PLASTIC
CH 203 Chemical Process Industries
INTRODUCTION TO
PLASTIC:
PLASTIC IS DEFINED AS ORGANIC POLYMER OF
HIGH MOLECULAR MASS. THEY ARE USUALLY
SYNTHETIC MOST COMMONLY DERIVED FROM
PETROCHEMICALS.
PLASTICS ARE USUALLY CLASSIFIED INTO
THERMOSETTING AND THERMOPLASTIC.
THERMOSETTING :
THERMOSEETING PLASTICS ARE THOSE
PLASTICS THAT CANNOT BE
REMOULDED.SUCH AS BAKELITE,POLYAMIDE.
THERMOPLASTIC:
THERMOPLASTICS ARE THOSE WHICH CAN
BE REMOULDED BY HEATING THEM SUCH AS
POLYETHYLENE,POLYSTYRENE.
1.POLYETHYLENE:
IT IS THE MOST COMMON PLASTIC WITH
PRODUCTION OF 80 MILLION METRIC TONS PER
YEAR.IT IS MANUFACTURED BY THE
POLYMERIZATION OF ETHENE MONOMER UNDER
HIGH OR LOW PRESSURE IN THE PRESENCE OF
ORGANIC PEROXIDE AS CATALYST WITH
TEMPERATURE RANGING FROM 100°-300°C.
PROPERTIES AND USES:
IT IS A THERMOPLASTIC HAVING MELTING
POINT RANGING FROM 105° TO 130°C . THEY
HAVE EXCELLENT CHEMICAL RESISTANCE.
BURNS SLOWLY WITH A BLUE FLAME . PE IS
SOLUBLE IN AROMATIC HYDROCARBONS . IT
IS USED IN MAKING POLYETHENE BAGS ,
BOTTLES.
2.POLYPROPYLENE:
POLYPROPYLENE IS FORMED BY THE
POLYMERIZATION OF PROPYLENE MONOMER.
IT IS CURRENTLY BEING MANUFACTURED BY
THREE PROCESSES NAMELY HYDROCARBON
SLURRY, BULK SLURRY, GAS PHASE.IN 2008 ,
POLYPROYLENE MARKET HAD A VOLUME OF
45.1 MILLION METRIC TONS.
PROPERTIES AND USES:
IT IS TOUGH,FLEXIBLE AND RESITANT TO
FATIGUE.THERMOPLASTIC WITH A MELTING
POINT RANGING FROM 130° TO 171°C.USED IN
BOPP,DIELECTRIC IN CAPACITOR,FOOD
CONTAINERS,CAR BATTERIES,WASTE BASKETS.
3.POLYSTYRENE:
POLYSTYRENE IS FORMED BY THE
POLYMERIZATION OF STYRENE MONOMER.IT IS
VERY INEXPENSIVE RESIN. IT IS ONE OF THE
MOST WIDELY USED PLACTICS WITH THE
PRODUCTION OF SEVERAL BILLION KILOGRAMS
PER YEAR.
PROPERTIES AND USES:
IT IS HARD, BRITTLE HAVING MELTING POINT OF
100°C. IT IS TRANSPARENT BUT CAN BE
COLOURED BY PIGMENTS.IT IS USED IN MAKING
CD,DVD COVERS , DISPOSABLE CUTLERY , SAFE
FOR USE IN FOOD CONTAINERS.
4. BAKELITE:
IT IS A THERMOSETTING PLASTIC FORMED BY
THE ELIMINATION REACTION OF PHENOL WITH
FORMALDEHYDE. IT WAS DEVELOPED BY
CHEMIST LEO BAEKELAND IN 1907. BAKELITE
WAS ONE OF THE FIRST PLASCTICS TO BE MADE
FROM SYNTHETIC COMPOUNDS. IT WAS
DESIGNATED A “NATIONAL HISTORIC CHEMICAL
LANDMARK” IN 1933 BY” AMERICAN CHEMICAL
SOCIETY”.
STRUCTURE OF BAKELITE
PROPERTIES AND USES:
IT IS A THERMOSETTING PLASTIC HAVE
EXCELLENT INSULATING PROPERTIES, GOOD
MECAHANICAL AND IMPACT STRENGTH .IT IS
USED IN MAKING ELECTRICAL SWITCHES,
BUTTONS, WIRE INSULATION ,BRAKE PADS
,AUTOMOTIVE COMPONENTS.
QUESTIONS AND ANSWERS:
Q1. WHAT ARE PLASTICS ? CLASSIFY THEM ?
A . PLASTIC IS DEFINED AS ORGANIC POLYMER OF HIGH
MOLECULAR MASS. THEY ARE USUALLY SYNTHETIC MOST
COMMONLY DERIVED FROM PETROCHEMICALS. PLASTICS
ARE USUALLY CLASSIFIED INTO THERMOSETTING AND
THERMOPLASTIC.THERMOPLASTICS ARE THOSE WHICH
SOFTEN ON HEATING AND HARDEN ON COOLING.
THERMOSETTING PLASTICS ARE THOSE WHICH ARE HEAT
CURING.
Q2. GIVE ADVANTAGES, DISADVANTAGES OF
PLASTICS?
A . ADVANTAGES:
PLASTICS ARE CORROSION RESISTANT AND ARE INERT TO
CHEMICAL ATTACKS.THEY HAVE GOOD INSULATING
PROPERTIES. THEY ARE EASY TO MOLD. THEY CAN BE
COLOURED TO DESIRED COLOURS. THEY ARE LIGHT IN
WEIGHT. THEY ARE LONG LASTING AS COMPARED TO
METALS.
DISADVANTAGES:
THEY ARE NOT BIO-DEGRADEABLE THUS CREATING
POLLUTION HAZARDS.THEY PRODUCE TOXIC FUMES WHEN
BURNT IN DEBRIS. SOME OF THEM ARE NOT SUITABLE FOR
FOOD STORAGE PURPOSES.
Q3. DEFINE TWO POLYMERIZATION REACTIONS USED IN THE
PRODUCTION OF PLASTIC?
A . TWO TYPES OF POLYMERIZATION REACTIONS ARE:
1 . ADDITION POLYMERIZATON:
IN THIS TYPE OF POLYMERIZATION, SINGLE MONOMER
POLYMERIZES ITSELF IN THE PRESENCE OF A CATALYST TO GIVE
RESPECTIVE POLYMER. THERMOPLASTICS ARE FORMED BY THIS
TYPE OF REACTION.
2 . CONDENSATION POLYMERIZATION:
IN THIS TYPE OF POLYMERIZATION TWO DIFFERENT MONOMERS
OR SMALLER MOLECULES COMBINE TO GIVE A LARGE MOLECULE
OR POLYMER WITH THE ELIMINATION OF SMALLER MOLECULE.
THERMOSETTING PLASTICS ARE FORMED BY THIS TYPE OF
POLYMERIZATION.