Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов
years and are widely available in international standard testing organizations such as ASTM and ISO. Many academic laboratories have also developed more sophisticated tests. One example is the measurement of composite critical fiber length [18]. As defined by Eq. (5), the critical fiber length (lc) is the minimum fiber length at which fibers with given diameter d reach their ultimate tensile strength σfu and the matrix/fiber interface experiences a maximum interfacial shear stress τy [18]. When l > lc, an increase in interfacial adhesion will result in a decrease in critical fiber length and may lead to improvements in other properties such as impact strength in certain resin systems. However, the sizing may also act to protect the fiber from surface damage and defects in addition to providing improved adhesion. In that case, reduction of fiber surface damage would lead to an increase in the critical fiber length by increasing σfu. Interestingly enough when l > lc, and the composite is stressed to failure, then the fiber will break at regular intervals of lc within the composite. This result can be used to estimate the interfacial shear stress:
(5)
This example also serves to illustrate that broader conclusions from micromechanical experiments should consider that different outcomes may result depending upon material selection. The most common material options include chopped or short fibers vs. continuous fibers and thermoset vs. thermoplastic resin systems, which of course complicates the task of the sizing chemist in product development.
It remains for the sizing chemist to complete the establishment of the final formulation from a virtually limitless palette of film formers, process aids, and modifiers to deliver the desired performance of the fiberglass as a commercial product. Commercially, the resultant amount of sizing on the fiberglass surface is typically in the range of 0.3–1.5 wt % of the dry fiberglass.
An excellent in‐depth review of the complexity of this field from the sizing chemists' point of view can be found in Thomason's book, Glass Fibre Sizings: A Review of the Scientific Literature [19].
Table 5 Common organosilanes.
| Chemical name | Structure | Class |
|---|---|---|
| γ‐Aminopropyl trialkoxy silane | (RO)3Si–(CH2)3–NH2 | Amine |
| γ‐Methacryloxypropyl trialkoxy silane | (RO)3Si–(CH2)3–OOC(CH3)C=CH2 | Methacryl |
| γ‐Glycidyloxypropyl trialkoxy silane | (RO)3Si–(CH2)3–O–CH2CHCH2O | Epoxy |
| Vinyl trialkoxy silane | (RO)3Si–CH=CH2 | Vinyl |
| R = CH3CH2– or CH3– | ||
4 Markets and Applications
4.1 Global Glass Fiber Reinforced Polymeric Composite Markets
The glass fiber reinforced polymeric composites market will grow from about $18 000 million in 2010 to an estimated $30 000 million in annual shipment value by 2017 according to a recent survey. These composites find many applications in commercial markets globally. A breakdown by major regions of the world is shown in Figure 5 for the Americas, EMEA (Europe, Middle East, and Africa), and Asia Pacific.
Construction and transportation dominate the Americas market place for GRP composites, with construction taking the largest share. Other segments are more or less equally distributed among industrial, oil and gas, and wind‐turbine blade applications, along with numerous smaller segments. In the EMEA region, construction and transportation are also the largest markets, but here the leading industry is transportation. The wind‐turbine blade segment is much higher in Europe, and the other segments hold similar shares as seen in America. In the Asia Pacific region, once again transportation and construction combined are the largest segments. In this region, however, electronics and industrial markets are more prominent, combined with a large “other” segment driven by the large variety of needs and applications in the region. The electronic segment is particularly strong, reflecting the strong position of the PWB industry and its supply chain of E‐glass fiber, fabric, and laminators in the Asia Pacific region.
Generally, GRP composite materials are classified into two categories: thermoplastic and thermoset. Thermoplastic GRP products most commonly use resins based on polypropylene, polyamides (nylon 6 and 6,6), polyesters (polybutylene terephthalate, polyethylene terephthalate), and many other specialized thermoplastic polymers. Thermoset GRP products commonly use resins based on epoxies, unsaturated polyesters, and vinyl esters, with smaller but growing applications use phenolic and urethane‐based resin systems as well as other specialty resins. Thermoplastic resins generally exhibit higher ductility and impact resistance, while thermoset resins offer better strength and modulus and higher thermal stability. There are many new developments underway in both processing and resin chemistry that often blur the traditional divisions between thermoplastic and thermoset‐based glass fiber composites. The glass fiber industry will continue to be at the forefront in supplying reinforcement solutions for these new developments.
Thermoplastic automotive applications include window frames, automobile body components, dashboard sections, and bumper beams. Typical processes for combining fiber forms with thermoplastics resins as intermediates for molding of final parts include extrusion compounding of short fibers, glass‐mat thermoplastic sheet, and long‐fiber thermoplastic compounding.
Major thermoset products include composite pipes for oil and gas, marine, and industrial applications; wind‐turbine blades; flue‐gas desulfurization tanks and towers; PWB; boats; construction beams and structures; composite leaf springs; and numerous sporting‐goods applications. Other components are countless and limited only by the imagination. Typical conversion processes for thermoset composites include filament winding, pultrusion, resin transfer molding, hand lay‐up, spray deposition, continuous laminating, centrifugal molding, sheet molding compounds, and bulk molding compounds.
Glass fibers can also be used as a reinforcement for cement structures, in many cases with AR‐glass fibers as already noted. Like E‐glass, it also finds utility in some of these applications where short‐term strength is the major requirement. Some geotextile reinforcements also use E‐glass as a base in a coarse mesh form. Chopped glass fibers are the predominant reinforcement for asphalt roofing shingles, primarily in North American markets (Source: fiber glass market study, PPG, 2014).
4.2 Emerging GRP Composite Markets
Traditional E‐glass still dominates total glass fiber volume produced around the world, with a well‐established history of delivering value in many markets for more than 70 years. This trend is expected to continue because of the E‐glass value in use and the maturity of the manufacturing technology. Along with its variants, E‐glass will continue to be the material of choice in most applications. Fiber manufacturers will continue to move toward more environmentally compliant variants, and product development scientists will continue to tailor the glass composition, form factor,