Influence of liquid media on the craze initiation in amorphous polylactide

The influence of various liquid media (aliphatic alcohols, water-alcohol solutions, saturated hydrocarbons, and organosilicon liquids) on the development of uniaxial deformation and nucleation of crazes in amorphous polylactide (PLA) films has been studied. It has been found that in the presence of the liquids the tensile stress during the polymer deformation decreases by 3–4 times. According to the Griffith's theory, linear dependences (with an accuracy of R2 = 0.96–0.97) have been revealed between the yield point or the flow stress of PLA and the square root of product of the elasticity modulus of the polymer in a liquid and the interfacial surface energy at the polymer-liquid medium interface calculated using the Owens-Wendt equation. The data obtained may be used to predict the critical mechanical stress at which crazes will be initiated in PLA.