Heating Elements and the Manufacture of Drinking Straws

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The crucial ingredient in any successful milkshake or cocktail; we’ve all used a straw or two in our lifetime – but what part do heating elements play in the manufacturing process of this fantastic invention?

Historically, straws have been made from paper but today polypropylene plastic is the material of choice.  The explosion of plastic technology led to techniques to manufacture plastic straws via extrusion using heating elements. Today, straws are made in a wide variety of shapes, colours, and functions.

Polypropylene has many properties which make it suitable for use in straw manufacturing.  This resin is light-weight, has fair abrasion resistance, good dimensional stability, and good surface hardness. It typically does not experience problems with stress cracking and it offers excellent chemical resistance at higher temperatures. Another key attribute of this plastic is that it is safe for contact with food and beverage.

The extrusion process begins with the polypropylene resin first being mixed with the plasticisers, colorants, antioxidants, stabilisers, and fillers. These materials, in powder form, are dumped into the hopper of an extrusion compounder that mixes, melts, and forms pellets of the blended plastic.

Once dried, the pellets are transferred to another extrusion moulder that is fitted with a die which produces a hollow tube shape. The pellets are poured in a hopper on one end of the machine and are forced through a long channel by a screw mechanism.  As the resin travels down the channel, heated by heating elements, it melts and becomes more flowable. By the time the resin reaches the end of the barrel, it is completely melted and can be easily forced out through the opening in the die.

Next, the resin exits the die in a long string in the shape of a straw and is cooled ready for the final stage of the process where the long tubes are cut to the proper length by a knife assembly.  Straws with special design requirements may undergo additional processing. For example, so called "crazy" straws, which have a series of loops and turns, may be bent into shape using special moulding equipment.

Thank heavens for heating elements – ‘cocktail happy hour’ in every bar around the world would never be the same without them!