PO film -- new trend of greenhouse coverage (III)

Comparison of types and advantages of greenhouse covering materials

Greenhouse covering material category

Soft film material

Polyvinyl chloride film (PVC)

Polyethylene film (PE)

Ethylene-vinyl acetate (PE-EVA)

Polyolefin copolymer film (PO)

Greenhouse covering material category

Soft film material

Polyvinyl chloride film (PVC)

Polyethylene film (PE)

Ethylene-vinyl acetate (PE-EVA)

Polyolefin copolymer film (PO)

Glass material

Float glass.

Tempered glass

Frosted glass

Hollow glass

F- clean

PC board

Polycarbonate board (PC)

Comparison of advantages and disadvantages of greenhouse covering materials

Soft film

1、 PE

Advantages of polyethylene film (PE): milky white translucent, 0.1~0.2mm thick, wide format, Z width up to 18m. Acid resistance

Alkali and salt resistance; It is not easy to produce toxic gas and is safe for crops; It is not easy to stick dust and has good light transmittance; Low density

(0.92g/cm3), so the coverage cost is low.

Disadvantages:

1) The infrared transmittance is very high (up to 80%), and the thermal insulation performance is poor. In the clear and windless early spring night, it may appear in the greenhouse

"Temperature inversion" phenomenon, freezing damage crops.

2) Poor strength, poor resilience, easy to tear.

2、 PVC

Advantages of polyvinyl chloride film (PVC): colorless and transparent, high strength, tensile strength up to 27.5MPa. Infra Red Transmission 

Smaller (20%), it has good thermal insulation, and is resistant to acid, alkali and salt. Spraying pesticides and fertilizers is not easy to cause deterioration.

3、 Functional composite membrane

1. The purpose of long life film can be achieved only by selecting heavy packaging resin with melt flow rate of MFR=0.3~0.8, and adding high efficiency hindered amine light stabilizer. For PVC long-life film, when ultraviolet absorbent is selected, it has a strong protective effect on the film.

2. The effective period of PE drip-free film is generally only 2-4 months, that of PVC drip-free film is 4-6 months, and that of PE-EVA is about 8 months. use

Non-ionic surfactants containing halogens have excellent anti-fogging performance of the drip-free film, and the drip retention period can reach 1~5 years, basically

Synchronize with anti-aging.

3. Multi-layer co-extruded PE/EVA/EVA composite functional film has an infrared barrier rate of about 50%, and because of its weak polarity, it is compatible with antifogging agent

It has good compatibility with heat preservation agent and long anti-fogging retention period; Weather resistance of outer PE resin and thermal insulation and anti-dripping of inner EVA resin

Sex. PO series membrane is also a PE/EVA composite membrane, with small expansion rate and high strength. After use, it can be directly burned without producing harmful gases.

4. Colored film: visible light with a wavelength of 400~700 nm plays a leading role in photosynthesis in the solar light, called photosynthesis

Effective radiation, of which the blue-violet light of 400~510 nm and the red-orange light of 610~720 nm have the smallest impact on photosynthesis.

4、 PO film

PO is the abbreviation of the English word polyolefin, which is polyolefin in Chinese. Usually refers to polymers of ethylene, propylene or higher olefins.

1. Strong attenuation of transmittance above 92% (less than 10 wire thickness).

2. With the special advanced coating technology of mist elimination and droplet, the continuous mist elimination and droplet life can be the same as that of the membrane.

3. Penetration-resistant metallocene material added.

4. Dust prevention treatment One surface of nano coating facing outward has no electrostatic treatment. In addition, the PO film itself has less impurities and static electricity, and its adsorption capacity for dust is greatly reduced. When the wind and rain wash, it is clean as before.

5. Anti-aging is characterized by durable anti-aging under the action of polyolefin and metallocene.

6. Thermal insulation performance to maintain the temperature in the greenhouse

7. High tear strength. In metallocene technology, it is stronger than other membranes to a certain extent, and its elasticity is very low after hanging

When stretched horizontally and longitudinally, only the white insulation layer can be seen without fracture. 7. Environmental degradation without poison pollution.

8. Environmental degradation without toxic pollutants

F-clean

Polyfluoroethylene film (PVF) is a hard film with a thickness of 0.06~0.1mm.

advantage:

1. High mechanical strength 2. Aging resistance is the film with a long service life Z at present, which can continuously cover 15~20Year.

2. The light transmittance is higher than 93%, and almost does not decay. 3. The surface is dust-resistant. 4. Mist elimination and anti-dripping. 5. No moss.

Disadvantages:

1. Due to the toxicity of fluorine itself, the fluorine should be sandwiched in the middle layer during the manufacturing process of polyfluoroethylene film to avoid environmental pollution during use. After use, it should be recycled by the manufacturer for special treatment.

2. At present, the width Z is only about 2.6 meters.

F-CLEAN is a kind of covering film called soft glass produced by Asahi subsidiary in Japan. At present, more and more greenhouses are used as top cover.

Glass

advantage:

1. Excellent light transmission performance and high light transmission retention rate.

2. Good thermal insulation performance.

3. Due to the low ultraviolet transmittance, the glass has good aging resistance and long service life.

4. The coefficient of thermal expansion and contraction is low, and the structural coefficient is reliable.

Disadvantages: large specific volume of glass (2500kg/m3), strict requirements for greenhouse foundation and framework, initial cost, maintenance cost and operation

High expenses and depreciation costs; Low impact resistance and fragile; Poor thermal insulation performance. At present, many large cities have discouraged construction

Glass greenhouse.

PC board

Polycarbonate plate (PC) is one of the most advanced polymers in plastic applications.

1. High mechanical strength and high impact toughness.

2. It has good dimensional stability and heat resistance, and can be used for a long time at - 60~120C. The thermal deformation temperature is greater than 310 ° C, the flammability specification is self-extinguishing resin, with small polarity, low water absorption, light stability and good weather resistance.

3. The service life is up to 10 years.

4. The thermal insulation performance is extremely high, and its heat transfer coefficient can be reduced to 1.6~2.2W/m2 ° C, which is 30%~60% less energy than the glass greenhouse.

There are mainly three types of flat plate, wave plate and multi-layer hollow plate. Plate thickness 0.7~1.2mm; Temperature covered by wave plate (corrugated plate)

The indoor light is relatively uniform, and the average light transmittance is slightly increased; The thickness of double-layer or three-layer polycarbonate hollow plate is 3~16mm.

Disadvantages:

The surface is easy to be stained with dust, the light transmittance decays quickly, and the anti-dripping function has a short service life. The initial investment price is high.