1 Scope
This document specifies the test method for plastic scratch performance under given conditions, including scratch formation and evaluation of results, as well as the optimal size of the specimen and the optimal geometry of the scraper.
This document is applicable to characterizing the scratch behavior of specific types of specimens under given scratch conditions.
This document applies to thermoplastic moulding materials and thermosetting moulding materials with uncoated and unpainted surfaces.
2 Normative References
The contents in the following documents, through normative references, constitute indispensable provisions of this document. Where, for dated references, only the version corresponding to that date applies to this document; For undated references, the latest version (including all amendments) is applicable to this document.
GB/T 2918 Standard Environment for Conditioning and Testing of Plastic Specimens (GB/T 2918-2018, ISO 29112008, MOD)
GB/T 17037.1 Plastics - Preparation of Injection Molding Specimens for Thermoplastic Materials - Part 1: General Principles and Preparation of Multipurpose Specimens and Long Strip Specimens (GB/T 17037.1-2009, 1SO 294-1; 201, MOD)
GB/T 17037.5 Plastics - Preparation of Injection Molding Specimens for Thermoplastic Materials - Part 5: Preparation of Standard Specimens for Anisotropy Evaluation (GB/T 17037.5-2020. ISO 294-5; 2017, Moy
GB/T37426 Plastic Specimens (GB/T 374262919.1so 20753.2018, MOD)
ISO 472; 2013 Plastics Terms and Definitions
ISO 10724-1 Plastics-Injection moulding of test specimens of thermosetting powder mouldingcompounds (PMCs)Part 1: General principles and moulding of multipurpose test specimens
3 Terms and definitions
The terms and definitions defined in ISO 472.2013 and the following apply to this document.
three point one
Scratch
Given the shape of the scraper, under the conditions of test load and test speed, the scraper moves on the surface of the sample, causing damage to the surface of the sample. Note: "surface" refers to macro scale surface rather than micro scale surface-
three point two
Test load
During the test, the force exerted by the scraper on the surface of the sample vertically. Note: The unit is Newton (N).
three point three
Test speedv
The relative displacement speed of the scraping head and the sample during the test. Note: The unit is millimeter per second (mm/s)
4 Principle
The scraping head applies load perpendicular to the surface of the sample and moves along the length direction of the sample at a constant speed, which forms a scratch. See Fig. 1 for the schematic diagram. During the test, the tangential scratch force, scraper displacement and scratch distance can be continuously measured and recorded. The tangential scratch force scratch distance curve and the scraper displacement scratch distance curve can describe the scratch behavior of the sample. The scratch test is divided into constant load (basic method) and linear growth load (optional method). In constant load test, under a series of test conditions (different test loads and different test speeds), scratch failure forms and scratch phase diagrams can be obtained; During the linear growth load test, the critical normal load can be obtained at the set test speed. A change in the slope of the tangential scratch force scratch distance curve and/or a spike in the curve may indicate a change in the form of scratch failure (e.g., from smooth grooving to repeated failure or material peeling).
5 Equipment
5.1 Scratch measuring equipment
5.1.1 General requirements
The scratch measuring equipment shall be composed of a test platform, a sample holder, a scraper and its fixing device, and a load application device. See Appendix C for the schematic diagram, and shall meet the requirements of 5.1.2~5.1.8.
5.1.2 Test platform
Under the maximum test load, the deformation of the test platform shall not exceed 3 xm
5.1.3 Scraper
The Rockwell hardness of the scraper shall not be less than 64 HRC, and the surface roughness shall be less than 0.20 um. After the test, the scraping head shall not be deformed or damaged.
The scraping head shall be hemispherical with a radius R of 0.5 mm ± 0.025 mm. Note: the scraping head made of hard steel or acid tungsten after polishing can meet the requirements
5.1.4 Test load
The error of the test load shall be within ± 1%. When it is vertically applied to the surface of the specimen, the error of its angle shall be within ± 5 °. 5.1.5 Test speed
The error of test speed shall be within ± 1%, excluding the distance of 10mm at both ends of the scratch. The test speed shall reach the set value within 10 mm of the scratch start end, start to drop within 10 mm of the scratch end, and return to zero at the scratch end.
5.1.6 Specimen holder
The specimen support shall be flat and smooth, and the specimen fixing area shall be free of holes. The clamping device on the sample holder shall be fixed with the scratch measuring equipment.
The clamping device shall not cause fracture of the specimen, and shall not cause slip of the specimen during the test.
5.1.7 Force sensor
The force sensor shall be able to display the real-time force in the horizontal direction of the scraper and the sample. At the set test speed, it shall not have any inertia lag, and the indication error of the force value shall be within ± 1%.
5.2 Specimen size measuring equipment
The width b of the sample shall be measured with a micrometer or other suitable measuring tools, and the error shall be within ± 0.01 mm. The thickness h of the specimen shall be measured with a flat ended round angle micrometer with an error of ± 0 Within 01 mm.
5.3 Video recording and inspection equipment (optional)
5.3.1 Video recording equipment
The video recording equipment shall not cause thermal effects on the specimen.
Note: The video recording equipment is used to track the change of the area around the scraper during the test.
5.3.2 Inspection equipment
The inspection equipment shall not cause the thermal effect of the sample.
Note. The inspection equipment refers to the equipment used to inspect the scratch surface of the sample during the test, such as magnifying glass, microscope, scanner or interferometer.
6 Specimens
6.1 Specimen shape and size
6.2 Sample preparation
The sample shall be injection molded according to GB/T 17037.1, GB/T 17037.5 or ISO 10724-1 and other appropriate standards, and shall meet the sample preparation conditions specified in relevant material standards.
