Haze Measurement of Plastic Composite Materials: Testing Standards, Methods and Applications

Haze measurement of plastic composite materials quantifies the degree of light scattering that occurs as light passes through transparent and translucent polymer products, directly affecting visual clarity and product quality. This technical article explains the principle of haze determination, applicable international standards such as ASTM D1003 and ISO 14782, sample preparation requirements, instrumental test methods, and typical industrial applications for plastic composites, films, and sheets.

Haze measurement of plastic composite materials quantifies the degree of light scattering that occurs as light passes through transparent and translucent polymer products, directly affecting visual clarity and product quality. This technical article explains the principle of haze determination, applicable international standards such as ASTM D1003 and ISO 14782, sample preparation requirements, instrumental test methods, and typical industrial applications for plastic composites, films, and sheets.

Technical Overview

Haze is defined as the percentage of transmitted light that deviates from the incident beam direction by forward scattering when light passes through a transparent or translucent specimen. In standard instrumental measurements, only light scattered at an angle greater than 2.5 degrees from the normal direction of the incident beam is counted as haze. For plastic composite materials, haze is a critical optical quality index because it quantitatively describes the milkiness or cloudiness of the material and directly determines visual clarity in end-use applications.

Plastic composites, including multilayer coextruded films, fiber-reinforced transparent panels, laminated glazing, filled polymers, and coated plastic sheets, often exhibit elevated haze due to scattering at phase boundaries, filler particles, internal interfaces, crystalline regions, and surface texture. Haze determination allows manufacturers to control raw materials, optimize processing parameters, verify product conformity, and support research and development of optical-grade composites.

Quantitatively, haze is calculated from four luminous transmittance measurements: T1 (incident light), T2 (total light transmitted by the specimen), T3 (light scattered by the instrument itself), and T4 (light scattered by both the instrument and the specimen). Haze is expressed as the ratio of diffuse transmittance to total transmittance, typically reported as a percentage. A perfectly clear material approaches zero haze, while heavily diffusing materials may exceed 50 percent haze.

Testing Samples

Films and Flexible Laminates

Thin plastic composite films such as BOPP, PET, PE multi-layer laminates, EVA photovoltaic encapsulant films, and metallized or coated flexible substrates are among the most frequently tested sample types. Films are usually tested in flat form, and when a single layer is thinner than the minimum measurable thickness, multiple plies may be stacked, with the result reported accordingly.

Rigid Sheets and Panels

Rigid transparent and translucent composites including polycarbonate glazing, PMMA sheets, glass-fiber-reinforced polyester panels, transparent PC/PMMA blends, and laminated safety glazing can be tested provided the thickness does not exceed the instrument's geometric capability. Surface-textured, prismatic, or embossed panels can be measured, but the influence of surface structure should be noted in the report.

Molded and Formed Parts

Injection-molded plaques, thermoformed covers, headlamp lenses, and display window components can be evaluated by cutting flat sections from the part. Specimens must be representative of the material condition and free from molding defects, stress birefringence extremes, scratches, fingerprints, and dust.

Sample Preparation Requirements

• Specimen size should exceed the illuminating aperture of the instrument, typically at least 50 mm × 50 mm.
• Surfaces must be clean and free from dust, oil, fingerprints, and abrasion; avoid touching the optical surfaces during handling.
• Specimens should be conditioned at 23 °C ± 2 °C and 50 % ± 10 % relative humidity prior to testing.
• A minimum of three specimens per sample is recommended, and the arithmetic mean is reported along with individual values.
• Thickness must be measured and reported, since haze generally increases with thickness for scattering materials.

Testing Items

A typical optical characterization program for plastic composite materials includes the following measurable parameters:

• Total luminous transmittance (Tt): the ratio of total transmitted light to incident light, describing overall light-passing capability.

• Haze (diffuse transmittance ratio): the percentage of transmitted light scattered more than 2.5 degrees from the incident direction.

• Diffuse transmittance (Td): the scattered component of transmitted light expressed as a percentage of incident light.

• Parallel transmittance (Tp): the unscattered transmitted component, useful for evaluating image clarity through the material.

• Clarity (see-through quality): a supplementary parameter distinguishing fine-image degradation from wide-angle scattering, relevant for display and glazing applications.

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. Method A employs a calibrated hazemeter with an integrating sphere and a light trap adjusted to the 2.5-degree collection geometry. Method B permits the use of a spectrophotometer equipped with an integrating sphere, calculating haze from spectral scan data. The standard covers both wide-angle scattering measurement and total transmittance determination, with defined procedures for instrument calibration using reference standards traceable to a national metrology institute.

