A method of preparing a plasticised particulate polyvinyl alcohol (PVA)
composition is provided, comprising: mixing, in a mixer, at a mixer speed
and for a time sufficient that the mixture attains a temperature of at
least 50.degree. C.: particulate PVA resin in an amount from 80% to 90%
by weight of the mixture; and plasticiser in an amount from 10% to 20% by
weight of the mixture, wherein at least a portion of the plasticiser is
water; monitoring the apparent viscosity of the mixture during mixing and
continuing mixing until the apparent viscosity of the mixture has peaked
to a maximum and dropped off to a substantially constant level, thereby
to obtain a plasticised particulate mixture having a moisture content in
the range from 7% to 14%; preferably adding an anti-caking agent in an
amount from 0.05% to 0.5% by weight of the plasticised particulate
mixture, and continuing mixing until the anti-caking agent is blended to
the plasticised particulate mixture; and stopping mixing, and removing
the mixture from the mixer, wherein the mixture temperature is kept below
100.degree. C. at all times during mixing. The properties of the
plasticised particulate composition are such that it can be processed, by
extrusion and blowing, to a film having advantageous characteristics in
terms of structure and properties. Accordingly, also provided is a PVA
film characterised in that, when viewed using polarising light
microscopy, it has a nonuniform texture consisting of distinct short
range areas, e.g. 10 to 500 micrometers, each short range area showing
anisotropic orientation within its area, each short range area being
oriented isotropically.