Pyrolysis of bacterial polyalkanoates

Abstract

HIROMICHI MORIKAWA and ROBERT H. MARCHESSAULT. Can. J. Chem. 59,2306(1981. Pyrolysis products from bacterial polyesters, poly-P-hydroxybutyrate (PHB), and froma heteropolyester(P-hydroxyvalerate and P-hydroxybutyrate) were identified. Different physical forms of PHB were studied: PHB purified by dissolution in chloroform, native granules of PHB, and PHB in bacterial cells. The products were characterized by gc, ms, and nmr analysis. The yield of crotonic acid obtained by the pyrolysis of purified PHB was 60 to 65%. Pyrolysis of PHB native granules yielded crotonic acid as well as oligomers of PHB with a terminal crotonate. Upon direct pyrolysis of dry bacterial cells, the yield of crotonic acid was 20 to 25% of the PHB in the cells. From the heteropolymer, 2-pentenoic acid and terminally unsaturated oligomers of polyhydroxyvalerate were obtained. The usefulness of the pyrolysis method for obtaining vinyl compounds from bacterial cultures containing polyalkanoates is discussed.HIROMICHI MORIKAWA et ROBERT H. MARCHESSAULT. Can. J. Chem. 59,2306(1981. On a identifie les produits provenant de la pyrolyse des polyesters bactiriens poly-P-hydroxybutyrate (PHB) et du polyester heterogene (P-hydroxyvalirate e t P-hydroxybutyrate). On a Ctudie les differentes formes physiques du PHB: le PHB purifie par dissolution dans le chloroforme, les granules naturels de PHB et le PHB des cellules bacteriennes. On acaracterise les produits par chromatographie en phase gazeuse, par spectrometrie de masse et par la rmn. Le rendement en acide crotonique provenant de la pyrolyse du PHB purifie est de 60 a 65%. L a pyrolyse des granules naturels de PHB conduit aussi bien 5 I'acide crotonique qu'a des oligomkres du PHB avec un crotonate terminal. La pyrolyse directe des cellules bacteriennes s6ches conduit a un rendement en acide crotonique qui represente 20 a 25% du PHB contenu dans les cellules. On a obtenu du polymere hkterogkne I'acide penten-2 I oique et des oligomkres du polyhydroxyvalerate insaturk en position terminale. On discute de I'utilite de la methode de pyrolyse en I vue d'obtenir des composes vinyliques a partir des cultures bacteriennes contenant des polyalcanoates.

Reprocessability of PHB in extrusion: ATR-FTIR, tensile tests and thermal studies

“…For all samples, the residual weight is lower than 0.5 wt%. Each TGA curve indicates a single step degradation, which means that the thermal degradation of PHB polymer chains occurs by only one mechanism [39] .…”

“…Also studies seeking to improve the thermal stability of PHB by grafting chemicals in PHB chain [33,36] , and adding polymeric additives in PHB matrix [37,38] have been developed. The thermal degradation behavior of PHB has been discussed in many works [14,20,21,30,[39][40][41][42] , in which a random chain scission reaction (β-elimination) involving a six-membered ring transition state ( Figure 1) has been considered as the main mechanism based on typical structures of pyrolysis products, i.e., crotonic acid and oligomers with a crotonate end group, i. e., unsaturated end groups. Since the proposed mechanism is a non-radical random chain scission the conventional stabilizers and antioxidant was not efficient to prevent PHB degradation [38] .…”

Melt reaction in blends of poly(3‐hydroxybutyrate) (PHB) and epoxidized natural rubber (ENR‐50)

“…The melt reaction starts with a random thermal scission of long chain PHB molecules to shorter chains bearing carboxyl ends according to reaction (1), where the reactivity depends on the average chain length and decreases exponentially with reaction time. 11,12 Reactions between the epoxide group of ENR and carboxyl group of various carboxylic acids have been reported where the reactivity was observed to increase with decreasing pKa value of the acids.…”

“…First, it degrades at temperatures slightly above its melting point, producing shorter chains with carboxyl chain ends. 1 This gives PHB a narrow window of thermal processing. Second, its high crystallinity makes it brittle, giving rise to inferior mechanical properties.…”

Aminolysis of poly (.BETA.-hydroxybutyrate) and its copolymer.

“…PHB and P (HB-co-HV) are degradable either by enzymatic or hydrolytic degradation processes (1,2). Thermal degradation of PHB and its copolymer has been reported by several authors (3)(4)(5)(6)(7)(8). PHB has been degraded by aqueous methylamine (9) or gaseous methylamine (10), where the fragment lengths equal to once and twice the value of the lamellar thickness have been found.…”