Photoacoustic Monitoring of Internal Plastification in Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Copolymers: Measurements of Thermal Parameters

Abstract

Basic data on thermophysical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymers poly(3HB-co-3HV) were investigated with the aim of understanding the role of 3-hydroxyvalerate monomeric units (3HV) incorporated during random copolymerization. The results show strong evidence that internal plastification is produced by the introduction of 3HV units in the copolymer. It was observed that copolymer thermal conductivity increased approximately linearly with the 3HV content. On the other hand, thermal diffusivity was very sensitive to the change in the copolymer composition showing a sudden rise that attained a saturation plateau. Amplitude-frequency plots indicate that a thermoelastic bending mechanism is operating. In this paper a new photoacoustic arrangement for the measurement of thermal effusivity is presented.