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Starch urea‐formaldehyde matrix encapsulation. IV. Influence of solubility and physical state of encapsulant on rate and mechanism of release
Author(s) -
Shukla P. G.,
Rajagopalan N.,
Sivaram S.
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.1993.070480709
Subject(s) - solubility , swelling , urea formaldehyde , chemical engineering , urea , materials science , polymer , starch , polymer chemistry , chemistry , matrix (chemical analysis) , composite material , organic chemistry , adhesive , layer (electronics) , engineering
The influence of the physical state and solubility of the encapsulant on the rate and mechanism of release and swelling of the cross‐linked starch‐urea formaldehyde (St‐UF) matrix has been studied by encapsulating model organic compounds. The release and swelling data have been analyzed in terms of the generalized equation M t / M ∞ = kt n applicable for swellable controlled‐release systems. This matrix system shows and an inverse relationship of release rate with the cross‐link ratio for all the encapsulants studied. The solid encapsulants have n values in the range of 0.22–0.41, indicating a Fickian or anomalous mechanism. Further, the release rate increases with solubility of the encapsulant. The liquid encapsulants have n values in the range of 0.5–1.5, indicating Case II transport mechanism. The release rates for liquid encapsulants are lower by one to three orders of magnitude than those for solid encapsulants and are not influenced by encapsulant solubility. This indicates a polymer chain relaxation‐controlled mechanism of release for liquid encapsulants. © 1993 John Wiley & Sons, Inc.