Plastic Sample Panel Haze Testing: Standards, Methods, and Applications

Haze testing of plastic sample panels quantifies the wide-angle light scattering that causes cloudiness and loss of see-through clarity in transparent and translucent materials, making it a critical quality-control parameter for optical plastics. This technical article explains the measurement principle, applicable international standards such as ASTM D1003, ISO 14782, and GB/T 2410, sample preparation requirements, test procedures, result calculation, and typical industrial applications of haze testing performed by manufacturers and accredited third-party laboratories.

Technical Overview

Haze is defined as the percentage of transmitted light that, after passing through a plastic specimen, deviates by more than 2.5 degrees from the direction of the average incident beam due to forward (wide-angle) scattering. In transparent plastic panels, haze produces a milky, cloudy, or foggy appearance and directly reduces see-through clarity, even when the material transmits a high proportion of the incident light.

Haze must be clearly distinguished from luminous transmittance. Transmittance describes how much light passes through the specimen in total, while haze describes how much of that transmitted light has been scattered away from the straight-through direction. A panel can exhibit high transmittance and high haze at the same time, which is why both parameters are typically reported together in optical quality specifications.

Haze is measured using an integrating-sphere hazemeter or a UV-Vis spectrophotometer equipped with a haze measurement accessory. The principal test standards are ASTM D1003 (Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics), ISO 14782 (Plastics — Determination of Haze for Transparent Materials), GB/T 2410 (the Chinese national standard for light transmittance and haze of transparent plastics, technically aligned with ASTM D1003), and the corresponding Japanese standard JIS K 7136.

Testing Samples

Injection-Molded Plaques and Panels

Flat plaques molded under controlled temperature, pressure, and cooling conditions are the most common sample format for haze testing. Standard molding plaques with smooth, polished mold surfaces allow the intrinsic optical quality of the resin to be evaluated without interference from processing-induced surface defects.

Extruded and Cast Sheets

Flat sheets of PMMA (acrylic), PC (polycarbonate), PS, PETG, PVC, PP, and PE produced by extrusion, casting, or calendering can be tested directly, provided both surfaces are flat, parallel, and free of visible defects. Sheet thickness must be measured and reported, since haze increases with specimen thickness.

Coated, Textured, and Multilayer Panels

Hard-coated panels, anti-glare or anti-reflective treated surfaces, textured light-diffusing sheets, and coextruded or laminated multilayer structures can also be evaluated. Because surface texture contributes strongly to measured haze, the test report must clearly state the surface condition of the specimen.

Sample Preparation and Conditioning

Reliable haze results depend on careful specimen preparation and conditioning. The following requirements apply:

• Specimens must be flat and large enough to fully cover the instrument measuring port, typically at least 50 mm × 50 mm.
• Surfaces must be clean, free of fingerprints, dust, scratches, and stress marks that introduce artificial scattering.
• Specimens should be conditioned at 23 ± 2 °C and 50 ± 5 % relative humidity for a minimum of 40 hours in accordance with ASTM D618 before testing.
• A minimum of three specimens per material is recommended, and individual values plus the mean should be reported.

Testing Items

A haze test on a plastic sample panel typically delivers the following optical parameters:

• Total luminous transmittance (Tt) — the ratio of total transmitted light to incident light.
• Diffuse transmittance (Td) — the portion of transmitted light scattered from the incident beam direction.
• Haze (H) — the percentage of wide-angle scattered light relative to total transmitted light.
• Regular (specular) transmittance — the unscattered, straight-through component of transmission.
• Optional color coordinates (for example CIE L*a*b* values under illuminant D65) when optical appearance is evaluated together with clarity.

Testing Methods

Hazemeter Method (ASTM D1003 Method A / GB/T 2410)

The hazemeter method uses a light source, an integrating sphere, and a photopic detector. Four successive readings are taken: T1 (total incident light, no specimen), T2 (total light with specimen), T3 (instrument scattered light with light trap, no specimen), and T4 (light scattered by specimen with light trap). This method provides fast, routine measurement and is the standard approach for production quality control.

