Comprehensive Explanation of the Production Principle and Application Standards of
Fiberglass Chopped Strand Mat
The formation of glass fiber chopped strand mat involves taking glass fiber rovings (untwisted yarn can also be used) and cutting them into 50mm long strands using a cutting knife. These strands are then scattered and arranged in a disorderly manner, settling on a stainless steel mesh conveyor belt to form a mat. The next steps involve applying a bonding agent, which can be in the form of a spray adhesive or a sprayed water-dispersible adhesive, to bind the chopped strands together. The mat is then subjected to high-temperature drying and reshaped to create emulsion chopped strand mat or powder chopped strand mat.
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I. Raw Materials
The glass commonly used in fiberglass products is a type of calcium-aluminum borosilicate with an alkali content of less than one percent. It is often referred to as “E-glass” because it was developed for electrical insulation systems.
The production of glass fiber involves transporting molten glass from a melting furnace through a platinum bushing with numerous small holes, stretching it into glass filaments. For commercial purposes, the filaments typically have diameters between 9 and 15 micrometers. These filaments are coated with a sizing before being gathered into fibers. Glass fibers are exceptionally strong, with a particularly high tensile strength. They also exhibit good chemical resistance, moisture resistance, excellent electrical properties, are impervious to biological attacks, and are non-combustible with a melting point of 1500°C—making them highly suitable for use in composite materials.
Glass fibers can be used in various forms: chopped into short lengths (“chopped strands”), gathered into loosely bound rovings (“rovings”), or woven into various fabrics through twisting and plying continuous yarns. In the UK, a widely used form of glass fiber material is chopped strand mat, which is made by chopping glass fiber rovings into approximately 50mm lengths and bonding them together using polyvinyl acetate or polyester binders, forming them into a mat. The weight range of chopped strand mat can vary from 100gsm to 1200gsm and is useful for general reinforcement.
II. Binder Application Stage
Glass fibers are transported from the settling section to the conveyor belt, where a binder is applied. The settling section must be kept clean and dry. The binder application is carried out using two powder binder applicators and a series of demineralized water spray nozzles.
On the chopped strand mat, both on the upper and lower sides, a gentle spray of demineralized water is applied. This step is essential for better adhesion of the binder. Special powder applicators ensure even distribution of the powder. Oscillators between the two applicators help transfer the powder to the underside of the mat.
III. Binding with Emulsion
The curtain system used ensures thorough dispersion of the binder. Excess binder is recovered through a special suction system.
This system allows air to carry away excess binder from the mat and the binder is evenly distributed, eliminating excess binder. Clearly, the filtered contaminants in the binder can be reused.
The binder is stored in containers in the mixing room and transported from small troughs near the mat plant through low-pressure pipes.
Special devices maintain the level of the tank constant. Recycled binder is also conveyed to the tank. Pumps transport the adhesive from the tank to the adhesive application stage.
IV. Production
Glass fiber chopped strand mat is a non-woven material made by cutting long filaments into 25-50mm lengths, randomly laying them on a horizontal plane, and holding them together with an appropriate binder. There are two types of binders: powder and emulsion. The physical properties of the composite material depend on the combination of filament diameter, binder selection, and quantity, mainly determined by the type of mat used and the molding process.
The raw material for producing chopped strand mat is glass fiber manufacturer’s roving cakes, but some also frequently use rovings, partly to save space.
For mat quality, it is crucial to have good fiber cutting characteristics, low static electrical charge, and low binder consumption.
V. Factory Production consists of the following parts:
Fiber Creel
Chopping Process
Forming Section
Binder Application System
Drying Oven
Cold Press Section
Trimming and Winding
VI. Creel Area
Rotating creel stands are placed on the frame with an appropriate number of bobbins. Since these creel stands hold fiber cakes, the creel area should be in a humidity-controlled room with a relative humidity of 82-90%.
VII. Chopping Equipment
Yarn is pulled from the roving cakes, and each chopping knife has several strands passing through it.
VIII. Forming Section
The formation of chopped strand mat involves even distribution of the chopped strands at equal intervals in the forming chamber. Each equipment is equipped with variable-speed motors. The cutting devices are independently controlled to ensure even distribution of fibers.
The air underneath the conveyor belt also draws in fibers from the top of the belt. The discharged air passes through a purifier.
IX. Thickness of Glass Fiber Chopped Strand Mat Layer
In most fiberglass-reinforced products, glass fiber chopped strand mat is involved, and the quantity and method of use of chopped strand mat vary depending on the product and process. The layer thickness depends on the required manufacturing process!
For example, in the production of fiberglass cooling towers, one layer is coated with a resin, followed by one layer of thin mat or 02 fabric. In between, 6-8 layers of 04 fabric are laid, and an additional layer of thin mat is applied on the surface to cover the joints of the inner layers. In this case, only 2 layers of thin mat are used in total. Similarly, in the manufacturing of automobile roofs, various materials such as woven fabric, non-woven fabric, PP plastic, thin mat, and foam are combined in layers, with thin mat typically used in only 2 layers during the manufacturing process. Even for Honda automobile roof production, the process is quite similar. Therefore, the quantity of chopped strand mat used in fiberglass varies depending on the process, and some processes may not require its use while others do.
If one ton of fiberglass is produced using chopped strand mat and resin, the weight of chopped strand mat accounts for approximately 30% of the total weight, which is 300Kg. In other words, the resin content is 70%.
The quantity of chopped strand mat used for the same process is also determined by the layer design. Layer design is based on the mechanical requirements, product shape, surface finish requirements, and other factors.
X. Application Standards
The use of alkali-free glass fiber chopped strand mat is becoming increasingly widespread and encompasses various high-tech fields such as automotive, maritime, aviation, wind power generation, and military production. However, you may not be aware of the relevant standards for alkali-free glass fiber chopped strand mat. Below, we will introduce the requirements of an international standard in terms of alkali metal oxide content, unit area mass deviation, combustible content, moisture content, and tensile breaking strength:
Alkali Metal Content
The alkali metal oxide content of alkali-free glass fiber chopped strand mat should not exceed 0.8%.
Unit Area Mass
Combustible Content
Unless otherwise specified, the combustible content should be between 1.8% and 8.5%, with a maximum deviation of 2.0%.
Moisture Content
The moisture content of the mat using powder adhesive should not exceed 2.0%, and for the mat using emulsion adhesive, it should not exceed 5.0%.
Tensile Breaking Strength
Typically, the quality of alkali-free glass fiber chopped strand mat meets the above requirements to be considered compliant. However, depending on the product’s intended use, the production process may have higher requirements for tensile strength and unit area mass deviation. Therefore, it is essential for our procurement personnel to be familiar with the manufacturing process of their products and the specific requirements for chopped strand mat so that suppliers can produce accordingly.”
Post time: Oct-23-2023
