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Reprocessability of PHB in extrusion: ATR-FTIR, tensile tests and thermal studies

“…The peak at 1277 cm -1 denotes the -C-O-C-group and at 970 cm -1 is assigned to bending vibrations of olefinc -C-H [61,62] . As the thermal degradation proceeds, it incorporates vinyl (crotonate) ester and carboxyl groups end groups in PHB structure [20,30,31,41] . Therefore, a gradual increase in crotonate ester groups with extrusions paths can be expected, as well as a decrease in hydroxyl groups present in the original polymer.…”

“…According to the literature [20,30,31,41] , as PHB degradation proceeds, an ester chain with an unsaturated ester as end group, and an ester chain with a carboxylic acid as end group are formed. Each of these two types of ester may react at a distinct rate.…”

“…Also studies seeking to improve the thermal stability of PHB by grafting chemicals in PHB chain [33,36] , and adding polymeric additives in PHB matrix [37,38] have been developed. The thermal degradation behavior of PHB has been discussed in many works [14,20,21,30,[39][40][41][42] , in which a random chain scission reaction (β-elimination) involving a six-membered ring transition state ( Figure 1) has been considered as the main mechanism based on typical structures of pyrolysis products, i.e., crotonic acid and oligomers with a crotonate end group, i. e., unsaturated end groups. Since the proposed mechanism is a non-radical random chain scission the conventional stabilizers and antioxidant was not efficient to prevent PHB degradation [38] .…”

Effect of glassy carbon addition and photodegradation on the biodegradation in aqueous medium of poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/glassy carbon green composites

“…It is probable that the UV radiation offered sufficient energy to break some PHBV chains and to induce the organization of the resultant smaller chains, reducing the amorphous regions and promoting higher X c values. 43 The increase in the X c values of the samples exposed to UV radiation will be shown later, in the DSC analysis section. The increase in the X c values of neat PHBV and PHBV/GC green composites (Table 2) hindered the diffusion of water molecules and the action of enzymes involved in the biodegradation process, which explain the decrease in the biodegradability of all the samples exposed to C.4 condition when compared to the samples exposed to C.2 condition (without previous photodegradation).…”

“…The increase in the X c values of neat PHBV and PHBV/GC green composites (Table 2) hindered the diffusion of water molecules and the action of enzymes involved in the biodegradation process, which explain the decrease in the biodegradability of all the samples exposed to C.4 condition when compared to the samples exposed to C.2 condition (without previous photodegradation). 17,43 Considering that the residual weight of the samples submitted to the biodegradation tests followed an approximately linear behavior over time, it was calculated that the average rate of weight loss (%) of neat PHBV and PHBV/GC samples submitted to C.2 and C.4 conditions were 1.1% and 0.4% per day, respectively. Thus, it was estimated that the time necessary to the total biodegradation of these samples when exposed to C.2 and C.4 conditions is approximately 91 and 250 days, respectively.…”