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The molecular basis of fracture in poly(methyl methacrylate) latex films
Author(s) -
Sambasivam Mahesh,
Klein Andrew,
Sperling Leslie H.
Publication year - 1996
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/(sici)1099-1581(199605)7:5/6<507::aid-pat535>3.0.co;2-a
Subject(s) - materials science , annealing (glass) , composite material , glass transition , poly(methyl methacrylate) , methyl methacrylate , dispersity , polymer , atmospheric temperature range , activation energy , fracture toughness , reptation , polymer chemistry , monomer , thermodynamics , chemistry , physics
Latex films of poly(methyl methacrylate) (PMMA) (M n = 485,000 g/mol); (polydispersity index, PDI=1.85), were prepared by molding the dry latex powder. Two different conditions of molding and annealing temperatures (T) were used : (a) low conditions (mold T = 130 and anneal T = 140°C), and (b) high conditions (mold T=150 and anneal T=180°C). Fracture studies on the annealed latex films were carried out using a dental burr grinding instrument (DGBI) at a burr rotational frequency of 16 Hz. The DGBI cuts the films at a depth of 500 nm per pass. In the latex films, the fracture energy increased with annealing time for both sets of processing conditions. For the lower annealing temperature, however, a maximum in the fracture energy was observed around 30 min, apparently related to the reptation time. For the higher annealing temperature, no peak was observed, and the fracture energy approached a plateau value after 24 hr of annealing. Also, the molecular weight dependence of the fracture energy in fully annealed PMMA latex films was studied in the number‐average molecular weight range 2–48 × 10 4 g/mol. The experimental chain pullout energy for fully annealed PMMA was 211×10 6 J/m 3 , close to that predicted by Mark, but somewhat larger than that predicted by Evans. Mer frictional coefficients suggest that the actual temperature of a chain being pulled out is in the range of 220°C, above the glass transition temperature of the polymer.