Extrusion is a manufacturing process in which the polymer is melted and formed into a continuous profile. At Lynx our extrusion process forms blown film to provide pallet protection during transportation. In the extrusion of plastics, raw material in the form of small beads or polymer is gravity fed from a top mounted hopper into the barrel of the extruder. This is also where we add our masterbatches or additives, such as anti-block. The material enters through the feed throat (an opening near the rear of the barrel) and comes into contact with the screw. The rotating screw (normally turning up at up to 120rpm) forces the polymer forward into the barrel which is heated to the desired melt temperature ofthe molten plastic (usually around 200 °C/400 °F). There some controlled heaters gradually increase the temperature of the barrel from the rear (where the polymer enters) to the front. This allows the polymer to melt gradually as they are pushed through the barrel and lowers the risk of overheating which may cause degradation in the polymer. Extra heat is contributed by the intense pressure and friction taking place inside the barrel..

Once it has passed through the breaker plate, the polymer enters the die. The die is what gives the final product its profile and is designed so that the polymer flows evenly from a cylindrical profile to the products profile shape. Uneven flow leads to unwanted stresses in parts of the film which can cause warping upon cooling. The die in the process is an upright cylinder with a circular opening similar to a pipe tie. The molten plastic is pulled upwards from the die by a pair of nip rolls high above the die, changing the speed of the nip rollers changes the gauge (thickness) of the film, around the die sits the air ring which cools the film as it moves upwards. In the middle of the die is an air outlet from which compressed air can be forced into the center of the extruded circular profile, creating a bubble (see figure 4). This expands the extruded circular profile by the ‘blow-up ratio’. The nip rolls then flatten the bubble into a double layer of film. Which is then supplied on the roll or converted.