Influence of crystallinity on gas barrier and mechanical properties of pla food packaging films

Crystallinity is well-known to have major effects on the gas barrier properties. However, its effect on gas barrier properties is often dependant on the studied material and is difficult to anticipate because two aspects of crystallinity have to be considered: the crystallinity degree and the crystalline morphology. PLA is known to recrystallize when heated at a temperature higher than its Tg ("cold" recrystalllisation). Different recrystallized samples have been obtained by compression-molding the extruded films in different conditions of heating. The crystallinity degree and morphology have been investigated and related to the gas barrier properties of the films. Since crystallinity also affects mechanical properties, the yield strength and the elongation at break have been measured.