Before you can recycle plastic items, you need to wash and separate them based on the resin identification codes printed on the bottom of every plastic product. Two of the most easily recyclable plastic types are PET, used to make plastic beverage bottles, and HDPE, used to make containers for milk and plastic bags. They have the resin identification codes 1 and 2. Recycling facilities, however, accept different types, so ask what types of plastics you can recycle in the facility closest to your home. In many facilities, plastic beverage bottles such as water, juice and soft drink bottles are redeemable for cash. Remember to remove the caps from the bottles before recycling because most of the time the caps have a different resin identification number than the bottles. Today, many grocery stores also have Waste plastic recycling for plastic grocery bags.

After 1970, plastic prices rose again due to OPEC raising the cost of petroleum feedstocks and recycling practices again increased. Interest increased not only in processes for reclaiming waste plastics, such as product evaluation for chemicals and fuels, but also in the necessary step of separation of plastics from other waste material. A review of this early history of plastics recycling is given by R. J. Ehrig in Plastics Recycling, Oxford University Press, NY, 1992, hereinafter referred to as Ehrig (1992). Some of the early operating plants for recycled plastic included a Department of Energy funded plant in LaPorte, Tex., which used a fluidized bed of sand and was designed for 17 million pounds per year of atactic polypropylene. It ran from 1980-82. In 1984 at Ebenhausen, Germany, a 20 million pound per year plant used molten salt with a fluidized bed reactor to process plastic wastes and tires.

The biggest advantage in plastic recycling machines is the need to produce new plastic items is reduced. Oil is one of the components used to make plastic, so decreasing the need will conserve non-renewable fossil fuels, reduce energy consumption and reduce CO2 emissions. In addition, plastic products are bulky and do not decompose in landfills, so recycling them reduces the amount of solid waste going into our landfills.There are many different types of plastics with several resin identification codes, but only the same type of plastics can be recycled together. Separating different types of plastics can be confusing and not all types are accepted in all recycling facilities. Because of this, new technologies are needed to make some plastic types recyclable. Until these technologies are developed, many plastic products will remain unrecycled. Instead, they are taken to landfills, being incinerated or shipped to foreign countries for recycling. Everyone of us needs to change our consumer habits and that is not an easy task. Using a canvas bag at the grocery store, not purchasing new plastic containers but reusing the ones you already purchased and recycling your plastic beverage bottles are actions we are still learning.

In all cases economics governed whether such plants continued operation. Since 1985 plastic recycling line has become more economically feasible due to continued plastics technological growth and increased environmental concern, however, significant cost impacts remain due to the level of the elevated temperatures previously required.The first two steps in recycling plastics are sorting and separating. After this, each plastic type is either melted down and molded into a new shape or shredded into flakes and then melded and processed into granulates. What is made out of the recycled plastic determines which recycling process is used.

Drying, together with cutting, is one of the difficult step of any plastic recycling machines.

Drying is easy when talking about thick flakes of any plastic material.

For example drying HDPE flakes from plastic drums is the easiest job in this world because thickness is in the range of two or three millimeters, the material is elastic so you can put it into any spin dryer and you get them dry.

The matter becomes a little different when happening to thin flakes out of a film line, and for thin around 20 microns (of millimeter) or less, or brittle materials like Polystirene, PC, etc.

Let’s see one problem at a time.

This film first.

If your centrifugal dryer leaves one milligram of water per square centimeter (or change the units but the general concept remains) and your flakes weighs one gram, moisture content will be 0,1% and everybody is happy.

Because the centrifuge performs the same way, doesn’t matter the thickness of your flakes, the same one milligram of water per square centimeters means 10% if the flake weighs 0, 01 gram.

Most of everybody uses hot air for final drying, and because hot air cost a lot of energy, one matter is to start from a moisture content of 2% and a completely other one is a10% starting point.

So, before sizing the hot air drying system, you better care about the % of moisture out of your dryer, whatever it is.
We do love centrifuges for quite many reasons:
First is the fact we can get very low moisture content, even with very thin materials, and very proud of this.
Second because any centrifuge, while drying, it washes as well because it is the combination of friction with water presence.
Third because even the most sophisticated centrifuge is nothing but a rotor spinning into a screen basket that means it is an easy to maintain machine and cannot give lots of problems.
So, as far as today, the very best way we know to get plastic flakes dry, is to go with a well performing centrifuge.
Centrifuges can be very different and the one that makes thin film dry will make 30% fines running Polystirene so diameter, shape of the paddles, size of screen holes and may be something else should change accordingly.
After getting flakes mechanically dry, for some plastics, we will need further drying to get the best possible quality.
We’ll talk about Crystalline Polymers later in this chapter because they need something very specific.
For all other polymers, what we do suggest, is to get a good extruder with a venting, better with two, and feed it straight with the flakes you got after the centrifuge.
This what we do in all cases but one; dealing with film, doesn’t matter the thickness, washing and drying is done with flakes of about 30-40 mm. in size and any force feeding (we know of) accepts only way smaller flakes so further cutting is needed.
Because any granulator will make friction by cutting, meaning developing heat, and then, by blowing, flakes lose some more humidity and by the time they get to the extruder, will be dry enough for pelletizing.
Crystalline Polymers, as we said, need a chapter by its own
PET and PC in fact don’t like the mixture of water (moisture) and heat together plus the fact they are hygroscopic by themselves. (PA performs the same way even not being crystalline)
So if you dry and leave them in a storage place they will get moisture from the air and the energy you have been using to dry them is just thrown away.
Drying should occur just before extrusion and moisture content is measured in PPM and not a %
Both material need a dryer where they stay for sometimes (few hours) with or without vacuum and this because they should release the moisture that’s inside the flakes, or pellets
If these polymers are not completely dry, during extrusion IV (Intrinsic Viscosity) will decrease a lot and polymer loses its characteristics.
Mechanical drying at the end of the pp film drying line should deliver a flake with a moisture content of 0,5-0,6% and after this it will be a dryer unit job to decrease it to nothing (a good dry flakes should have 20 PPM before extrusion)

There are about 50 different groups of plastics, with hundreds of different varieties. All types of plastic are recyclable with plastic recycling machines.

To make sorting and thus recycling easier, the American Society of Plastics Industry developed a standard marking code to help consumers identify and sort the main types of plastic.

These types and their most common uses are:

1.PET - Polyethylene terephthalate - Fizzy drink bottles and oven-ready meal trays, peanut butter jars . PET types can be recycled by PET bottle washing line.

2.HDPE - High-density polyethylene - Bottles for milk and washing-up liquids, motor oil HDPE types can be recycled by PE granulating line.

3.PVC - Polyvinyl chloride - Food trays, fast food service items and shampoo, cooking oil bottles

4.LDPE - Low density polyethylene - Grocery bags and can liners.

5.PP - Polypropylene - Margarine tubs, microwaveable meal trays, bottle caps, yogurt containers, straws. PP types can be recycled by PP granulating recycling line.

6.PS - Polystyrene - foam meat or fish trays, hamburger boxes and egg cartons, vending cups, plastic cutlery, protective packaging for electronic goods and toys (packing peanuts).

7.OTHER - Any other plastics that do not fall into any of the above categories. - An example is melamine, which is often used in plastic plates and cups.