Spectrophotometer Method (ASTM D1003 Method B / ISO 14782)

A UV-Vis spectrophotometer fitted with an integrating sphere measures the specimen spectrally, from which photometric haze and transmittance are calculated using the defined illuminant and standard observer response. This approach offers better traceability and is preferred when spectrally resolved data or strict metrological documentation is required.

Calculation of Results

Haze is calculated as the ratio of diffuse transmittance to total transmittance, expressed as a percentage: Haze (%) = (Td / Tt) × 100. Using the four reading sequence of ASTM D1003, haze is equivalently computed as: Haze (%) = (T4/T2 − T3/T1) × 100. Total luminous transmittance is calculated as Tt (%) = (T2/T1) × 100 after appropriate correction for instrument scatter.

Factors Affecting Test Results

Several material and procedural factors can influence measured haze values and should be controlled or documented:

• Specimen thickness — thicker specimens scatter more light and show higher haze; thickness must always be reported with the result.
• Surface texture and finish — matte, textured, or abraded surfaces dramatically increase wide-angle scattering.
• Internal structure — crystallinity, spherulites, inorganic fillers, pigments, impact modifiers, and phase separation in polymer blends all raise haze.
• Contamination and handling — dust, fingerprints, and electrostatically attracted particles on the specimen surface cause falsely high readings.
• Instrument calibration — zero calibration and verification against certified haze and transmittance reference standards must be performed regularly.

Applications

Haze testing of plastic sample panels supports material qualification, process control, and product certification across many industries:

• Automotive — headlamp lenses, glazing, interior trim panels, instrument covers, and light guides where optical clarity is safety-relevant.
• Displays and consumer electronics — cover lenses, touch panel substrates, display windows, and transparent housings requiring low-haze, high-clarity materials.
• Lighting — LED diffusers, light guide plates, and luminaire covers where controlled (deliberately high) haze distributes light evenly.
• Packaging — transparent containers, thermoformed trays, blister packs, and films where product visibility depends on low haze.
• Construction and agriculture — polycarbonate and acrylic glazing, greenhouse films, and skylight panels balancing light transmission with diffusion.
• Medical devices — IV containers, diagnostic consumables, and transparent device housings with defined optical requirements.
• R&D and quality control — resin grade comparison, formulation development, incoming material inspection, and batch release testing at manufacturers and accredited third-party laboratories.

FAQ

What is the difference between haze and transmittance?

Transmittance measures the total amount of light passing through the specimen, while haze measures the fraction of that transmitted light that is scattered more than 2.5 degrees from the incident direction. A material can transmit most of the light yet still appear cloudy if its haze is high.

Which standards are used for plastic haze testing?

The most widely applied standards are ASTM D1003, ISO 14782, GB/T 2410, and JIS K 7136. They all use integrating-sphere optics, but differ in details such as illuminant specification, reading sequence, and report format, so the standard used must always be stated in test reports.

What sample size is required?

The specimen must be flat and completely cover the instrument aperture, which typically means a panel of at least 50 mm × 50 mm. Thickness must be uniform and reported together with the haze value.

What haze level is considered acceptable?

It depends on the application. Optical-grade PMMA and PC panels for lenses and display covers usually require haze below 1–2 %. General transparent packaging typically tolerates haze below about 5 %, while lighting diffusers are intentionally formulated with haze values of 30 % or more to spread light uniformly.

What causes high haze in plastic panels?

Common causes include crystallinity and large spherulites (for example in PP or PET), dispersed fillers and pigments, phase separation in polymer blends, impact modifiers, voids, surface roughness from mold or die finish, and processing defects such as melt fracture or moisture-induced degradation.

How does specimen thickness affect the result?

Because scattering occurs throughout the bulk of the material, haze increases with thickness. Haze values are only comparable between specimens of the same nominal thickness, which is why thickness is a mandatory part of the test report.

Can textured or frosted panels be tested?

Yes. Haze testing quantifies total wide-angle scattering regardless of whether it originates from the bulk or the surface. For textured panels, the result should be interpreted as an appearance parameter rather than a pure material property, and the surface condition should be documented.