Plastic Film Haze Testing: Principles, Standards, and Test Methods

Plastic film haze testing quantifies the light scattering that occurs when light passes through transparent and translucent polymeric films, a critical optical quality parameter for packaging, agricultural, photovoltaic, and display materials. This technical guide explains the measurement principles, applicable international standards, sample requirements, instrumentation, and practical considerations for accurate haze and luminous transmittance determination in plastic films.

Technical Overview

Haze is defined as the percentage of transmitted light that, in passing through a specimen, is scattered by more than 2.5 degrees from the direction of the incident beam. In plastic film evaluation, haze is one of the most important optical performance indicators because it directly determines how "clear" or "cloudy" a film appears to the human eye. High haze reduces the distinctness of objects viewed through the film, while low haze is essential for applications requiring excellent visual transparency.

Haze testing is typically performed together with total luminous transmittance measurement. Transmittance describes how much light passes through the film in total, whereas haze describes how much of that transmitted light has been scattered off-axis. Both parameters are measured using a hazemeter or a spectrophotometer equipped with an integrating sphere, which collects both regularly transmitted light and diffusely scattered light.

Light scattering in plastic films originates from several sources, including crystalline structures within semi-crystalline polymers such as polyethylene and polypropylene, inorganic or organic additives such as anti-blocking agents and slip additives, surface roughness introduced during extrusion or embossing, gel particles, and thickness variations. Because haze depends strongly on film thickness, microstructure, and processing conditions, standardized testing under controlled environmental conditions is essential for reliable, comparable results.

Testing Samples

Flexible Packaging Films

Common samples include blown and cast films of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (CPP, IPP, BOPP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). For food packaging, low haze is often a key requirement so consumers can clearly see the packaged product.

Agricultural Films

Greenhouse covering films, mulch films, and silage films are tested to characterize light diffusion behavior. Moderate haze can be beneficial in greenhouse films because diffuse light distributes irradiation more evenly across the crop canopy, reducing scorching and promoting uniform growth.

Optical and Display Films

Protective films for touch panels, polarizer films, anti-glare films, hard-coated films, and window films require very precise haze control. In the display industry, haze specifications are often tighter than one percent tolerance.

Photovoltaic Encapsulant Films

EVA (ethylene-vinyl acetate) and POE (polyolefin elastomer) encapsulant films used in solar modules are tested for both transmittance and haze, since optical losses directly reduce module power output.

Laminating and Barrier Films

Multilayer coextruded films, metallized films, and barrier films for electronics and medical packaging are evaluated to verify optical consistency between production lots.

Testing Items

The core optical parameters determined during plastic film haze testing include:

• Haze (percent of transmitted light scattered more than 2.5 degrees from the incident beam)
• Total luminous transmittance (ratio of total transmitted light to incident light, expressed as a percentage)
• Diffuse transmittance (the scattered component of transmitted light)
• Regular (specular) transmittance, calculated as total transmittance minus diffuse transmittance
• Clarity or see-through quality assessment, where required for high-specification optical films

Test reports typically present haze and total transmittance values for each specimen together with the arithmetic mean, standard deviation, film thickness, test standard applied, and conditioning environment.

Testing Methods

ASTM D1003

ASTM D1003, Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics, is the most widely referenced method in North America and in international trade. Method A uses a hazemeter with a broadband light source, illuminating the specimen with unidirectional light and measuring four luminous flux quantities: incident, total transmitted, scattered by the instrument, and scattered by the specimen and instrument together. Haze is then calculated as the ratio of diffuse transmittance to total transmittance. Method B uses an illuminant-A spectrophotometer, allowing measurement across the visible wavelength range.

ISO 14782

ISO 14782, Plastics — Determination of haze for transparent materials, specifies the measurement of haze for transparent plastics using an integrating sphere geometry. It is harmonized in principle with ASTM D1003 and is commonly required for European markets and by international buyers.

