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:recycle: POLYETHYLENE :recycle: NUREZLIN AZIERA BINTI ROSIDIN…
:recycle: POLYETHYLENE :recycle: NUREZLIN AZIERA BINTI ROSIDIN (2016249968) CPE666 - EH2208C
Introduction :pen:
Polythene
Primary use in packaging
Chemical formula of PE is (C2H4)nH2
Obtained by polymerizing ethylene gas, H2C=CH2
Grades of polyethylene (LDPE, HDPE, LLDPE)
Physical Properties
Melting point (120-180C)
LDPE exhibits high flexibility
Thermoplastic polymer
Chemical Properties
excellent chemical resistance
burns slowly with a blue flame
Polymerization
used to make polymers from vinyl monomers
Reaction mechanism
radical mechanism with the addition of an organic peroxide radical initiator/Zielger Nata catalyst
Steps
Initiation
Oxygen bond dissociate into 2 radicals and CO2
Act as electrophiles and attack the double bond form stabilize intermediate
Propagation
formed radical can add on to itself by attacking another ethylene molecule
Termination
terminated when two radicals react with each other to produce a product with paired electrons
Catalyst
Ziegler-Natta Catalyst
Used to polymerize terminal 1-alkenes
Employed in solid and supported catalysts
Used in the synthesis of polymers of 1-alkenes
Phillips catalyst
Used in polymerization process
Prepared by impregnation of chromium oxide
Products
LOW DENSITY POLYETHYLENE (LDPE)
produced under high pressure in the presence of a free radical initiator
use for both rigid container and plastic film application: plastic bags
HIGH DENSITY POLYETHYLENE (HDPE)
produced by low pressure process in the presence of ziegler type catalyst
use in packaging products: detergent bottle, garbage container, water pipe
3 process
Solution Process
Gas Phase Process
Slurry process
LINEAR LOW DENSITY POLYETHYLENE (LLDPE)
produced in the gas phase under low pressure
use in gas pipe and fittings, packaging film, film wraps
Properties and Uses
inexpensive thermoplastic
molded into almost any shape
Products
packaging (largest market), bottles, irrigation pipes, film, sheets, and insulation materials
high density polyethylene is the largest-volume thermoplastic
LDPE is flexible and transparent
produce film and sheets
Process
CALENDERING MACHINE FOR FOIL AND SHEET
PLASTIC FILM CALENDERING MACHINE
PLASTIC EXTRUSION PROCESS
INJECTION MOLDING MACHINE
Safety Measure
Hazard identification
Eyes
Vapours formed whenpolyethylene is heated may be irritating to the eye
Heated polyethylene can cause serious thermal burns
Dust may cause mechanical irritation to eye
Inhalation
Nuisance dusts can be irritating to the upper respiratory tract
Irritating vapors may form
Potential hazards
Fines and Dust
Dust particles dispersed in air
Regrind, dry colorants and additives in powder form
Static Electricity
Discharge entire metal surface in a single spark
Steamers
Plug filters, feeders, silo outlets, and reduce resin flow
Create feed and product quality problems
Personal protection
Personal protection
Workplace Exposure Guidelines
Respiratory equipment
Engineering control
Handling
controlled through a comprehensive dust control program
Packaging & Shipping
Used dense phase system for conveying and transportation
Used stretch hood
Storage
Keep storage temperatures preferably below 40°C.
Pallets of LLDPE grade should be stacked in a single layer
Environmental issue
Pollution control
Massive awareness campaign and enlightenment about the danger polythene
Government should provide public waste bins in strategic position
Segregate plastic waste from other solid waste
Waste management
Waste generated during start-up, breakdowns or machinery problems
Polyethylene film manufacturers recycle this waste
Using a contract recycler