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HIGH DENSITY POLYETHYLENE (HDPE)
Transcript of HIGH DENSITY POLYETHYLENE (HDPE)
RAW MATERIAL AND PRODUCTION OF HDPE
Raw material of HDPE is ethylene/petroleum (a simple hydrocarbon). It is produced in a low-pressure reactor containing a liquid hydrocarbon solvent in the presence of metallic catalysts (Ziegler catalysts).
POLYMER RECYCLING TECHNIQUES
SOCIAL REVIEW TO HDPE
Polyethylene (PE) is an addition polymer that is created by the polymerization of ethylene monomer units.
HDPE is a type of PE which is classified as a thermoplastic.
DESCRIPTION OF POLYETHYLENE
Two of the most common polyethylenes are HDPE and LDPE.
HDPE is characterized by a linear structure consisting of no branching.
That makes HDPE stronger and more resistant to chemicals.
STRUCTURE OF PE
It is most commonly used for items requiring blow molding techniques, such as:
cutting boards for foods
APPLICATION AREAS OF HDPE
PHYSICAL PROPERTIES OF HDPE
CHEMICAL PROPERTIES OF HDPE
Have excellent chemical resistance so it is not attacked by strong acids or strong bases.
Resistant to gentle oxidants and reducing agents.
Burns slowly with a blue flame. Crystalline samples do not dissolve at room temperature.
HDPE is produced by two polymerization techniques such as addition polymerization and coordination polymerization.
HDPE by gas phase (addition) polymerization technique
Temperature ~ 300 degree Celcius.
1 atmosphere pressure (101.3kPa)
Aluminium-based metal oxide catalyst. (metallocene catalyst)
The catalyst can be used in a variety of operating modes including fixed-bed, moving-bed, fluid-bed or slurry processes.
The ethene (ethylene) monomer is fed with a paraffin or cycloparaffin diluent (diluting agent).
After polymerization the polymer (polythene) is recovered by cooling or by solvent evaporation.
HDPE by slurry type coordination polymerization technique
Temperature 50-75 degree Celcius
A coordination catalyst is prepared as a colloidal suspension (TiCl4) in a solvent such as heptane (C7H16).
The polymer (polythene) forms as a powder or granules which are insoluble in the reaction mixture. When the polymerization is completed, the catalyst is destroyed by adding water or alcohol to the reaction mixture.
The polymer (polythene) is then filtered or centrifuged off, washed and dried.
TYPE OF PE ACCORDING TO PRODUCTION CONDITIONS
Polyethylene was first produced by the high pressure process and Figure 1 is observed after this process.
Figure 1. Molecular weight and long chain branching for 'high pressure' LDPE
Polymerization of ethylene with aluminium based catalyst at much lower pressures than the first process and after this process applied Figure 2 is observed.
Figure 2. Molecular weight and long chain branching for 'low pressure' HDPE
HDPE RECYCLING PROCESS
Used HDPE bottles are recycling into recycled plastic lumber and sheeting.
These are some of the examples of types of HDPE bottles (#2 resin code) that are recycled at the plant.
RECYCLING CODE FOR HDPE
Recycling codes are used to identify the material from which an item is made, to facilitate easier recycling or other reprocessing.
HDPE plastic is often used to make bottles for beverages with short shelf life, such as milk and juice.
HDPE is the type 2 plastic.
The bottles and containers are chopped up into small pieces called "flake" or "regrind" in this machine.
The flakes are washed in water and biodegradable soap and then dried
The clean flake is then stored in boxes until it is ready to be processed into a mass of hot mix.
This is the container where the flake is melted and ready to be forced into the dye to make lumber.
The two-by-four is emerging from the machine. It is over 200 degrees Fahrenheit. As the lumber is pushed out from the dye, excess globs of it fall off. This is called "purge."
The two-by-four is pushed through a long trough of water to cool it before being cut into lengths.
The lumber is cut to the length specified by the customer. In our case, the lumber was cut into 2" X 2" X 4" pieces.
Since the board shrinks when it cools, the board is made larger than the two-by-four dimensions. Herehe board is planed to size and uniformity. The mass of a 2" X 6" X 12" piece is about 3.3 pounds. Themass of our piece is about 3.84 pounds.
Red, gray, blue, and black lumber are waiting for shipping.
The finished products are displayed. A picnic table, deck, gazebo, playground, and many other things can all be made from recycled plastic lumber.
• Under normal conditions HDPE exists as a solid granule.
• HDPE is susceptible to degradation by exposure to sunlight .
• HDPE is insoluble in water. Floats on water. The
product has low mobility in soil.
• The product is non-biodegradable.
• Low toxicity to aquatic organisms.
• Unlikely to affect biological treatment processes.
HDPE does not decompose in the air and does not release any harmful gases or other products.
• HDPE is non toxic non hazards material and can be considered as material safe for contact with humans and animals.
• Ingestion: Low oral toxicity.
• Inhalation: Low acute toxicity. Dusts and vapours evolved during thermal processing may cause
irritation to the respiratory system.
• Skin Contact: No evidence of irritant effects from normal handling and use.
• Eye Contact: Dust may have irritant effect on eyes. Permanent damage is unlikely.
• Long Term Exposure chronic effects are unlikely.
Worldwide capacity of HDPE in 2010 was in excess of 41 Million Metric Tonnes.
As the world’s largest HDPE consumer, China is driving global HDPE demand.
ECEM PINAR KAYA
CEREN SELEN APA
RECYCLE AND REUSE OF PLASTICS
WORLD CONSUMPTION OF HDPE
GAS PHASE PROCESS
ENVIRONMENTAL BENEFITS OF RECYCLING
Green house benefits of recycling per household (kg carbondioxide per year)
Energy Savings from Recycling per Household (megajoules per household per year)
HDPE RECYCLED PRODUCTS
Liquid laundry detergent bottles
In 1999 HDPE accounted for 47% of plastic bottle resin sales, making it the second most widely used resin in plastic bottles. HDPE and PETE together accounted for 95% of plastic bottle resin usage.
Water Savings from Recycling
GAS EMISSIONS FROM PRODUCTION