Background

A straw is a prepared tube used to suck a beverage out of a container. Historians theorize the first straws were cut from dried wheat shafts and they were named accordingly. With the advent of industrial age, methods were developed to mass produce straws by rolling elongated sheets of wax-coated paper into a cylindrical, hollow tubes. This was accomplished by coiling paraffin-coated paper around a rod-shaped form and then securing the paper with an adhesive. The entire straw was then coated with wax to further water-proof it. The wax coating was important since the straw was paper and would eventually absorb some of the liquid being sucked up it. Thus, inevitably these paper straws became soggy and useless. In the 1960s, paper was largely replaced by plastic which were becoming less expensive and increasingly more sophisticated. The explosion of plastic technology led to techniques to manufacture plastic straws via extrusion. Today, straws are made in a wide variety of shapes, colors, and functions. The modern drinking straw was patented in 1888 by Marvin C. Stone.

Raw Materials

Straws are made from a formulated blend of plastic resin, colorants, and other additives.

Packaging materials

Straws are typically wrapped in paper sleeves for individual use or bulk packed in plastic pouches or cardboard boxes.

The Manufacturing Process

Straw manufacturing requires several steps. First, the plastic resin and other components are mixed together; the mixture is then extruded in a tube shape; the straw may under go subsequent specialized operations; and finally the straws are packaged for shipment.

Quality Control

Drinking straw quality is determined at a number of key steps during the compounding and extrusion phases of the manufacturing process as well as after extrusion is complete. During compounding, the mixing process must be monitored to ensure the formula components are blended in the proper ratios. Before beginning the extrusion process, it is a common practice to purge some resin through the extruder. This purging helps clean out the barrel and acts as a check to make sure all molding systems are operating properly. At this stage, sample straws can be checked to make sure they achieve the proper dimensions. These samples can also be used to ensure manufacturing equipment is operating at the proper line speed.

During the extrusion process, it is critical that the resin is be kept at the proper temperature. Depending on the processing temperature (and the molecular weight of the polymer), plastic can flow as slowly as tar or as quickly as corn syrup. If the temperature is too cool, the viscosity increases dramatically, and the resin will not flow through the die. If the temperature is too high, thermal breakdown can occur. Over-heating can cause chemical changes in the resin, weakening the plastic and rendering it unsuitable for use in straw manufacturing. Under certain circumstances, die buildup occurs. When this happens, a glob of plastic gets stuck somewhere in the die. This glob eventually breaks free, becomes attached to the molded straw, and ruins its appearance. Unwanted chemical interactions can also effect the quality of the finished straws during the extrusion process. One problem is oxidation, which results from contact with air. This reaction can negatively impact the plastic. Similarly, the plastic interacts with any moisture that is present; too little moisture can make certain plastic blends too brittle.

After the manufacturing process is complete, it is critical that the extruder be properly cleaned. Thorough cleaning is necessary because different types of different colored plastics can be left behind in the extruder barrel. This residue can cause contamination in the next batch that is made. Die cleaning is done when the machine is still hot and traces of resin can be easily scraped from the metal.

The Future

There are a number of interesting new developments in straw technology. First, new and improved plastic blends are constantly being evaluated. This is necessary to keep costs down, meet regulatory requirements, and improve quality. In addition, new processing and design methods are being developed. These can expand the straws into new areas. For example, thermoliquid crystals, a special colorant that responds to changes in temperature, can be added to straws to make them change color when they come in contact with hot or cold liquid. Other unique applications include ways of printing straws with the identity of the beverage (e.g., diet, root beer, etc.). The straw can then be used to mark what the drink contains. Other advances include straws made by a blow molding process, which creates faces or other artifacts in the middle of the straw.

Where to Learn More

Books: Richardson, Paul. Introduction to Extrusion. Brookfield Center, CT: Society of Plastic Engineers, 1974.

History of Drinking Straws

Wikipedia for Drinking straw

Drinking straw explained

The Amazing History and the Strange Invention of the Bendy Straw