Poly(3-hydroxybutyrate) chain extension in the solution using bi- and trifunctional additives

abstract

English

For those, who are working with it, thermal degradation of poly(3-hydroxybutyrate) (PHB) is a well-known phenomenon. What is not very clear is how to overcome this. Upon heating to the temperatures between 170 and 200 °C, which are the typical processing temperatures for PHB, the degradation is manifested by the change in molecular weight and viscosity of the system. Random scission is carried out by cis-elimination mechanism, also called McLafferty rearrangement [1-3]. One of the formed sub-molecules has an unsaturated crotonate end group and the other has carboxylate end group, which is theoretically prone to chain extension reaction which should lead to improvement of the thermal and mechanical performance of this polymer [4]. In this work, four functional groups reactive towards carboxyl group were studied: isocyanate, carbodiimide, hydroxyl and epoxy. Bifunctional reagents: hexamethylene diisocyanate, carbodiimide Stabaxol LF, diethylene glycol, and diglycidyl ether bisphenol A and trifunctional reagents: poly(hexamethylene diisocyanate), glycerol and trimethylol-propane triglycidyl ether were used. For the reactions, PHB was firstly pre-degraded in a laboratory hot press to mimic the degradation state obtained during processing. 5 wt% solution of PHB in chloroform was prepared and after adding the reagent, the solution was kept under reflux for 6 hours. The reagent was added in two amounts corresponding to 2-fold and 100-fold overdose. The effect of reagent addition was studied indirectly via change in the solution viscosity and directly by the change of molecular weight and thermal properties of the polymer. For almost all the samples with bifunctional additives the solution viscosity was increased. The highest effect was observed in the case of diethylene glycol (+13.3 % in the case of 100-fold overdose). In the case of trifunctional additives, there was only slight rise for glycerol and trimethylol-propane triglycidyl ether for 2-fold overdose. Similarly, the influence on molecular weight measured by gel permeation chromatography was more apparent for bifunctional additives. All trifunctional additives, together with some of the bifunctional successfully increased the number average molecular weight. The increase in weight average molecular weight was observed mainly in the case of 100-fold overdose of hexamethylene diisocyanate and carbodiimide samples, suggesting their potential use for chain extension of PHB during processing.

poly(3-hydroxybutyrate); stabilization;, isocyanates; carbodiimides; alcohols; epoxy

MELČOVÁ, V.; PŘIKRYL, R.

26. 11. 2021

Vysoké učení technické v Brně, Fakulta chemická

Brno

978-80-214-6002

Sborník abstraktů Chemie je život 2021

1.

92

93

106

https://www.fch.vut.cz/vav/konference/sok/vystupy/sbornik-konference-2021-abstrakty-a5-pdf-p213391