Bioplastics are plastics derived from vegetable products, such as soybean oil, corn or potato starch, as opposed to conventional plastics, which are derived from petroleum.
Conventional plastic when discarded remains in the environment for centuries and in many cases is impossible to collect. It clogs sewers and drains, kills animals on land, rivers and oceans, and disfigures streets, beaches and landscapes.
One of the main problems with conventional plastic is the greenhouse emissions produced as a result of its manufacture. Bioplastic emits between 0.8 and 3.2 tons less carbon dioxide per tonne than petroleum-derived plastic. The use of crops for the production of bioplastics has been shown to reduce greenhouse gas emissions.
The use of crops for the production of plastics is controversial, as there is greater concern about reducing famine rates than the production of bioplastics, also obtaining plastic from renewable raw materials, does not imply that it has social improvements, as it does not ensure sustainable practices, does not ensure that the plastic is biodegradable or even that its production and use can be viable.
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The new BPA-free plastic could replace current polycarbonates in items such as baby bottles and food containers, and because the plastic is biocompatible, it could also be used for medical implants or as scaffolds for growing tissues or organs for transplantation.
Antoine Buchard, Whorrod Research Fellow in the University’s Department of Chemistry, said, “With a growing population, there is an increasing demand for plastics. This new plastic is a renewable alternative to fossil fuel-based polymers, potentially cheap as it is biodegradable, and will not contribute to the growth of ocean debris.
“Our process uses carbon dioxide instead of the highly toxic chemical phosgene, and produces a plastic that is BPA-free, so not only is the plastic safer, but the manufacturing process is cleaner as well,” he added.
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The use of plastic is widespread because it offers unparalleled advantages at the moment: it is lightweight, easily moldable, insulating, corrosion-resistant and, above all, very cheap to produce.
To combat the invasion of plastic on Earth, groups of researchers around the world are studying how to manufacture materials with plastic-like characteristics from plant fibers that can disintegrate after use.
One example of a bioplastic is lactic polyacid, known as PLA. This material has properties similar to PET, the plastic used in bottles, but is made from renewable resources. PLA already has a wide range of applications, from packaging to medical implants.
But it is not perfect: PLA does not insulate gases well. This means it cannot be used in carbonated soft drink bottles or for vacuum-packing food. In addition, it cannot withstand temperatures above 45°C: if we were to put hot coffee in a PLA glass, it would melt.
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“A rigid, cellular plastic material made from the molding of pre-expanded beads of expandable polystyrene or one of its copolymers, exhibiting a closed, air-filled cellular structure.”
The main by-products obtained from the processing of natural gas and petroleum are ethylene and various aromatic compounds. This styrene monomer, together with the blowing agent, undergoes a polymerization process in a reactor with water, giving rise to expandable polystyrene, the raw material for the manufacture of expanded polystyrene.
When the newly expanded particles cool down, an internal vacuum is created, which must be compensated by the penetration of air by diffusion. This gives the beads greater mechanical stability and improves their ability to expand, which is advantageous for the next stage of processing. This process takes place during intermediate resting of the pre-expanded material in ventilated silos. At the same time, the beads are dried.