Aging, of glasses

Pfund, A.H. (1946). The aging of glass surfaces. Journal of the Optical Society of America 36 95-99. 

Figure 4. Oven aging of glass- and mineral-filled PPS in air...

E.P. Gellert, D.M. Turley, Seawater immersion ageing of glass—fibo- reinforced polymer laminates for marine applications. Compos. Part A—Appl. Sci. 30. 1259-1265 (1999)... 

Bigg, D.M., Kanellopoulous, V. Physical Ageing of Glass-Fiber-Reinforced Nylon 6,6 in Automobile Underhood Parts, Journal of Thermoplastic Composite Materials 8 (1995) 8... 

All expressions show a linear variation of the stress intensity factor K with the applied force F. Interestingly on loading the specimens, the crack propagation can be measiu-ed in a domain where K < K, that is, before catastrophic feiliu-e. This domain is referred to as the subcritical domain. Subcritical crack growth has important implications on the ageing of glass, that is, its behavioiu- with time. This issue is addressed extensively in Chapter 9. It should also be noted that an indentation method may be employed to determine toughness when small quantities of material are available. This issue is discussed in more detail in Chapter 8. 

Ageing of glass may also be observed because of the physical transformation of internal defects like metastable nickel sulfide (NiS) inclusions. These imdergo a slow transformation at room temperature from a dense to a less dense phase. These inclusions can be of different compositions, namely NiS, Nii or M7S6 (Barry and Ford, 2001 Yousfi et al., 2010), with sizes in the range 1-100 pm (Barry et ah, 1998). S comes from the raw materials and combustion, while Ni comes from the abrasion of the tools used for batching (Chapter 10). In fact, it remains impossible to eliminate these NiS inclusions. Their content is estimated at about 1 particle for 10 tons of glass. 

A. Bentur and S. Diamond, Effect of aging of glass fibre reinforced cement on the response of an advancing crack on intersecting a glass fibre strand , int. J. Cem. Comp Ltwt. Concr. 8,1986, 213-222,... 

Table 12. Color change, mass loss and oxidized layer thickness at aging of glass-filled, stabilized PPA-2 compoundings...

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