Barrier Capacity

Changes in local permeability due to the molecular level of transformation in a polymeric matrix in the presence of silicate layers has been considered as another factor affecting barrier properties in nanocomposites, according to Gusev and Lusti [128]. In agreement, Sinha Ray et al. [118] repOTted a higher O2 barrier capacity for nanocomposite films formed by layered silicates capable of reacting with the PLA matrix. Chowdhury [127] reported a better interaction at the MMT/ PLLA than the MC/PLLA interface, and as a result, they proposed that a stiffer local environment may also contribute to the better barrier properties of MMT-PLLA composites compared to those of MC-PLLA composites. 

With respect to aroma compounds, PLA presents barrier properties similar to those of conventional polymers. However, there is a lack of information on the interaction between these organic volatiles and PLA and on how gas and water vapor barrier capacities are affected during and after volatile-polymer interaction. Our research group has observed some effects after carrying out initial trials that indicate the need for further studies. 

It shows good oxygen barrier capacity and UV resistance, but has poor resistance to acids and bases. 

As mentioned above, the most abundant lipids in the stratum comeum intercellular space are cholesterol and ceramides. Cholesterol is the most abundant lipid species in the stratum corneum intercellular space. It has been reported that cholesterol is likely to be a key component that determines the barrier capacity for stratum comeum. It has also been reported that cholesterol gives plasticity and increases chain mobility of lipids in the gel and crystalline states (68, 69). Basically, by stabilizing single and coherent gel phases, cholesterol seems to promote the desirable effects of protecting the barrier capacity of stratum corneum against the sudden change in environmental conditions. 

Take an apparently simple example. Skin is a multilayered tissue, the outermost layer being the epidermis, which is indeed composed of four distinct layers the one directly in contact with the outside world is called the stratum comeum, and going inside the body, we have the stratum granulosum, the stratum spinosum and the stratum basale. We now know that skin barrier capacity is contfolled by lipids fdling the extracellular space of the skin s surface layer—the stratum comeum. 

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