Thermal Degradation of Environmentally Degradable Poly(hydroxyalkanoic acid)s

Abstract

Aliphatic polyesters have attracted industrial attention as environmentally degradable thermoplastics to be used for a wide range of applications. Besides intensive studies on the biodegradability of aliphatic polyesters, understanding of the thermal stability has importance for processing, application, and recycling. The details of thermal degradation processes of five types of aliphatic polyesters; namely, poly(L-lactide), poly(3-hydroxybutyric acid), poly(4-hydroxybutyric acid), poly(delta-valerolactone), and poly(epsilon-caprolactone), were investigated by means of several thermoanalytical techniques under both isothermal and non-isothermal conditions. In this feature article, the thermal degradation behaviors of aliphatic polyesters with different numbers of carbon atoms in the main chain of the monomeric unit are reviewed. In addition, the effects of chain-end structure and residual metal compounds on the thermal degradation processes of aliphatic polyesters consisting of hydroxyalkanoic acid monomeric units are presented. Schemes of thermal degradation reaction of poly(hydroxyalkanoic acid)s.

Stability of Poly(ε-caprolactone) Microparticles Containing Brucella ovis Antigens as a Vaccine Delivery System Against Brucellosis

“…PEC is a semicrystalline biodegradable polyester polymer that degrades slowly and does not generate an acid environment unlike the PLA/PLG polymers (26). Although the permeability of macromolecules in PEC is low, such low permeability may be sufficient enough for protein delivery (27).…”

Development of materials and technologies for control of polymer recycling

“…PHB has been attracting much interest from researchers not only as an environmentally compatible thermoplastic, but also as a polymeric material obtainable from renewable resources such as sugars, fatty acids, plant oil 107 and even from H 2 , O 2 and CO 2 . 108 PHB has a highmelting temperature of around 180 1C and has recently been demonstrated to be a chemically recyclable material with valuable end products such as crotonic acid, linear oligomers having a crotonate end group 109 , and a cyclic trimer 110 (Scheme 27).…”

Particular thermal properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) oligomers

“…However, it is the widely-held view that the random chain scission by cis-elimination mechanism, also called Mclafferty rearrangement [see Fig. 1(a)] had been considered as the general pathway of PHBV thermal degradation up to now [11,13,[35][36][37][38][39][40][41][42]. For the cis-elimination at the ester linkage, it is necessary to present the β-C-H to the ester oxygen and to form a six-membered ring ester as a transition state [11,41].…”

“…1(a)] had been considered as the general pathway of PHBV thermal degradation up to now [11,13,[35][36][37][38][39][40][41][42]. For the cis-elimination at the ester linkage, it is necessary to present the β-C-H to the ester oxygen and to form a six-membered ring ester as a transition state [11,41]. The formation of the six-membered ring ester is determined mainly by the negative inductive effect of the group at γ-position to the ester oxygen [11,41,42] and the electron-donating effect of a substituent group of carbon atoms at α-position to the ester oxygen [11,13].…”

“…For the cis-elimination at the ester linkage, it is necessary to present the β-C-H to the ester oxygen and to form a six-membered ring ester as a transition state [11,41]. The formation of the six-membered ring ester is determined mainly by the negative inductive effect of the group at γ-position to the ester oxygen [11,41,42] and the electron-donating effect of a substituent group of carbon atoms at α-position to the ester oxygen [11,13]. The stronger the negative inductive effect of the group at γ-position is, more strongly the β-C-H of the methylene group in the β-position to the ester oxygen is activated, which makes it easy to form the six-membered ring ester [11,41,42].…”