Greenhouse plastic film performance testing evaluates the mechanical, optical, thermal, and long-term durability properties of agricultural covering films to confirm they can withstand wind, snow, hail, ultraviolet exposure, and chemical loading throughout their designed service life. This guide summarizes the main test items, applicable standards such as ISO 527, ASTM D882, EN 13206, and GB/T 4455, sampling and conditioning requirements, testing methods, and typical applications in protected horticulture and film manufacturing quality control.
Technical Overview
Greenhouse plastic film, also referred to as agricultural covering film, is primarily manufactured from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate (EVA), polyvinyl chloride (PVC), and multilayer co-extruded polyolefin (PO) structures. As the main barrier between crops and the external environment, the film governs light availability, heat retention, humidity management, and the structural reliability of protected cultivation systems. Performance testing verifies that the material meets minimum requirements for mechanical strength, optical transmission, infrared (IR) retention, ultraviolet (UV) stability, and functional additives such as anti-drip and anti-dust agents before installation.
In service, greenhouse films experience combined stresses: tensile clamping forces at installation points, repeated wind flutter, snow and hail loads, abrasion against structural members, exposure to sulfur and chlorine-containing agrochemicals, and continuous solar irradiation. A comprehensive testing program therefore combines mechanical characterization, optical measurement, accelerated weathering, and functional performance evaluation. Commonly applied frameworks include EN 13206 for thermoplastic covering films in agriculture and horticulture, GB/T 4455 for agricultural polyethylene blown film, and ISO and ASTM methods for individual properties. Testing is typically carried out by accredited third-party laboratories, certification bodies, or in-house quality control departments.
Testing Samples
Samples are normally taken from full-width production rolls at defined positions across the web (for example, near both edges and at the center) to account for thickness and additive distribution variations inherent to the blown-film process. Unless otherwise specified, specimens are conditioned at 23 ± 2 °C and 50 ± 5% relative humidity for a minimum of 40 hours in accordance with ISO 291 or ASTM D618 before mechanical and optical testing. Test orientation (machine direction versus transverse direction) must be recorded, because blown films exhibit significant anisotropy.
Polyethylene (PE) Blown Greenhouse Films
Single-layer and three-layer LDPE/LLDPE blown films with typical thicknesses ranging from 80 µm to 200 µm. These are the most widely tested products and commonly contain UV stabilizers (hindered amine light stabilizers), IR-blocking minerals, and anti-fog surfactants. Testing focuses on tensile properties, dart impact resistance, and light transmittance.
EVA and Multilayer Co-extruded Films
EVA films, typically with vinyl acetate contents of 5% to 14%, provide superior IR absorption and flexibility at low temperatures. Multilayer structures place functional additives in specific layers, so testing includes interlayer adhesion, overall mechanical performance, and verification that additive migration does not degrade long-term stability.
PVC and Polyolefin (PO) Films
PVC films offer high transparency and good IR retention but require evaluation of plasticizer loss and low-temperature flexibility. PO films, often produced as multi-layer structures with nylon or other barrier layers, are tested for high tensile strength, outstanding anti-aging performance, and long rated service lives of five seasons or more.
Testing Items
Testing items are grouped into five categories covering mechanical, optical, durability, thermal, and functional performance:
Mechanical Properties
- Tensile strength and elongation at break (machine and transverse directions)
- Elmendorf tear resistance
- Free-falling dart impact resistance
- Puncture and propagation tear resistance
- Seam and joint strength for heat-welded sections
- Low-temperature impact resistance and cold flexibility
- Thickness and thickness uniformity across the film web
Optical Properties
- Total luminous transmittance in the visible range (400–700 nm)
- Haze and light diffusion characteristics
- Ultraviolet transmittance (280–380 nm)
- Infrared transmittance in the 7–14 µm thermal radiation band
- Photosynthetically active radiation (PAR) transmission
Aging and Weathering Resistance
- Accelerated weathering using xenon-arc and fluorescent UV lamps
- Retained tensile strength and elongation after irradiation exposure
- Carbonyl index measurement by infrared spectroscopy to quantify photo-oxidation
- Heat aging resistance and thermal stability
- Chemical resistance to sulfur and chlorine-containing agrochemicals
Thermal and Barrier Properties
- Heat retention efficiency derived from IR transmittance data
- Water vapor transmission rate
- Thermal shrinkage at elevated greenhouse operating temperatures
Functional and Surface Properties
- Anti-drip (anti-condensation) persistence and drip density
- Anti-dust performance and surface cleanliness retention
- Coefficient of friction relevant to installation and wind-induced movement
- Blocking resistance between film layers in storage
Testing Methods
Tensile Strength and Elongation
Tensile testing is performed on strip specimens, typically 10 mm to 15 mm wide, using a universal testing machine in accordance with ASTM D882 or ISO 527-3. The test determines tensile strength at yield and at break, elongation at break, and secant modulus. Because films fail most frequently along tear lines initiated during installation or storm events, retention of elongation after weathering is one of the most critical acceptance indicators.
