Photo-induced change in wettability and binding ability of azoaromatic polymers

Photochromic polymers containing p-phenylazoacrylanilide were synthesized and the photo-induced hydrophobicity change on the surface of the polymer film was studied by measuring water wettability. The wettability increased with UV irradiation and returned to the original value with visible light irradiation. This photo-induced reversible change in wettability was considered to be caused by the large change of dipole moment across the azo bonds due to the isomerization of azo dye from trans to cis form. Furthermore, the photoresponsive polymeric adsorbent prepared from the azo polymer having adsorption behavior of a low molecular weight compound was studied. The binding ability of this polymeric adsorbent was decreased by UV irradiation. These results were attributed to the decreased hydrophobic interaction between the adsorbent and the adsorbate.     

Prediction of the change in density in systematic series of fibre-forming polymers

The density of aliphatic polyamides is determined by the concentration of amido groups and additively increases in systematic order. The packing coefficient of aliphatic polyamides determined by the ratio _a/ _c increases with an increase in the concentration of amido groups. The density of cellulose acetateis determined by the concentration of acetate groups and decreases additively in systematic order. The calculation with the group contribution method can be used to predict the density of crystallites of fibreforming polymers. but this method only gives approximate results for amorphous regions.St. Petersburg University, of Design and Technology. Translated from Khimicheskie Volokna. No. 2, pp. 21–22, March–April, 1996.     

Structural change of polydomain in the liquid crystalline polymers by weak shear flow

Steady-state shear stress (τ₁₂) and first normal stress difference (N₁) of liquid crystalline polymers at low shear rates were examined by using a mesoscopic constitutive equation set including the idea of initial domain size. For the applicability to the weak shear flow at low shear rates, a Hinch-Leal closure approximation was adopted in the calculation of the constitutive equation set. The steady-state rheological behaviors predicted by adopting the Hinch-Leal approximation were compared with those by the Doi simple decoupling approximation. It could be predicted from the plot of N₁ versus τ₁₂ that smaller domains distributed isotropically at a quiescent state might maintain the isotropic domain distribution even at the imposition of moderate shear rate, and then could be changed to the ordered (or partially elongated) domain phase by a further increase of shear rate. Such change of the polydomain structure with the increase in shear rate could be proved more precisely by the transient rheological behaviors of N₁ and τ₁₂ after the start-up of shear flow.     

The change in mechanical behavior of linear polymers during photochemical aging

Films of low-density polyethylene, polypropylene, and rigid poly(vinyl chloride) were exposed for 1700 h to artificial aging in a Weather-O-Meter. Photochemical aging was characterized by tensile measurements. We noted that only ultimate properties are affected, whereas properties defined in the low strain range remain unchanged. The kinetics of strain and stress at break depend as much on the polymer's initial rheological characteristics as on the rate of the chemical degradation. The results show that aging results in localized chain breaking leading to defects at the supermolecular level. The average decrease of molecular weight does not seem to influence the mechanical behavior.     

Volume change on first drying of hydrated portland cement with and without admixtures

The effect of admixtures of several types on the volume change characteristics of portland cement pastes is reported. Samples were cut in the form of wafers and dried step by step through several humidities down to 40 per cent; other samples were dried to the d-dried state. Large first drying shrinkages were obtained with extra dosages of calcium lignosulphonate, hydroxy carboxylic acids, and triethanolamine. Below 40 per cent RH all samples showed similar behavior with further drying or rewetting. It is suggested that the effect of admixture is mainly one of degree of dispersion in terms of alignment of sheets and displacement of ends of sheets.     

The constitution of woolwax

Summary Extensive analyses have been made of American and Australian woolwaxes. Combined hydroxy acids have been shown to be the most characteristic and important components of these waxes. Both contained considerable amounts (about 91.5% in the case of the American wax and 31.7% in the Australian sample) of diestolidic esters of the alcohols of the unsaponifiable fraction. This conclusion is supported by calculations of composition, by observations of viscosity and emulsifying properties, and by determinations of mean molecular weight by the Prahl method. Fifteenth scientific publication of the N. V. Ned. Research Centrale, The Hague, Holland.     

调整结构之杂谈

作者列举近10年来的经济数据,说明涂料行业及部分地区的品种结构发生较大变化,并对我国涂料工业今后如何以市场为导向,加强联合,发挥各自优势,因地制宜地进行产品结构调整提出了思路。     

Experimental investigation and modeling of the dissolution of polymers and filled polymers

Dissolution of Polymers is important in various areas, including microlithography, controlled drug and herbicide/fertilizer delivery, and recycling. The dissolution rates of an oxetane polymer in ethyl acetate were obtained and well correlated with a quasi-stationary dissolution model. Equilibrium solubility values obtained from the mathematical model on the basis of the best fit to the dissolution data were found to be in good agreement with equilibrium solubilities obtained in independent experiments. Mass transfer coefficients were also obtained from the mathematical model on the basis of the best fit, and the calculated activation energies were typical for diffusion controlled dissolution. The dissolution of highly filled polymers in various solvents was also investigated using the oxetane polymer filled with ammonium sulfate and aluminum fillers. The dissolution rates for the highly filled polymer were well correlated with a pseudo-homogenous diffusion model.     

