Poly(3-hydroxybutyrate)(PHB)is a biothechnological and biodegradable thermoplastic polymer from the polyhydroxyalkanoates(PHAs)family,whose chain regularity,high molecular weight,and physical and mechanical properties...Poly(3-hydroxybutyrate)(PHB)is a biothechnological and biodegradable thermoplastic polymer from the polyhydroxyalkanoates(PHAs)family,whose chain regularity,high molecular weight,and physical and mechanical properties comparable to polypropylene(PP)are characteristics that have made PHB a prominent commercial bioplastic.Nevertheless,its susceptibility to thermal degradation and hydrolysis has limited many applications.To address the challenges associated with processing,a random copolymer of 95.86 mol%3-hydroxybutyrate and 4.14 mol%3-hydroxyvalerate(referred as PHB)was compounded without(neat PHB)and with 0.25,0.5,1,and 1.5 wt%of chain extender(Joncryl■ADR 4368),consisting of multifunctional epoxy groups,and melt mixed in an internal mixer at 170℃,50 rpm,and residence times of 5,10,and 15 min.The effect of chain extender concentration and residence time on the effectiveness of Joncryl■ADR 4368 to recover the pristine PHB properties were investigated through torque rheometry,melt flow index(MFI),differential scanning calorimetry(DSC),tensile testing,and thermogravimetric analysis.The results indicated that an increase in residence time strongly influenced the prevalence of thermomechanical degradation reactions over chain extension reactions of PHB during processing in the molten state.Shorter residence times favored chain extension,while longer times favored chain scission.This trend led to no enhancement of PHB mechanical properties processed for 10 and 15 min,regardless of additive content used.Melt flow index,thermogravimetric analysis and tensile strength exhibited an asymptotic behavior with the increase in additive concentration,exhibiting a noteworthy improvement in tensile strength and temperature at the highest rate of thermal degradation(TMAX),and a decrease in melt flow index of neat PHB with only 0.25 wt%of additive mixed for 5 min.The results found in this work allow additional data for processing PHB by manipulating the ratios of multifunctional chain extender and mixing time,which can create new approach in various applications.展开更多
基金The research described in this manuscript received funding from National Foundation for Scientific and Technological Development,CNPq(grant numbers:405428/2022-7 and 406925/2022-4).
文摘Poly(3-hydroxybutyrate)(PHB)is a biothechnological and biodegradable thermoplastic polymer from the polyhydroxyalkanoates(PHAs)family,whose chain regularity,high molecular weight,and physical and mechanical properties comparable to polypropylene(PP)are characteristics that have made PHB a prominent commercial bioplastic.Nevertheless,its susceptibility to thermal degradation and hydrolysis has limited many applications.To address the challenges associated with processing,a random copolymer of 95.86 mol%3-hydroxybutyrate and 4.14 mol%3-hydroxyvalerate(referred as PHB)was compounded without(neat PHB)and with 0.25,0.5,1,and 1.5 wt%of chain extender(Joncryl■ADR 4368),consisting of multifunctional epoxy groups,and melt mixed in an internal mixer at 170℃,50 rpm,and residence times of 5,10,and 15 min.The effect of chain extender concentration and residence time on the effectiveness of Joncryl■ADR 4368 to recover the pristine PHB properties were investigated through torque rheometry,melt flow index(MFI),differential scanning calorimetry(DSC),tensile testing,and thermogravimetric analysis.The results indicated that an increase in residence time strongly influenced the prevalence of thermomechanical degradation reactions over chain extension reactions of PHB during processing in the molten state.Shorter residence times favored chain extension,while longer times favored chain scission.This trend led to no enhancement of PHB mechanical properties processed for 10 and 15 min,regardless of additive content used.Melt flow index,thermogravimetric analysis and tensile strength exhibited an asymptotic behavior with the increase in additive concentration,exhibiting a noteworthy improvement in tensile strength and temperature at the highest rate of thermal degradation(TMAX),and a decrease in melt flow index of neat PHB with only 0.25 wt%of additive mixed for 5 min.The results found in this work allow additional data for processing PHB by manipulating the ratios of multifunctional chain extender and mixing time,which can create new approach in various applications.
