The role of chain scission in fracture of amorphous polymers

1986 ◽  
Vol 24 (11) ◽  
pp. 2583-2589 ◽  
Author(s):  
J. L. Willett ◽  
K. M. O'Connor ◽  
R. P. Wool
Keyword(s):  
Amorphous Polymers ◽  
Chain Scission

Free Radicals Generated in Rubber during Fracture

1975 ◽  
Vol 48 (3) ◽  
pp. 445-461 ◽  
Author(s):  
K. L. DeVries
Keyword(s):  
Failure Criteria ◽  
Chain Scission ◽  
Systematic Investigation ◽  
Matrix Interaction ◽  
Filled Elastomers ◽  
Final Note ◽  
Ozone Stress ◽  
Type Of Failure ◽  
Insight Into

Abstract EPR has been used to measure molecular phenomena during fracture of elastomers. To date, because of various technical limitations, the studies have been largely confined to identification of the polymer chain scission site during fracture at low temperature in rubbers, to studying ozone-stress-induced cracking of rubber, to development of a micro-macro Griffith-type failure criteria for this type of failure, and lastly to systematic investigation of the role of filler-matrix interaction in fracture of filled elastomers. It is hoped that the brief outline presented here will give the reader some insight into the uses and potential of the EPR methods for the study of fracture. As a final note, while we have concentrated almost totally on EPR fracture studies in rubbers, there has been fairly extensive EPR work on fracture in oriented plastic, fibers, and films. Even though some of this knowledge may be transferable, directly or indirectly, to elastomers, it has not been reviewed here, but important aspects of these studies have been reviewed elsewhere.

Antioxidant Properties of Carbon Black in Unsaturated Elastomers. Studies with cis-Polybutadiene

1965 ◽  
Vol 38 (3) ◽  
pp. 636-646
Author(s):  
J. T. Gruver ◽  
K. W. Rollmann
Keyword(s):  
Antioxidant Activity ◽  
Carbon Black ◽  
Antioxidant Properties ◽  
Chain Scission ◽  
Oxygen Absorption ◽  
Hydroxyl Groups ◽  
Carbon Blacks ◽  
Crosslinking Reactions ◽  
Absorption Measurements

Abstract The thermal antioxidant behavior of carbon black was studied in vulcanized cis-polybutadiene and related to the surface chemistry of the black. Continuous and intermittent stress relaxation and oxygen absorption measurements were employed to determine the antioxidant ability of the carbon blacks. The blacks were characterized by the surface concentrations of oxygen-containing functional groups, using methods described in the literature. Antioxidant activity was found to be highest in carbons containing relatively large amounts of bound oxygen. These carbons are also acidic and decompose peroxides by the ionic mechanism. This was demonstrated with cumyl peroxide. However, even though the acidity and ability to decompose cumyl peroxide to phenol and acetone could be destroyed by methylation, this treatment did not seriously impair the antioxidant activity, so that the role of acidic groups appears to be minor. Evidence is presented which suggests strongly that the antioxidant behavior of carbon blacks is due to surface quinones, possibly hydrogen-bonded with adjacent hydroxyl groups. Measurements made on samples vulcanized in peroxide and sulfur curing systems indicate that the antioxidant behavior of carbon black is independent of the method of vulcanization in the absence of other antioxidants. A characteristic feature of the antioxidant action of carbon blacks is their tendency to repress the oxidative crosslinking reactions, the relative amount of compensation of chain scission by crosslinking being smaller than in gum vulcanizates.

scholarly journals Improvement of Filler-Matrix Interactions in Polypropylene/Montmorillonite Nanocomposites by Usıng Irradiated Polypropylene

2018 ◽  
Author(s):  
Fatma Zengin ◽  
Tahsin Çağlayan ◽  
Semra Ide ◽  
Olgun Güven
Keyword(s):  
Molecular Weight ◽  
Dose Rate ◽  
Chain Scission ◽  
Clay Nanocomposites ◽  
Melt Flow Rate ◽  
Clay Surface ◽  
Knowing That ◽  
Matrix Interactions ◽  
Organically Modified

