2. INTRODUCTION
Monofilaments are wire-like polymeric strands of
diameter 0.09 to 1.52 mm.
Usually they have a circular cross section.
Enhancement of the tensile properties are achieved
by stretching (orientation).
Extrusion process for monofilaments in two types of
die are use.
1. T-die
2. Circular die
3. Monofilaments are produced in a melt spinning
process.
The polymer is melted in the extruder and
conveyed under pressure to the spinning unit, then
it is quenched, stretched, annealed to get the
filament of enhanced properties.
8. EXTRUSION
•The material is fed into a
standard extruder where it is
plasticated. The
homogeneous melt is
extruded through die plate
containing small holes.
9. DIE
•Most monofilaments are extruded downwards into a
quench bath. This means that the head assembly must
contain an elbow to turn the plastic stream 90°. The die
is circular in shape, with holes from the centre. This
ensures equal flow through each hole, hence equal filament
size.
•Dies are in two types, T-Die and Circular Die.
10. QUENCH BATH
•The material coming out from
the die plate is cooled in the
quenching bath. Its purpose is
to cool the filaments quickly to
get a tougher molecular
structure of smaller crystallites.
• The quenching bath
temperature is maintained
below the crystalline melting
point of the material. Cooling
medium is usually water with
temperature at 40 to 90°C.
12. GODET ROLL
There are two sets of large godet rolls, one on
either end of the orientation stage.
The stretching is done by running the second set of
rolls much faster than the first.
The stretch ratios range from 2:1 to 12:1.
Three sets of godet rolls are used.
The Ist, IInd rolls used for stretching the filaments.
The IInd, IIIrd godet rolls are used to keep the
filament in tensional during the annealing stage.
13. ANNEALING
•The filaments pass between
two heaters or heated surfaces
that quickly bring the plastic up
to the orientation temperature.
The system is used for such
plastics as PA and PP.
