Plastics Pellets: From Petroleum to Plastics

Plastics Pellets: From Petroleum to Plastics

Plastics are used in our everyday life and come in many shapes and sizes. The plastic industry is continually growing due to the increase in consumer products made from plastic. Thousands of products we use on a daily basis are made from plastic including toys, cooking equipment, computers, some automobile parts, sports and medical equipment, and even some clothing articles contain plastic.

There are many steps taken to achieve a final plastic product. In many cases, plastic is derived using petroleum as the building block. The following document will give you a short look into the general process of making plastic- from petroleum to pellets.

Plastic Pellets

First, petroleum is extracted and then sent to a refinery where it is refined into ethane and propane (as well as other forms). With a high-temperature heating system, ethane and propane are then converted into ethylene and propylene. Then, these chemicals are combined with a catalyst to become a polymer. A polymer is essentially a chain of many molecules linked together, and can differ depending on the type of plastic that is desired. The three most common polymers used in plastics are thermoplastic, thermosets, and elastomers. These are classified according to their chemical composition. To learn more about the three types of plastics, click here.

The next step would then be the polymer being fed into an extruder to melt and then cooled into a hardened form. A pelletizer will cut the thin tubes of plastic into small pellets. Vibrating screens can even be used to aid in the filter of oversized or damaged pellets, to ensure pellet consistency. Once the plastic is cut into small pellets, they can be used to make a wide variety of plastic products.

Contact Malvern Plastics Group for all of your plastic pellet buying and selling needs, as well as your plastic compounding and plastic recycling requirements.

Processing Methods

The desired product will determine what processing method will be used to convert the plastic pellets into finished products. Some of these many processes include:

Extrusion- This is a continuous process used to make products such as rods, tubes, pipes, electrical wire, and films (such as food wraps). The plastic pellets (or sometimes other forms) are loaded into a hopper where there is a long heated chamber and a continuous rotating screw. The plastic is melted and then forced through a small opening, known as a die, to form the desired shape. The plastic is fed onto a conveyer belt, onto rollers, or into a water tank to cool. The cooled product may then be cut into a desired shape or length.

Injection Molding- In this process, the plastic pellets are also fed into a hopper and then feed into an extruder. Much like extrusion molding, an extruder screw forces the plastic into a long heated chamber to melt. At the end of the extruder, the molten plastic is then forced into a cool, closed container for molding. Upon cooling, the finished product is ejected from the mold. Injection molding is used to make products such as food tubs, yogurt containers, car panels, computer monitors and bottle caps.

Blow Molding- This process is used to make products such as soda bottles and milk jugs. It is used in combination with the extrusion or injection molding process. In extrusion blow molding, a mold is clamped around the die. A semi-molten plastic is forced into the die, and then air is blown into the mold, allowing the plastic to expand to the mold’s shape. This process allows a hollow plastic product to be formed without having to mold two or more parts together to form the same product. In injection blow molding, an intermediate shape (known as a preform) is injection molded. Then, the preform is heated and blown into its final shape using a cool mold.

Rotational Molding- In rotational molding, a closed mold is placed on a rotating machine. Plastic pellets or liquid resin are then placed in the mold and heated. The machine rotates the mold and in turn, uniformly distributes the melted plastic to cover the mold. The mold is cooled and the plastic product is ejected. This process is used for the production of hollow products such as large toys, kayaks, shipping drum, and storage containers.

Contact Malvern Plastics Group for all of your plastic pellet buying and selling needs, as well as your plastic compounding and plastic recycling requirements.

Recycling Plastic Pellets

Once, a pellet is melted and formed by some process into a finished product, it still could return to pellet form by being recycled. Recycled material is separated and sorted according to the plastic type (such as: PE, PET, PETE, HDPE, LDPE). Then these separated plastics are flattened and squeezed into a bale to be sent to a plastics manufacturer like Malvern Plastics Group. The plastic bale is separated and placed on a conveyer belt that grinds the plastic into tiny flakes. These flakes are washed, dried, heated and formed into long small strands. The strands are then cut into the pellet shape. During the extruding process, color may be added but generally plastic pellets are bought in clear color.

Contact Malvern Plastics Group for all of your plastic recycling needs.

Plastics are made in a wide variety of shapes, sizes, colors and processes. The life cycle of a plastic pellet is just one small look into what occurs in the plastics industry. For further information regarding plastic pellets, plastic pellet recycling or plastic manufacturing processes, please contact Malvern Plastics Group.