Sealing and cutting of PLA bio-plastic

Vogel, Julius
Major Professor
David Grewell
Sriram Sundararajan
Committee Member
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Mechanical Engineering
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Mechanical Engineering

Recently, there has been an increased interest in bio-based plastics due to environmental concerns as well as fluctuating oil and gas prices. Bio-based plastics, as defined here, are those plastics that are fully or partially produced from renewable feedstock. As with

many products, sealing and cutting of semi-finished parts are required. This is particularly true with packaging applications, such as food packages, where there is a natural fit for bio-plastics because of the product's short life cycle (<1 year) and large

amount of waste associated with this product (12.5 million tons of containers and packaging per year). In order to increase the acceptance of polylactic acid (PLA a starch derived bioplastic), its weldability and cuttability was studied in detail. Ultrasonic and

heat welding, which are two common welding techniques in industrial applications, are examined in terms of weld strength, cycle time, and weld strength consistency. While the ultrasonic welding of PLA is very effective, heat welding is examined in great detail to

find the activation energy for diffusion in such processes. In addition, the ultrasonic cutting that is often done simultaneously with ultrasonic welding processes is examined here too. The cuttability of PLA was studied by examining the cutting speed, the mechanical properties of the material after cutting as well as the surface of the cut. In addition, a new kind of cutting tool was developed that can cut and seal simultaneously. However, the manufacturing of products from bio-based plastics may result in more energy consumption, waste, and emissions than traditional plastics, which would reduce

or eliminate the acceptance of PLA. In order to address this issue, a model was generated to examine the `Carbon Footprint' of bio-plastics such as zein (a corn based protein polymer), soy protein isolate (SPI) (a soy bean based protein polymer), and polylactic

acid (PLA) which compares these materials to petroleum based plastics with similar mechanical properties and potentially similar applications, such as polyethylene (PE) and polystyrene (PS). The results show the energy consumption, greenhouse gas emissions,

and costs during the life cycle steps of material production, manufacturing of plastic products, and the beneficial as well as non-beneficial effects of the end-of-life recovery processes of the considered materials.