Plastic Haze Measurement Testing: Principles, Standards, Methods, and Applications

Plastic haze measurement testing quantifies the light-scattering behavior of transparent and translucent plastic materials, delivering essential data for quality control, product development, and compliance with international standards. This technical article explains the optical principles of haze determination, the governing test methods such as ASTM D1003, ISO 14782, and GB/T 2410, specimen requirements, instrumentation, and typical applications across the packaging, automotive, optical, and construction industries.

Technical Overview

Haze is defined as the percentage of transmitted light that, when passing through a specimen, is scattered by more than 2.5 degrees from the direction of the incident beam. In practical terms, haze quantifies the milky or cloudy appearance of a transparent plastic material: the higher the haze value, the greater the loss of image contrast when viewing objects through the material. Haze is distinct from total luminous transmittance, which measures how much light passes through the specimen regardless of scattering direction.

Mathematically, haze is calculated as the ratio of diffuse transmittance to total transmittance multiplied by 100 percent. A perfectly transparent, scattering-free material would have a haze value approaching zero, while a light-diffusing material such as an LED diffuser plate may intentionally exhibit haze values above 85 percent. The dominant international standards for this measurement include ASTM D1003, ISO 14782, GB/T 2410, and JIS K 7361, all of which rely on an integrating-sphere geometry to separate regularly transmitted light from diffusely scattered light.

Testing is typically performed using a dedicated hazemeter or a spectrophotometer equipped with an integrating sphere. Standard illuminants used for measurement include Illuminant C (as traditionally specified in ASTM D1003) and D65 (as specified in ISO 14782), and results are reported using photopic or standard observer response functions. Accurate haze determination requires clean, flat, scratch-free specimens, a calibrated instrument, and careful control of ambient conditions.

Testing Samples

Transparent Plastic Films

Flexible films are the most frequently tested specimen category, including polyethylene (PE), polypropylene (PP), cast polypropylene (CPP), biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET), and biodegradable polymer films. Film specimens should be at least 50 mm by 50 mm, free of wrinkles, creases, and surface contamination, and should fully cover the instrument transmission port without stretching.

Rigid Transparent Sheets and Boards

Rigid materials such as polycarbonate (PC), polymethyl methacrylate (PMMA/acrylic), polystyrene (PS), rigid PVC, and glass-reinforced composite sheets are tested for architectural, lighting, and glazing applications. Because haze increases with thickness, the nominal thickness of each specimen must be measured and reported together with the test result.

Molded and Thermoformed Parts

Injection-molded lenses, blister packs, display windows, headlamp covers, and thermoformed packaging components can be tested directly, provided the measured area is flat and sufficiently large to cover the optical port. Curved or textured surfaces should be avoided, as geometry-induced scattering will bias the result.

Coated, Laminated, and Multi-Layer Materials

Hard-coated films, anti-glare coatings, adhesive laminates, and multilayer coextruded structures can also be evaluated. Each interface in a multilayer structure contributes additional scattering, so the construction of the test specimen must be documented to make results comparable.

Testing Items

A haze measurement experiment typically reports the following optical parameters:

• Haze (percent): the ratio of wide-angle scattered light (beyond 2.5 degrees) to total transmitted light.
• Total luminous transmittance (percent): the proportion of incident light transmitted through the specimen in all directions.
• Diffuse transmittance (percent): the portion of transmitted light that has been scattered by the specimen.
• Regular (specular) transmittance (percent): the calculated portion of light transmitted without deviation, obtained as total transmittance minus diffuse transmittance.
• Specimen thickness and conditioning state, which are mandatory reporting elements under the relevant standards.

Testing Methods

ASTM D1003 Test Method

ASTM D1003, Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics, is the most widely referenced procedure. The instrument records four fundamental readings: T1, the incident light flux; T2, the total light transmitted by the specimen; T3, the light scattered by the instrument itself; and T4, the light scattered by both the instrument and the specimen. Total transmittance is calculated as T2/T1 multiplied by 100 percent, and haze is calculated as (T4/T2 minus T3/T1) multiplied by 100 percent. The standard supports both a traditional hazemeter (Procedure A) and a spectrophotometer-based method (Procedure B).

