(1) Degradable Products
Degradable products are made from plastic material that is oil or petroleum based. They do not decompose or completely deteriorate through natural processes. Their state of degradation will result in a loss of properties, resulting in a reduction of quality. This form of degradation is merely the breaking down of the original material, which includes oil or petroleum, into smaller fragments. A degradable product is capable of being converted into a different chemical structure, and will often leave residues in the environment.
Degradable plastics are made from polymers, which are described as having a chain-like structure. Polymer sources in this case can be natural starch, protein, rubber and cellulose, or man-made, like polyethylene, polypropylene, phenol-formaldehyde resin (Bakelite) or urea-formaldehyde resins, polyester resins, vinyl acetate, methyl acetate or vinyl chloride.
The following is a brief description on how degradable products are manufactured:
At the extrusion stage of the plastic production, a pro-degradant will be introduced to the material. The pro-degradant is in the form of metal-salt and will be added to the polymer to act as a catalyst. This now will cause the breakdown of the polymer’s molecular chain structure. It is said that only 1 to 3% of the pro-degradant additive needs to be added to an entire master batch of plastic being processed. The plastic material will become brittle, thus giving it the capability to disintegrate into tiny flakes.
- Some type of stabilizers will also be added to the master batch to serve as protection for the pro-degradant substance when the plastic pellets go through the melting process. The amount of stabilizer added however, will depend on the purpose of the plastic product being formed; hence, the amount of stabilizers required will depend on the time-scale fit for the product’s purpose.
As a note, extrusion is described as the stage when the plastic, still in its pellet form, will enter a machine called Extruder. This is where the plastic pellet will be softened by heat and friction. It will then be forced or extruded out of the machine, and goes into cool water where it will solidify.
Please proceed to the next page for information on how biodegradable products are made.