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Study of the effect of annealing, draw ratio, and moisture upon the crystallinity of native and commercial gutta percha (transpolyisoprene) with DSC, DMTA, and X‐rays: Determination of the activation energies at T g
Author(s) -
Arvanitoyannis Ioannis,
Kolokuris Ioannis,
Blanshard John M. V.,
Robinson Colin
Publication year - 1993
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1993.070480606
Subject(s) - crystallinity , gutta percha , glass transition , materials science , annealing (glass) , melting temperature , thermal stability , dynamic mechanical analysis , melting point , activation energy , composite material , thermal analysis , analytical chemistry (journal) , chemistry , thermal , thermodynamics , polymer , dentistry , organic chemistry , physics , medicine , root canal
The transitions occurring in gutta‐percha (transpolyisoprene) below the melting point were determined with DMTA and DSC. A comparison of the results obtained with these two methods showed satisfactory agreement. The thermal properties of native and commercial gutta‐percha samples ( T g = 38 ± 2°C and T m = 69 ± 3°C) were investigated, both before and after annealing (at different times and temperatures), and at environments of different relative humidities. An increase in the draw ratio also proved to enhance the percentage crystallinity (% K ) and improve the thermal stability (higher T g s and T m s) of gutta‐percha. Finally, the activation energies Δ E (33.9–40.2 kj/mol × K ) at glass transition temperature were determined and correlated to the percentage content (%) of the commercial gutta‐percha samples in native gutta‐percha. © 1993 John Wiley & Sons, Inc.