It is not that simple to decide which foil will be most suitable for your product. A choice must be made between the large range of available foil types. When you are advised, you will be confronted with several technical terms, quickly causing you to loose track. To prevent this from happening, a short explanation will follow on the meaning of several frequently used terms:
- Blown and cast foil
- Co-extrusions (multiple layered foils)
- Machine foil
- Limited, Power and Oriented
- Hand rolls
- Clear, colored or printed
- Cover foil
- Mini stretch
- Cling wrap foil
Two frequently mentioned quality indications in packaging films are "Blown" and "Cast". These terms were deducted from the production process. Every process leads to specific properties. A short description of both these procedures follow below.
The granulate is mixed (1) and extruded through a ring shaped mold (2) and forms a thin layered tubular cylinder. Air is blown in through a hole in the middle of the mold through which the granulate is pressed. The cylinder then moves upwards while it is continuously cooled by air. The external dimensions of the cylinder is determined by a ring system (3) that surrounds the cylinder. The wall thickness of the cylinder is also measured in the meantime(4) and this information is fed back to the extruder where adjustments take place if necessary. If the cylinder has cooled off enough, this passes through two converging roller systems (5), where the cylinder is flattened to form a flat foil.
The foil is then cooled further and through a system of air-cooled and actuated reduction rollers (6)it is guided down. The flattened foil is then ready for use or it is cut off on both sides, thus forming two flat foils. This is finally rolled up (7). The operating panel (8).
2. Blowing the film with air-cooled ring
3. Measuring unit
4. Thickness measuring unit
5. Clamping unit
6. Turning unit
7. Winding up
- The width and thickness of the film could be accurately defined by the regulation of the output of the extruder, the dimensions of the air bubble and the reduction speed.
- Absence of irregularities in the edge finishing and uniform cooling.
- Possibility of biaxial orientation of the film or foil. This offers increased quality of the mechanical properties, especially the point load.
Just like in a Blown line, a Cast line starts with the extruder (1). In the extruder, the granulates are heated and pressed through a worm wheel to a long diagonally situated outlet opening (2). The liquid substance is dosed through this opening and cast on to a moving roller as evenly as possible.
From here, the substance is guided between two rollers (3). The rollers are water cooled from within and thus ensure that the substance is processed at the correct temperature. The film that has now developed is kept stretched out and guided through various rollers. This also gives the Cast film its specific properties. Finally, the film is wound up on to a tube (4). Throughout the process, measurements are performed via the control system (5) that are fed back into the production process.
2. Outlet Opening
Apart from the differentiation between "Blown" and "Cast" the term "Coex" is also often used to typify a foil. This term also relates to the production process. Co extrusion implies that a foil is structured from multiple layers. The number of layers can increase to as many as seven. By combining the properties of the various layers, a large range of new options arise. For packaging of food, one can think of a non-pervious intermediate layer.
When wrapping the package it is important that the package is well stabilized with the lowest possible use of foil. It is also important to cover the edges, thus completing the winding process without unintended interruptions. When using on the machines, several aspects are of importance:
According to the principle, "a chain breaks at its weakest link" it is important for the foil to not go below a minimum thickness but that it also does not exceed a maximum thickness.
When the foil is stretched , the stretch must be distributed evenly over the surface of the foil. Less stretch at one point requires more stretch elsewhere. Any deviation in density can therefore lead to a tear.
High resistance to piercing
A high resistance to piercing ensures that the foil, when this is shaped around sharply protruding load points, will not tear.
Low Neck down
Neck down is the property in foil to become smaller width wise, when stretched length-wise. Especially with a greater pre-stretch, this can lead to an increase in the required number of windings, causing the use of foil to be increased per packed unit. The extent of neck down is determined by the composition and the orientation of molecules from which the foil was structured.
The foil must cling to the inside of the pallet, and must be smooth on the outside. The bonding capacity on the inside, also called the cling, ensures that the winds form a single unit and that the ends do not come loose from the pallet. The outside must be smooth to prevent two pallets situated next to each other from clinging to each other during storage or trans-shipment.
The stretch and strength properties of film can be improved by "stretching" the film. Although the foil becomes thinner during this stretching process, it is stronger than before this action. This is because the molecules, from which the foil is structured, are directed.
