The classification of leather is quite intricate. Based on tanning methods, it includes chrome-tanned leather, vegetable-tanned leather, oil-tanned leather, aldehyde-tanned leather, and combination-tanned leather, among others. In terms of layers, leather is divided into top-grain leather and split leather. Top-grain leather further includes full-grain leather and corrected-grain leather, while split leather includes pig split leather and cattle split leather. Beyond these classifications, leather is also commonly categorized by animal type, with the primary categories being natural leather and synthetic leather.
Natural leather, often referred to as "genuine leather," is predominantly made from cattle hide, sheepskin, pigskin, and other animal hides. Cattle hide, sheepskin, and pigskin are the three major raw materials used in leather production. Synthetic leather, termed "artificial leather," encompasses materials like PVC and PU, which are chemically synthesized to mimic the appearance and texture of natural leather.
Judging and Testing Methods for Leather Abrasion Resistance
Leather abrasion resistance refers to its ability to withstand wear and tear, a critical factor in leather durability. Although abrasion resistance is not yet a mandatory national standard, it remains an essential indicator for evaluating leather quality and performance in practical applications.
Judging Methods
Two primary methods assess leather abrasion resistance:
- Endpoint Method
- Measures the number of abrasion cycles required to remove 1mm of leather thickness. The rotation count at this endpoint serves as the abrasion resistance index.
- Appearance Change Method
- Evaluates visible changes in the leather sample after a specified number of abrasion cycles, such as color fading or surface wear, to determine abrasion resistance.
Testing Methods
1. Flat Abrasion Method
- Reference Standard: GB/T 21196-2007 Martindale Method for Determining Abrasion Resistance of Fabrics.
- Testing Instrument: The Martindale Abrasion Tester is widely used in the industry.
- Testing Principle: A circular leather specimen, mounted in a Martindale tester fixture, undergoes planar motion in a Lissajous pattern under specified load, rubbing against an abrasive material (standard fabric). The fixture rotates freely around an axis perpendicular to the horizontal plane. The total friction cycles before specimen failure determine abrasion resistance.
- Procedure: A specimen of defined dimensions is placed under controlled pressure against standard abrasive material, moving in a Lissajous trajectory to simulate multi-directional, uniform wear.
2. Taber Abrasion Method
- Reference Standard: GB/T 2726-2005 Leather - Physical and Mechanical Tests - Determination of Abrasion Resistance.
- Testing Instrument: Taber Abrasion Tester.
- Testing Principle: After a 25-cycle pre-abrasion phase, the specimen is rotated on a horizontal platform under specific pressure from two abrasive wheels. One wheel rotates outward, the other inward, with a combined load of 500g. Changes in the specimen are recorded over time.
- Procedure:
- Cut a sample with an outer diameter of 108mm and an inner diameter of 8mm.
- Affix a rigid backing paper of identical size to the sample's reverse.
- Secure the sample on the tester's rubber pad using a retaining ring and locking screws.
- Attach two H18 abrasive wheels to the support arms, applying 250g ± 10g force per wheel (500g total).
- Connect a vacuum cleaner to the machine's intake port and activate it.
- Set the test cycles and rotation speed (72rpm) as per standards.
- Initiate the test, observing wear patterns and recording the cycle count at specimen failure.
Key Considerations
- Comparing results across different materials using the same test method may yield limited direct relevance, but consistent conclusions about material performance can be drawn.
- Natural leather, being softer, generally exhibits lower abrasion resistance compared to coated leather, which has a harder texture and superior wear resistance.
This comprehensive approach to leather classification and abrasion testing ensures informed material selection for diverse applications, from fashion and automotive interiors to industrial products.
