Blocker Mulch Film

1.Basic Performance Characteristics

1.1 Material Composition and Structure

1. Base Polymer Components
   1. Polyethylene(PE): 70-95% of mulch films use LDPE or LLDPE as base material
   2. EVA copolymers: 5-18% content, improves, flexibility and weatherability
   3. Recycled materials: 15-40% PCR (post-consumer recycled) content in certain non-food applicatons
   4. Bio-based PE: 2-5% in newer mulch films, derived from sugarcane ethanol
2. Additive System
   1. Carbon black(black mulch): 2.0-3.5%, provides light blocking and UV protection
   2. Colorants(colored mulch): 1.0-3.0% organic or inorganic pigments
   3. UV stabilizers: 0.5-1.5% HALS and/or benzotriazole compounds
   4. Antioxidants: 0.1-0.3% hindered phenols and phosphites
   5. Anti-drip agents: 0.3-0.8% in silver reflective films
   6. IR enhancers: 0.5-1.5% in heat-retaining mulch films
3. Multilayer Structures
   1. Single-layer mulch: 60-65% market share, thickness 15-50μm
   2. Co-extruded multilayer: 35-40% market share, typically 3-layer structure
   3. Layer composition: outer layer(stabilizers + anti-aging)/ middle layer (base + recycled) / inner layer (special functions)
   4. Layer thickness ratio: Three-layer films typically 20/60/20 or 15/70/15
   5. Special structures: Dual-color mulch (black top/ white bottom) providing light blocking on top and reflection below

1.2 Physical Properties

• Thickness Range
  • Standard Thickness:15-20μm (0.6-2.0mil)
  • Light mulch film: 15-20μm, single-season use
  • Medium mulch film: 25-35μm, standard applications
  • Heavy mulch film: 40-50μm, multi-season or harsh conditions
  • Ultra-thin biodegradable film: 8-15μm
  • Thickness tolerance: ±7% within same roll, ±10% between batches
• Optical Properties

  Film Type	Visible Light Transmission	Visible Light Reflection	Infrared Blocking	Light Diffusion
  Black		4-8%	85-95%	-
  Transparent	85-92%	8-12%	10-20%	15-25%
  White	20-30%	60-75%	30-40%	80-90%
  Silver	10-15%	65-80%	60-80%	70-85%
  Colored (red/blue/yellow)	30-60%	20-40%	20-40%	40-60%

• Mechanical Properties

  Property	LDPE Mulch	LLDPE Mulch	Biodegradable Mulch
  Tensile Strength (MD/TD, MPa)	18-25/16-22	28-40/25-35	12-20/10-18
  Elongation at Break (MD/TD, %)	250-450/300-550	500-700/600-800	200-400/250-450
  Tear Resistance (MD/TD, N/mm)	20-40/40-80	50-100/100-200	15-30/25-50
  Puncture Resistance (N)	5-12	12-25	3-9
  Initial Stretch (%)	10-15	8-12	12-18

• Thermal Properties
  • Black Mulch:
    • Daytime soil warming: 3-7°C higher than bare soil
    • Night-time heat retention: 1-3°C higher than bare soil
    • Solar absorption: 90-95%
  • Transparent Mulch:
    • Daytime soil warming: 5-9°C higher than bare soil(greenhouse effect)
    • Night-time heat retention: 1-2°C higher than bare soil
    • Early maturation effect: 7-14 days advancement
  • Colored mulch temperature effects:
    • Red: +4-6°C
    • Blue: +2-4°C
    • Silver: +1-3°C
• Aging and Durability
  • Stand service life: Black LDPE 4-6 months, LLDPE 6-9 months
  • UV degradation rate: unstabilized LDPE loses 10-15% tensile strength per month of exposure
  • Light transmission retention (transparent films): 85-90% after 3 months, 75-85% after 6 months
  • Environmental condition impact: lifespan reduced by 30-40% in 50°C high-temperature soil
  • Biodegradable film complete degradation:12-24 months in soil (depending on environmental conditions)

1.3 Functional Properties

1. Moisture Regulation Capability
   1. Soil evaporation reduction: 70-95% (compared to bare soil)
   2. Water retention gains: 180-350m³/ha water savings per season
   3. Water vapor transmission rate(WVTR):15-25g/m²·day (standard PE film)
   4. Condensation recovery:20-40 g/m²·day collected on the inner surface of transparent films
2. Temperature Regulation Function

   Film Type	Daily Average Temperature Increase	Morning Temperature Rise	Night Retention	Daily Temperature Range
   Black	+2-5°C	+1-3°C	+1-3°C	-4-8°C
   Transparent	+4-8°C	+2-5°C	+0.5-2°C	-1-3°C
   Silver/White	+1-3°C	+0.5-2°C	+0.5-1°C	-3-6°C
   Colored (Average)	+2-4°C	+1-3°C	+0.5-2°C	-2-5°C

      Measurement Depth:10cm soil layer

1. Weed suppression effectiveness: Black film > 95%, colored films 80-90%, transparent film
2. Soil-borne pathogen reduction: black film 30-50%, transparent film(solarization) 60-95%
3. Specific pest repellence:
   • Silver reflective film: reduces aphids by 60-80%, whiteflies by 50-70%
   • Blue film: reduces thrips by 40-60%
   • Yellow film: attracts certain insects(useful for monitoring)
4. Nematode control: Transparent film solarization efficiency 70-90%
5. Spectral Selectivity Functions
   1. Red film: Increases red:far-red ratio (R:FR) to 1.2-1.5 (natural light 1.1)
   2. Black film: Blocks 95-98% of photosynthetically active radiation (PAR) from reaching soil
   3. Silver film: Reflects 55-75% of incident light, increasing PAR to lower canopy
   4. Special spectral films: Selectively filter UV-B, enhance specific pigment synthesis
   5. Yield impact: Red mulch increases yield 5-15% (strawberries, tomatoes), silver mulch 3-12% (most vegetables)

2.Chemical Properties and Formulations

2.1 Chemical Composition and Molecular Structure

• Polyethylene(PE) Based Films
  • LDPE chemical Formula: -(CH₂-CH₂)n- with branched structure
  • LLDPE Chemical Formula:-(CH₂-CH₂)n- with controlled short-chain branching
  • Molecular Weight: Mw 100,000-300,000 g/mol
  • Density Range
    • LDPE： 0.915-0.925g/cm³
    • LLDPE: 0.918-0.928g/cm³
    • HDPE: 0.940-0.965 g/cm³
  • Crystallinity: LDEP 40-50%, LLDPE 30-45%, HDPE 60-80%
  • Branch Frequency: LDPE 15-30 branches/1000C, LLDPE 10-25 branches/1000c
• EVA Copolymer Component:
  • Chemical Formula: -(CH₂-CH₂)x-[CH₂-CH(OCOCH₃)]y-
  • Vinyl Acetate Content: 5-18% in agricultural films
  • Functional Properties: increases flexibility, improves low-temperature performance
  • Crystallinity Range: 20-35% (decreases with increasing VA content)
  • Melting Point Range: 85-105°C (vs. 105-115°C for pure LDPE)
  • Polarity: Moderately polar due to acetate groups
• Biodegradable polymer systems:
  • PBAT chemical formula: polybutylene adipate terephthalate, complex polyester structure
  • PLA Chemical Formula: [CH₃CH(CO₂H)]n
  • Starch-based blends: modified starch(C₆H₁₀O₅)n combined with polyesters
  • Molecular Weight Range: 50,000-200,000 g/mol
  • Crystallinity: PLA 10-40%, PBAT 20-35%, PBS 35-45%
  • Glass Transition Temperature: PLA 55-60°C, PBAT -30°C, PBS -35°C

2.2 Additive Chemical Systems

2.2a UV stabilizer Chemistry

• HALS(Hindered Amine Light Stabilizers)
  • Chemical Structure: Based on 2,2,6,6-tetramethylpiperidine
  • Mode of Action: Nitroxyl radical formation trapping free radicals
  • Effective Range: 315-400nm (UV-A)
  • Migration Rate: 0.2-0.8% loss/month from surface
• Benzotriazole UV Absorbers
  • Chemical Structure: 2-(2-hydroxyphenyl)-benzotriazole derivatives
  • Mode of Action: UV absorption and energy dissipation
  • Effective Range: 290-350nm (UV-B and partial UV-A)
  • Synergistic Effect: 1.5-2.5× effectiveness when combined with HALS

2.2b Antioxidant Chemistry

• Primary Antioxidants
  • Chemical Types: Hindered phenols (BHT, Irganox, series)
  • Mechanism: Hydrogen donation to peroxy radicals
  • Structure-Activity: 2,6-di-tert-butyl phenolic structure most effective
  • Dosage Range: 0.05-0.2% in agricultural films
• Secondary Antioxidants
  • Chemical types: Phosphite esters, thioethers
  • Mechanism: Hydroperoxide decomposition
  • Synergistic Ratio: 1:2 to 1:4 (primary:secondary) for optimal protection
  • Thermal Stability: Effective up to 280-300°C processing temperatures

2.2c Pigment and Colorant Chemistry

• • • Carbon Black
      • Chemical Structure: Amorphous carbon, particle size 20-80nm
      • Surface Chemistry: 2-5% oxygen-containing functional groups
      • Loading Range: 2.0-3.5% in black mulch films
      • UV protection mechanism: Free radical scavenging, UV absorption
    • Color Pigments
      • Red: Iron oxide (Fe₂O₃) or organic azo compounds
      • Blue: Copper phthalocyanine derivatives
      • Yellow: Chrome yellow (PbCrO₄), organic diarylide yellows
      • Particle Size Range: 0.01-0.5 μm for optimal dispersion
      • Migration Resistance:

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        2.3 Surface Chemistry and Modifications

        2.3a Corona Treatment Effects

        • Chemical Changes: Oxidation of surface polymers, introducing -OH, -COOH, -C=O groups
        • Surface Energy Increase: From 29-31mN/m to 38-42mN/m
        • Treatment Half-life: 2-4 weeks under standard storage conditions
        • Depth of Modification: 5-10nm from surface
        • Wettability: Contact angle reduction from 90-100° to 50-65°

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        2.3b Anti-fog Additives

        • Chemical Types: Non-ionic surfactants, glycerol esters, ethoxylated alcohols
        • Mechanism: Migration to surface, reducing water surface tension
        • Hydrophilic-Lipophilic Balance (HLB): 6-10 optimal for PE films
        • Migration Rate: 0.1-0.3 mg/m²·day at 25°C
        • Effectiveness Duration: 1-4 months depending on temperature and humidity

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        2.3c Chemical Interaction with Soil

        • Leaching Compounds:
          • Low molecular weight PE oligomers: 0.01-0.05% of film mass
          • Additive Migration: Antioxidants 0.1-0.3%, plasticizers 0.2-0.5% over 3months
          • Metal Content: Heavy metals
          • Chemical Resistance:
            • Fertilizer interaction:pH 4-9 resistant, concentrated NH₄NO₃ causes stress cracking
            • Pesticide Compatibility: Resistant to most water-based formulations
            • Oxidizing Agent Sensitivity: Accelerated degradation with peroxides permanganates
          • Surface adsorption Properties:
            • Soil particle Adhesion: 10-50g/m² depending on soil type
            • Microbial Biofilm Formation: begins within 7-14 days of soil contact
            • Hydrophobic Pollutant sorption:10-50× higher than soil for certain pesticides