In the preparation of polymer-clay nanocomposites the chemical incompatibility between the clay surface and polyolefins can be overcome by using clays organically modified with short chain organic cations. The compatibility can be further enhanced by using functionalized polymer that wets the clay surface while being miscible with the non-polar polymer matrix. In this work we tried to modify the host polymer polypropylene (PP) by irradiating it with gamma-rays in air knowing that it undergoes oxidation and chain scission simultaneously. Thus lower molecular weight PP with highly polar surface due to oxidation can be expected to play double role of clay modifier and functional compatibilizer. This has been observed to be the case. Finely ground PP granules were irradiated in air in a 60Co γ-irradiator at the dose rate of 0.08 kGy/h (low dose rate to enhance oxidation) to 5, 10, and 20 kGy total doses. The extent of oxidation and change in molecular weight were determined by ATR-FTIR and Melt Flow Rate measurements respectively. PP/MMT nanocomposites were prepared by using 20% γ-PP, 1-5 % MMT and pristine PP to make up the total 100 in a torque rheometer. Maleated PP was also used in similar quantities to compare the effectiveness of γ-PP as a compatibilizing agent. Nanocomposites prepared with 10 kGy irradiated PP was found to show optimum mechanical properties among all formulations, with 26% increase in E-modulus and 10% increase in tensile strength as compared to pristine PP. Ternary PP nanocomposites were characterized by XRD, SAXS and PALS studies.

Degradation of Rubber by Chemical Agents in Solution

1961 ◽  
Vol 34 (4) ◽  
pp. 1212-1219
Author(s):  
G. H. Foxley
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Model Compound ◽  
Polymer Degradation ◽  
Chain Scission ◽  
Redox Systems ◽  
Chemical Agents ◽  
The Subject ◽  
Partial Fulfillment

Abstract It is clear that the subject of polymer degradation by chemical agents is an active branch of polymer chemistry. This is reflected in the large number of patents applying to polymer degradation and no attempt has been made to include every appropriate patent. Much of the comparative work is based on equal weights, rather than equal numbers of molecules, so that the true comparisons of the efficiency of peptizers are often difficult. It has been shown that polymer degradation can proceed via several mechanisms all of which involve free radicals and the main points can be summarized as follows :— In solutions at low temperatures the initiatory free radicals come from the added peptizer such as benzoyl peroxide or bis-azoisobutyronitrile. Although oxygen accelerates the reaction, it is not essential, and there is appreciable degradation in the absence of oxygen. Thiols are active only when oxygen is present even at high temperature. This is somewhat surprising, since the rubber radicals produced by thermal scission should be just as active as those produced by mastication and be capable of reaction with thiols, and serves to emphasize the importance of the role of oxygen in peptization by thiols and disulfides. Oxygen is also necessary for degradation by redox systems and in its absence structurizing takes place. The lack of work on triphenyl methane derivatives is somewhat surprising in view of the ease with which they undergo homolysis to give free radicals. However, it is not sufficient to introduce any type of free radical and expect degradation: stabilized free radicals are the best peptizers, unstable radicals can add to olefinic bonds and cause crosslinking rather than chain scission. Squalene has been used as a model compound for the study of the reactions of natural rubber with free radicals in a similar manner to the use of methylcyclohexene as a model compound for oxidation studies. This review forms part of a dissertation submitted in partial fulfillment of the requirements for the London University M.Sc. (External) Examination.

Role of chain scission in cross-slot flow of wormlike micellar solutions

2017 ◽  
Vol 2 (7) ◽  
Author(s):  
Arthur Kalb ◽  
Larry A. Villasmil U. ◽  
Michael Cromer
Keyword(s):  
Chain Scission ◽  
Micellar Solutions
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