Plastic prep¶
Learn how to make your plastic ready for melting
Collecting¶
The first thing a Precious Plastic recycling workspace needs is plastic to recycle. Pretty simple right? Without plastic to work with all processes will come to an halt. It is essential to always have enough plastic waiting to be sorted, shredded and worked with in order to run the workspace effectively. Plastic at this stage is still mixed and dirty.
Precious Plastic workspaces have one collection bag (with appropriate signage) outside of the space for people to drop plastic and one inside to be sorted in different typesthis cycle enables a continuous process. When the collection bag outside is full the team should bring it inside and replace it with another empty collection bag. Once inside the bag has to be emptied from the plastic and sorted as soon as possible. When the bag outside is full again the process is repeated. This cycle should run at all time to ensure a smooth operation of the workspace.
The actual collection of plastic can happen in a number of ways depending on the cultural and economic context of your country as well as the partners you decide to work with. Some examples are:
-People from the Precious Plastic workspace collect plastic daily or weekly from their surrounding environment, friends and families. Very time consuming but powerful from a community perspective, and free.
-Find local shops or manufacturer that wants to get rid of their plastic because of production offcuts, leftovers or waste. This could mean greater quantities of plastic at once but it might come with a small financial compensation.
-Work with local waste pickers that are already collecting plastic in your town. You might have to pay pickers for their work but this could save you a lot of time and you could help them get a better living.
-Find a local waste stream that can offer you a constant supply of plastic (eg. industry, agriculture, fishing etc..)
The collected plastic can be exchanged for money, awards or a big thank. This depends on your preferred choice, business plan, local environment and who your partners are.
Sorting¶
The sorting system is a crucial element for all recycling activities. A thorough and precise sorting effort guarantees smoother processes, better products and easier maintenance. An efficient sorting system allows the team to know exactly what plastic type is being used, which is crucial in order to figure out its melting temperature and set the Precious Plastic machines correctly to run the workspace efficiently.
Sorting is done manually (really?? Yes, even big industries still do it manually) by checking the SPI code (see 2.4 Plastic Types). Once the unsorted plastic comes in the workspace you should separate it in the relevant sorting bags (labelled with appropriate SPI code). Check each product for the small code (it can be numbers or letters in the triangular recycling sign), this is usually very small and can be difficult to find. Usually, it is embossed in the plastic itself at the bottom/inside of the product or printed on the label. Once you spot what plastic type the product is you can drop it in the appropriate sorting bag with the same SPI code.
Sometimes products don’t have the SPI code because it either wasn’t there in the first place or got eroded with time. In this case, you should put the product in the mix bag (number 7). If you have many of the same products without an SPI code you can try a number of alternative ways to discover what kind of plastic it is. The following techniques are less precise and not fully tested by Precious Plastic team and are intended to be a starting point for your own research on them.
Floating, this technique takes advantage of the different densities of plastic types. Each plastic type has its own specific density that will make it float differently in liquids. The floating liquid can be salted water, alcohol, vegetable oil and glycerin. This technique is used intensively by the industry. However, it can be very tricky, particularly because of the additives mixed with plastic that can change its density making it inaccurate.
Fire, this is a more extreme technique but it can work on certain occasions. Plastics have different properties when set on fire. For this technique, you should cut a piece of the un-known plastic and light it up observing the flame colour, nature and smell.
Smashing, plastic breaks in different ways when hit violently with a hammer. Some will smash in many pieces, others in bigger chunks while others will not break at all. Again, not perfect technique but it can help in certain situations.
Sound, different plastic sound different if dropped on a paved floor. PP and PE, for example, sound very low while PS has a very high pitch and distinctive sound.
Scratch, thermoplastic and thermoset can easily be identified with this technique. When cut with a standing knife thermoplastic leaves a clean cut while thermoset creates little dust around the cut.
Type of object, often products are made from specific types of plastic. Water bottles PET, cd cases PS, jerrycans HDPE etc. This can be a way to distinguish which type of plastic it is.
Shredding¶
Once the plastic is sorted by their specific plastic type it’s time to shred it. At this stage, bigger plastic objects are chopped into small granulate to reduce its size, enable washing, store more efficiently and be used with the other machines. It is good practice at this stage to separate plastic by colour. More info on the shredder and how it works coming up next in the Create Chapter (see 4.2 Shredder).
Washing¶
Plastic needs to be clean before undergoing recycling processes. We always reccomend people the bring plastic clean. Dust, dirt and impurities will cause problems to Precious Plastic machines and processes. Dirty plastic can result in extra maintenance, breakdowns, problematic productions and low-quality products.
If plastic isn’t clean collectors can wash it in barrels filled with water. A more effecient way is to wash after shredding using a basic filtering system. Plastic flakes are placed on a mesh and immersed in water. It is then thoroughly stirred 5-10 times and taken out. At this point, you should place the plastic on a drying plate for a few hours waiting for water to evaporate. It is important that the plastic is dry before being melted.
Storing¶
Once the plastic is dry it can be stored in the provided buckets. Ideally, buckets should be stackable, strong and transparent so you can see the colour and nature of the plastic. The SPI coding should be respected when storing the plastic using the provided Precious Plastic stickers. For example, if you have sorted, shredded and eventually washed PS it is essential that you put it in a bucket with the PS code sticker so that plastic does not get mixed up. The templates for making the labels can be found in our download-kit