摘要:

AbstractTheoretical and practical evidence is put forward to show that copolymers can be treated like solutions of small molecules in the interpretation of packing phenomena, and that ideal volume‐additivity of the repeating units in copolymers is frequently realized. On this basis equations are derived for predicting θ, the second‐order transition temperature, of binary copolymers from the two second‐order transition temperatures of the pure polymers and their coefficients of expansion in the glassy and rubbery states. Previous mechanistic theories of the second‐order transition temperature of such copolymers are thus superseded by a general reduction of the problem to the mechanism of thermal expansion. Practical applications to the choice of monomers in producing synthetic rubbers are outlined, and attention is drawn to the importance of second‐order transitions in kinetic measurements on the reactions o

ISSN:0021-8871    

DOI:10.1002/jctb.5010020901

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractExperimental methods are described for the evaluation of the important mechanical properties of (a) hard plastics, (b) elastomers, when only small amounts of the materials are available. For thermoplastics of type (a), the impact strength was determined by a Charpy‐type test on notched square‐section bars of dimensions 4 cm. × 0·3 cm. × 0·3 cm. cut from strain‐free moulded plates. Softening point was determined by measuring the dilatometric second‐order transition temperature. A qualitative indication of moulding properties was obtained using an Atkinson–Nancarrow plastometer.For materials of type (b), tensile and elongation testing of dumb‐bell specimens in which the effective portion measures 20 mm. × 5·3 mm. × 0·5 mm. gave reproducible results for plasticized polyvinyl chloride. Details of methods of preparing the stock, if high reproducibility is to be obtained, are given. Refractometric determination of second‐order transition temperature was used to measure the brittle temperature. Resilience testing was carried out on specimens measuring 1 cm. × 1 cm. × 4 mm., the apparatus being described.A method for investigating the volatility of plasticizers in small specimens of plasticized poly

ISSN:0021-8871    

DOI:10.1002/jctb.5010020902

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe value of the specific surface for a given powder obtained by the application of Carman's equation is in general found to depend on the porosity of the bed on which the test is made. In this paper a correction is developed that largely eliminates this variation.Furthermore, for those powders which have also been analysed by alternative techniques, the values of specific surface, as determined by the use of Carman's equation and corrected by means of the data of the present paper, and those obtained by the application of the photo‐extinction and nitrogen‐adsorption techniques, show the deviations which would be predicted from the known limitations of the alternative methods of analy

ISSN:0021-8871    

DOI:10.1002/jctb.5010020903

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe action of dilute aqueous solutions of representative anionic, cationic and non‐ionic wetting agents on mild‐steel sheet has been studied. Three types of water have been used: London tap‐water, distilled water, and tap‐water softened by the zeolite base‐exchange process. The effects of varying the pH of the water used from 2 to 12, and of temperature changes, have been investigated.Most of the anion‐active agents used caused adsorption of organic anions, either on the metal itself, or on the initial corrosion products, so modifying the normal action of plain waters. The cation‐active agents did not produce adsorbed films, but the alkalinity of triethanolamine solutions reduced the extent of rusting.Changes in the pH of the water used to prepare solutions produced little effect, although increased pH caused greater activity in solutions of cationic agents containing bromine.In general, rise of temperature caused increased attack, although the reduced solubility of oxygen mitigated this effect.Results have been expressed graphically and a mechanism

ISSN:0021-8871    

DOI:10.1002/jctb.5010020904

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe action of dilute aqueous solutions of representative wetting agents on sheet tin has been studied. Solutions have been prepared from distilled water, and London tap‐water with and without zeolite softening. The effect of varying the pH of these waters, and of temperature changes, has been investigated.‘Sulphonated’ castor oil, triethanolamine, and the non‐ionic agents were without effect on tin, but all other agents produced attack. A feature of this attack was the formation of white crusts of corrosion product, surmounting a deep black pore surrounded with interference tints. Tap‐water solutions were generally less corrosive than those prepared from softened or distilled water.Increase of temperature caused increased attack, and in some instances reduced pH also encouraged corrosion.All results have been expressed graphically, and a mechanism is

ISSN:0021-8871    

DOI:10.1002/jctb.5010020905

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe chemical, and to a more limited extent the physical, properties of coal tars of different origins are reviewed to serve as a background to the work to be described in later parts, mainly on tars derived from down‐jet combustion of bituminous coal. To the same end, the chemistry of the amorphous constituents of coal tars is separately considered, and a classification on the basis of known data is give

ISSN:0021-8871    

DOI:10.1002/jctb.5010020906

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe features of the process of down‐jet combustion of coal bearing on the quality of the tar produced are considered. The physical properties of the tar from a high‐volatile, weakly caking coal (Haunchwood peas) and examination of the fractions obtained by distillation show it to be of low‐temperature type. The fraction obtained between 370° and about 400° was a resinous organo‐gel containing high‐boiling phenols, neutral substances and bases. The main chemical classes of compounds were separated from this tar by solvent extraction, and the fractions obtained were further subdivided with organic solvents for comparison with other tars and to obtain sufficiently simple materials for more detailed examination later. Analyses, yields and descriptions of the fractions obtained are given. Similar solvent‐extraction of a down‐jet tar from a low‐oxygen (high‐rank) coal showed that differences and similarities in the coal structures were reflected in the composition of the tars. Further evidence of the primary nature of down‐jet t

ISSN:0021-8871    

DOI:10.1002/jctb.5010020907

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe acid‐catalysed reaction of excess propan‐1‐ol with commercial aqueous glyoxal solution (cf. MacDowell&McNamee, 1944) readily yielded 1:1:2:2‐tetra‐n‐propoxyethane as main product. When excess propan‐2‐ol was employed complex acetals were obtained, including 2:3:5:6‐tetraisopropoxy‐1:4‐dioxan and stereoisomeric forms of 2:3:6:7‐tetraisopropoxyperhydro‐1:4:5:8‐tetraoxanaphthalene. Unsuccessful attempts were also made to prepare 1:1:2:2‐tetraisopropoxyethane from ‘polymeric glyoxal hydrate’ and from glyoxal bis‐bisulphite compound.The analytical determination of 1:1:2:2‐tetra‐n‐propoxyethane was investigated and a gravimetric method em

ISSN:0021-8871    

DOI:10.1002/jctb.5010020908

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe technique used at the Chemical Research Laboratory for the removal of oxide films from metal surfaces has been improved, with the objects of obtaining larger pieces of film and of facilitating their manipulation. The improved technique, entailing reinforcement of the film by Formvar (polyvinylformal) resin, is described and examples are given of the application of the method.

ISSN:0021-8871    

DOI:10.1002/jctb.5010020909

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe equilibrium volume‐temperature relationship for solid polystyrene has been investigated by a dilatometric method. The results show that, under equilibrium conditions, the volume is a strictly linear function of the temperature in the range 50–120° and that an apparent transition point is observed only when non‐equilibrium conditions obtain, thus confirming claims of previous workers over which there has been some contr

ISSN:0021-8871    

DOI:10.1002/jctb.5010020910

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY