What is the manufacturing process of glass fiber?

The Making of Glass Fiber

Glass fiber was the first reinforcement used in modern polymeric composites but springs from an ancient art. Here, glass fiber ends are wound side-by-side onto warp beams (large rolls or cylinders) which will be used later in a fiberglass fabric-weaving operation. Source | AGY

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Fiberglass is the original fiber reinforcement of modern composites. Though the ancient Phoenicians, Egyptians and Greeks knew how to melt glass and stretch it into thin fibers, it wasn't until the 1930s that these practices scaled into commercial manufacturing of continuous fibers. Patent filings between 1933 and 1937 by Owens-Illinois Glass Co. employees, Games Slayter, John Thomas, and Dale Kleist, were pivotal. Their work transitioned the industry from producing discontinuous-fiber glass wool to continuous glass filaments with diameters as small as 4 microns. These breakthroughs simplified production, making the process feasible and cost-effective on a commercial scale.

The final patents in this series, "Textile Material" and "Glass Fabric", hinted at glass fiber's future role as textile reinforcement. Awarded in 1938, the same year Owens-Illinois and Corning Glass Works formed Owens-Corning Fiberglas Corp, the patents introduced Fiberglas, setting a standard in the industry. Soon, other manufacturers joined the market, driving numerous innovations. By 2018, the global structural composite reinforcements market had grown to 2.5 billion pounds, according to Lucintel.

Glass fiber, hence force, is produced by mixing raw materials, melting them in a three-stage furnace, extruding the molten glass through a forehearth bushing, cooling the filaments with water, and then applying a chemical size. These filaments are collected and wound into packages. Source | OCV

The Glass Fiber Manufacturing Process

Step 1: Batching

While commercial glass fiber could be made from pure silica, additional ingredients are often mixed in to lower working temperatures or add specific properties. For instance, E-glass, developed for electrical applications, includes SiO2, AI2O3, CaO, and MgO for enhanced alkali resistance. Later, boron was added via B2O3 to help prevent nozzle clogs during subsequent fiberization.

S-glass fibers, designed for higher strength, contain higher levels of SiO2 for applications demanding greater tensile strength. At this stage, precise measurements and mixing (batching) are critical. Modern batching uses computerized weighing systems and enclosed transport systems for accuracy and efficiency.

Step 2: Melting

From the batching area, the mixture is pneumatically transferred to a high-temperature natural gas-fired furnace, typically hitting 1400°C. The furnace has three sections to aid in increasing uniformity and reducing bubbles. Next, the molten glass moves to the refiner where the temperature drops to about 1370°C. The final stage, the forehearth, prepares the glass for extrusion into fibers.

Technological advancements have boosted furnace efficiency. For instance, the direct melt furnace at OCV's Amarillo, Texas plant processes 30,000 tonnes annually. Furnaces now employ digital controls for precise temperature management, ensuring consistent fiber quality and lowering emissions significantly.

Furnace maintenance has also evolved. Rebuilding furnaces is costly—up to $15 million—thus, extending their service life is crucial, with modern furnaces averaging 12-15 years between rebuilds.

Step 3: Fiberization

Upon exiting the furnace at approximately 1340°C, the molten glass is extruded through bushing plates containing 200 to 8,000 orifices. The high-speed winders apply tension, drawing the glass into fine filaments, which are then cooled by water jets and coated with size to enhance compatibility with various resins.

Nozzle design in bushings is vital as it determines filament diameter and overall fiber yield. AGY and OCV have developed bushings to optimize production flexibility and meet specialized requirements.

Step 4: Coating

A chemical size, typically weighing from 0.5% to 2.0% of the filament, is applied to protect the fibers during handling while enhancing resin bonding. The specific composition of the size varies, with proprietary chemistries tailored to different resin systems to maximize performance.

Step 5: Drying/Packaging

Finally, the filaments are bundled into strands and wound onto drums creating forming packages. These packages are then dried and prepared for shipping or further processing into chopped fiber, roving, or yarn. This final stage ensures the glass fibers are ready for their diversified end-use applications.

One Process, Many Products

Despite the continuity of the glass fiber manufacturing process, refinements over the years have enhanced throughput and reduced costs. Manufacturers strive concurrently to improve production efficiency and the performance attributes of the finished product, thereby making fiberglass universally applicable across numerous industries. Visit Fiberglass Yarn manufacturer for more information and a detailed overview.

Glass Fiber: The Market

Evolution of Process and Products

Thirty years ago, glass reinforcements for composites were limited mainly to E-glass and S-glass. Today, the range of glass fiber products has diversified greatly to meet specific demands for performance, cost, and specific application requirements. Notably, the move towards boron-free E-glass indicates a shift towards more environmentally friendly and cost-effective production without compromising quality.

Other high-performance glass fibers such as S-2 Glass, developed for military applications, and the more cost-efficient S-1 Glass, tailored for wind blades, exemplify the industry's push to create specialized products for particular needs while balancing performance and cost.

Focus on Lower Cost Drives Future Growth

The fiberglass industry is driven by dual trends: massive growth and decreased costs. China plays a pivotal role in this by being the largest producer and consumer, thereby affecting global production dynamics. Chinese fiberglass production is characterized by low labor costs and favorable export conditions, making it a focal point for labor-intensive glass fiber products.

The ongoing effort to elevate performance while bringing down costs is a constant in the industry. Companies strive to develop products that offer high performance akin to materials like carbon fiber but at a price closer to traditional materials, thereby expanding the applications of fiber-reinforced composites.

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This article was originally published on 6/1/2020 and updated on 6/30/2022.