Weather Resistance and UV Resistance

Construction waste chutes are used outdoors long-term under sun and rain, so weather resistance and UV resistance directly affect service life. Longkang HDPE chutes are added with UV stabilizers and have excellent weather resistance. This article details the weather resistance parameters.

1. Principle of UV Aging

Ultraviolet (UV) rays carry high energy; long-term exposure breaks the polymer molecular chains:

1. Molecular chain scission makes the material brittle
2. Surface chalkiness appears
3. Tensile strength and elongation decrease
4. Darkening or fading of color
5. Eventually cracking and failure

The molecular chains of HDPE undergo photo-oxidative degradation under UV exposure.

1. Longkang UV-Resistant Formulation
2. Carbon Black Addition

• Addition: 2%–3% (by weight)
• Carbon black particle size: 20–40 nm
• Functions of carbon black:
• Absorbs UV rays
• Blocks UV penetration
• Traps free radicals
• It is the most effective UV stabilizer

2. Antioxidant

• Addition: 0.1%–0.3%
• Type: hindered phenolic antioxidant
• Function: inhibits thermal-oxidative aging
• Works synergistically with carbon black

3. UV Absorber (Optional)

• Addition: 0.2%–0.5%
• Type: benzotriazole
• Function: absorbs UV energy
• Further improves weather resistance

III. Weather Resistance Parameters

1. Outdoor Exposure Test

• Test conditions: outdoor exposure in Hainan (region with the strongest UV)
• Property retention after 5 years:
• Tensile strength: ≥80%
• Elongation at break: ≥50%
• Impact strength: ≥70%
• Appearance: no obvious chalkiness, no cracks

2. Artificial Accelerated Aging

• Test standard: GB/T 16422.3 (fluorescent UV lamp)
• After 1000 h of aging:
• Tensile strength change ≤±20%
• Elongation change ≤±30%
• No chalkiness, no cracks

3. Service Life

• Normal outdoor use: ≥5 years
• Indoor use: ≥10 years
• With regular maintenance (covering): up to 8–10 years

1. Effect of Temperature Cycling
2. Effect of High Temperature

• In summer, the pipe surface can reach 60–70 ℃
• HDPE heat deflection temperature is 70 ℃
• The material softens slightly at high temperature
• But the wall thickness design has margin, so it does not affect use

2. Effect of Low Temperature

• In winter, pipe temperature ranges from -20 to -30 ℃
• HDPE low-temperature embrittlement temperature is -40 ℃
• Remains tough in winter
• Unaffected by freezing

3. Temperature Cycling

• Day-night temperature difference of 20–30 ℃
• Thermal expansion and contraction: linear expansion coefficient 1.5×10⁻⁴/℃
• Temperature-change expansion for a 50 m pipe: 50×1.5e-4×30=0.225 m
• Socket-and-spigot joints can absorb expansion
• Expansion joints provided (for high-rise projects)

1. Effect of Rain and Humidity
2. Rain Erosion

• HDPE water absorption <0.01%
• Rainwater does not penetrate the material
• Does not affect strength
• Surface rain erosion helps keep it clean

2. Humid Environment

• HDPE does not mold or rot
• Performance unaffected in humid southern regions
• Does not rust unlike metal

3. Effect of Freezing

• Water accumulated inside the pipe expands when frozen
• But HDPE is tough and can withstand ice expansion
• It is recommended to drain water after shutdown

1. Weather Resistance Comparison

Carbon-black-loaded HDPE is the best plastic choice for outdoor weather resistance.

VII. Recommendations for Extending Outdoor Service Life

1. Avoid direct sun: wrap the pipe with a sunshade layer during summer heat
2. Winter freeze protection: drain water after shutdown
3. Regular inspection: check the surface annually for cracks
4. Avoid chemicals: do not flush the pipe with strong acids or alkalis
5. Cleaning: natural rain cleaning is sufficient

VIII. Longkang Weather Resistance Guarantee

1. Uses a weather-resistant formulation containing carbon black
2. The product is black (carbon black), with the best weather resistance
3. 5-year outdoor use warranty
4. Enhanced weather-resistant formulations can be provided based on project location (southern high-UV regions)
5. Wear-prone sections are supplied separately for easy replacement