Hybrid polymers, barrier coatings

TABLE 21 -5. SUMMARY OF IMPORTANT REFERENCE DATA AND PROPERTIES OF NEW HYBRID POLYMER BARRIER COATING MATERIALS (FOR SEE FIG. 21-11)... 

In order to obtain hydrophobic materials, fluorosilanes in quantities of < 1 mol% were added to the coating sols (see Fig. 21-11, compounds 9,10). This has a favorable effect on the barrier properties to polar permeants such as water vapor (PES/SiO /hybrid polymer WVTR 0.18 g/m d PES/SiO /hydrophobic hybrid polymer WVTR 0.03 g/m d, layer thickness in both cases 4 fim). 

Figure 21-16. Migration barrier coating against plasticizers, hybrid polymer coating on PVC, concentration of plasticizer 33 wt%, plasticizer octylphthalate.

Secondly, at the interface of the MeO and the hybrid polymer, covalent Me-O-Me bonds can be formed leading to an area ofhigh inorganic network density, thus producing an additional barrier effect. Both models are confirmed by the fact that the OTRs of the BOPP/SiO /hybrid polymer film does not depend on the thickness of the hybrid polymer coating. 

Thirdly, experiments have shown that the application of an initial hybrid polymer coating, acting as a planarizing layer (see Fig. 21-22(c)), has a positive influence on the barrier properties of the overall PET/MeOj laminate (see Table 21-4). 

TABLE 21 -4. OTRs OF PET FILMS COATED WITH HYBRID POLYMER AND AIO (BIF BARRIER PROPERTIES OF THE UNCOATED SUBSTRATE RELATIVE TO THE COATED SUBSTRATE)... 

Polymer-clay nanocomposites (PCN) are a class of hybrid materials composed of organic polymer matrices and organophilic clay fillers, introduced in late 1980s by the researchers of Toyota (Kawasumi, 2004). They observed an increase in mechanical and thermal properties of nylons with the addition of a small amount of nano-sized clays. This new and emerging class of pol miers has found several applications in the food and non-food sectors, such as in constmction, automobiles, aerospace, military, electronics, food packaging and coatings, because of its superior mechanical strength, heat and flame resistance and improved barrier properties (Ray et al., 2006). 

The hybrid coating materials were applied to various polymer films, some of which already had inorganic oxide barrier layers (MeO SiO , AiO ). Selected results for BOPP and PET films are given below. The thickness of the hybrid layers varied between 1 and 5 /trm, whilst the thickness of the inorganic oxide layers are normally between 30 and... 

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