During preparation, the melt flow direction, the cavity corresponding to the sample (when using a multi cavity mold) and the sample surface corresponding to the inside of the mold (moving template side or static template side) shall be marked outside the test area of the sample,
Note 1: See Annex B of ISO 10724-1:1998 for marking examples
Note 2: Due to the influence of the test surface of the sample and/or the melt flow direction, some types of materials may show different scratch damage forms. When the measured value of a certain property given by the sample prepared by the single cavity mold is different from the measured value of the sample prepared by the GB/ISO mold, if the sample prepared by the single cavity mold is used for measurement, a description shall be given in the test report.
Note 3: 4.1.2 of GB/T 17037.1-2019 gives the difference between single cavity mold and GB/ISO mold in sample preparation and performance measurement
Reason for
During sample preparation, process parameters shall be controlled to ensure that all samples are in the same state.
6.3 Sample inspection
The sample can be inspected visually or with the help of knife edge ruler, square ruler and flat plate. The sample shall be free of distortion, and the surface and edge shall be free of scratches, pits, dents, flash and other defects. The unqualified sample shall be removed.
Scratches can change the thickness of the specimen, causing changes in the form of scratch damage. The same e-sample shall not be tested for many times, and even the reverse side of the test surface of the sample shall not be reused.
6.4 Number of samples
Determine the scratch damage form according to 8.1. When there is only one scratch damage form in a single test, the test condition of this group is I sample. When there are multiple scratch damage forms in a single test, the test condition of this group is at least 3 samples.
The scratch phase diagram shall be obtained according to 8.2. The test conditions shall not be less than 25 groups (for example, five constant test loads and five test speeds, see 7.2.3.2 and 7.2.4), and the number of samples for a single test shall meet the requirements for determining the scratch damage form.
Determine the critical normal load of the sample according to 8.3. At least 3 samples shall be tested at each test speed (excluding the number of pre test samples, see 2.3.3).
6.5 Sample state adjustment
Unless otherwise specified, the sample shall be conditioned for at least 16 h in accordance with the standard environment specified in GB/T 2918, with a temperature of (23 ± 2) ℃ and a relative humidity of (50 ± 10)%.
7 Test procedures
7.1 Test environment
Unless otherwise agreed by relevant parties, the test shall be conducted in the same standard environment as the state adjustment.
7.2 Test preparation
7.2.1 Inspection of scraper head
When the scraper moves along the scratch direction, measure the displacement of the scraper according to the baseline. Before the test, it shall be ensured that the baseline is constant within 10 u. m. Note 1: The flat metal strip with a thickness of several microns clamped on the sample holder can be used to check the displacement baseline of the scraper head.
7.3 Testing
Before starting the test, slowly move down the scraper and contact the surface of the sample, and maintain an initial load not exceeding 0.5N. Set the displacement extensometer value of the scraper to 0. After starting, slowly apply the load within 5s, and within 30s to 60s, the scraper starts to move on the surface of the sample.
During the test, the tangential scratch force, scraper displacement and scratch distance shall be recorded, and the corresponding data shall be used to draw the tangential scratch force scratch distance curve and scraper displacement scratch distance curve. When the moving distance of the scraper head does not reach the scratch distance set in the test, the recording shall not be interrupted.
During the test, use the equipment in 5.3.1 to record the scratch damage form (optional)
After the test, check the scratch table with the equipment in 5.3.2 (optional, T
Note. During the test, the N-scratch damage form recorded in the video and the scratch surface inspected after the test can provide useful information for the result presentation (see
8.1 and 8.3)
8 Expression of results
8.1 Mode of scratch damage
According to the tangential scratch force scratch distance curve and scraper displacement scratch distance curve obtained during the test, the scratch failure form of each sample can be classified as smooth notch (p), repetitive failure (w) or material peeling (c).
When the load is constant (basic method), select a 50 mm long scratch in the narrow parallel part of the sample, and obtain the corresponding tangential scratch force scratch distance curve and scraper displacement scratch distance curve. Observe whether the tangential scratch force and the displacement of the scraping head keep constant or periodically vibrate or change disorderly with the scratch distance, such as whether there are smooth grooves (p VIII, repetitive failure (w) or material peeling (c) described in 3.7.1~3.7.3 and Figure 2 on the curve
The weak and sporadic signal vibration caused by the equipment itself during the test can be ignored (the amplitude of tangential scratch force is less than 3 N, and the amplitude of wiper displacement is less than 10 u. m)
During the test, video recording of the scratch damage form and/or inspection of the specimen surface after the test are helpful to determine the scratch results, as shown in the photo at the bottom of Figure 2.
For specimens with multiple scratch failure modes, material peeling is preferred, followed by repeated failure, and finally smooth grooving. Note 1: Compared with scraper displacement d, tangential scratch force F is more sensitive to the change of scratch damage form.
Note 2: Compared with smooth grooving or repeated failure, the average value of scraper displacement d corresponding to material stripping is larger. Under constant load, the results of a single sample can be expressed as follows:
9 Test report
Appendix A (Informative) Structure Number Comparison List
Appendix B (informative) Schematic Diagram of Scratch Failure Forms
Appendix c (informative) Schematic Diagram of Scratch Measuring Equipment
contents
1 Scope
2 Normative References
3 Terms and definitions
4 Principle
5 Equipment
6 Specimens
7 Test procedures
8 Expression of results
9 Test report
Appendix A (Informative) Structure Number Comparison List
Appendix B (informative) Schematic Diagram of Scratch Failure Forms
Appendix c (informative) Schematic Diagram of Scratch Measuring Equipment