ISO 14782 and ISO 13468

ISO 14782 specifies the determination of haze for transparent plastics using a hazemeter geometry in which only regular transmittance within 2.5 degrees is excluded by a light trap. ISO 13468-1 and ISO 13468-2 cover total luminous transmittance determination using integrating-sphere instrumentation. These international standards are commonly specified for global supply chains and are technically harmonized with the ASTM approach in terms of geometry.

GB/T 2410

The Chinese national standard GB/T 2410 specifies the measurement of haze and luminous transmittance for transparent plastics and is broadly equivalent to ASTM D1003 in measurement principle and angular geometry. It is frequently required for products sold in the Chinese market and for conformity assessments referencing national technical specifications.

JIS Standards

JIS K 7361-1 addresses total luminous transmittance and JIS K 7136 addresses haze determination for plastics, providing a consistent optical geometry for materials supplied to Japanese industrial sectors.

Instrumental Procedure Summary

• Calibrate the hazemeter or integrating-sphere spectrophotometer with certified reference standards for zero, haze, and transmittance.
• Record the four readings T1, T2, T3, and T4 for each specimen at the standard illuminant and photopic observer condition (typically Illuminant D65 or CIE Standard Illuminant A with the photopic response).
• Calculate haze as (T4/T2 − T3/T1) × 100 and total transmittance as (T2/T1) × 100.
• Repeat measurement on all specimens, report mean values, standard deviation, thickness, conditioning conditions, and the standard used.
• For anisotropic or textured composites, rotate the specimen and average readings, or note directional effects where significant.

Result Interpretation

For optical-grade composites such as display films and glazing, haze values below 1–2 percent are typically expected, whereas light-diffusing products intentionally achieve haze values of 60–95 percent. Interpretation must always reference the product specification, since both excessively high and excessively low haze can constitute nonconformity depending on the design intent. Accredited third-party laboratories issue test reports that state the applied standard, specimen details, and measurement uncertainty, which supports supplier qualification and customer acceptance.

Applications

• Flexible packaging: controlling clarity and print-through appearance of multilayer food and pharmaceutical packaging films.

• Photovoltaic modules: verifying haze and transmittance of EVA or POE encapsulant films to balance light trapping and light transmission in solar cells.

• Automotive: evaluating polycarbonate and PMMA glazing, headlamp lenses, and interior trim transparent composites for regulatory and aesthetic requirements.

• Electronics and displays: qualifying cover lenses, touch-panel substrates, brightness-enhancement films, and anti-glare coatings.

• Construction and agriculture: assessing diffuse-light glazing panels and greenhouse films where controlled haze improves light distribution for plant growth.

• Lighting: characterizing LED diffuser plates and light-guide composites engineered for high haze and high transmittance simultaneously.

• Quality control and R&D: comparing resin formulations, filler dispersion quality, processing windows, and aging effects such as UV yellowing and surface crazing.

FAQ

What is the difference between haze and transmittance?

Transmittance measures how much incident light passes through the specimen in total, while haze measures what fraction of that transmitted light is scattered away from the incident direction by more than 2.5 degrees. A material can have high transmittance and high haze, meaning it passes abundant light but scatters it, producing a milky appearance without clear see-through imaging.

Which standards govern haze measurement of plastic composites?

The principal standards are ASTM D1003, ISO 14782 for haze, ISO 13468 for total luminous transmittance, GB/T 2410, and JIS K 7361/JIS K 7136. All specify consistent sphere-based geometry with a 2.5-degree scattering criterion, allowing broad comparability of results when specimen preparation and thickness are aligned.

What sample size and thickness are required?

Specimens should be larger than the instrument aperture, generally at least 50 mm × 50 mm, and flat. Very thin films may be stacked in multiple plies, and very thick or strongly curved parts must be sectioned into flat coupons. Thickness is always reported because haze increases with thickness in scattering media.

Can colored, tinted, or textured composites be tested?

Yes. Tinted materials are measured, although strong absorption reduces transmitted signal and increases measurement uncertainty. Textured or embossed surfaces can be measured, but the surface contribution to scattering should be acknowledged, and comparison against an untextured reference is recommended when evaluating bulk material quality.

What factors commonly cause high haze in plastic composites?

Frequent causes include poor dispersion of fillers or impact modifiers, large spherulites or high crystallinity, interfacial incompatibility between blend phases, delamination in multilayer structures, surface roughness or abrasion, entrapped moisture or volatiles, and degradation from overheating or UV exposure during processing and service.

How are haze results reported in a professional test report?

A compliant report identifies the applied standard, specimen description and thickness, conditioning environment, number of specimens, individual and mean haze and transmittance values, instrument type, calibration reference traceability, and measurement uncertainty. Reports from accredited third-party laboratories provide the evidentiary basis for buyer acceptance, regulatory demonstration, and internal quality control decisions.