Study on the Thermal Degradation Kinetics of Biodegradable Poly(propylene carbonate) during Melt Processing by Population Balance Model and Rheology

Abstract

The degradation behavior of poly(propylene carbonate) (PPC) was investigated during melt processing to infer the mechanism and kinetics of thermal degradation. First, the degradation experiments were carried out in a miniature conical twin-screw extruder at different temperatures, rotating speeds, and processing times. Gel permeation chromatography (GPC) was applied to analyze the molecular weight and molecular weight distributions (MWDs) of melt processed PPC samples. The degradation process at various processing conditions was described by the population balance equations (PBEs) with random chain scission and chain end scission. By comparing the prediction of PBE model with the experimental evolution of molecular weight, it is proposed that random chain scission and chain end scission occur simultaneously. At temperature higher than 160 °C, random chain scission dominates with the activation energy about 120 kJ/mol. Second, a method combining the PBE model and rheology was suggested to determine the kinetics of degradation directly from the torque of mixer during melt processing without further measurements on molecular weight. Such method was applied to melt mixing of PPC in a batch mixer, from which a higher kinetic parameter of thermal degradation and similar activation energy were successfully determined as compared to those obtained from extrusion experiments.

Linear Rheological Properties of Poly(Propylene Carbonate) with Different Molecular Weights

“…Note also that the obtained K g value for PPC (5.4 × 10 5 K g/mol) is consistent with the reported values of other polymers, for which K g values distribute within a range of K g = 1 × 10 4 ~ 5 × 10 5 K g/mol 15,17,18) . Rouse relaxation, plateau and terminal regions, which have not been reported in previous studies on PPC [9][10][11][12] . Here, the reference temperature T r is set as T g,DSC + 60 °C to compensate the T g difference among the samples.…”

“…In particular, the plateau modulus is one of the essential parameters because this parameter characterizes the entanglement properties of polymers [4][5][6][7][8] . There have been several reports available in the literature for linear rheology of PPC [9][10][11][12] . Thorat et al 9) synthesized a series of aliphatic polycarbonates from ring-opening polymerization and studied their linear rheology.…”

“…Cao et al 11) also reported the plateau modulus of PPC as 698 − 299 kPa, which depends on the molecular weight (91.9 − 48.2 kg/mol). Lin et al 12) studied the relation between thermal degradation and linear viscoelasticity of a commercial PPC. They obtained the plateau modulus of PPC as 150 kPa.…”

Fully bio-based, highly toughened and heat-resistant poly(L-lactide) ternary blends via dynamic vulcanization with poly(D-lactide) and unsaturated bioelastomer

“…The obvious change in initial stage corresponds to the addition of solid materials and their melt. After melting completely, the melt torques of neat PLLA and PLLA/VUB decrease slightly which may be attributed to the shear thinning and possible thermal degradation of the aliphatic polyesters during melting processing [50,51]. It is interesting to find that the PLLA/ VUB/PDLA ternary blends show higher melt torque after melting compared to the PLLA/VUB binary blends, and the torque value increases with increase in the PDLA content.…”

Use of decomposable polymer-coated submicron Cu particles with effective additive for production of highly conductive Cu films at low sintering temperature

“…It can be used to reduce white pollution in the environment. [37][38][39] PPC can decompose at 200-250 1C (Fig. S4, ESI †), but its decomposition temperature can be lowered via an aminolysis reaction with amine or amino alcohol (Fig.…”