Abstract
Brazilian poly(3-hydroxybutyrate), P(3-HB), and its copolymer, poly (3-hydroxybutyrate-co-3-hydroxyvalerate), P(3-HB-co-3-HV) were irradiated with gamma radiation (60Co) at room temperature and in the presence of oxygen. The viscosity-average molar mass (Mv) was analyzed by viscometry using an Ostwald-type capillary viscometer. Both polymers showed a decrease in molar mass with the increase in dose, reflecting that random main chain scissions occurred. The value G (scissions/100 eV of energy transferred to the system) and the parameter α (scissions per original molecule) were also determined. Mechanical properties decrease with the increase in dose, revealing that P(3-HB) underwent significant changes, especially at doses higher than 50 kGy. Tensile at break and impact resistance properties were the most affected by radiation, while the elastic modulus remained virtually unaltered up to 100 kGy dose.
Highlights
Poly(3-hydroxybutyrate) (P(3-HB)) and its copolymer, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3‐HB)-co-3-HV), are biodegradable thermoplastic polymers generally referred to as Poly(hydroxyalcanoates) (PHA’s)
Samples were washed with hydrochloric acid (HCl) 0.1 mol.L–1, water, and vacuum dried under a 150 w infrared light for over a week
A lower G value of 5.4 scissions/100 eV found in the reprecipitated P(3-HB) suggest that the degradation of this sample after irradiation is less severe when compared to as-received P(3-HB) films (G value = 7.0 scissions/100 eV)
Summary
Poly(3-hydroxybutyrate) (P(3-HB)) and its copolymer, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3‐HB)-co-3-HV), are biodegradable thermoplastic polymers generally referred to as Poly(hydroxyalcanoates) (PHA’s). El-Hadi et al.[31] studied the influence of the morphology and glass temperature on mechanical properties (elongation, stress, impact strength) According to these authors, P(3-HB) is a hard and brittle polymer, its elongation at break is less than 10%, its modulus and fracture stress are 1.7 GPa and 35 MPa, respectively. P(3-HB-co-3-HV) is brittle, its elongation at break is less than 15%, its modulus and fracture stress are 1.2 GPa and 25 MPa. In the present work, the P(3-HB) and its copolymer P(HB-co-3-HV) were irradiated and evaluated as to the radiolytic degradation by main chain scissions reflected in molar mass reduction. While most reports in literature investigated film samples, our work focused on test specimens results, bring the knowledge of gamma-irradiation effects on P(3-HB) and its copolymer P(3-HB-co-3-HV) a step forward in terms of performance estimations aiming future practical applications
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
