Mechanical performance under severe stress conditions of plasticized polylactic acid/poly(3hydroxybutyrate) blends

IGLESIAS MONTES, MAGDALENA L.; PETTARIN, VALERIA; L. A. FASCE; D'AMICO DAVID ALBERTO; L. B. MANFREDI; V. P. CYRAS

Sevilla

Simposio; Frontiers in Polymer Science 2017; 2017

The development of new biobased and biodegradable packaging materials is constantly growing.Polylactide acid (PLA) and poly (3hydroxybutyrate)(PHB) are environmentally friendly polyesterswith highly promising perspectives for shortlifeapplications. However, the inherent brittleness ofPLA and PHB leads to rigid films which need to be modified to enhance their flexibility. Onecommon practice is plasticizer addition.In a previous work, blends with different ratio PLA (Nature Works)/PHB (PHB Industrial) (70/30and 60/40), plasticized with 10, 15 and 20 wt% of glyceryl tributyrate (TB) (Fluka), were obtainedin a Haake mixer (185ºC and 50 rpm) and characterized. The blends containing 15 wt% of TBpresented the best mechanical properties regarding uniaxial tensile tests, showing good balancebetween stiffness and deformation capacity. Nonetheless, when the stress conditions are moresevere the materials? performance could change from ductile to fragile. Therefore, the presentwork aims to evaluate the fracture and impact performance of the selected blends. Fracture testswere carried out on mode I double edgenotchedtensile specimens (DENT) at constantdeformation rate (1 or 10 mm/min). Different Fracture Mechanics approaches were applieddepending on the materials´ fracture behaviour. The Essential Work of Fracture methodology wasadopted for blends that exhibited ductile fracture behaviour, JIntegralat instability (Jc) for ductileinstability performance, and the stress intensity factor (KIc) for films that presented brittlebehaviour. Dart impact experiments were conducted on a Fractovis Ceast falling weight typemachine at room temperature at 0.5 m/s. Thickness related energy (U/t) and disc maximumstrength (σd) were determined.The PLA70/PHB30TB15%blend showed the highest value of tenacity and presented ductilebehaviour even under impact conditions, evidenced by a whitening area.