摘要:

AbstractInvestigations are being conducted on the factors involved in the breakup of Newtonian and non‐Newtonian (viscoelastic) liquids in high velocity airstreams. Viscoelastic solutions are formed by the addition of small amounts of polymeric modifiers to the test liquid. The mechanism of breakup is shown to be significantly different between the thickened and unthickened solutions. It was found that Newtonian liquid drops are broken into very fine particles by a breakup mechanism which begins with a stripping of the liquid from the surface of the drop. On the other hand, drops of non‐Newtonian liquids break up by formation of ligaments rather than by surface stripping and are broken into much larger particles. An increase in viscosity by a factor of 25 in the Newtonian liquids showed no significant change in the breakup mechan

ISSN:0021-8995    

DOI:10.1002/app.1961.070051301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

ISSN:0021-8995    

DOI:10.1002/app.1961.070051320

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

ISSN:0021-8995    

DOI:10.1002/app.1961.070051321

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractAlthough sodium disulfide is one of the chief reactants in the preparation of polymeric disulfides, it has the ability to cleave the disulfide links in the polymer, as is shown in this paper. This cleavage is responsible for losses in yield of polymer through solubilization of fragments of low molecular weight, but is it also necessary in producing high polymers. The unreactive terminal hydroxyl groups produced by the side reaction of alkaline hydrolysis of reactive chloride terminals would ordinarily limit the chain length of the polymer; however, the preferential solubilization of the terminal fragments, because of the hydrophilic hydroxy group, permits the molecular weight of the polymer to be increased greatly. An excess of sodium disulfide is thus needed in order to obtain disulfide polymers of high molecular weight, in contrast to the usual condensation polymerization wherein an exact equivalence of reactants is needed. The cleavage of the aliphatic disulfide groups in the polymer by aqueous sodium polysulfide is a reversible reaction with the equilibrium favoring re‐formation of the disulfide linkage. The equilibrium is displaced if a reagent capable of binding sulfur is present. A mixture of sodium sulfide, in particular sodium hydrosulfide, with sodium sulfite can be used in an efficient and controllable manner to convert polymer disulfides of high molecular weight to polymers of low molecular weight with terminal thiol group

ISSN:0021-8995    

DOI:10.1002/app.1961.070051302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractThe possibility of grafting and polymerizing unsaturated monomers, styrene chiefly, on cellulose acetates of different acetyl contents after introduction of an unsaturated group in the cellulosic ester was studied. This group was introduced by further esterification with unsaturated anhydrides (maleic and crotonic) or by etherification with methacryloylethylenimine. The samples, examined by infrared spectrometry and by analytical methods, show a maximum of 6–8% of grafted styrene with respect to the cellulosic este

ISSN:0021-8995    

DOI:10.1002/app.1961.070051303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractThe rate of emulsion polymerization of vinylidene chloride has been measured as a function of catalyst and surfactant concentration in the system consisting of vinylidene chloride, water, ammonium persulfate, sodium metabisulfite, and sodium lauryl sulfate. The polymerization may be divided into three rather well‐demarcated stages. In the first, a normal emulsion polymerization occurs at a rate which depends on the 0.6‐power of the catalyst concentration and the 0.6‐power of the surfactant concentration. In the second stage, the rate drops to less than half that of Stage I. The percentage conversion at which Stage II begins increases with increasing surfactant concentration. Stage II is absent at very high surfactant concentrations (10 g./100 g. monomer). In the third stage, the rate increases and may exceed the rate of Stage I; it depends on the first power of the catalyst concentration and is independent of surfactant concentration. Addition of catalyst at the end of the first stage does not affect the rate of Stage II but increases the rate of Stage III. These results are discussed in relation to the theories of Harkins, Smith, and

ISSN:0021-8995    

DOI:10.1002/app.1961.070051304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractIn seeking an explanation for the unusual kinetics observed in the persulfate‐catalyzed emulsion polymerization of vinylidene chloride, the role of particle coalescence has been examined. A theory has been proposed and the predicted results have been compared with experiment. Development of the theory assumes that after excess surfactant (sodium lauryl sulfate) has been removed from the solution by adsorption on the surface of growing polymer particles, coalescence commences as a second‐order process with an invariant specific rate constant, and that the rate of polymerization per particle increases linearly with particle volume (it is assumed that more than one growing chain can exist in a particle). The equations derived involve two adjustable parameters:B, a measure of the coalescence rate which is fixed from best fit of one experimental resin, andA, a function of the catalyst concentration. The equations predict a minumum in the conversion rate at some time after the coalescence starts. Data for the third stage of the per‐sulfact‐catalyzed polymerization of vinylidene cholride can be explained by this theory. It is shown that particle coalescence alone cannot completely explain all of the observations which have been made on this system, however; in particular, the extent of slowdown in Stage II greatly exceeds that predicted by

ISSN:0021-8995    

DOI:10.1002/app.1961.070051305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractThe effect of stirring speed on the rate of the persulfate‐catalyzed polymerization of vinylidene chloride has been determined. It was found that the first‐stage rate decreases with increasing stirring speed, that the second‐stage rate increases with increasing stirring speed, and that the rate of the third stage is independent of stirring speed. These results, as well as those of an earlier paper, may be explained in the following manner. The second stage slow‐down results from monomer starvation, caused by slow diffusion from coalesced droplets. Recovery is caused by transfer of monomer at the time of collision between a polymer particle and a monomer droplet. These collisions are allowed when the repulsive forces between monomer droplet and polymer particle are reduced because of surfactant def

ISSN:0021-8995    

DOI:10.1002/app.1961.070051306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractThe component of clarity of polymer films, dependent on optical resolution, was conveniently and objectively determined from light‐scattering measurements at low angles (i.e., below 1°). The width of the scattering curve at half the maximum intensity was used as an index of clarity. This quantity is essentially equivalent to the minimum angle of resolution obtained when viewing a test object through the film. By applying a correction for the resolution of the instrument, the range of the instrument was extended in the direction of high clarity, and within the precision of the measurements the clarity ratings are independent of instrument characteristi

ISSN:0021-8995    

DOI:10.1002/app.1961.070051307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY

摘要:

AbstractMany cured, black‐loaded rubbers contain varying amounts of inorganic fillers: to characterize the rubber, absorptions due to fillers must be recognized and identified. Reference spectra of all the common inorganic fillers used in the rubber industry have been recorded and their recognition in infrared spectra of ultra‐thin microtomed sections of known and unknown samples is described. Both rubbers and inorganic fillers can usually be identified in cured samp

ISSN:0021-8995    

DOI:10.1002/app.1961.070051308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1961

数据来源: WILEY