Polythene film manufacturing Polythene film manufacturing

Polythene Film Manufacturing

Polybags is the UK's number one polythene manufacturer.

We produce all of our own polythene packaging on site in our 50,000 sq ft factory, operating 13 blown-film extruders to make the polythene and 12 converting machines to turn it into the huge range of bags and sheets that our customers need.

Polythene extrusion lines work best when they run continually, so we operate 24-hour production to ensure that the quality of your products is first rate. This round-the-clock operation also improves production capacity, allowing us to manufacture and dispatch over 80 tonnes of quality polythene packaging products every week.

What's more, 24-hour production helps us keep costs down and provides us with the flexibility to prioritise key jobs, so your order is not only at rock-bottom price but our lead times are the best in the business.

With Polybags, you can guarantee you'll be getting the best value products on the market. There is a lot of polythene packaging to choose from so, if you are new to the manufacturing process, or just interested in how things are made, our handy guide (below) will give you an good idea of what we produce, how we produce it and the various options available to you.

Of course, you don't need to learn any of this unless you want to. You can always leave the manufacturing side to us and you just choose the product you require. If you have any questions the Polybags customer service team are always on hand to help, so please get in touch.

The polythene manufacturing process The polythene manufacturing process

The polythene manufacturing process

At Polybags we make our polythene packaging through the process of blown film extrusion - one of the most common manufacturing methods, in which an extruder heats and inflates raw polymer like a tubular balloon before cooling and flattening it ready for conversion into a huge range of plastic film or bags.

The diagram below gives an overview of the polythene extrusion process, which we will outline for you here.

Silo-fed raw material

The production of plastic film and bags begins with the raw materials used - granules or pellets of polyethylene, so how these are handled is a fundamental part of the process.

Polybags has eight huge external silos which each store up to 60 tonnes of these raw materials until the extrusion process begins as they are fed from the storage silos into the extruder. The advantages of this method include:

Polythene production chain Polythene production chain

The extruder

The raw polythene materials are fed via a hopper into the extruder - a machine with a long horizontally-mounted barrel 20-30 times as long as its diameter, which contains an Archimedes screw turned by a large electric motor and is heated as it moves.

As the raw material is forced through the barrel via the screw it is melted by both the heater elements and the action of the screw. Once it reaches the end of the barrel, the molten polythene is pushed through some gauze filters and then upwards into the extruder die - which contains 2 circular steel pipes placed one inside the other with a gap of 1mm at the exit.

The polythene exits the die in a circular tube and - aided by a set of nip-rollers drawn up a tower reaching several metres above - forms a tall tubular bubble with the die at the base. Air is forced into the bubble until it reaches the required diameter whilst, at the same time, a high-speed air ring blows cold air onto the polythene to cool it down.

The film continues to cool as it is drawn up the tower, before passing through the nip rollers at the top, which flatten the polythene tube to create a layflat tube. This is then drawn through a series of rollers back down the extrusion tower, during which process it may pass through a treatment point and a printer, which can customise your polythene - most frequently when making bags - with your very own company logo or design.

At this stage, the polythene can be kept in the form of a layflat tube or it can be slit on one or both edges to produce various types of plastic sheeting products (see below). These are all wound onto a roll around a cardboard core ready for dispatch.

Polythene film products Polythene film products

Polythene film products

The layflat tube of polythene that exits the blown film extruder provides versatility as, depending on how it is cut, it can be turned into a range of polythene film products.

The diagram below provides an overview of the main polythene film products available from Polybags, which we will provide further detail on here.

Polythene sheeting Polythene sheeting

As well as these various types of polythene film, the layflat tubing that is created during the extrusion process can also be converted into a range of polythene bags. See our page on polythene bag manufacturing for more information.

Layflat tubing Layflat tubing

Types of polythene film

As the UK's number one manufacturer, Polybags can not only offer the range of polythene film products listed above, but we also offer a huge range of sizes, thicknesses and types of polythene film to meet your exact needs.

We can manufacture film from as narrow as 25mm (1") to as wide as 1.4m (55") and varying in thickness from thin 20 micron (80 gauge) film in special high melt films, through to 250 micron (1,000 gauge) heavy-duty films.

Our main types of film are listed below but please note that all film is available in a wide range of grades and colours and with blends and additives to order.

We take bespoke requests and manufacture film to a huge range of specifications so, if you have particular requirements for your polythene film, then please get in touch.

Standard Melt 2 Low Density Polythene (LDPE) - Polybags' standard film blend produces products that are easy to open or handle and are food-grade approved. Contains both an anti-blocking agent and a slip agent to help during the extrusion process. Used for: General packaging applications

High Melt 4 Low Density Polythene (LDPE) - This soft and flexible film has limited strength properties, which makes it perfect for light-duty applications and means we can produce our very thinnest films - as slender as 20 micron (80 gauge) thick. This allows us to save on the amount of film used in production, thus keeping costs down for the customer. Used for: Garment film and dust covers

Garment covers Garment covers

Low Slip Melt 1 Low Density Polythene (LDPE) - Less slippy than standard LDPE film, this blend is useful for making heavy-duty sacks and other products that will be stacked. Its higher molecular strength also makes it suitable for shrink applications. By expanding the film whilst still molten and then quickly solidifying it, the polythene structure means it contracts when heated by shrink gun or heat tunnel. Used for: Shrink films and sack applications

High Tensile Films - This blend of polymers, which include Medium Density Polythene (MDPE), provide the maximum strength to thickness ratio - i.e. films that are both strong but thin. High tensile films have a rough, crinkly feel with reduced clarity and flexibility, but the material is ideal for thin food-grade tint sheets and other tinted or coloured films. Used for: Food bags and food sheeting

Electroconductive Blends - This electrically-conductive film is designed to protect electronic components which may be sensitive to static electricity. A blend of highly-conductive carbon and Low Density Polythene (LDPE), these products can be used for everything from protecting electrical devices to storing explosive devices. Used for: Protective antistatic packaging

Metallocene Blends - Films produced with metallocene - polyethylene raw material manufactured using a metallocene catalyst - are strong and of very high clarity. The films are more expensive than regular polythene due to the cost of manufacturing metallocene but, when you see the clarity of the finished product, you'll understand why. Used for: Premium high-clarity films

Reprocessed Films - Polythene produced with recycled raw material will not produce a product as high in quality as when using virgin polymer, but the resulting film offers an eco-friendly and low-cost packaging solution. Polybags recycles whatever raw material we can and we will always offer to extrude processed film when we can, although lack of supply is often our biggest problem. Used for: Low-cost and reduced-quality products

Biodegradable film Biodegradable film

Biodegradable Film - Polybags' wide range of eco-friendly packaging is made from biodegradable film with an additive blend which provides first oxidative and then biological degradation, typically within 6 - 24 months of being placed in compost or landfill. A fantastic green alternative to regular polythene, this cost-effective, strong and recyclable film offers a superior solution to many other eco-friendly products on the market. Used for: Food waste bags, dog poo bags and other compostable packaging solutions

Film additives

Polybags can introduce a series of additives to the polythene manufacturing process, blending them during production to give your polythene film or bags the specific properties you need.

We have a huge range of additives that we can add - so contact us if you have any queries - but here are some of the most common requests: