 POLYPROPYLENE
(PP )
Definition and Features
Polypropylene is obtained by radical polymerizing the high purity
polypropylene (99.9%) gas by the help of Ziegler-Natta catalysts. This
crystal structured polymer with the density between 0.902 and 0.910 g/cm³ is
one of the lightest of thermoplastics. Its melting point is 164 °C.
Polypropylene has a high dielectric coefficient and heat isolation as it’s
not polar. In application, it is very resistant against all chemicals except
for concentrated sulphuric acid, nitrite acid, potassium dichromate,
kerosene and tetrachloride. Homopolymers have an average of 175000 psi
flexibility modules and about 4900 psi tensile strength. Flexibility module
can be increased up to 350,000 psi by the reinforcement with stuffing
material. Polypropylene is resistant to 80% suphuric acid and concentrated
hydrochloric acid up to 100 °C. Besides, its resistance to organic solvents
under 80 °C is also good. Just like other oleic resins, it is slowly
affected by oxidant acids. Impact of organic compounds on polypropylene is
rather low. Absorption is directly proportionate with temperature and
inversely proportionate with the polarity of solvent. Polypropylene is not
resistant to sunlight due to irreversible carbon atom in its molecule
structure. AYPE and YYPE are better than PP with respect to this aspect.
PP Processing Technologies and Fields of Application:
Polypropylene can be processed by all methods applied for thermoplastic. By
molding with injection technique, pieces with good size stability and smooth
surfaces can be obtained by using small moulds with small details.
BOPP (bioryente polypropylene) film is used with the meaning of double sided
stretched film.
In recent years, BOPP is being used widely in dry food and textile packaging.
Fiber is obtained after the extrusion of polypropylene in an air cooled area,
by passing from one side to the other through the thin nozzle and wrapping
around a roll.
Polypropylene is shaped by heat and lathered by injection molding and
extrusion molding techniques.
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