(4.27), we obtain. In the PVAC coatings, decrease of adhesion to the substrate during thermal aging is observed. For PVAC coverage k2=4.0531×10−4 s−1. 4.4): Figure 4.4. We have analyzed the change of the function characterizing the influence of hereditary factors on the properties of the coatings, depending on the type of coating and aging.
Table 4.6. Water-based sealers are gaining wider acceptance because of the increased handling problems associated with polymer solutions based on hydrocarbon solvents. Strong autumn rains can wash out water-soluble compounds and cause mechanical damage to the coatings.
The experimental and calculated data allow us to understand in more detail the mechanism of aging of coatings and to establish the factors that regulate the rate of structure-forming and destructive processes, which will improve the life of coatings. Carrying out calculations for other coatings, we have (Table 4.10).
After 10 days of testing, the change in the adhesion strength of coatings is 0.023 MPa/day and shine 0.1%/day.
Corrections? The calculation shows that the values of A and B for PVAC coatings are −4 and −1.1856 and for the lime −6 and −2.1093, respectively. According to Refs. They are thermoplastic solids with a range of molecular weights, typically supplied in the form of small beads. Experience shows that it can not be asserted that the intensity of the change in the properties of the coating is the same at different stages of the active stage of damage accumulation.
Analysis of the experimental data (Fig. Table 4.7. They are accompanied by a slight decrease in shine and a strong change in the adhesion strength of organosilicon KO-168 coatings, for example. Thus, in the active stage of damage accumulation, significant changes occur in the structure and properties of the coating (color change, gloss, cracking, etc.).
The total effective activation energy of aging of the coating after 1200 hours of moistening with a 10% loss of brightness is U=5.l59 kJ/mol for PVAC, and for coating based on AK-111 paint, 8.39 kJ/mol.
where Δm is the change in mass of the coating, t is the time and k is a constant. 4.11A) shows that during the first period of aging the swelling processes predominate.
Don’t let the complicated name fool you: polyvinyl acetate is another term for wood glue, white glue, carpenter’s glue, and school glue. Gong et al. Polyvinyl acetate (PVAc), a synthetic resin prepared by the polymerization of vinyl acetate. The coefficients α1,α2,α3 characterize the rate of change of the controlled parameter at different stages of coating aging. An ideal adhesive for bookbinding and paper projects, this solution dries clear and fast. Consider the aging process of the coating when moistened by changing the operational properties indicators.
Accounting for the balance of the substance at diffusion leads to the equation, The hydrolysis reaction of the polymer binder has the first order. Such adhesive is available for bonding wood, paper and fabric etc.
For AK-111 coatings after 120 hours of aging, the decrease in mass m is 55%, for coatings PVAC- 45%.
Thermal aging causes a decrease in the elastic modulus of the coatings over time. Further reduction of cohesive strength indicates the beginning of the processes of destruction in coatings. Thus, after 120 days of humidifying, the adhesive strength of the PVAC covering becomes as much as 66% (after drying) of the initial value. Polyvinylpyrrolidone, 4. These data show that at the first moment of moistening in the silicone-organic coating of KO-168 swelling processes prevail. PVA is used as an emulsion adhesive for bag, sack and carton making. After curing which the samples were subjected to moistening-drying. (4.25) can be represented in terms of the change in the indices characterizing resistance of coatings. Function h(τ) is usually approximated by the equation.
This indicates that a change in the shine (characterizing the еhe destruction of coatings) is associated with the loss of mass in the surface layer 1 μm thick.
For the account of a prehistory of aging, the function of forgetting K(t,τ) is used.
It is seen (Fig. where h(τ) is the function describing the aging process of the coating. US2614087A US179093A US17909350A US2614087A US 2614087 A US2614087 A US 2614087A US 179093 A US179093 A US 179093A US 17909350 A US17909350 A US 17909350A US 2614087 A US2614087 A US 2614087A Authority US United States Prior art keywords weight polymerization monomer water vinyl acetate …
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