The effect of gamma radiation on mechanical properties of biodegradable polymers poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Abstract

B r a z i l i a n p o l y ( 3 -h y d r o x y b u t y r a t e ) , P ( 3 -H B ) , a n d i t s c o p o l y m e r, p o l y (3-hydroxybutyrate-co-3-hydroxyvalerate), P(3-HB-co-3-HV) were irradiated with gamma radiation ( 60 Co) 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.

Evaluation of Fracture Toughness of Ultraviolet-Irradiated Polycarbonate Using the Essential Work of Fracture Method

“…By contrast, a smaller reduction in the tensile strength of 9-10 % is noticed for both UV time exposures. The elongation reduction is attributed to a smaller molecular weight, as found in gamma irradiated samples 19,31,8,32 , which reduces the plastic deformation capacity of the material. In the case of tensile strength, the relatively small reduction might be assigned to the decrease in PC molecular length due to chain scission 12 .…”

Effect of Radiation Crosslinking and Surface Modification of Cellulose Fibers on Properties and Characterization of Biopolymer Composites

“…The radiation probably caused the uncontrolled decay of large crystals, which subsequently served as nucleation nuclei for the formation of new crystalline formations [ 34 ]. Evidence of the influence of gamma radiation on the change of the crystal structure and on the modulus of elasticity in tension is also given in the studies of L. M. Oliver and colleagues [ 34 , 35 ], where the modulus of elasticity in tension remained almost unchanged even at 100 kGy.…”

“…Therefore, it can be assumed that a biopolymer with a higher content of the crystalline phase (see Table 3 ) was characterized by a higher resistance to radiation and thus a lower decrease in mechanical properties [ 34 ]. However, scissions in the linked molecules are the ones that causes the highest losses in mechanical properties to a crystalline polymer [ 35 ].…”

Drug Micro-Carriers Based on Polymers and Their Sterilization

“…The authors found that an increase in irradiation dosage increases the molar mass of the material and the polydispersity. As for the polymers with methyl groups, the predominant consequence of irradiation is the chain scission, such as is observed in PHB, PLLA and PLGA [296,[308][309][310][311][312][313][314][315].…”