GB/T 2410

The Chinese national standard GB/T 2410, Transparency and haze of transparent plastics, is technically equivalent in measurement principle and is widely applied to domestic film products. Results from GB/T 2410 are generally consistent with ASTM D1003 and ISO 14782 when identical specimen geometry and conditioning are used.

JIS K 7136 and JIS K 7361

Japanese industrial standards JIS K 7136 (haze) and JIS K 7361 (total luminous transmittance) are often specified for films supplied into Japanese electronics and display supply chains.

Instrumentation and Procedure

Regardless of the standard applied, testing follows a common sequence:

• Condition specimens at 23 ± 2 °C and 50 ± 5% relative humidity for a defined period (typically 40 hours or more) in accordance with ISO 291 or ASTM D618.
• Cut at least three to five representative specimens free of wrinkles, creases, fingerprints, scratches, and visible defects; specimen size must fully cover the instrument aperture.
• Perform instrument calibration and blank measurements, including unobstructed aperture, light trap, and certified reference standards.
• Place the specimen flat against the transmission port without stretching or deforming the film.
• Record haze and transmittance readings at multiple positions or on multiple specimens and calculate mean values.
• Report results together with film thickness, since haze generally increases with thickness for the same material.

Measurement uncertainty is influenced by specimen flatness, static charge attracting dust, aperture edge leakage, ambient light, and instrument sphere condition. Textured or embossed films should be measured with the texture orientation documented, and each face should be tested to identify directional effects.

Applications

Haze test data from plastic films are used across many industries and decision points:

• Incoming material inspection and supplier qualification for film converters and packaging manufacturers.
• Quality control during film extrusion, including evaluation of resin lots, masterbatch effects, antiblocking and slip additive levels, and cooling conditions.
• Product development of optical films, anti-glare coatings, and light-diffusing films where haze is engineered to a target value.
• Greenhouse film selection and crop-lighting studies based on direct versus diffuse light transmission balance.
• Photovoltaic module material qualification and energy-yield optimization.
• Compliance demonstration against customer specifications, industry standards, and regulatory requirements, supported by test reports issued by accredited third-party laboratories.

FAQ

What is the difference between haze and transmittance?

Transmittance measures the total quantity of light passing through the film, while haze measures the fraction of that transmitted light that has been scattered more than 2.5 degrees off-axis. A film can have high transmittance but high haze (light passes through but images look milky), or low haze with lower transmittance. Both parameters are needed to fully characterize optical quality.

What haze values are typical for common plastic films?

General-purpose LDPE packaging films typically show haze in the range of 5–20%, highly clarified polypropylene films can achieve haze below 3%, and premium optical films for displays may be specified below 1–2%. Greenhouse diffusing films may deliberately target haze values of 30% or higher. Acceptance limits always depend on the application and customer specification.

How does film thickness affect haze?

For a given material and process, haze normally increases with thickness because the optical path contains more scattering centers such as crystals, gels, and additives. Therefore, haze specifications must always be referenced to a defined thickness, and comparing films of different gauges without normalization can be misleading.

Which standard should be selected for testing?

The choice depends on the target market and customer requirements: ASTM D1003 for North America, ISO 14782 for Europe and international trade, GB/T 2410 for the Chinese market, and JIS K 7136 or JIS K 7361 for Japan. Because the measurement principles are aligned, results are generally comparable when specimen preparation and conditioning are consistent.

How should specimens be prepared and how many are required?

Specimens must be flat, clean, free of wrinkles and surface contamination, and large enough to completely cover the instrument aperture. Most laboratories test three to five specimens per sample and report the average along with individual values, following the conditioning requirements of the applicable standard.

Can translucent, colored, or embossed films be tested?

Yes. Translucent and lightly colored films can be measured, although very dark or heavily filled materials may produce low-signal conditions that increase uncertainty. Embossed or matte films can be tested, but the surface orientation and which face faces the light source should be documented, since directional texture influences the result.