PLA: From plant to plastic packaging
PLA: From plant to plastic packaging
5 things you should know about the bioplastic
A plastic made from natural “ingredients”, known as PLA. Because this material is derived from plant starch, from production to properties to disposal, we have compiled some interesting facts about this plastic for you.
How PLA is made
PLA is one of the bioplastics. The term refers to plastics made from renewable raw materials – i.e. biobased – as well as for those that are biodegradable or compostable. The latter can also be partly produced from fossil raw materials. In the case of PLA, both of these properties apply. The material consists of renewable raw materials and can be composted according to DIN EN 13432.
PLA is the abbreviation of polylactides and is colloquially called polylactic acid. To obtain this lactic acid, you need starch produced in plants such as corn, potatoes, or sugar beets through photosynthesis. If starch obtained from plants is fermented mainly from corn plants in PLA, lactic acid is formed.
These synthetic polymers can be formed by the process of polymerization in further steps into granules, which are necessary for plastic products.
In the same way, CPLA is obtained. However, 20% to 30% talc powder is still added. As a result, PLA crystallized, which explains why “C” also stands for “crystalline PLA”. In response to talc powder, the material becomes opaque, harder, and more resistant to heat. In this state, it can also be melted, which is why it is used, for example, for disposable cutlery.
These characteristics distinguish PLA.
PLA is the most important bioplastic in the packaging market because it can be supplied in large quantities and is easy to process. It belongs to the polyester family and has high transparency and resistance. In addition, it can permeate water vapour and retain the aroma of food for a longer period of time. The range and uses of PLA packaging are correspondingly diversified. It ranges from the coating of coffee cups to the viewing window for takeaway packaging or cake boxes and carrier bags. As mentioned above, the CPLA variant does not provide transparency, but the heat-resistant temperature is as high as + 85°C. Therefore, cutlery or lids for hot beverage cups are made from it, for example.
Why PLA is considered sustainable
For various reasons, bioplastics are considered a sustainable packaging material. On the one hand, it is made of renewable raw materials, thus providing an opportunity to protect non-renewable fossil raw materials and be independent of them. The basis of bioplastics is corn.
However, industrial maize is used, not food. It usually grows in soil that is not suitable for food maize. In addition, only about 0.02% of corn crops in the world are currently used for PLA.
On the other hand, PLA has a good carbon dioxide (CO2) balance; it is already in production because it has lower carbon dioxide emissions compared to other plastics such as PET or PP.
If the material is incinerated during disposal, only the amount of CO2 absorbed by the plant during its growth will return to the atmosphere.
Last but not least, PLA is compostable and will, under certain conditions, decomposes into CO2 and water, with no toxic waste. However, you can find out what needs to be considered in this degradation in the following point.
PLA offers these disposal options
PLA can be disposed of in various ways. As mentioned above, it is compostable according to DIN EN 13432. The standard states that materials in industrial composition plants decompose under certain temperature, oxygen, and humidity conditions within three months, and the residue does not exceed 10% when sieved through a 2 mm sieve. As described, PLA does not produce toxic residues. However, such certification does not mean that bioplastics will degrade in indoor garden compost or in nature or that humus or nutrients can be obtained from them. Furthermore, compared to bioplastics, traditional bio-waste takes less time to decompose. Since PLA is currently used in very small amounts in industrial composting plants, it is therefore not economical for operators to separate the bioplastic from other plastics and waste and have it composted for longer.
The same applies to the recycling of PLA. Since the quantities are currently still too small, this processing is not worthwhile. Therefore, there is no sorting and recycling process in the plants, although the material shows promise for recycling. The most rewarding disposal at present is, therefore, incineration. In the case of thermal recovery, part of the energy used for production can continue to be used. As mentioned earlier, only the amount of carbon dioxide (CO2) absorbed by plants during growth is removed, so greenhouse gases are also reduced.
This is how recyclable PLA is
PLA received a better life cycle assessment during the recycling process. With the increase in production and the increase in waste volume, this may be the best disposal method in the future, especially because the classification and separation of other plastics are technically feasible.
Some tests at research have shown that recycled plastic can replace virgin material or even have the quality of virgin material in certain processing. If already produced PLA is reused, the cultivation, fertilization, and harvesting of the crops are eliminated, further improving the substance’s life cycle assessment. Thus, PLA proves to be a material with a sustainable future outlook!
Read our blog on Materials science PLA – everything worth knowing about the bioplastic