IDM Instruments has released its new film free shrink tester. Linear thermal shrinkage, or free shrink, is defined as the irreversible and rapid reduction in linear dimension, in a specific direction, occurring in film exposed to elevated temperatures, under conditions where none, or negligible restraint to prevent shrinkage is present, usually expressed as a percentage of the original dimension.
Shrinkage in this way is related to the material of the film and internal stresses locked into the film (by the manufacturing process), to be released later by heating.
Such a tendency to shrink may be undesirable, betraying an unsatisfactory manufacturing control, or deliberate and sought after, as in the case of film made for "shrink-wrapping", in either case the percentage shrink is an important factor in quality control for performance and end-use suitability.
The method will measure, at given temperatures, the free-shrink of film up to 0.76mm in thickness.
The tester consists of a small, circular, aluminium block electrically heated and controlled by a temperature controller using aluminium foil disks with silicon oil within and the test piece placed into oil to accelerate shrinkage at selectable temperatures.
This testing device is useful to plastic film manufacturers and flexible packaging producers. IDM Instruments 03 9706 7837.