Thermal degradation of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) in drying treatment

Abstract

This study examines the isothermal treatment of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) powders and films. The PHB and PHBV crystallinities were determined using X-ray diffractometry, and shown to increase with temperature (130-150 C) and then decreased from 55% to 45% at 180 C. The crystal morphology of crystal planes (101) and (111) became sharp at a high temperature. The weight average molecular weight (M w ) of PHB decreased from 1,028,000 to 41,800 g/mol when heated at 180 C for 30 min. The molecular weight of PHB decreased more rapidly than that of PHBV with time. No peak signal was observed in gel permeation chromatography after heating at 150 C because the solubility of PHB changed with crystallinity. The thermal behaviors of PHB and PHBV were analyzed by differential scanning calorimetry and thermogravimetric analysis. The roughness, contact angle, and surface morphology of PHB and PHBV films were also measured to determine the surface properties.

From obtaining to degradation of PHB: A literature review. Part II

“…This finding is in agreement with the study of CHEN et al [10] that indicate a reduction of molar mass of PHB when submitted to temperatures above the melting range, due to thermal degradation. The increase in the exposure time and temperature influence the reduction of molar mass of PHB [10], [11]. This can be seen in Table 1 which shows the dependence of the molar mass of PHB on various temperatures.…”

“…The reactions involved in this process leads to changes in physical properties and optical drive from PHB, and an example of this is the shift in the molecular mass of the material [2], which causes a greater mobility of its polymeric chains [9]. This finding is in agreement with the study of CHEN et al [10] that indicate a reduction of molar mass of PHB when submitted to temperatures above the melting range, due to thermal degradation. The increase in the exposure time and temperature influence the reduction of molar mass of PHB [10], [11].…”

From Obtaining to Degradation of PHB:Material Properties. Part I

“…These bacteria can be found in a variety of environments, in soil, water, sewer microbiologically treated [40] and even of mangrove [15]. Some of the most known species of PHB bacteria are: Ralstonia eutropha [41] (nowadays Cupriavidus necator [42]), Escherichia coli [9], Burkholderia cepacia and Zobellela denitrificans [15], Bacillus megaterium and Pseudomonas oleovorans [26], Protomonas extorquens, Protomonas oleovorans, Alcaligenes latus and Azobacter vinelandii [43]. These bacteria can be divided into two groups according to the composition of the culture medium necessary for the synthesis of PHB.…”

“…Due to the characteristics of the biodegradability and biocompatibility previously submitted, the PHB presentes great potential for applications in pharmacological area [92], environmental [9], packaging [11], veterinary and industrial [17], agricultural [18] and biomedical [21], [25]. Some examples of applications are presented in Table 3.…”

“…This material is nontoxic [9], optically active [26] and when pure, has a yellowish coloration [6], [27], presents barrier to permeability of water and gas [6] and stability to ultraviolet radiation [28], and can be processed by extrusion, injection, blowing and thermoforming [29].…”