What are the core quality indicators for fiberglass cloth?

I. Examine the Raw Fiber Skeleton (Fundamental Core)

The fundamental quality of fiberglass cloth depends on the raw fiber, its skeleton.

 

Key Indicator: Alkali Content (Sodium Oxide/Potassium Oxide Ratio)

 

Classification Reference: Alkali-free (≤0.8%), Medium Alkali (11.6%-12.4%), High Alkali (＞12%) (National Standard GB/T 18370 for Grinding Wheel Mesh Cloth). For corrosion protection, insulation, and harsh working conditions, stricter alkali content standards are required.

 

Procurement Verification: Do not rely solely on vague terms like "alkali-free/medium-alkali/high-alkali." Confirm the source of the glass raw materials and the alkali content indicator. If necessary, check the batch test reports of the raw materials to ensure the alkali content is stable and avoid fluctuations affecting overall performance.

 

Simple Corrosion Resistance Test: Immerse a sample in 5% dilute hydrochloric acid for 24 seconds. Hours (wear gloves for protection), wash and dry, then stretch and twist. The less strength loss and the better the shape retention, the better the corrosion resistance.

 

Core Principle: The raw yarn material and alkali stability directly determine the long-term lifespan and structural strength of the fiberglass cloth.

 

II. Examine the weaving process (structural stability)

 

Basic Inspection

Light Transmission Observation: High-quality cloth has evenly distributed yarns, consistent light transmission, and no cloudiness, broken yarns, knots, or lumps, indicating uniform weaving tension and balanced overall strength.

 

Mainstream Weaving Methods

 

Plain Weave: Dense and stiff, scratch-resistant and wear-resistant, suitable for heat insulation outer cladding, external wall crack prevention, and other protective scenarios.

 

Twill Weave: Balances strength and flexibility.

 

Satin Weave: Smooth surface, good resin impregnation, suitable for fiberglass and FRP products (yachts, cooling towers, etc.), reducing internal defects and improving overall strength.

 

Simple Test: Gently tear along a 45° corner; it should not tear easily, and there should be no frayed edges or loose threads. Yarn cohesion is acceptable; if it tears easily, the cohesion is insufficient and it will be easily damaged later.

 

Core principle: Choose the weaving method as needed, prioritizing uniform texture and sufficient cohesion.

 

III. Examine the sizing agent coating (hidden core value)

 

The sizing agent (surface chemical coating) is a key control point for experts, determining the bonding ability between the glass fiber and the matrix material.

 

Type differences:

Reinforcing sizing agents (silane coupling agents, etc.): can chemically bond with resin, achieving a strong bond and significantly improving the overall strength of the composite material.

Non-reinforcing/temporary coatings (starch, paraffin): only convenient for weaving, require subsequent washing, not suitable for direct structural reinforcement.

 

Simple self-inspection methods:

Water droplet test: In high-quality chemically coated fabric, water droplets form beads and are not easily penetrated; rapid penetration usually indicates inferior/temporary coatings.

 

Resin impregnation test: Lay the fabric, pour resin, and smooth it out. Uniform penetration speed and no white dry spots indicate good sizing agent compatibility.

 

Core principle: For structural/ For fiberglass products, a reinforcing impregnating agent compatible with the resin system must be selected.

IV. Avoid the misconception of weight per square meter and verify the overall density.

 

Common pitfalls: Focusing only on weight per square meter; some products rely on a loose structure and gaps to increase weight, resulting in low bulk density and poor actual strength.

 

Key parameters: Verify weight, thickness, and warp and weft yarn density simultaneously.

 

Check the number of warp and weft yarns per unit length to confirm yarn tightness.

 

Hand feel tensile test: High-quality fabric exhibits minimal tensile deformation, significant skeletal resistance, and moderate light transmission.

Comparison principle: At the same weight, thinner fabric with higher density... Higher weight generally indicates better structural performance.

Core principle: Quality cannot be determined solely by weight; comprehensive density and skeleton strength are key.

 

Summary

 

When purchasing fiberglass cloth, don't just look at price and weight:

Check the raw yarn material and alkali stability to control the quality of the basic skeleton.

Check the weaving uniformity and weaving method's suitability for the application to ensure overall structural stability.

Check the quality of the sizing agent coating to ensure effective bonding with the matrix material.

Comprehensively verify density parameters to avoid inferior products with inflated thickness and weight.

If necessary, conduct acid and alkali resistance immersion tests to verify long-term stability.