An unexpected plasticization phenomenon and a constant of the change rate of viscoelastic properties for polymers during nanoindentation test

The effect of loading force, loading rate and unloading rate on the viscoelastic behavior of three representative polymers: poly(methyl methacrylate) (PMMA, amorphous polymer), polyvinylidene fluoride (PVDF, semicrystalline polymer), and epoxy (crosslinked polymer) have been investigated using nanoindentation. The results showed that the maximum indentation depth increased with the increase of loading force, and the relationship between loading force and depth became linear when the loading force is beyond 3000 μN. At the beginning, the plasticity index changed substantially with the increase of loading force, and after reaching a critical loading force, the plasticity index almost remained constant. The maximum indentation depth decreased with the increase of loading rate, which followed a power law curve. With the increase of loading rate, a plasticization phenomenon happened, and a possible reason is that the heat may accumulate and raise the local temperature. The plasticity index initially followed the power law with the increase of unloading rate and then almost remained constant. A constant, the change rate of viscoelastic properties with the unloading rate, for the three representative polymers studied in this research, around ?0.033, has been obtained, which may be another manifestation of the phenomenon that many polymers have similar time/temperature shifts and that their WLF equation constants are approximately the same. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Oxidation behavior of isoprene polymers and butadiene polymers

The oxidation behavior of cis-1,4-polyisoprene, emulsion polyisoprene, emulsion isoprene/styrene copolymers, and emulsion butadiene/styrene copolymers by heat aging or ultraviolet irradiation has been investigated from the change of gel fraction and molecular weight distribution. It was determined that the oxidation behavior of both isoprene and butadiene polymers is strongly dependent on the composition of the polymers as well as on the microstructure of the polymers. In the case of oxidation by heat aging, the probability ratio of chain scission to crosslinking of both isoprene and butadiene copolymers increases gradually with increasing styrene fraction. In the case of oxidation by ultraviolet irradiation, isoprene copolymers show a remarkable increase in the probability ratio of chain scission to crosslinking, whereas butadiene copolymers show substantially no change with increase in styrene fraction. It was also demonstrated that both isoprene and butadiene polymers show a greater tendency for crosslinking with oxidation by ultraviolet irradiation than with oxidation by heat aging.     

Preparation of crosslinked polymers using acenaphthylene and the chemical modification of these polymers

Acenaphthylene was homopolymerized, was copolymerized with divinylbenzene, and was copolymerized with both styrene and divinylbenzene using free radical initiated suspension polymerizations. The acenaphthyl residues in these polymers were more reactive to electrophiles than the phenyl residues in polystyrenes. Thus, bromo, chloro, and iodo groups were introduced using reaction conditions under which polystyrenes did not react. Other groups introduced were sulphonic acid, nitro, 2-chlorobenzoyl, carboxylic acid via cleavage of 2-chlorobenzoyl or via direct metalation then reaction with carbon dioxide, chloromethyl, and formyl.     

难沉降煤泥水组成及特点的研究

以山东某选煤厂的难沉降煤泥水为研究对象,利用现代分析测试手段,分析难沉降煤泥水的水质特性、矿物组成、粒度组成、表面电性等。结果表明导致煤泥水难沉降的主要原因是煤泥水中粘土矿物含量较高,泥化现象严重,颗粒粒度小,表面带有很强的负电荷,具有胶体稳定特性,从而导致其难以沉降。     

论构成艺术与现代陶艺创作观

自然界的物质结构及其生物、生理所构成的美的规律，显示出了巨大的生命力和感染力。同样，艺术中关的形式，有美的法则，也和其它事物的发展一样，逐渐形成了自己的规律性，找到了美的规律、美的法则。然而，任何视觉艺术的形式美规律，都是美的一种表现形态，它必须通过一定的组织结构和艺术语言体现出来。这种形式美规律包含着秩序与和谐、节奏与韵律、条理与反复、比例与尺度、空间与分割、对称与平衡、动与静等。而构成主义艺术就是充分聚集了这些形式美规律应用在其组织结构和艺术语言中。     

Adhesion of glow discharge polymers to metals and polymers

Adhesion of glow discharge polymers to metals and polymers in an adhesive joint was measured by lap-shear test and immersion in hot water of 70°C °C for an extended time. A glow discharge polymer was deposited onto polymers [polyethylene and poly(tetrafluoroethylene)] and metals (aluminum and stainless steel) prior to when the polymer and metal were joined. It is found that the lap-shear strength is enhanced by coating the surfaces of these substrates with plasma film produced from methane, ethylene, and acetylene, and that deterioration of the adhesive bonding part, when immersed in hot water of 70°C, is strongly dependent on the gas used as well as operational conditions where a polymer film is formed. The adhesion of a polymer produced from methane on the polymer and metal is strong enough to apply for durable, adhesive joints.