Olefin polymers are most chemical resistant inert material available
in their commercial category for industrial applications. The last era dominated
uses of olefin polymer in commodity applications eliminating traditional metals
and non metals. The future is poised for domination of thermoplastic polyolefin
(TPO) in engineering polymer applications. Among a few converters all over the
world, Entremonde has commercialized and patented TPO coating on polypropylene fabric
(PP). The TPO coated PP fabrics have many advantage over PVC, PU and rubber
coated fabrics.
Use of coated fabrics in manufacture of
protective covers,storage systems, agriculture coverings and pond linings has a
long history. The products mainly categorized as PVC coated fabrics, PU coated
fabrics, acrylic polymer coated fabric, wax coated fabrics (canvas) and
rubber-coated fabrics. The common usage of coated fabrics are for example (i)
Tarpaulins (ii) Vehicle covers or truck tarpaulins (iii) Tents (iv) Agriculture
coverings and fumigation sheets (v) Awnings (vi) Canopies, Tents, Covers etc.
In all the types of coated fabrics, fabric component impart desired mechanical
property, i.e. Breaking strength, tearing strength, bursting strength,
dimensional stability etc. There are number of types of yarns used for
manufacturing a fabric, they are polyester, nylon (polyamide), cotton,
regenerated cellulose etc. There are number of types of processes that are used
in manufacturing a fabric, they are weaving, knitting and random laying of
fibers to make a non-woven. The mechanical properties desired in coated fabrics
are decided by various properties of fabric used viz. weight, type of yarn,
structure whether monofilament, multifilament or texturised, twists, polymer material
property like crystallinity, chemical and thermal resistance etc. One can
choose a fabric material from almost unlimited options available for the
purpose of coating as per the end usage requirement.
The coating formulations are based on main
polymer categories viz. PVC (Polyvinyl Chloride), PE and other Poly olefins, PU
(Polyurethane), Acrylics, Rubber (natural or synthetic) and waxes.Cotton fabric
coated with wax formulations are called canvas, is a most common and primitive
form of coated fabric. With the invention of new materials and their
formulations the number of options available are plenty. The most common are
PVC and rubber based formulation where a number of additives are used to
prepare a suitable fluid to coat on a fabric. The categories of additives are –
fillers, pigments and dyes, solvents, plasticizers and functional additives are
used in almost all types of polymers to formulate a compound having desired
property. The coatings impart or modify surface properties, barrier and aesthetics
of a coated fabric for the required function or end use.
The biggest problem is, disposal of waste, generated after the use of
coated fabrics. Recycling of coated fabrics is not an easy or a common task. In
almost all of the cases the family of the polymer used in manufacturing a fiber
and coating compound are heterogeneous hence their physical mixing to
regenerate in the form of recyclable goods, is not possible even by applying high
temperature or pressure. The second option, though not environment friendly
remain to dissolve, but again common solvent or mixture of solvents cannot
dissolve entire coated fabric for recycling purpose. There are solvents
available to partly dissolve a coating but it is not an economical and
environmentally friendly process, because of volatility of solvents. The only
option remains is to safely incinerate the waste, which has long-term economic
effects, if all the precautions are taken from environmental point of view.
INTRODUCTION:-
There are two polyolefin
polymers used to make synthetic fibres, polypropylene and polyethylene, with
polypropylene being by far the most important. The definition for polyethylene fibres
is "fibre composed of linear macromolecules of unsubstituted saturated aliphatic
hydrocarbons" and for polypropylene fibres "fibre composed of linear macro molecules made up of saturated aliphatic carbon units in which one carbon
atom in two carries a methyl side group...". Polyethylene was first
produced in the UK Germany
PRODUCTION:-
Polyolefin fibres are
made by melt spinning. Usually polymer granules made by specialist producers rather than fiber companies are fed to an extrude which
melts the polymer which is then pumped through a spinneret. The filaments are
cooled in an air stream before being wound on a package or collected in cans as
a tow. Because the fibers are difficult to dye, colored pigments are often
added to the polymer stream before extrusion
An
alternative process is to produce a film, cut the film into strips and then
fibrillate the individual strips before winding onto a package. Recently a new
family of catalysts to make polypropylene has been developed called metallocene
catalysts. It is claimed that the polymers made from these catalysts can be
spun to finer counts and drawn to give higher tenacities than existing
polymers.
