8 Questions
Which greenhouse covering material is known for requiring frequent recoating to maintain high light transmittance?
Fiberglass Reinforced Plastic (FRP)
Which sheet has the highest impact strength?
Polycarbonate Structured Sheet
Which property describes the PE film used in greenhouses?
It has excellent thermal insulation performance.
Which property is unique to polyvinyl fluoride (PVF) compared to polyvinyl chloride (PVC)?
Presence of fluorine instead of chlorine
What is the main reason polycarbonate structured sheets are favored in greenhouses?
High strength and impact resistance
What makes ultraviolet stabilized polyethylene film preferable for covering?
Longer life span and reduced heat loss
Which material has the smallest typical sheet size?
Acrylic Structural Sheet
What is the primary advantage of using polyvinyl fluoride (PVF) in greenhouses?
Longest life span and high light transmission
Study Notes
Acrylic Structural Sheet
- Provides additional thermal insulation due to its internal rib and two surfaces
- Available in various thicknesses and sizes up to 1.2m x 12m
Polycarbonate Structured Sheet
- Offers high impact strength, approximately 200 times that of glass
- Has a life span of 10-15 years, despite a higher initial cost
- Less light transmission compared to acrylic, but is more flexible and stronger
- Resistant to flammability, except when an active flame is maintained in contact
Fiberglass Reinforced Plastic (FRP)
- Available in large corrugated sheets and various thicknesses
- Requires recoating every 5-6 years to maintain high light transmittance due to surface erosion
Polyethylene Film
- LDPE film is the most common covering material due to its low cost and large sheet size
- Ultraviolet stabilized films have a 2-3 year life span, reduce heat loss, and are stronger
- Can be used in a double layer for added benefits
Greenhouse PE Film
Characteristics
- Good transparency, thermal insulation, aging resistance, and long service life
- Excellent weather resistance, tear resistance, and ease of installation and maintenance
Advantages
- Ensures sufficient sunlight and promotes plant growth
- Reduces heat loss and maintains optimal temperatures
- Long-lasting and reduces the frequency of replacement
- Withstands external forces and ensures film integrity
Colors and Thickness
- Available in White, Blue, and Transparent colors
- Thickness ranges from 0.08mm to 0.2mm
Life Span
- Can last for 3-5 years
Polyvinyl Fluoride Film (PVF)
- Structurally similar to polyvinyl chloride (PVC) with a fluorine atom instead of chlorine
- Offers high light transmission and strength
- Long-life film suitable for use over aluminum extruded or steel frames
Comparison of acrylic and polycarbonate structural sheets used in greenhouses, highlighting their thermal insulation, size, and physical properties.
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