ASTM D1746 specifies the transparency of plastic sheeting by measuring the regular transmittance (Tr). The method primarily applies to nominally clear and colorless thin plastic sheeting and provides results that correlate with the commonly observed “see-through” characteristic. The test helps manufacturers and laboratories evaluate the “see-through” quality of plastic sheeting. Higher regular transmittance generally indicates better visual clarity because more image-forming light passes through the sheet.
This standard covers measuring transparency in plastic sheeting using regular transmittance (Tr). Although the method can generally apply to translucent and transparent materials, it is principally intended for nominally clear and colorless thin sheeting. The ASTM D1746 test method-
- Evaluates transparent plastic sheeting by measuring the regular transmittance of light through the sheet to determine its transparency.
- Evaluates nominally clear and colorless thin plastic sheeting by measuring how effectively the material transmits image-forming light and supports clear see-through viewing.
- Assesses translucent and transparent materials by determining their regular light-transmission behavior when the materials fall within the applicable scope of the method.
- Compares plastic sheets with different optical clarity by measuring their regular transmittance under controlled optical conditions.
- Supports evaluation of commercial plastic sheeting by providing transparency data that engineers can use to compare optical performance and material consistency.
- Provides regular-transmittance data for optical quality assessment because the measured value correlates with the commonly observed “see-through” characteristic of plastic sheeting.
What Properties Does ASTM D1746 Evaluate?
ASTM D1746 primarily measures regular transmittance and transparency, not a wide variety of optical properties.
- Regular Transmittance: Measures the proportion of image-forming light transmitted regularly through the plastic sheet.
- Transparency: Evaluates the sheet’s ability to transmit image-forming light and provides an objective measure of its clarity.
- See-Through Characteristics: Provides regular-transmittance data that can correlate with an observer’s ability to distinguish a relatively distant target through the sheet. ASTM notes that this correlation becomes poor for highly diffusing materials because scattered light interferes with visual assessment.
What Materials Can Be Tested According to ASTM D1746?
ASTM D1746 principally targets thin, nominally clear and colorless plastic sheeting, while its scope also allows general application to translucent or transparent materials.
- Clear Plastic Sheeting: Evaluates transparent sheets by measuring regular transmittance to determine their optical clarity.
- Colorless Plastic Films: Evaluates nominally colorless thin films to determine how effectively they transmit image-forming light.
- Transparent Plastic Sheets: Measures the regular transmission of light through transparent sheet products to support optical-performance comparisons.
- Translucent Plastic Sheeting: Can evaluate translucent materials when the material and its optical behavior fall within the applicable scope of the method.
How Does ASTM D1746 Work?
The laboratory places the plastic sheeting specimen in the optical path of a regular-transmittance measuring device. The instrument focuses the light upon the specimen and determines the amount of light that passes through at normal angles. The laboratory then reports the regular transmittance as the transparency measurement. ASTM elaborates that “the sensitivity and the measured result depend upon the incident-beam and receptor-aperture geometry. So laboratories should be careful when comparing measurements taken with different instruments, especially for specimens with low regular transmittance.
Why is ASTM D1746 Testing Important?
Clearness is directly linked to the transparency of plastic sheeting seen by users. Compared to previous subjective visual judgments, ASTM D1746 offers an objective measurement of regular transmittance. Engineers and manufacturers can use the results to compare clear plastic materials to check optical consistency, determine product requirements, and assess whether a plastic sheet offers the desired see-through clarity.
What are the Applications of ASTM D1746 Testing?
ASTM D1746 testing measures the see-through clarity (regular transmittance) of clear, thin plastic sheeting and films. It gives an absolute number of the ability of image-forming light to penetrate a material without scattering, a vital parameter for quality control of packaging, fabrication, and optical components. ASTM D1746 testing-
- Enables manufacturers to compare the transparency of plastic products between production runs, facilitating QC of transparent plastic products.
- Supports quality control of transparent plastic products by allowing manufacturers to compare regular transmittance values between production batches.
- Supports material selection by helping engineers compare plastic sheets with different transparency levels for applications requiring clear or see-through materials.
- Supports product development by providing quantitative transparency data that engineers can use when developing or modifying clear plastic sheeting.
- Helps to ensure specification compliance with a standardized regular-transmittance measurement to compare plastic sheeting with existing optical requirements.
