Activated gas plasma surface treatment of polymers for adhesive bonding

Polyethylene, polypropylene, poly(vinyl fluoride) (Tedlar), polystyrene, nylon 6, poly(ethylene terephthalate) (Mylar), polycarbonate, cellulose acetate butyrate, and a poly(oxymethylene) copolymer were treated with activated helium and with activated oxygen. Mechanical strengths of adhesive-bonded specimens prepared from treated and from untreated coupons were compared. Polyethylene (PE) and polypropylene (PP) showed the greatest increases in bond strength. Oxygen and helium were both effective with polyethylene, but polypropylene showed no improvement when treated with activated helium. The results with excited helium parallel the effects of ionizing radiation on these two polymers, as does the appearance of unsaturation bands in the infrared (965 cm^?1 in PE, and 887 and 910 cm^?1 in PP). Active nitrogen produced excellent bond strength with polyethylene but not with polypropylene. Of the remaining polymers examined, Tedlar, polystyrene, and nylon 6 showed the greatest improvement in bondability after treatment, and Mylar showed moderate improvement. Polycarbonate, cellulose acetate butyrate, and the poly(oxymethylene) copolymer gave approximately two-fold increases in lap-shear bond strength. In several cases, significant differences in response to time of treatment and type of excited gas were found.     

Water for the Dyer

The present and estimated future use of water in England and Wales is compared with available resources. Use is overtaking easily available supply. The changes in procurement of water and disposal of effluent implied in recent legislation (setting up River Authorities and the Water Resources Board) are discussed, particularly as they are likely to affect the dyeing industry. The quality of water for use in the dyeworks is discussed in terms of dissolved and suspended impurities; and the methods available for the control of the effects on the dyeing process of ionic solutes, residual hardness, heavy metals, and bicarbonate are summarised. The problems of disposal of dyeworks' effluent are considered in so far as they impinge on national water-management policy. Savings in the cost of effluent treatment may be possible in an integrated textile industry where all processes, including disposal, are considered together in planning. Instances of process modification to avoid effluent-disposal problems are cited.     

Novel Gas-Liquid-Solid Reactors

Multiphase reactors involving gas, liquid, and solid phases have several important applications in the chemical industry, particularly in catalytic processes. Some of the well-known examples are: hydrogenation and oxidation of organic compounds, hydro-processing coal-derived and petroleum oils, Fischer-Tropsch synthesis, and methanation reactions. Due to the presence of three phases, the problem of reactor design is often important to achieve effective mass and heat transfer as well as a mixing pattern favorable to the particular process. The reactors are mainly of two types: (a) solid catalyst is suspended either by mechanical agitation or gas-induced agitation and (b) solid catalyst is in a fixed bed with concurrent or countercurrent feed of gas and liquid re-actants. The reactor types conventionally used in industry are: (a) mechanically agitated or bubble column slurry reactors and (b) trickle-bed or packed-bed bubble reactor. The various design and modeling aspects of these reactors have been reviewed by Satterfield [1], Chaudhari and Ramachandran [2], Shah [3,4], Ramachandran and Chaudhari [5], Shah et al. [6], and Herskowitz and Smith [7]. In several industrial processes these reactor designs are modified to achieve a certain specific objective, such as better heat or mass transfer, higher catalyst efficiency, better reactor performance and selectivity, etc. Similarly, specially designed reactors are often used for laboratory kinetic studies or to understand a certain phenomenon. Thus, novel multiphase reactors are becoming important from both academic and industrial viewpoints. Some of the recently introduced novel gas-liquid-solid reactor types are: (a) loop recycle slurry reactors, (b) basket-type reactors, (c) ebullated-bed reactors, (d) internal or external recycle reactors, (e) multistage slurry or packed-bed reactors, (f) column reactors with sieve trays or multiple agitators, (g) gas-induced agitated reactors, and (h) horizontal-packed-bed reactors. are being used in several new commercial processes, and various design aspects, such as hydrodynamics and mass and heat transfer, have been the subject of investigations in the last few years. However, no attempt to review the scattered information on these novel gas-liquid-solid reactors has been made. Therefore, the main objective of this paper is to review important developments in novel gas-liquid-solid reactors. For each type of reactor, advantages, disadvantages, and applications are discussed. Further, the status of information on hydrodynamics and mass transfer parameters and scale-up considerations is reviewed. These novel reactor designs are being used in several new commercial processes, and various design aspects, such as hydrodynamics and mass and heat transfer, have been the subject of investigations in the last few years. However, no attempt to review the scattered information on these novel gas-liquid-solid reactors has been made. Therefore, the main objective of this paper is to review important developments in novel gas-liquid-solid reactors. For each type of reactor, advantages, disadvantages, and applications are discussed. Further, the status of information on hydrodynamics and mass transfer parameters and scale-up considerations is reviewed.     

