An Exploration Of The Application Of Fiberglass Cloth And Fiberglass Mat in Fiberglass Anti-corrosion Engineering

Fiberglass, or glass fiber reinforced plastic (GFRP) for short, is renowned for its excellent mechanical strength and corrosion resistance, and is considered one of the three major lining materials in the anti-corrosion industry, alongside brick and rubber. From a composite material structure perspective, GFRP resembles reinforced concrete: epoxy resin, unsaturated polyester, and vinyl ester resins act as the "concrete," while fiberglass cloth and fiberglass mat serve as the reinforcing substrate, acting as the "steel reinforcement." Together, they form a protective barrier for corrosion-resistant equipment, tanks, and chemical pools, finding increasingly widespread application in the chemical corrosion protection field.

 

Both fiberglass cloth and fiberglass mat share the same raw materials, primarily quartz sand, soda ash, flux, and stabilizers. These are melted in a high-temperature furnace to create molten glass, which is then drawn into continuous glass filaments through a stencil. Subsequent processing differentiates them into two types of products. Fiberglass cloth is woven from these filaments in a single warp; fiberglass mat, on the other hand, has these filaments cut to approximately 50mm short strands, bonded with powder or emulsion binders, and then heated and shaped in an oven. These different processing techniques result in distinct product performance and applicable scenarios.

 

I. Classification and Performance Characteristics of Fiberglass Cloth

 

Fiberglass cloth comes in many varieties, and the industry mainly classifies it according to three dimensions: raw material composition, weaving process, and yarn specifications.

 

Based on the glass raw material composition, it can be divided into alkali-free E cloth, medium-alkali C cloth, high-alkali cloth, and alkali-resistant AR cloth. Alkali-free E-type fiberglass cloth has an alkali metal oxide content of less than 0.8%, exhibiting excellent water resistance, insulation, and mechanical properties, making it the preferred reinforcing material for heavy-duty chemical corrosion protection projects. Medium-alkali C-type fiberglass cloth has an alkali metal oxide content controlled between 11.5% and 12.5%, offering superior acid resistance compared to alkali-free products and lower production costs, but with weaker strength and electrical properties. It is primarily used for general corrosion protection, asphalt waterproof membrane bases, and low-end fiberglass products. High-alkali fiberglass cloth has an alkali metal oxide content exceeding 13%, making it prone to corrosion and aging upon contact with water, acids, and alkalis, resulting in rapid strength loss. Its use in corrosion protection projects is explicitly prohibited by regulations, and it can only be used for temporary simple buildings and low-grade insulation materials. Alkali-resistant AR-type fiberglass cloth containing zirconium can resist the erosion of strong alkalis during cement hydration, making it a dedicated substrate for GRC fiberglass cement components and European-style exterior wall decorations.

 

Based on weaving techniques, fiberglass cloth is available in plain weave, twill weave, satin weave, and untwisted roving (grid cloth). Plain weave fabric features a one-over-one interlacing of warp and weft yarns, resulting in a dense and flat structure with low deformation rate, making it suitable for flat anti-corrosion linings and pipe outer anti-corrosion applications. Twill fabric, woven with a two-over-two-under or three-over-three-under weave, offers excellent flexibility and can tightly conform to irregular curved surfaces, making it a common material for hand lay-up construction of non-standard storage tanks and irregularly shaped chemical equipment. Satin weave fabric has long floating yarns, resulting in good resin impregnation and high product strength, but its high cost limits its use, primarily in high-end aerospace composite materials and rarely in anti-corrosion applications. Untwisted roving fabric, commonly known as checkered fabric, features a coarse plain weave, large mesh size, strong load-bearing capacity, and moderate cost-effectiveness, dominating the heavy-duty anti-corrosion structural layer material market.

 

Based on yarn type, untwisted roving fabric is divided into untwisted roving fabric and fine roving fabric. Untwisted roving fabric has a robust yarn body and excellent tensile strength, and is used in over 90% of anti-corrosion fiberglass projects. Fine roving fabric has a delicate and smooth surface, primarily used for electronic insulation materials and fiberglass surface decoration. According to the national standard GB/T 18370-2014, alkali-free woven fabric is designated EWR, and medium-alkali woven fabric is designated CWR, facilitating industry selection and procurement. Commonly used engineering specifications include 01, 02, 04, 06, and 08 fabrics. 01 and 02 fabrics are only 0.1mm and 0.2mm thick, respectively, and are mostly used for local repairs and thin-layer corrosion protection. 400g/㎡ (04 fabric) is a general-purpose corrosion protection specification, while 0.6mm (600g/㎡) and 0.8mm (800g/㎡) thicker fabrics are used for equipment load-bearing layers and heavy-duty corrosion protection structures.