ISO 14782 Test Method

ISO 14782, Plastics — Determination of Haze for Transparent Materials, defines haze as the fraction of transmitted light scattered more than 2.5 degrees from the incident beam axis. The method specifies D65 illumination with a 10-degree standard observer and includes the unscattered baseline correction procedure, making it the preferred method for international supply chains and CE-related declarations. ISO 13468 is the companion standard for total luminous transmittance when both parameters are required.

GB/T 2410 Test Method

GB/T 2410, the Chinese national standard for the determination of light transmittance and haze of transparent plastics, is technically aligned with ASTM D1003 in geometry and calculation. It is commonly specified for products sold in the Chinese market, including packaging films, sheets, and building materials, and results from GB/T 2410 and ASTM D1003 are generally comparable when specimen preparation is consistent.

Specimen Preparation and Conditioning

Specimens should be cut to at least 50 mm by 50 mm, cleaned with lint-free wipes and, if needed, a suitable solvent that does not attack the polymer, and visually inspected for scratches or inclusions. Standard conditioning of 40 hours at 23 ± 2 degrees Celsius and 50 ± 5 percent relative humidity, following ASTM D618 or ISO 291, is recommended before measurement. A minimum of three to five specimens per material should be tested, and the arithmetic average reported along with the thickness of each specimen.

Instrument Calibration and Measurement Procedure

Before testing, the hazemeter must be zeroed and calibrated using certified reference standards for transmittance and haze. The measurement sequence involves recording the baseline flux readings without a specimen, then measuring each specimen in turn, ensuring that the same surface orientation is maintained and that specimens are not bent across the port. Any surface film, protective liner, or processing residue must be removed before the specimen is mounted, and static-charged films should be discharged to avoid dust attraction.

Applications

Haze measurement data directly supports material selection, process optimization, and incoming inspection in many industries:

• Flexible and rigid food packaging: low-haze BOPP, PET, and PE films allow clear product visibility on retail shelves, and haze limits are frequently written into material specifications.
• Optical and display devices: cover lenses, touch panel substrates, and window elements require tightly controlled haze to preserve image contrast and readability.
• Automotive: headlamp lenses, instrument covers, and glazing components are qualified against haze and transmittance targets for both appearance and photometric performance.
• LED lighting: diffuser plates and films are engineered for deliberately high haze combined with high transmittance to achieve uniform illumination without visible hot spots.
• Agriculture and construction: greenhouse films and skylight glazing balance haze and transmittance to manage light diffusion, plant growth, and interior daylighting.
• Medical packaging: transparent blister films and sterile barriers must maintain low haze so that contents can be inspected without opening the package.

FAQ

What is the difference between haze, transmittance, and clarity?

Haze measures wide-angle scattering beyond 2.5 degrees and reduces image contrast; transmittance measures how much light passes through in total; and clarity measures narrow-angle scattering (typically evaluated separately, for example by ASTM D1746) that affects the sharpness of fine detail seen through the material. A film can have high transmittance yet high haze, meaning it lets light through but blurs the view.

Which haze test standard should be selected?

The choice depends on the market and specification: ASTM D1003 dominates in North American supply chains, ISO 14782 is preferred for international trade and European requirements, GB/T 2410 is used for the Chinese market, and JIS K 7361 is used in Japan. Because geometries are similar, correlation between methods is generally good when specimens are identical.

How does specimen thickness affect haze results?

Haze generally increases with thickness because scattering centers such as crystallites, voids, and additives scale with the light path length. For this reason, haze values are only comparable between specimens of the same nominal thickness, and thickness must always be reported with the result.

What factors in material processing influence haze?

Semi-crystalline polymers develop haze from spherulitic crystallinity, pigments, anti-block and slip additives, filler dispersion, surface roughness from rollers or molds, gel particles, and orientation during film blowing or stretching. Process optimization targets these variables to reach the specified haze window.

What haze level is considered acceptable?

Acceptance limits are application specific: premium packaging films often require haze below 2 to 5 percent, general transparent sheets may be specified between 0.5 and 2 percent, while LED diffusers are deliberately engineered above 85 percent haze. The specification should always state the test standard, illuminant, and specimen thickness alongside the haze limit.

Can haze testing be performed by an external laboratory?

Yes. Accredited third-party laboratories routinely conduct haze and transmittance testing to ASTM D1003, ISO 14782, and GB/T 2410, providing calibrated instrumentation, controlled conditioning, and test reports suitable for supplier qualification, regulatory submission, and customer certification.