The raw materials for all FRP products are glass fibers. Most of the distinction between glass fiber quality comes from its own technical indicators. The well-known alkali content, monofilament diameter, water content and the like are all reference standards. Below we will introduce the technical parameters related to glass fiber from these aspects.
1, alkali content
In daily production, everyone knows that glass fiber is divided into alkali-free and medium-alkali, but how to define it, I believe many of my friends are not very clear. This is related to the problem of a base content, mainly referring to the content of alkali metal oxides.
Glass fiber has the difference of no alkali, medium alkali and high alkali. It involves the problem of alkali content, and the alkali content refers to the content of alkali metal oxide.
1 alkali-free glass fiber (sodium oxide 0% to 2%, belonging to aluminoborosilicate glass)
2 medium alkali glass fiber (sodium oxide 8% ~ 12%, is a soda lime silicate glass containing boron or boron)
3 high alkali glass fiber (more than 13% sodium oxide, is a soda lime silicate glass)
It is often said that the alkali-free is not really alkali-free, but the alkali metal content is less than 2%. High alkali has been eliminated for many years, but some areas are still in use. Generally used in composite materials are alkali-free and medium-alkali glass fibers. For example, glass chopped strand mats, plaid fabrics, usually only medium and alkali-free products.
2, monofilament diameter
The diameter of the monofilament of the glass fiber is generally several micrometers to twenty micrometers, which is equivalent to 1/20-1/5 of a hair strand.
Crude fiber: The diameter of the monofilament is generally 30 μm.
Primary fiber: its monofilament diameter is greater than 20 μm.
Intermediate fiber: monofilament diameter 10-20μm.
High-grade fiber (also known as textile fiber): its monofilament diameter is 3-10μm.
Glass fibers having a monofilament diameter of less than 4 um are also referred to as ultrafine fibers. The different diameters of the monofilaments not only affect the properties of the fibers, but also affect the production process, yield and cost of the fibers. Generally, 5-10 um fiber is used as a textile product, and 10-14 um fiber is generally suitable for roving, non-woven fabric, glass fiber chopped strand mat, and the like.
The diameter of the monofilament is determined by the pore size and drawing speed of the platinum leakage plate. Generally, the finer the fiber, the more expensive the fiber. On the one hand, it is related to the production process is difficult and the yield is low; on the other hand, the finer the monofilament, the more the coupling agent per unit area.
3, tex (tex)
Tex (tex), referred to as special, is a linear density unit, also known as the number. Refers to the weight of the 1000 m long yarn at the specified moisture regain, tex = g / L * 1000, where g is the weight of the yarn (or silk) (g), L is the length of the yarn (or silk) (m) . It is a fixed length unit, the larger the weight, the thicker the yarn.
Each bundle of fiber strands consists of hundreds or even thousands of monofilaments, so in simple terms tex is the thickness of a single strand of glass fiber yarn. Our common 1200, 2400, and 4800 numbers refer to the linear density of yarns, that is, the weight of yarn per kilometer is 1200g, 2400g, and 4800g.
4, moisture content
Glass fiber needs to strictly control the water content during the production process. According to the industry standard, the moisture content of glass fiber should be less than 0.2%. We often ignore this parameter in daily production. Due to the imperfect storage conditions in most factories, the randomly placed glass fiber is easy to absorb moisture, which will cause the moisture content to be too high and affect the curing of the resin.
This phenomenon requires special attention when returning to the South in the South. The glass fiber can be slightly baked before use to control the moisture content.
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