance from the centroid; a coefficient of static friction between polyvinylchloride and polymerized thermoset polyester of 1.24 was calculated from the data.     

Degradation and by-product formation of diazinon in water during UV and UV/H(2)O(2) treatment

Kinetics and degradation products resulting from the application of UV and UV/H(2)O(2) to the US EPA Contaminant Candidate List pesticide diazinon were studied. Batch experiments were conducted with both monochromatic (low pressure [LP] UV 253.7 nm) and polychromatic (medium pressure [MP] UV 200-300 nm) UV sources alone or in the presence of up to 50 mg l(-1) H(2)O(2), in a quasi-collimated beam apparatus. Degradation of diazinon by both UV and UV/H(2)O(2) exhibited pseudo first order reaction kinetics, and quantum yield of 8.6 x 10(-2) and 5.8 x 10(-2) mol E(-1) for LP and MP lamps respectively. Photolysis studies under MP UV lamp showed 2-isopropyl-6-methyl-pyrimidin-4-ol (IMP) to be the main degradation product of diazinon at aqueous solution pH values of 4, 7 and 10. Trace levels up to 1.8 x 10(-3) microM of diazinon oxygen analogue diethyl 2-isopropyl-6-methylpyrimidin-4-yl phosphate (diazoxon) were detected only during the UV/H(2)O(2) reaction. Decay of both products was observed, as the UV/H(2)O(2) reaction prolonged, yet no mineralization was achieved over the UV fluence levels examined. Photolysis kinetics, quantum yield and UV/H(2)O(2) degradation of the reaction product IMP was determined using MP UV lamp at pH values of 4, 7 and 10.     

Characterization and use of high surface area activated carbons prepared from cane pith for liquid-phase adsorption

Carbonaceous adsorbents with controllable surface areas were chemically activated with KOH at 780 degrees C from char that had been carbonized from cane pith at 450 degrees C. The pore properties including the BET surface area, pore volume, pore size distribution, and mean pore diameter of these activated carbons were characterized and derived using the t-plot method based on N(2) adsorption isotherms. The activated cane pith carbons, with KOH/char ratios of 2-6, exhibited BET surface areas ranging from 912 to 2299 m(2) g(-1). The scanning electron microscopic (SEM) observations revealed that the surface morphology of honeycombed holes on all activated cane pith carbons was significantly influenced by the KOH/char ratio. The adsorption kinetics and equilibrium isotherms of acid blue 74, methylene blue, basic brown 1, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water at 30 degrees C on the activated carbons were studied. The adsorption kinetics were suitably described by a simplified kinetic model, the Elovich equation. All adsorption equilibrium isotherms were in agreement with the Langmuir equation, and were used to compare the covered area (S(c)/S(p)) of the activated carbons at different KOH/char ratios. The high-surface-area activated carbons were proven to be promising adsorbents for pollution control and for other applications.