{"@context":"https://schema.org","@type":"ScholarlyArticle","headline":"Fracture processes in polymeric materials. II. The tensile strength of polystyrene","author":[{"@type":"Person","name":"J. P. Berry"}],"datePublished":"1961","isPartOf":{"@type":"Periodical","name":"Journal of Polymer Science"},"identifier":"https://doi.org/10.1002/pol.1961.1205015405","description":"AbstractThe Griffith treatment of brittle fracture predicts that the tensile strength of a material should vary inversely as the square root of the length of a crack or flaw which it contains, the proportionality constant being a function of the surface energy. This relation has been verified experimentally for a series of polystyrene samples which contained deliberately introduced cracks. The value of the surface energy obtained from the results is 1.7 × 106 ergs/cm.2. This is much larger than would be predicted from the molecular constitution, and also higher than the value found from similar experiments on poly(methylmethacrylate). Deviation from the theoretical relationship occurs at small crack sizes, an effect which is attributed to the tendency of the polymer to craze. The effective size of the crazing cracks is estimated to be ∼0.04 in. Because of its higher surface energy, polystyrene is intrinsically stronger than poly(methyl methacrylate). However, the effective flaw size of poly(methyl methacrylate) is only ∼0.002 in., and the tensile strength of conventional samples of this polymer is higher than that of similar samples of polystyrene. These results indicate the importance of two factors which determine the strength of glassy polymers: (1) the surface energy, and (2) the effective flaw size. It is believed that a viscous flow process which occurs during fracture makes a large contribution to the surface energy, but the factors which govern the effective flaw size are, at present, little understood.","url":"https://innscience.ca/en/community/literature/f63ed5ae-e1c1-455a-8f17-e40924298a1d"}