 

II. Subcategories and Applications of Fiberglass Mat

 

Fiberglass mats are classified according to four dimensions: molding process, fiber morphology, application, and composite structure. According to processing technology, fiberglass mats include chopped strand mat, stitch-bonded mat, wet-laid mat, and needle-punched mat: Chopped strand mat is formed by randomly laying and bonding short chopped fibers, and comes in two types: powder adhesive and emulsion adhesive; stitch-bonded mat relies on polyester yarns to stitch together short chopped fiberglass blanks; wet-laid mat borrows from papermaking technology, using water to draw fibers and a special adhesive; needle-punched mat is formed by combing and needle punching, resulting in a highly porous internal structure. According to fiber morphology, they are divided into continuous filament mat (MS) and chopped strand mat (MC). Continuous filament mat is laid out in a figure-eight pattern and bonded, while chopped strand mat uses 50mm short chopped fibers randomly arranged and shaped, corresponding to the national standards EMC alkali-free chopped strand mat, CMC medium-alkali chopped strand mat, EMS alkali-free continuous mat, and CMS medium-alkali continuous mat.

 

According to application scenarios, fiberglass mats are divided into surface mats, roofing mats, and filter mats. Surface felt with a thickness of only 0.2mm and a surface density of 30-50g/㎡, after impregnation, optimizes the density of the fiberglass surface, improves its impermeability and corrosion resistance, and smooths out the fabric texture. Roofing felt, used as the base for SBS and APP modified bitumen rolls and fiberglass asphalt shingles, significantly improves the tensile and tear resistance of waterproofing materials. Special fiberglass loose felt for air filtration has well-developed pores and a large dust holding capacity, widely used in industrial waste gas and fresh air purification filtration industries. Composite structural felt includes fabric-felt composite felt, sandwich-core flow-guiding felt, and needle-punched composite felt. Through integrated fabric-felt composite, the layup performance is optimized, and it is mostly used in flow-guiding layers and high-strength composite fiberglass.

 

The mainstream chopped strand mat specifications for corrosion protection construction are 200g, 300g, 450g, and 600g/㎡: 200g chopped strand mat is thin but absorbent, used for lining base repair; 300g (1.4~1.6mm) is the industry-wide standard model; 450g thick mat is suitable for tank bottom plates and heavy-duty equipment foundations; 600g ultra-high grammage chopped strand mat consumes a large amount of adhesive during construction and is mostly used for heavy-duty corrosion protection under extreme working conditions.

 

III. Application Process of Fiberglass Cloth-Mat Composite Structure in Hand Lay-up Corrosion Protection

 

In fiberglass hand lay-up corrosion protection construction, the industry-standard classic composite layer structure of mat + cloth + mat is used, with each layer performing its specific function to achieve a balance between corrosion protection and structural integrity. The bottom layer is made of chopped strand mat, which, due to its high adhesive absorption, accumulates resin to form a dense, resin-rich layer, preventing the penetration of corrosive media. The middle layer uses untwisted woven fabric, whose interwoven warp and weft structure provides overall mechanical strength, preventing the anti-corrosion lining from cracking under stress. The top layer is made of surface felt, which seals the pores of the fabric, improves the product's appearance, and isolates the internal substrate from acid, alkali, and moisture.

 

Long-term construction practice has summarized a practical calculation rule: the thickness of a single layer of fiberglass mat after resin impregnation and curing is approximately equal to the product's weight divided by 250. For example, the thickness of 300g/m² chopped strand mat is approximately 1.2mm. When designing a 5mm anti-corrosion lining, four layers of 300g chopped strand mat plus the surface felt layer are sufficient. Meanwhile, each specification of woven fabric has a fixed resin consumption range: 300g fabric consumes 300-450g of resin per square meter, 400g fabric 400-600g, 600g fabric 600-900g, and 800g fabric 800-1200g. These values ​​fluctuate depending on the construction skill, resin type, and ambient temperature, and can provide a reference for raw material procurement and cost accounting.

 

IV. Summary of Engineering Material Selection Strategies

 

In actual projects, material selection cannot rely solely on material properties. It requires comprehensive consideration of the acidity/alkalinity, temperature, concentration, and dynamic/static pressure of the corrosive medium, combined with the project budget, the designed thickness of the anti-corrosion layer, the number of layers, and resin consumption. For mild corrosive environments such as ordinary wastewater, alkali-based products can be selected to control costs; for harsh conditions such as strong acids, high temperatures, and strong solvents, alkali-free E-series fabrics combined with vinyl ester resin are preferred. A proper combination of fiberglass cloth and fiberglass mat can not only ensure the service life of fiberglass anti-corrosion linings, but also optimize raw material costs and maximize the engineering value of fiberglass composite materials.