Phenolic resin (Oasis) plugs and granulate
Origin
Poly-Urethane is synthesised out of oil products.
Carbon dioxide (CO2) liberates during one
of the chemical reactions taking place. The material starts foaming. The
synthetic foam is mainly used for furniture. Most of the time flakes, the
waste material of this industry, is used as a substrate. To make slabs
the material is rebounded by mixing the flakes with some chemicals to a
certain density. The flakes are glued together when steam of 140 oC
is blown through the material.
Phenolic resin is also made by foaming oil products.
The size of the pores can be influenced. For substrate purposes most of
the time only one type is brought on the market. Most of the time a coarse
granulate is used.
Urea formaldehyde is a new low weight substrate
and is on the market as e.g. FytoCell. It is an hardened
Amino plastic foam.
Characteristics
Most of the time Poly-urethane contains a lot
of air and hardly no water. The irrigation frequency should be high. At
least when staring the culture. In the past some problems occurred with
slabs holding some phytotoxic substances. At present the producers are
aware of the causes of this phyto-toxicity and problems hardly ever occur.
Poly-urethane is flexible, has a low EC and a pH of 6.
Phenolic resin contains a lot of water but by the
granular structure it also contains a lot of air. After producing the material
it is acid (pH 3.5). Therefore the material should be limed before use.
When starting a culture a correction of the pH is necessary. The material
is soft and brittle. It pulverises when crushed.
Urea formaldehyde has a low bulk density and a
high air content. The water holding capacity can be a problem. Not all
types are suitable as a growing medium. The material is soft and brittle.
It pulverises when crushed.
Durability
Poly-urethane lasts very long, at leats 10 years.
It is flexible and can hardly be broken down by acids and micro-organisms.
It can be steamed without any problem. Because of its durability the waste
stage is of less importance. The product is recycled by the producers and
can be used for e.g. roof gardens. Eventually the products can be burned
quite easily.
Phenolic resin can be steamed but it is not an
easy job to do because the granulate itself holds a lot of water. Heavy
handling is not advisable because of its brittle structure. If composted
the foam breaks down to small not recognisable particles. As far as known
no dangerous substances are released.
Urea formaldehyde brakes down to CO2,
H2O and nitrogen. The material
can be composted.
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