Silawrap - Technical Information

Manufacturing Silawrap

Silawrap is produced from polyethylene resins which are made from oil and gas.  Polyethylene or PE resins are broken into different groups depending on their properties.  High density polyethylene or HDPE is used to make soft drink bottles and milk containers.   Crop Packaging Systems use Linear Low Density Poly Ethylene or LLDPE resins in the production of Silawrap.  LLDPE resins are split into C4, C6 and C8 resins.  This details the number of bonds between the molecules.  A C8 resin has 8 bonds and is therefore stronger.  Crop Packaging Systems selects its resins for elasticity or ability to stretch and strength or resistance to puncture and tearing.  The resins come in granules similar in size to prilled urea.  We use 100% C8 resins.  These are dearer than other materials but produce a stronger better quality film.

Other raw materials include colour called master batch, UV light inhibiter and tack or glue.  Sun light causes film to break down. UV light inhibiter prevents this from happening.  UV light levels vary around the world.  For example UV levels are higher in Australia than Ireland.  Therefore more UV light inhibiter is added to Silawrap destined for this market. 

Tack is used to seal the film, in other words it is the glue.  There are many types.  Crop Packaging Systems uses a viscous or thick formulation.  This has to be heated in order to flow properly in the manufacturing process.  Some of our competitors use a more liquid form of tack. This evaporates from between the layers of film during storage, allowing in air and reducing silage quality.

Crop Packaging Systems guarantee that no recycled resins are used in the manufacture of Silawrap.  This is to ensure farmers receive top quality film every time.  Recycled resins when used lead to impurities in the film, reduced strength and variations in the tack level or seal.   

160 Million Bales Wrapped Worldwide

Extruding Silawrap

Silawrap extrusion is a continuous process, operating 24 hours per day, 7 days a week.  Lines shut down for annual maintenance and at regular intervals for service.  It costs over £1,800 or €2000 to start a line.  Extruders are built for a specific purpose, for example manufacturing silage wrap or pallet wrapping film.  It is very difficult to make quality bale wrapping film on an extruder built to make pallet wrapping film. 

Silawrap is a triple layered film which means 3 layers of molten resins are fused together.  This makes Silawrap tougher.  It also allows Crop Packaging Systems to vary the resin mixture from layer to layer to maintain high quality and durability. 

Quality Silage from Quality Grass

‘Grassland reseeding is one of the best paying investments available to grassland farmers. With the current price / cost squeeze facing lifestock farmers, spending should be focused on areas that can bring about a reduction in production costs. Grazed grass is the cheapest feed for cows and drystock and grass silage is among the cheapest winter feeds you can produce. Reseeded pastures will produce higher annual yields of grass compared to old swards. Grass digestibility and intake potential will improve. Based on recent research at the Irish Research Centre Moorepark the biggest impact on improved profitability from reseeding comes from a substantial increase in spring grass yields and also autumn yields. In a recent trial at Moorepark pastures with 100% perennial ryegrass produced February growth rates of more than twice those of pastures with 40% perennial ryegrass. The annual improvement in profitability is worth over €200 per ha for the 100% perennial ryegrass sward versus the 40% perennial ryegrass sward’.