GB/T 6595-2025 Plastics - Test method for fish eye count of polypropylene resin
WARNING - Persons using this document shall be familiar with relevant laboratory practice. This document does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
1 Scope
This document describes the test method of counting fish eyes in polypropylene resin film specimens using projectors and standard orifice plates, and specifies the technical requirements for using image acquisition and analysis system to detect fish eyes in continuous uniform motion during the preparation of polypropylene resin film, and the technical content such as the representation of test results.
This document is applicable to the preparation of film specimens and the counting of polypropylene resin fish eyes using the tape casting method (Method A: projector method) as well as the counting of polypropylene resin fish eyes during film preparation (Method B: dynamic image analysis method). Polypropylene resin films are transparent or translucent.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
fish eye
spherical particles that are not sufficiently fused with the surrounding material
Note 1: Fish eyes in polypropylene films are spheres or ellipsoids formed of transparent or translucent resins.
Note 2: Fish eyes are sometimes referred to as "crystal dots".
3.2
image acquisition
process of capturing images through image sensors, converting the image information into system-recognizable image data, and utilizing it for display and analysis
3.3
image analysis
process of performing data processing on an image to obtain a numerical or logical result
3.4
pixel
smallest unit in an image represented by a digital sequence
3.5
pixel effective size
actual size of the measured object corresponding to each pixel of the image acquisition system
Note 1: In micrometers (μm).
Note 2: The pixel effective size is determined by the physical pixel size of the sensor and the magnification of the optical system. The smaller the value, the higher the measurement accuracy.
3.6
sensor resolution
absolute number of pixels on the sensor
Note: Sensor resolution is in pixels.
3.7
optical system resolution
ability of imaging systems to resolve details of imaged objects
Note 1: In microns (μm)/pixel.
Note 2: The optical system resolution is related to all factors affecting the system, such as sensor resolution and magnification of the optical system.
3.8
gray level
value associated with the pixel representing the brightness from black to white
Note 1: Most dynamic image methods use 8-bit cameras, and their gray level ranges from 0 to 255, with 0 indicating black and 255 indicating white.
Note 2: Gray levels are also called gray scales, gray levels, and gray values.
3.9
matrix gray level
average gray level of each pixel in the image set for controlling the brightness of the film substrate at the time of image acquisition
Note: Different matrix gray levels may cause differences between test results.
3.10
detection limit value
gray level set during image analysis to distinguish fish eyes from the film substrate and used for their identification and measurement
Note 1: Different detection limits may lead to differences between test results.
Note 2: The detection limit value is also referred to as the detection threshold or sensitivity.
3.11
equivalent circle diameter
diameter of the circle with the same area as the fish eye digital image
4 Projector method (Method A)
4.1 Apparatus
4.1.1 Projector
The magnification of the projector shall not be less than 8 times, and the size of the observation board shall not be less than 200 mm × 200 mm.
4.1.2 Projection area
The projection area is a screen or other suitable flat object with a flat surface, uniform color and no pollution. The projection area is perpendicular to the horizontal plane.
4.1.3 Standard orifice plate
The standard orifice plate is made of plexiglass or other transparent materials, with a specification of 230 mm × 230 mm × 3 mm. It has 3 standard holes with hole diameters of φ0.8 mm, φ0.4 mm and φ0.2 mm respectively, with smooth edges and a hole diameter distance of about 12 mm. The hole is roughly located in the center of the plate.
Contents
1 Scope
2 Normative references
3 Terms and definitions
4 Projector method (Method A)
5 Dynamic image analysis method (Method B)
6 Precision
7 Test reports
Annex A (Normative) Preparation requirements for fish eye film specimens of polypropylene resin by casting method
Annex B (Normative) Verification method of dynamic image analysis method
