Technical Properties of Bale Silage Wrap

Making a top quality bale wrap film

The first step in the production of a bale wrap film is the manufacture of a polyethylene (PE) resin by a company such as Dow, which produces DOWLEX™ PE Resins specifically for the production of bale wrap film. This means the properties can be tailored specifically for efficient wrapping and long-term performance in conserving valuable forage.

The resin is turned into film by a converter. Effectively the converter melts the resin and cools it in the form of a thin layer. This is done in closely specified conditions to provide a film with optimum and consistent properties. The film is then slit to the appropriate widths and rolled ready for distribution through the agricultural supply chain.

The technical properties of stretch film

A plastic film derives its physical properties from the original resin. For silage wrap, the desirable properties are:

  • Consistent quality and thickness
  • Good stretch properties even in warm weather
  • No tendency of ‘windowing’ when being stretched
  • Good cling between layers
  • Puncture resistance
  • Retention of strength over many months in the open
  • Impermeability to air and moisture

The best resins will be those that are tailor-made for the silage market. Tailor-made resins mean improved consistency and better processability for the converter, which in turn means better quality and a more reliable film for bale wrap.

According to Dr. Antonio Manrique, Dow Plastics European Application Technology Leader for Stretch Film, the key properties for silage wrap are:

  • Good thickness distribution in the film at 25 microns optimum
  • Stretch level at approximately 100%
  • Outstanding cling level for good sealing
  • Very good puncture resistance
  • Excellent UV resistance (one year outdoors)
  • High load retention (for bale integrity)
  • Low oxygen and water permeability

The right resin provides the right combination of processability and mechanical performance.


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