Transmission Efficiency of plastic Films Part 1

TRANSMISSION EFFICIENCY OF PLASTIC FILMS
One interesting example of the use of a coextruded high barrier film is that of the
packaging of shredded coconut from Sri Lanka. The product was previously being
tainted in transit by other aromatic materials stored in the boat. The answer was
found in the use of 5-ply Kraft paper sacks lined with a heat sealed co extrusion
based Of EVOH.
3.3 AGRICULTURE USE:
Water Conservation:
Plastics films provide a cheap method of conserving water supplies. One widespread
use is the making of temporary reservoirs, using black plastics film of about 25µm
thickness as a lining on the soil surface of suitable excavations. After bulldozing the
soil to a suitable depth the film is laid, preferably on a sand layer in case the soil
contains stones liable to puncture the film. Enough film is laid to extend over the
sides of the reservoir so that weeds are prevented from growing at the water’s edge.
The cost of such a reservoir is very much less than that of a cement lined one, the
cost ratio is roughly in a ratio of one cement to ten film, based on a capacity of
around 65 0001(14 300 gallons). Large capacities are possible and in Canada two
lagoons have been constructed with capacities of 27 million liters (6 million gallons)
each. The question of seepage has been investigated and in the U.S.A. it has been
shown that even film of only 150µm thickness gives complete protection against
seepage for over five years.
An even more striking use of polyethylene film in water conservation has been
developed in the Sahara where the land is first excavated, then lined with film. Before
the earth is replaced, perforated plastic pipes are placed near the base of the
excavation. When the soil is replaced and plants have been placed in position, water
is pumped through the perforated pipes at low pressure. The roots of the plants are
attracted downward to the water and it has been shown that less water is required for
plant growth using this method than if conventional irrigation methods were used.
REARING OF LIVESTOCK
A sheep house has been constructed from 250µm polyethylene film sandwiched
between two layers of nylon netting, spread over tubular steel arches. The sheep
house is in Wales and is situated on an exposed hillside. The structure houses 150
sheep and cost only one eighth of the cost of a permanent sheep house.
A minor but interesting use of plastics film is in an automatic battery chicken system
where the conveyor belts for transporting food and removing eggs and hen droppings
are made from poly ethylene terephthalate (PET) film. Another aid to animal
husbandry is the use in Australia of polyethylene film coats which are fitted to newly
sheared sheep to cut down deaths from cold.
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