The Low Density Polyethylene (PEBD), a by-product of naphtha, is the most used material in Plasticulture for mulching, and covering of tunnels and greenhouses.
Transparency of the Polyethylene solar irradiation is within 80%. It means that inside the greenhouses there is 20% less light than outside.
While transparency of the plastic lets the most possible quantity of light pass through the wall of the material, it is dependable on three factors:
The Light Absorption Power - the sunrays absorbed by the material may vary in a greater or lesser percentage degree.
Reflection Power – the sunrays that do not pass through the plastic are reflected on the plastic outer surface, depending on the angle of attack that the radiation is received.
Diffusion Power – the solar irradiations are diffused when passing through the plastic and consequently more light enters into the greenhouse.
The plastic thickness has no significant effects on the polyethylene transparency. It is in the order of 1 to 2% for thicknesses between 100 and 200 micra.
The polyethylene opacity effect to the night radiations consist of not letting pass through the material, at night, the heat from the plants, the soil, and the greenhouse structures.
The PEBD activated with absorbers of ultra-violet irradiation lasts an estimate period of 18 months when exposed to the sun, for the anti-UV additives contained inside allow them resist most of all to the ultraviolet actions, during this period of exposition to the sunrays irradiation.
Of all ultraviolet irradiation that reaches the earth (ground surface), about 5% consist of B level ultraviolet (UVB) and the remaining 95% is made up of A level ultraviolet.
Although the 5% of UVB irradiation give us the idea of a small participation, it is the principal responsible for sunburns, photo-degradation, and photo-aging.
A polyethylene without any protection against the sunrays irradiation, particularly the ultraviolet (UV), would not resist more than 90 days exposed to the sunrays.
The most updated anti-UV additives, which are commonly used to protect agriculture films against photo-degradation, for greenhouses and tunnels, are currently the HALS (Hindered Amine Stabilizers), a photo-stabilizer of amine kind.
The HALS light stabilizers belong to a class of chemically reactive substances that hinder the free radicals created by degradation of carbon double link, which is the matrix of polymer, provoked and put into activity by the noxious action of ultraviolet rays.
It is worthwhile mentioning that the light stabilizers on HALS basis are inclined to suffer from acidic chemical products (insecticides, fungicides, herbicides, etc.), which contain ingredients of brimstone and/or halogenous products derivatives.
The Trifilme line is well-known for its quality. These films have Anti-UV additives, a reason why they last much longer, for while the sunrays irradiation action is stabilized, precocious aging is prevented. Trifilme is manufactured by co-extrusion (three layers), providing the material with a cutting-edge quality and resistance. This process is used to manufacture the Milky, Light-Diffusing, Thermal, Anti-Static, and Photo-Selective Telefilmes products.
The films with Anti-UV additives, manufactured by Plastisul for covering of tunnels and greenhouses are commercialized in bobbins with widths that vary from 2.20 m, 4 m, 6 m, 7.6 0m , 8 m to 10 m and lengths of 100 m and 105 m.
Trifilme Plastilux
Films in three layers, with moderns additives, that present advantages as:
- lesser reaction of additives with the agricultural defensives;
– bigger efficiency in the stabilization of the carbon chain of the films;
– film selective photo, possesss additives that filter 80% of radiation UVB more than (film of 150 micra). Radiation UVB is harmful to cultivating them and to the man, it is responsible for the photo aging, burnings. This absorption , is known popularly , as effect anti virus, therefore the absence of this specter of light, inhibited the presence of the insect vector (minador, fly, white, greenfly, trips.
– This product absorb high permanence in the film. Its power of absorption remains 24 months for more than , with low losses.
– Follows picture of absorption of the Trifilme Plastilux 150 micra. In the vertical column, the percentage of absorption reveals, and in the horizontal column the specter of the light.
Thermal
Trifilme
The
"Thermal Effect" of the thermal polyethylene
lies in its property of being relatively
opaque to the infra-red irradiations
of long-wave length emitted by the
ground, the plants, and the greenhouse
structures , with a consequent decrease
in thermal inversion risks and in
improvement in the Greenhouse Effect.
The films thickness is of major influence on the thermal effect, for it diminishes in a large degree the capacity to retain long waves / calorific energy in case of a thickness reduction. For instance: a 200 micra thermal polyethylene (0.2 mm) has a capacity to retain 30% of the calorific energy, while in a thermal film of 100 micra (0.1 mm) the thermal capacity is reduced to 13%.
The polyethylenes incorporated with the EVA Copolymer (Acetate of Ethylene Vinyl) have characteristics similar to the pure EVA Copolymer, when compared to the global transmission of light.
The blades with EVA are more flexible and more resistant to impacts, but they have a lower resistance to tearing. They are more transparent to the sunrays irradiation and are more diffuse to light than the pure PEBD.
The EVA incorporated PEBD duration correspond to the same guarantees offered by the PEDB with anti-UV additive.
Anti-Dripping
Trifilme
The air always contains an amount of water vapour. The maximum amount the air can hold depends on the surrounding temperature.
On an ordinary day, when air temperature is 20º C, with a relative humidity of 70%, we will for sure have 10.3 grams of water vapour per dry air kilogram.
