How to Assess the Quality of Fiberglass Yarn
May 20, 2026
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Preliminary Visual Inspection
High-quality yarn features uniform, soft coloration and a smooth surface free from obvious broken filaments, impurities, oil stains, or color variations; the fiber bundles are neatly arranged without excessive loose fuzz. Inferior products often exhibit localized blackening, severe yellowing, or jagged cross-sections; a magnifying glass can be used to inspect for detailed defects.
Core Performance Testing
Mechanical Properties: Tensile strength and elongation at break are determined via tensile testing. Qualified E-glass direct roving should have a tensile strength of no less than 2400 MPa; higher values indicate more stable mechanical performance.
Linear Density: The weight per kilometer of yarn (tex value) is measured using the skein method. Smaller deviations indicate better uniformity in yarn thickness, ensuring consistency in subsequent processing.
Moisture and Combustible Content: High-quality products require a moisture content of less than 0.2% to avoid compromising resin impregnation. Combustible content (sizing/coupling agents) should be controlled within the 0.5%–1.2% range to ensure compatibility with the specific resin system.
Compliance and Traceability Verification
Prioritize products that meet industry standards such as GB/T 18369-2022 and JC/T 575-1994. Request the Certificate of Analysis (COA) for each batch to confirm that core chemical components-such as silicon dioxide-meet specifications. Additionally, verify complete labeling on the packaging, including batch numbers and applicable standards, to avoid inferior products from small, non-traceable manufacturers.
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