Polyethylene: Implication to Society
Polyethylene has become part of our lives.
The plastic bags that are used in supermarkets, the plastic containers used for taking away food and the bottles used for drinking are examples of polyethylene that we used in our daily lives.
As mentioned in the previous video, there are two types of polyethylene.
HDPE is High-Density Polyethylene.
It is commonly used in water bottles, chairs, tables and fuel tanks in vehicles.
Picture adapted from: https://www.alibaba.com/product-detail/5ft-regular-plastic-folding-table-152cm_60104942859.html
LDPE is Low-Density Polyethylene.
It is widely used in general purpose container (Tupperware), plastic wrap, and bottles.
Picture adapted from: http://attemptnwin.com/rating-plastics/
Plastic recycling became somewhat commonplace in the 1990s.
Thermoplastics were melted and used again and thermoset plastics were ground up and used for filler. Unfortunately, the purity of these plastics was compromised each time it was reused. To assist in the plastic recycling program, the Plastic Bottle Institute of the Society of Plastics Industry created a method for marking plastic bottles in order to determine what type of plastic it is made of.
A triangular symbol made of three “chasing arrows” containing a number in the middle and special letters on the outside is used to identify the different types of plastic. The following are the letters of identification and their meaning for the two polyethylene that is being discussed:
- HDPE – High-Density Polyethylene – HDPE is commonly used for milk jugs and detergent bottles.
- LDPE – Low-Density Polyethylene – LDPE is often used for trash cans liners, dry-cleaning bags, produce bags and food storage containers.
Pictures adapted from: http://letsgohealthy.net/bottled-water-check/
Polyethylene is regarded largely as non-biodegradable but is thermoplastic. It can be melted to reuse for other purposes. It is accepted at most recycling centres in the world.
Firstly, it is sorted and cleaned to remove unwanted debris to ensure that there are no other plastic polymers.
The presence of other plastic polymers will ruin the recycled end-product. Polyethylene is shredded and melted before leaving it to cool as pellet before manufacturing.
To reduce the high percentage of discardance, we should promote recycling.
In 2013, Singapore has accumulated 832000 tonnes of plastic waste. However, only 11% are being recycled. The remaining plastics are incinerated and are disposed of into Pulau Semakau.
By burning plastics, it generates toxic gases.
Singapore can benefit from promoting recycling. Firstly, it is more cost efficient to produce recycled HDPE than to manufacture ‘new’ plastic.
Studies have shown that 1kg of HDPE is produced from 1.75kg of crude oil. This will not only save monetary cost, but also cut down on the limited natural resources we have left.
References:
2. Plastic and the Environment. The Environment Impact of Plastic – Environmental Impact of Plastic Products. 2017 [accessed 2017 Mar 1]. http://www.plasticsindustry.com/plastics-environment.asp