摘要:

AbstractA study of the dilution effect of four hydrocarbons (biallyl, hexane, 3‐methyl‐1‐butene, and isopentane) on the rate of polymerization of butadiene and on the characteristics of the resulting polymer has shown that chain transfer of the following type is an unimportant reaction in butadiene polymerization:The above result is consistent with the kinetic treatment of crosslinking as developed by Flory. The results of a comparison of the emulsion polymerization of 2,2′‐azobisisobutyronitrile‐ and of persulfate‐catalyzed butadiene are adequately accounted for without considering the effect of the catalysts on branching or crosslinking. As previously suggested, the differences noted between 2,2′‐azobisisobutyronitrile‐ and persulfate‐catalyzed polybutadienes are probably due to a different molecular‐weight distribution. This difference in molecular‐weight distribution is partly produced by a large difference inrvalues for the two systems. The unmodified emulsion polymerization of butadiene with 2,2,‐azobisisobutyronitrile in an oxygen‐and peroxide‐free system produc

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137201

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

摘要:

AbstractPolyethylene can be heat‐oxidized in air when temperatures in excess of 125°C. are employed or photo‐oxidized when exposed to ultraviolet radiation during weathering. Infrared spectrophotometric studies show that during these types of oxidation carbonyl groups are formed and the concentrations of the three types of carbon to carbon double bond groups present are altered. Grating spectra in the 5.6–6.0 micron region reveal that the carbonyl groups formed by heat‐oxidation are mainly ketonic (5.81 microns) although some aldehyde (5.77 microns) and acid (5.84 microns) groups are also present. In photo‐oxidized samples, the carbonyl groups are rather well distributed among the aldehyde, acid and ketone forms. For oxidized samples showing intense carbonyl absorptions, there is a small increase in the concentration of RHCCHR groups (10.35 microns) for both types of oxidation. At this same degree of oxidation both the heat‐and photo‐oxidized samples show decreases in the concentration of RRCCH2groups (11.25 microns). However, this decrease is considerably more pronounced in the photo‐oxidized samples. Finally, there is a small decrease in the concentration of RHCCH2groups (10.07 and 11.00 microns) in the heat‐oxidized samples which stands in contrast to a large increase in concentration of RHCCH2groups produced by photo‐oxidation. The presence of an absorption maximum at 2.81 microns as the heat‐oxidation of polyethylene is occuring is indicative of

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137202

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137203

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137204

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

摘要:

AbstractA comprehensive study of the dynamic mechanical and dielectric properties of acrylic polymers (polymethyl methacrylate, polymethyl‐α‐chloroacrylate) has been made; these two properties were found to be intrinsically correlated; results are given in graphic form. The hypothesis is proposed that each of several mechanical and dielectric dispersion regions found in a given polymer is associated with a definable structural feature,i.e., a group of atoms, in the polymer, such that each group gives rise to a mechanical dispersion and, if polar, also to a dielectric dispersion in the same temperature and frequency region; it should also be possible to trace the same dispersion from one polymer to another, provided they all contain the same g

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137205

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

摘要:

AbstractThe transfer constant for the butadiene‐polybutadiene system at 50°C. has been calculated from data obtained from a graft polymerization study of that system. This constant (K= 1.1 × 10−3) has been used to calculate that polybutadiene prepared in an emulsion system at 50°C. contains an average of one branch for every 800 monomer

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137206

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137208

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137209

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1954.120137210

出版商:Interscience Publishers, Inc.    

年代:1954

数据来源: WILEY