Jp. Onteniente et al., Fully biodegradable lubricated thermoplastic wheat starch: Mechanical and rheological properties of an injection grade, STARCH, 52(4), 2000, pp. 112-117
Pellets of lubricated and fully biodegradable thermoplastic wheat starch fo
rmulations were produced by extrusion. The lubricants used were a vegetable
oil or an internal biodegradable release agent such as magnesium stearate.
After being conditioned for one week at 20 degrees C at 65% of relative hu
midity, (HR). the pellets were injected to produce ISO/R 527 standardised s
amples for tensile tests. These samples were conditioned in the same Nay as
the pellets, before determining the mechanical properties and the moulding
shrinkage of these fully biodegradable materials. The automatic injection
mode for production of samples was only possible with pellets lubricated wi
th magnesium stearate. This formulation is considered hereafter as the refe
rence injection grade. The rheological study in this paper emphasises, all
other factors being equal, that the injection parameters depend on the rela
tive humidity of the conditioning atmosphere of the pellets.