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Plastic Polyethylene sheet

In general, all over the world, the coatings used to build greenhouses are nylons, which are low polymer materials
LDPE - Polyethylene Density are made.

Types of plastic are:

- Soft plastic (thermoplastic)
- Hard plastic (Duroplast)

Ordinary polyethylene

Features of ordinary polyethylene as a greenhouse cover:

1) The rate of light passing through it is 88-90%, which is less compared to glass.
2) Transmits ultraviolet light. This radiation in the summer season causes plastic to be destroyed and used once
it becomes It also causes fragility and darkening and eventually tearing of the plastic. The UV absorber increases the life of the plastic.
3) It is a weak barrier against infrared rays. Using infrared (FR) or (IR) preservative materials in the production of polyethylene preserves about half of the radiant heat. On clear and cold nights, these types of plastics retain 25% of radiant heat, and on cloudy nights, this figure reaches 15%.
4) Polyethylene has more heat transfer than glass and therefore increases energy costs over time
It is exploited.
5) Its initial cost is lower than glass and can be used in temporary and permanent skeletons.
6) Compared to glass (40-60 years), it has a short lifespan. The lifetime of thin polyethylene sheet with the highest quality, resistant to ultraviolet light
Purple and 0.15 mm thick, about four years old.
7) The humidity inside the plastic covered greenhouse is high and the amount of oxygen and carbon dioxide is lower than that of the glass greenhouse.
The collision of hot and humid air inside the greenhouse with cold polyethylene causes the water vapor on the surface of the polyethylene to turn into water droplets (condensation). Because the surface is water repellent. Water droplets stick together and form larger droplets and drip on plants, which increases fungal diseases. As the soil moisture increases due to dripping, the amount of oxygen in the soil decreases. Drops of water on the plastic reduce the light passing through the plastic.

The formation of drops can be prevented with the following methods:
• Ventilation and heat regulation
• Spraying the inner roof of the greenhouse with cleaning materials causes faster water removal and smaller and faster droplets.
• Use of double layer plastic cover