All Kinds of Farm Equipment

Poly Plastic

Defects of Plastic Film Ought to be Caught

Copyright (c) 2008 David Banig

Plastic Film defects ought to be detected and eliminated by the extruder operator before the rolls get shipped to the customer.

First is the appearance and a good looking finished plastic roll of film this aspect can be half of the battle. Keep in mind is that first impression what you see is what you get! A superficially ugly looking roll which may convert on the filling machine or bag machine can have the operator looking at the roll much closer for the entire lot for real or imaginary defects.

A roll that has a machine cylinder look means no scuff marks, damaged edges, and fuzzy ends, protruding or buried core ends, or crushed cores. The solutions to these problems are self evident. There are other finer detailed defects that can be buried in the roll, and may be if the production line is never approached by the operator except during a roll change. There is no excuse for the customer being the first to see these.

I have a couple of areas for helping prevent roll defects:

How to Tackle Blocking of the Plastic Film - a common reason for blocking is too much winding tension. There is an area over looked and it is the tension which is set so great as to crush the core as the film is being wound on the roll. This makes it impossible for the operator to remove the roll from the winder shaft. With a case of crushed cores, the rolls may be hard to get off of the shaft, only to have the customer find them impossible to remount on a un-wind stand. Just as bad of a problem can arise if the winding tension is too light, no blocking but the film may telescope from one end of the roll, making it impossible to convert into finished product. Hot weather can bring its share of blocking problems. Plastic Film is insufficiently cooled and the inner surface blocks as they pass through the nip rolls. For a cure you must reduce the output, raise the tower height or nip rolls, or use refrigerated air or other means of improving cooling efficiency. It also can be an inefficient air ring. The cause of blocking can be using to much additive when producing 1 mil that has slip and anti-block additive level designed for heavier guages like 3 mil. Sometimes there isn't enough additive to do the proper job. Over-treatment and or high gloss can aggravate if not cause blocking with any of the above conditions.

Tendency to Split - Plastic Film with splits tendencies can also be overlooked unless samples are taken to examine, or actually tested. Insufficient cooling, a high frost line or to low of a blow up ratio, separately or a combination can accentuate the machine direction or orientation of the film causing the film to become splits. Also your nips in the tower maybe to tight particularly with an old and hardening nip roll which can deform the plastic film in the edge crease and make it splits. Die lines or another name is weld lines from the extrusion die make splits film as can scratches from the collapsing frame in the extrusion tower or a bur that has developed if using wooden collapsing frames. But not so readily detected are the fine weld lines caused by degraded particles of resin or dirt lodged under or in the die lips that make the film extremely split at the weld.

Good operator observations to equipment maintenance, quality testing of roll samples and putting the proper procedures in place will help in building customer loyalty.

About the Author

P&R Flexible is the innovator and consultant of todays packaging industry. http://www.prflexbag.com

Molding our World: Plastics as Part of our Daily Lives

What are plastics?

Plastics as we broadly understand it today are synthetic or semi synthetic products or raw materials, formed by polymerisation, and are largely derived from oil. Polymerisation is the formation of polymers i.e. repeated numbers of smaller structures (monomers) joined together.

It wasn’t until the 1860s that the first semi synthetic materials or plastics were first brought to the attention of the world, and since the development of thermoplastics throughout the 1900s it’s hard to imagine how difficult life would be without plastic. The main reasons why plastics replaced more traditional materials are quite straightforward when you think about them.

What’s so good about plastics?

Plastics are relatively light and very durable. The hundreds of different plastic varieties are ultimately recyclable, although it’s only in recent years that our UK society has begun to take advantage of plastic recycling, often in tandem with our weekly waste collections. Plastics have great thermal and insulating properties (clothes, carpets, bedding etc). Plastics are resistant to many chemicals and water, as well as being very strong.

Most notably though, plastics have proven relatively inexpensive to produce, and are so versatile that they can take on almost any form and colour.

What are the popular types of plastics and what’s the difference between them?

Acrylics

These were developed in the 1930s. Acrylics are particularly resistant to the weather and the sun. Acrylic is particularly effective as ‘clear’ plastics, and transmits light brilliantly. Applications include leaflet holders, signs, display cases, boat windows and point of sale to name but a few.

Plexiglas

Often wrongly spelled as Plexiglass, Plexiglas is actually a brand name for a kind of clear thermoplastic resin that’s basically a cross between acrylic and polycarbonate.

Polycarbonate

First developed in the 1950s, these thermoplastics most popularly have engineering applications. This is due to polycarbonate’s strength coupled with versatility, and its electrical insulating properties. Applications include machine guards, capacitors, gaskets etc.

Perspex

This is a variety of polycarbonate. It is popularly developed in sheet form and is widely recognised as a kind of ‘clear’ plastic.

Polypropylene

Another plastic developed in the 1950s with industrial applications, this is particularly suitable for hot fill packaging because it has low density but is very rigid. Other applications include carpeting and packaging.

PVC

Poly Vinyl Chloride (PVC) can be shaped and moulded into an exceptionally wide variety of products. Chemical Plant Industry applications of PVC include water tight tanks, and ducting for Clean Air Systems.

PETG

Polyethylene Terephalate Glycol (PETG) is another industrial thermoplastic. Applications include frames, sign holders and point of purchase displays.

How it takes shape

Modern advances in plastic fabrication, moulding, casting, extrusion, thermoforming, cutting, bending, machining, gluing, welding, stamping of sheets, plastic engraving, fibres and solid blocks mean that our imagination provides the only real limitations to what form plastics can take.

Conclusion

If you asked most people, they would be unlikely to know what plastics actually are, and even more unlikely to be able to tell you the difference between the many types. Despite this, plastics are a central and essential part of modern daily life.

About the Author

Plastic Fabrication Hampshire
Bespoke plastic fabrication