PROJECT 1: CHEMISTRY OF PLASTIC RECYCLING
Date November 12, 2009
History of plastic recycling
Today, plastics are found in everywhere and many of the products such as grocery carts, packaging materials, and components of automobiles are made ofplastic, due to its enormous production. Though it appear in early times, its real impact was found only in the year 1950 and its continuous usage by number of people in the world, led to fill the lands cause environmental and health concern due to release of toxic materials from them. This initiated to start plastic recycling program in the year 1990s, where many countries started to recycle theplastics leading to new products from the reclaimed plastics (1)
Plastics: It actually comes from greek word, which means “plastikos” meaning moldable (2). Plastics are the group of materials or organic compounds produced by the process of polymerization which are capable of being shaped, extruded, cast through applying heat (3).
Polymers on the other hand are the largermolecules which are made of chains or rings which linked with many monomer units with high melting and boiling point (4).
Thermoplastics are the materials that can be re-melted and reused, by applying high temperature and low temperature it can be softened and hardened respectively with no cross link (5).
Thermo set are the materials, which can form permanent three dimensional strong structures bychemical action of heat, catalyst and ultraviolet rays which are heavily cross-linked (5).
Discovery of 4 popular commercial plastics and their uses
1) Phenolic: This was discovered in the year 1907 by the scientist George Baekland and its is thermosetting resin made of phenol and an aldehyde. They are used in several applications such as to create molds for the consumer products,insulations, and acts as a binder (6).
2) Polyethylene: Gibsson and Fawett in the year 1933 found polyethylene, when they mixed ethylene and benzaldehyde and heated to 170 degree Celsius, with a pressure of 1700 atm, a resultant material was polyethylene. Polyethylene was used in number of applications such as grocery bags, shampoo bottles, toys and bullet proof vests (7).
3) Polypropylene: Hogan andBanks discovered polypropylene in the year, 1951, where they used chromium oxide as a catalyst instead of nickel, which resulted in solid material called Polypropylene. They are used variety of applications ranging from consumer goods such as bottles, cook ware to industrial application such as tapes, woven bags, office furniture etc (8)
4) Natural Rubber: This is 500 years older whenChristopher Columbus in the year 1496, returning from his voyage from West Indies, he brought the first rubber balls. These were used in the water proofing of leather and fabrics in the year 1615 by Spanish people. Finishing product was done at Mexico and exported
Plastic Resin Code (10)
The Society of the Plastic Industry (SPI), developed the resin codes with the chasing arrows are printed in thecontainers which are made of plastics in the late 1980’s. Mainly this code was developed for the industrial purpose to identify the products and sort them for the purpose of recycling. Though there are 7 codes to identify the plastic products, there are ten thousands of types of plastic available in the market. The plastic resin codes are referred mainly to the following plastics they include:Polyehtylene terephthalate, high density polyethylene, vinyl, low density polyethylene, polypropylene and polyesterene.
General characteristic of 7 plastic resin codes
[pic] Polyethylene Terephthalate (PET, PETE)
Polyethylenes are common and most popular polymer. They are optically smooth surface, heat resistant and for solvents; barrier to oxygen, carbondixode and water. They are used in...