Наведено результати експериментальних досліджень двостадійного термоусідання поліпропіленової термоусадної плівки. Визначено залежності коефіцієнта усідання поліпропіленової плівки в поперечному та поздовжньому напрямках від температури. Порівняно одно- і двостадійне термоусідання.
Shrinkage called polymer films capable to contract under the influence of a temperature exceeding the softening temperature of the polymer. Different polymers have different properties at shrink, among which the most important is the shrink degree (shrink coefficient) and shrink stress. Shrink coefficient determines the multiplicity of reducing the linear dimensions shrink film, so that it gets the ability to tightly encircle the products subject to packaging, reproducing its outer contours.
The process of packaging products in shrink film consists of two phases: formation package by sealing it in shrink film; shrinkage of the film through its blowing hot air. Hot air is blowing of package realizing by heat chamber or by heat tunnel.
The aim of the paper is to investigate the shrink coefficient polypropylene film in the transverse and longitudinal directions, depending on the process temperature.
During the implementation of the shrink method in case the object is subjected packing, sharp transitions or sharp edges possible undesirable deformation and/or damage to the object itself, or injury (up to fracture) packaging film (that is destroying the integrity of the package), it would be appropriate to use a two-step incremental shrinkage. Stepwise shrinkage was carried out in two stages: the first stage of the film was in the heat chamber 2 s, and at the next shrink stage – 5 s. In carrying out the experiment was seen addiction at the time that the first shrink stage exceeding 2 s, the relaxation of the film makes it almost fully realized and further shrinkage is negligible. After finishing shrinkage processes coefficient determined after the first stage and the overall shrink and total in the transverse and longitudinal directions, depending investigated transverse and longitudinal coefficients shrink temperature.
A comparison of the experimentally obtained graph of the one-step and two-step in shrink follows that when shrink film at one stage, shrink ratio is increasing with increasing operating temperature, whereas the two-stage shrink biggest factor shrink was obtained at a temperature 170oC . The total shrink degree in two-stage process is almost the same as in the one-step shrink.