Source: Link Testing Instruments Co.,Ltd.
GB/T 4850-2002, "Determination of Low-Speed Unwinding Strength of Pressure-Sensitive Adhesive Tapes," is a core standard for evaluating the unwinding performance of roll-type pressure-sensitive adhesive tapes without release liner. Its test method, by simulating real-world usage scenarios, provides a scientific basis for product quality control. Jinan Zhongke Electronics, as a professional testing instrument R&D enterprise, provides reliable support for enterprises to implement standards and improve product quality through its equipment and services. The following is a professional interpretation from the aspects of the standard's significance, technical details, operational points, and application practices:
The determination of low-speed unwinding strength is of great significance for ensuring the performance of adhesive tapes in practical applications. This standard provides a scientific and standardized test method for the low-speed unwinding performance of roll-type pressure-sensitive adhesive tapes without release liner, providing a reliable basis for product quality assessment.
This standard applies to the determination of the low-speed unwinding strength of roll-type pressure-sensitive adhesive tapes without release liner. In practical applications, these adhesive tapes are widely used in packaging, electronics, medical, printing, and other fields. Their unwinding performance directly affects the efficiency and reliability of products on automated production lines.
The standard measurement principle is clear and straightforward: the adhesive tape sample is mounted on a freely rotating unwinding fixture and placed on a constant-speed testing machine. When the machine fixture moves at a specified rate of (300±30) mm/min, the adhesive tape sample is unwound approximately 150 mm. The maximum load measured is the unwinding strength of the adhesive tape, expressed in N/mm.
Significance of the Principle: This test method highly simulates the real-world scenario of adhesive tape unwinding from a rolled state during actual use. It can intuitively and accurately reflect the performance of the adhesive tape during unwinding, providing a reliable basis for product quality assessment.
(1) Testing Machine Requirements:
The unwinding load should be within 20%~80% of the full-scale load of the testing machine. In this test, we adopt the XLW-500N Automatic Tensile Tester developed by Link Testing Instruments Co.,Ltd.
Force value indication error ≤1% (to ensure testing accuracy).
Clamping device movement speed: (300±30) mm/min
Equipped with an automatic load recording plotting device
(2) Requirements for unwinding fixtures:
The rotational force generated by the shaft of the conical chuck should be <0.2N
Rotational force test method: Assemble and suspend the fixture, fix a hair-like filament in the middle of the shaft with a small strip of adhesive tape, wrap it tightly several times, and then suspend a 20g weight. If the weight can drive the shaft to rotate, it meets the requirements.
(3) Requirements for measuring instruments:
Vernier calipers, minimum graduation value ≤0.05mm
(1) Sample requirements:
Width ≤80mm
No obvious deformation or damage
(2) Environmental conditions:
Temperature: (23±2)℃
Relative humidity: (50±10)%
(3) Sample pretreatment:
Temperature only requirement: Place for at least 2 hours under specified conditions
Temperature and humidity both requirement: Place for at least 24 hours under specified conditions
(1) Width Measurement: Take three roughly equal measurements on the sample and calculate the arithmetic mean.
(2) Pretreatment: Remove the outermost 3-6 turns of adhesive tape from the sample (to avoid potential quality issues in the outermost layer affecting the test results).
(3) Sample Installation: Fix the shaft frame of the unwinding fixture inside the test machine holder. Place the sample on the shaft and tighten the conical clamps from both sides to hold the sample in the center of the shaft.
(4) Test Preparation: Peel off approximately 200mm of adhesive tape from the sample by hand and fix the starting end inside the upper holder.
(5) Formal Test: Start the test machine and unwind approximately 150mm of adhesive tape at a rate of (300±30)mm/min. Record any abnormal phenomena (such as adhesive migration, tearing, or substrate delamination).
(6) Repeat Test: Repeat the test on 5 samples and record the average and maximum values of the unwinding strength.
Unwinding Strength Calculation Formula: J = F/b
J: Unwinding strength, N/mm
F: Unwinding load, N
b: Specimen width, mm
III. Application Scenarios
Medical Field: Medical dressings require moderate unwinding force to avoid skin irritation or accidental detachment. For example, a certain brand of wound dressing optimized its formula through testing, controlling the unwinding strength at 0.8-1.2 N/mm, meeting clinical requirements.
Electronics Industry: The unwinding force of protective films for electronic components needs to be matched with the lamination equipment. One company adjusted the release agent coating amount through testing, reducing the unwinding force from 1.5 N/mm to 1.0 N/mm, eliminating air bubble problems during high-speed lamination.
Packaging Industry: Sealing tape needs to balance unwinding force and adhesive force. A test case showed that an unwinding strength of 1.2-1.5 N/mm ensures both ease of opening and prevention of box cracking during transportation.
Summary:
GB/T 4850-2002, "Determination of Low-Speed Unwinding Strength of Pressure-Sensitive Adhesive Tapes," serves as an important standard in the performance testing system for pressure-sensitive adhesive tapes, providing a standardized and scientific testing method for the low-speed unwinding performance of roll-type pressure-sensitive adhesive tapes without release liner.
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