How polythene is manufactured?

Producing bags can be broadly split into 3 stages:

 Extrusion  Conversion  Packing



This first stage is to make polythene film. The virgin polymer granules are blended with colouring agents (known as Masterbatch) and other additives if required. This mixture of cold granules is then conveyed to a film extruding machine, in which the granules are heated until they are molten and again forced through a die resulting in a vertical molten tube of polyethylene tube.

This molten tube has air pumped into it, so that it inflates like an elongated balloon. This stretches the tube outwards, whilst at the same time the tube is being pulled by a pair of nip rollers, which stretch it the other direction.


The tube is cooled by cold air blowing onto it; it emerges beyond the nip rollers, still as a flattened tube (known as layflat tubing LFT) is then wound on to a cardboard or plastic tube (known as a core).

We have enforced stringent quality inspection measures and have trained the operators accordingly who ensures the correct width and thickness of the LFT. The finished rolls of film, typically 50 kg each and of up to 100 metres in length of tube depending on its thickness, are removed for the next stage.



There are 2 main methods of making bags - sideways or lengthways.

i. Sideways - with this method, the bags are produced sideways-on by a servo driven convertor using a hot knife to simultaneously cut and seal the tubular film to form the sides of the bag, the bottom being the fold in the tubular film. These are known as side-weld bags.

ii. Lengthways - using this method, the layflat tube is pulled through the convertor and a hot wire makes a seal across the tube while a flying knife (a sharp blade traveling at great speed), cuts the film below the seal whilst the film is motionless for the sealing process. Thus the seal forms the bottom of the bag and the folds of the layflat tubing, the sides. These are known as bottom-weld (or end-seal) bags.

The entire process is automated ensuing high level of accuracy



The side weld bags are carefully wrapped in robust 80gsm Kraft paper normally in 1000's whereas the bottom weld bags are packed in strong cardboard boxes in 200's. All the packs are then labelled, palletised and are finally ready for dispatch.