Gibt es eine Pflicht zum pr?natalen Nichtwissen?

Fall und Kommentare

Gibt es eine Pflicht zum pr?natalen Nichtwissen?     

Polymerization with zeolite catalysts: I. Polymerization of n-butylvinylether by H-mordenite

n-Butylvinylether sorbed from the vapor phase onto hydrogen mordenite powder has been found to polymerize readily near room temperature. In a polymer sample from this reaction the polymer molecules were found to contain a number average of ten monomer units. The reaction over a considerable time interval followed the relations Q_t = k √t + γk = (ap + b)F(H₂O) where Q_t is the mass uptake (mainly as polymer) at pressure p in time t; k, γ, a and b are coefficients and F(H₂O) is a function of the amount of water in the zeolite. The kinetics have been taken to indicate partial control by a diffusion process in which the monomer penetrates a growing layer of polymer formed around each catalyst particle. The monomer migrates to the catalyst-polymer interface and polymerizes at or near the interface. In small quantities water functioned as a cocatalyst, but around 5% weight uptake F(H₂O) passed through a maximum. The rate of the reaction appeared to reach a maximum between 28 and 30 °C. A carbonium ion mechanism of polymerization is proposed.     

Mass transfer modelling for GS heavy water plants: Part 1: Point efficiency on GS sieve trays

A model that takes into account the gas-phase and liquid-phase resistance to mass transfer has been developed, where the overall mass transfer coefficient (K_OGa) is expressed as a function of the equivalent Sauter-mean bubble diameter. This parameter was back calculated from mass transfer measurements made at a pilot plant on single pass sieve trays of 0.311 m diameter. Hydraulic parameters were measured for these trays as well. Mean bubble diameters were then correlated as a function of active area F-factor and dispersion height for various tray geometries, and these correlations are used to predict point efficiencies on production plant trays up to 8.5 m in diameter.     

Simulation of catalytic fluidized bed reactors by a transient axial dispersion model with invariant physical properties and nonlinear chemical reactions

This paper presents a transient axial dispersion model for an isothermal, catalytic fluidized bed reactor, which is frequently employed in synthetic production processes including coal gasification and liquefaction. A non-linear chemical reaction is considered to occur in the reactor. This model of a fluidized bed reactor takes into account the axial dispersion in the three phases, bubble, cloud-wake and emulsion. The physical properties along the axial coordinate are invariant in the model. Transient characteristics of the gas reactant, and the length of the transient period have been examined based on the model. The model compares favorably with experimental data in the steady state condition.     

The determination of polymer interfacial tension by drop image processing: Comparison of theory and experiment for the pair,poly(dimethyl siloxane)/polybutndiene

The interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co-workers. Qualitative agreement is obtained with both types of theory when the Flory-Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperature.     

Oxidation of unsaturated fatty acids with ruthenium and osmium tetroxide

The oxidation of the alkali metal salts of oleic and undecylenic acid with ruthenium and osmium tetroxides is reported. The oxidants are used in catalytic amounts in conjunction with an excess of the in-expensive cooxidant sodium hypochlorite. Ruthenium tetroxide cleaves the carbon-carbon double bond of potassium oleate, to give pelargonic and gives sebacic acid. With osmium tetroxide, hydroxylation of the double bond of potassium oleate gives a 95% yield oferythro-9,10-dihydroxystearic acid. The osmium tetroxide oxidation of sodium undecylenate results in the formation of 10,11-dihydroxyundecanoic acid and the cleavage product sebacic acid in varying yields.     

Gläser in der Geschirrspülmaschine I

Glasses in Dish Washing Machine I Efficiency of household dish washing machines, detergents and rinsing-aids has been considerably increased during the past years. A common problem is due to the diversity of articles to be washed. Even today, the behaviour of glasses causes some anxiety, because mechanical washing can lead to scratchy appearance and turbidities. These anomalies are mainly due to factors originating from the glass itself, although the external factors during the process of mechanical washing play a significant role as well. Results of investigations have shown that mechanical washing requires highly resistent glasses. The author has shown that it is possible to prepare standardized glasses that are required for such experiments. It is interesting to note that glasses certified as resistent a dish washing machines are already offered in the market.