Are you familiar with fiberglass?
In a broad sense, our understanding of glass fiber has been limited to it being an inorganic non-metallic material. However, with in-depth research, we know that there are actually many types of glass fiber, each with excellent properties and numerous outstanding advantages. For example, it has exceptionally high mechanical strength and excellent heat and corrosion resistance. Admittedly, no material is perfect, and glass fiber also has its own undeniable drawbacks, namely its poor wear resistance and susceptibility to brittleness. Therefore, in practical applications, we must leverage its strengths and mitigate its weaknesses. The raw materials for glass fiber are easy to obtain, mainly consisting of waste glass or glass products. Glass fibers are extremely fine; more than 20 glass monofilaments combined are only about the thickness of a single human hair. Glass fiber is commonly used as a reinforcing material in composite materials. Due to the deepening research on glass fiber in recent years, it has played an increasingly important role in our production and daily life. This article mainly studies the production process and application of glass fiber, introducing its properties, main components, main characteristics, material classification, production process, safety protection, main uses, current industry status, and development prospects. 1.1 Properties of Glass Fiber
Melting Point: 680℃
Molecular Structure:
Boiling Point: 1000℃
Density: 2.4~2.7g/cm3
Glass fiber also possesses a highly advantageous characteristic: its high tensile strength, reaching 6.9g/d under standard conditions and 5.8g/d under moist conditions. This excellent property makes glass fiber a commonly used reinforcing material. Its a density is 2.54. Glass fiber is also highly heat-resistant, maintaining its normal properties even at 300℃. Glass fiber is also widely used as a thermal insulation and shielding material, thanks to its electrical insulation properties and resistance to corrosion.
1.2 Main Components
The composition of glass fiber is relatively complex. Commonly recognized main components include silicon dioxide, magnesium oxide, sodium oxide, boron oxide, aluminum oxide, and calcium oxide. Glass fiber monofilaments have a diameter of approximately 10 micrometers, equivalent to 1/10 the diameter of a human hair. Each bundle of fiber consists of hundreds or thousands of monofilaments. Depending on the application of the glass fiber, the monofilament diameter varies slightly, and the drawing process also differs slightly. Typically, the silica content in glass fiber is 50%–65%. Glass fibers with an alumina content exceeding 20% have relatively high tensile strength and are usually considered high-strength glass fibers, while alkali-free glass fibers generally have an alumina content of around 15%. To achieve a high elastic modulus, the magnesium oxide content must be greater than 10%. Glass fibers containing a small amount of iron(III) oxide exhibit varying degrees of improved corrosion resistance.
1.3 Main Characteristics
1.3.1 Raw Materials and Applications
Compared to inorganic fibers, glass fiber offers superior performance. It is less flammable, heat-resistant, provides insulation, is more stable, and has high tensile strength. However, it is relatively brittle and has poor abrasion resistance. Glass fiber, used to manufacture reinforced plastics or to reinforce rubber, has the following characteristics as a reinforcing material:
(1) Its tensile strength is better than other materials, but its elongation is very low.
(2) Its elastic modulus is suitable.
(3) Within its elastic limit, glass fiber can extend for a long time and is very tensile-resistant, so it can absorb a large amount of energy when impacted.
(4) As glass fiber is an inorganic fiber, it also has many of the advantages of inorganic fibers, such as being non-flammable and chemically stable.
(5) It does not easily absorb water.
(6) It is heat-resistant and relatively stable, not easily reactive.
(7) It has excellent processability and can be processed into various excellent products such as strands, felts, bundles, and woven fabrics.
(8) It is translucent.
(9) Because the material is readily available, it is inexpensive.
(10) At high temperatures, it does not burn but melts into small liquid beads.
1.4 Classification
According to different classification standards, glass fiber can be divided into many types. Based on different shapes and lengths, glass fibers can be classified into three types: continuous fibers, fiber cotton, and fixed-length fibers. Based on different compositions, such as alkali content, they can be classified into three types: alkali-free glass fibers, medium-alkali glass fibers, and high-alkali glass fibers.
1.5 Raw Materials
In actual industrial production, to produce glass fibers, we need alumina, quartz sand, limestone, pyrophyllite, dolomite, soda ash, mirabilite, boric acid, fluorite, and ground glass fibers, etc.
1.6 Production Methods
Industrial production methods can be divided into two main categories: one is to first melt the glass fibers and then form them into small-diameter spherical or rod-shaped glass products. These are then remelted using different methods to produce fine fibers with a diameter of 3-80 μm. The other method also involves melting the glass, but instead of rods or spherical products, glass fibers are formed. The sample is then drawn through a platinum alloy plate using a mechanical drawing method. The resulting product is called continuous fiber. If fibers are drawn out using a roller device, the resulting product is called discontinuous fiber, also known as fixed-length glass fiber or short fiber.
1.7 Grading
Glass fibers are classified into various grades based on their composition, application, and properties. Internationally commercially available glass fibers have the following compositions:
1.7.1 E-Glass
It is borate glass, also known as alkali-free glass in everyday life. Its many advantages make it the most widely used. While widely used, it also has unavoidable drawbacks. It readily reacts with inorganic salts, making it difficult to store in acidic environments.
1.7.2 C-Glass
Also called medium-alkali glass in actual production, it has relatively stable chemical properties and good acid resistance. Its disadvantages include low mechanical strength and poor electrical properties. Different regions have different standards. In the domestic glass fiber industry, medium-alkali glass does not contain boron. However, in the international glass fiber industry, they produce medium-alkali glass containing boron. Not only do the contents differ, but the roles of medium-alkali glass also differ domestically and internationally. Internationally, medium-alkali glass is used in the production of fiberglass surface mats and fiberglass rods. It is also actively used in asphalt production. In my country, due to its very low price, it is widely used, appearing extensively in the wrapping and filtration fabric industries.
1.7.3 Glass Fiber A Glass
Also known as high-alkali glass in production, it belongs to sodium silicate glass. However, due to its poor water resistance, it is generally not produced as fiberglass.
1.7.4 Glass Fiber D Glass
Also called dielectric glass, it is generally the main raw material for dielectric glass fibers.
1.7.5 High-Strength Glass Fiber
Its strength is 1/4 higher than that of alkali-free glass fiber, and its elastic modulus is higher than that of E-glass fiber. Due to its many advantages, it should be widely used, but because of its high cost, it is currently only used in some important fields, such as military and aerospace.
1.7.5 Fiberglass AR Glass
Also known as alkali-resistant fiberglass, it is a pure inorganic fiber used as a reinforcing material in fiberglass reinforced concrete. Under certain conditions, it can even replace steel and asbestos.
1.7.6 Fiberglass E-CR Glass
This is an improved boron-free and alkali-free glass. Because its water resistance is nearly 10 times higher than that of alkali-free fiberglass, it is widely used in the production of water-resistant products. Furthermore, its acid resistance is extremely strong, making it dominant in the production and application of underground pipelines. Besides the more common fiberglasses mentioned above, scientists have now developed a new type of fiberglass. Because it is boron-free, it meets people's pursuit of environmental protection. In recent years, another type of fiberglass has become popular: double-glass fiberglass, which can be found in current glass wool products.
1.8 Identification of Glass Fibers
Identifying glass fibers is quite simple: immerse the glass fibers in water, heat until the water boils, and keep this process for 6-7 hours. If the warp and weft directions of the glass fibers become less compact, then it is high-alkali glass fiber. Glass fibers can be classified in many ways according to different standards, generally based on length and diameter, composition, and properties.