The water condensation on a polyethylene plastic covering is the result of thermal difference between the interior and exterior of the greenhouse, by condensation of hot and humid air. Drops are unified into a bigger drop that will lose its sustaining force and fall down on the plants, thus creating a more favorable condition for diseases.
If the internal greenhouse temperature is maintained at 10ºC, we will see that it contains 7.6 grams of water vapour, 10.3 g – 7.6 g = 2,7 grams of dry air that is condensed on the greenhouse plastic walls.
In order to control the drop formation, as it is impossible to avoid the water vapour condensation inside the greenhouse, Plastisul has developed the Anti-Dripping Trifilme. It consists of a transparent polyethylene with additive of a chemical element responsible for the Anti-fogging effect, e.g. it does not allow that a water drop be formed on the covering plastic, thus diminishing down to zero the superficial tension between either one, and making the water condensation flow out on the pellicle without falling onto the plants.
Anti-Static
Trifilme
We know that a large amount of dust is present sustained in the air we breathe. Polyethylene has a great degree of relation with this dust, for when it is exposed to the sunrays some micro-holes are formed on the plastic surface side exposed to the sun. Then the dust micro-particles make fit and lodge inside these small spaces, originating a certain opacity to the plastic.
Plastisul produces a transparent film with Anti-UV additive for tunnels and greenhouses with an anti-static additive, to reduce the static tension and prevent gathering of dust (it is repelled).
Anti-Fungi Trifilme
The plants are real machines that work by action of the sunlight. Light is the energy of photosynthesis, for the plants absorb the sun energy and transform it into substances that directly or indirectly sustain the greater number of life forms existing on the earth.
Light alone is not the only the energy of the plants, the future of a germinated seed does not depend just on the light, but also on the quality of light it receives. This light quality determines the plant growth, the volume of the leaves, blossoming, fructification, and aging effect. It makes clear that light is a determinant factor in every moment of a vegetal life, also acting on the process of the plants morphogenesis (genes) as well.
Considering that the photosynthesis bio-chemical reactions are known, so is the bio-chemical mechanism of the photomorphogenesis, particularly the genes activated by effect of the light, which are identified as photoreactive elements.
Once these photoreactive elements were controlled, it was possible to make progress with agricultural films, to cover greenhouses, exploiting all this knowledge. These agricultural films, called photoselective of absorbing action and photosensible, are composed of filters that modify the composition of the solar spectrum on the exact moment the light is transmitted into the greenhouse.
These agricultural films of photoselective action, incorporated to the absorbing and reflecting filters, are produced to control the action of fungi that originate disease to the plants inside the greenhouses. It happens on the account of the light quality that causes modifications on the sensibility of the plants bearing diseases, particularly the ones originated by aerial fungi, like Botrytis cinerea, Sclerotinia, Alternaria, Stemphylium and others.
Light-Diffusing
Trifilme
Just as the milky films have a propriety
to diffuse the sunlight in a proportion
greater than the normal polyethylene
films, Plastisul is offering a Light-Diffusing
Trifilme for every type of plants
cultivation, for there is a need to
diffuse the light inside the protected
tillage spots, and it depends on every
culture and on when is it necessary
to control the excess of straight
irradiation.
The Light-Diffusing Trifilme is composed of an organic additive of potent action to diffuse the light inside the greenhouses and is able to increase the sunrays irradiation from 30% to 65%.
Milky
Trifilme
The sunlight has a direct action on the plants development through the photosynthesis process. There are waves lengths that are indispensable for the chlorophyll formation. With our knowledge on such phenomena, we know that they can be controlled through polyethylene films, by adjusting the luminosity strikes on the green plants.
The sunrays radiation control on the plants is very important, for this way it is possible to keep the ambience inside the greenhouses under control, by adjusting the amount of light and temperature in the protected surrounding.
Among these radiation controller additives are the ones used to manufacture milky films. Such milky films help reduce the light intensity inside the greenhouses, thus allowing a better control of temperature and reducing the plants stress when the room temperature is amplified in the hot seasons.
That is why Plastisul is offering the Milky Trifilme, a product to be used in the flowers and strawberries cultivation. These are very sensitive cultures and deserve a very special attention due to the sunstroke exposure.
Super U-V Trilona for Greenhouses Darkening
Inside the greenhouses, the production of certain types of flowers is made possible with utilization of black films (impermeable to light). These films are used to control the light, for the solar rays excess interferes eventually in the production cycle.
Attentive to this circumstance, Plastisul is placing at disposal of the greenhouse flower growers the Super-UV Trilona film. This is among the most updated products for darkening of protected environments. Of particular importance to cultivate chrysanthemum, begonias, kalanchoe, and other flowers. The white face is turned upward (subjected to sunlight) and the black face downward, thus hampering the passage of sunlight and reducing to a minimum the difficulties with correct temperature.
The mushrooms growers, principally the ones who cultivate Champignons, (a plant that needs to be cultivated in places without a ray of sunlight), can use Super-UV Trilona for their benefit. To grow other mushrooms, like the abm mushroom (Agarius blazei murill mushroom), it is not necessary to have it cultivated inside a darkened place.