With greater use, it is advisable to use a film wrapping machine, where the stretching takes place in the "head" of the film machine. The added benefit of the" memory action" of the film which results in a draw-back movement after being stretched, can then be used. The film can be applied to the package with little tension. The memory action then ensures that the proper tension is excerted on the package.
Pre-stretching however has its limits. As a rule, the higher the limit of stretch, the better (recovering ability and strength) the film.
Depending on the composition of the raw materials and the production process, every foil has its own characteristics. For many applications, there usually are limited foils (foil with a lower pre-stretch ability). For more critical applications, it is better to use a higher quality film. For this purpose, Contimeta has a variety which is "power" driven. These foils can thus be pre-stretched (to 400 %) and it has excellent accompanying properties.
With only a limited number of pallets to be wrapped, the investment in an advanced "head" is not economically viable. In that case, one can opt for the use of pre stretched oriented foil.
The word oriented refers to the core process that takes place in these factories, orientation or stretching. During this process, the polypropylene resin balls are converted in an extruder into a thick foil. This foil, the film, is then stretched out. Because of this reorientation of the molecules, the film is much stronger.
This foil is not only suitable for machinery with a simple "head" but it is also excellent for use as manual wrapping foil. The foil is then supplied ready to use, pre-stretched, whereby the pre-stretch is such that "the memory" kicks in with only a slight extra stretching.
Perforated film is often used when the load must be able to "breathe" during transport.
This can be the case with transport of, for example, fruits and vegetables. This may also be required when the load still needs to cool down.
When using machines, one wants to limit the change of film rolls as much as possible. The use of film rolls weighing around 20 kg is also quite standard.
For manual use, these rolls are far too heavy. The manual rolls are therefore much smaller. The quantity of foil on these, are usually expressed in meters. In this context, the Coreless (foil roll without core) foil has an important advantage. A core easily weighs as much as a kilo. Leaving out this core, makes quite a difference. A hand roll without a core does not weigh more than approximately 1.7 kg.
As a rule, clear foil is used. The user usually wants the client to see what is on a pallet. This is however not always desired. There are at least two reasons why colored foil should be used:
1. In products that may be subject to theft, like consumer electronics, the load seems to regularly disappear during transport. In such case, colored foil (black, blue, green, red or white) is used to screen the load from immediate visibility.
2. With a load that may be sensitive to light, foil with "spax" coloring is used.
For promotional reasons, printed foil may also be used. There are many options for this.
More and more clients require a pallet that is delivered in an attractive and spotless state. To prevent dust from settling on the load, water from seeping in and also to prevent access to undesired intruders, cover sheeting or (pallet) cover film can be an excellent solution.
For grouping, bundling, packing of all kinds of products like wooden laths, profiles, books, boxes, etc. There is a very inexpensive and handy solution: Mini-Stretch film
For manual application, we have a standard film of 100 and 125 mm width in 17, 20 and 23 mµ.
We can also offer other sizes, colors and lengths without any problem. Adjusting and customization is our specialty!
For companies who have an automatic horizontal bundeling machine, we also have many kinds available from stock.
From 100 to 380 mm wide, from 12 to 50 mµ thick, on all kinds of cores and in all kinds of cling wrap qualities, everything is possible.
- Do you have problems with your stacked goods toppling over?
- Problems with applying corner profiles?
- For safety reasons, temporary stabilizing goods for internal transport?
- Recognition of goods that belong together?
- Sanstrap film solves all these problems!
- Sanstrap film is available in green, red and yellow.
Transporting your shipments internally:
You apply for example the 100 mm wide strap around your goods. Corner profiles can be applied between the strap and your goods. No issues anymore during packing using cling wrap.
Properties of Sanstrap film:
- keeps temporary shipments together for internal transport
- ideal to confirm corner profiles "SOFT".
- does not stick to the product
- can be applied easily and quickly
- can be re-used
- extremely economical
- can be used for identification (in blue, green, red and yellow)
- XXL Sanstrap, for pallets of 900 x 1400 mm
The wide 150 and 200 mm straps (for Euro pallets or larger, are only available in the "Metal-box" version with refills. In boxes with straps for Euro pallets and larger, there are 100 straps/box. In boxes with straps for mini pallets there are 200 straps/box.
Hand wrapping film type Blown. This film is suitable for products with sharp sides and has an extremely strong recovering ability. The film is supplied in a box containing 4 rolls.
A set of handles is included.