Tear and Impact Resistance
Tear resistance is measured with the Elmendorf pendulum method per ASTM D1922 or ISO 6383-2, which quantifies the energy required to propagate a tear. Impact resistance is assessed with the free-falling dart method per ASTM D1709 or ISO 7765-1, where a dart is dropped onto a clamped film specimen and the mass causing 50% failure is determined statistically. Puncture resistance against pointed loads such as tie wires and structural fasteners is evaluated using probe methods such as ASTM D5748.
Light Transmittance and Haze
Luminous transmittance and haze are measured with an integrating sphere spectrophotometer per ASTM D1003 or ISO 13468-2. Wavelength-specific measurements with a UV-visible spectrophotometer determine UV-blocking efficiency, which influences pest control and film longevity, while Fourier-transform infrared (FTIR) spectroscopy quantifies transmittance in the 7–14 µm band, the region responsible for radiative heat loss from the greenhouse interior at night. Diffuse light films are additionally characterized by their diffusion-to-direct transmission ratio.
Accelerated Weathering
Long-term durability is evaluated using xenon-arc exposure per ISO 4892-2 or ASTM G155, or fluorescent UV condensation exposure per ISO 4892-3 or ASTM G154. Irradiation cycles simulate sunlight, moisture, and temperature cycling, with total radiant exposure selected to correspond to rated service lives from one season up to five seasons or more. After exposure, specimens are re-tested for tensile strength and elongation retention, and photo-oxidative degradation is tracked through the carbonyl index measured by FTIR. EN 13206 and GB/T 4455 define minimum retention values for classifying films by expected lifetime.
Anti-Drip Performance
Anti-condensation behavior is assessed using climate chamber or inclined-plane procedures in which the film forms the cover of a heated, water-saturated enclosure. Evaluators record the time until first drip formation, the number of drips per unit area, and the persistence of the anti-fog effect under repeated condensation cycles, following the condensation behavior test described in EN 13206 and related internal laboratory protocols. Long-duration tests of several weeks distinguish films with season-long anti-drip performance from those with short-lived surfactant effects.
Water Vapor Transmission and Shrinkage
Applications
- Manufacturing quality control for outgoing film batches and incoming raw material verification
- Development and formulation comparison of UV stabilizer, IR blocker, and anti-fog additive packages
- Supplier qualification and incoming inspection by greenhouse operators and distributors
- Compliance demonstration against EN 13206, GB/T 4455, and customer technical specifications
- Service life classification and warranty substantiation for one-season through five-season films
- Failure analysis of premature embrittlement, delamination, tearing, or loss of anti-drip function in field-returned samples
- Support for product certification and export documentation through accredited third-party laboratories
FAQ
Which standards are most relevant for greenhouse plastic film testing?
The primary product standards are EN 13206, covering thermoplastic films for agriculture and horticulture, and GB/T 4455, covering agricultural polyethylene blown film in China. Individual properties are verified using ISO and ASTM methods such as ASTM D882 or ISO 527-3 for tensile properties, ASTM D1003 or ISO 13468-2 for transmittance and haze, ASTM D1922 or ISO 6383-2 for tear resistance, and ISO 4892 or ASTM G155/G154 for weathering.
How long does an accelerated weathering test take?
Exposure duration depends on the rated service life. Testing for a one-season film may require several hundred hours of xenon-arc exposure, while verification of a five-season film can require several thousand hours, corresponding to a defined total radiant energy dose. Laboratories select the dose based on the climatic zone and the classification system in EN 13206 or customer specifications.
What pass criteria are typically applied after weathering?
Common acceptance criteria require that the film retain at least 50% of its initial tensile strength and elongation at break after the specified exposure dose, with no visible cracking, severe chalking, or delamination. Retained elongation is usually the controlling parameter because it reflects the film's remaining ability to survive wind flutter without tearing.
How is anti-drip performance verified in practice?
A specimen is installed as the cover of a heated chamber held at high humidity so that continuous condensation forms on its underside. The laboratory records drip onset time, drip count per square meter, and anti-fog persistence over repeated condensation and drying cycles, distinguishing films designed for a full growing season from those with only temporary surfactant activity.
What sample quantities should be submitted for testing?
A typical program requires one or more full-width film rolls or sections at least one to two meters long, sampled from different production lots when batch consistency is being evaluated. Sufficient material must be provided for both initial testing and post-weathering retesting, since accelerated aging consumes additional specimens cut from the same sample.
Why do machine-direction and transverse-direction results differ?
The blown-film extrusion process orients polymer chains preferentially in the machine direction, producing higher tensile strength and lower elongation in that direction compared with the transverse direction. Standards therefore require reporting both directions, and greenhouse designs must account for the weaker axis when orienting film relative to structural supports and prevailing winds.
