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Differences between multi-layer and one layer (mono) Polyethylene film

Differences between multi-layer and one layer (mono) Polyethylene film
Process of co-extrusion (extrusion of multi layer film) with the selection of special materials enables for buyer remarkable financial savings the same time the product gets better mechanical characteristics and better optical look.

Advantages of multi-layer Polyethylene film

With the proper selection of raw materials three-layer Polyethylene film gives better optical (transparency, shininess…) and mechanical (toughness) characteristics with the reduced thickness (20-30 % less thickness then mono layer film). The Polyethylene film is been sold by it weight and been used by its length and that means significant financial saving. Plus because of the reduced thickness in process of packaging buyers get more film in a roll which means fewer roll changes, less needs for storage space and less packaging waste.

Disadvantages of multi-layer Polyethylene film

Selection of proper materials in multi-layer Polyethylene film raises film price per weight, but this film is still much cheaper then mono layer if you take in consideration that film is been used in its length. Multi-layer Polyethylene film usually needs higher temperature in thermo tunnel in the packaging process for 5-10°C and in the older packaging machines more frequently blade check is required.

What is PCR and what is PIR?

PCR stands for Post Consumer Recyled Materials or Resin. It is recyled plastic from products that have been used at least one for its original purpose: stretch film for wrapping pallets, shrink film for water packaging, plastic bags... PIR stands for Post Industrial Recycled Materials or Resin – this is industrials waste and restovers that haven’t been used for its original purpose. Like non complied rolls, edge trims, rolls with bad printing... Both are recycled plastic but PIR is better quality then PCR. Usually PIR doesn’t have smell, doesn’t need washing before recycling and can be almost as virgin material.

Why 6, 7, 8 print colors when you can get any color from the basic 3 colors?

In picture printing process the CMYK (cyan, magenta, yellow, black) color space is being used. Basic RGB (Red, Green, Blue) color space is being used just for monitors and that color space represent light color intensity (emitted energy). Light itself cannot be printed so that why there is difference between the printed picture and the picture on monitor. CMYK don’t have such problem because it uses basic color pigments. Pigments represent energy that is not absorbed by a substance such as ink or paint.  Basic pigments are cyan, magenta and yellow. Black (key) is being used for ink saving ant the fact that all 3 basic pigments can’t give good dark black color. CMYK have a limit. It can’t print very bright and metallic colors like silver or gold so other inks must be used.

The process of image print on Polyethylene film

For image print on the Polyethylene film a process called flexographic printing is being used. There are 4 basic operations in the flexographic printing operation:

1. Image Preparation

Image, picture or illustration is made or transferred to digital image. Image is additionally processed and printed on special paper. Because of the simulation of print, if the customer finds that the quality of the cool poof is satisfactorily the customer gives the approval for Flexographic Plate Making.

2. Flexographic Plate Making

Flexographic printing uses special made Flexographic Plate – plates with raised images (relief) made of flexible material, such as plastic and rubber. For each color one Flexographic Plate is made.

3. Flexographic Print

Flexographic Plate is attached to a special roller and trough 4 or more roller system ink (image) is transferred to the Polyethylene film.

4. Finishing

Printed Polyethylene film may run through the additional processes like cutting, folding and binding and it’s ready for transport.

For getting colored Polyethylene film (white, black, blue…), in the extrusion process the ink in the shape of granulates (master batch) is added and that film doesn’t require additional printing. Problem colors in flexo are: violet, purple, reflex blue and rhodemin area.

Corona process

Unprocessed Polyethylene have low surface energy and as such represents essentially "non- stick" plastics and isn’t good for merging (gluing) with other materials. Corona process is a process that raises the surface energy of Polyethylene film. It raises the surface energy level to approximate 38-42 dynes/cm and enables processes like printing and lamination of Polyethylene film.

Minimum quantities?

MURAPLAST producess medium and big jobs. The minimum quantity depends of the dimension and thikness of the product. For film in roll minimum quantity is approximately 500 kg and for bags is approximately 30.000 pieses.