The current work focuses on fundamental investigations regarding the barrier properties of grafted PVOH layers produced by the Transfer Method. The layers (or papers) used for the different experiments were produced and grafted during the course of this work. Papers with different types of PVOH (different Mowiol types) were produced by coating. Experiments using different parameters (temperature, reaction duration, and concentration) were performed using the Transfer Method. Contact angle measurements and Cobb60measurements were carried out on the grafted and untreated PVOH layers. Furthermore, the water vapour transmission rate of the PVOH layers was determined. The results of this work showed that the method of chromatogeny or chromatogenic chemistry improves the water vapour barrier properties of grafted PVOH layers enormously.

This study investigates chemical grafting with fatty acid chlorides as a method for the surface modification of hydrophilic web materials. The resulting changes in the water repellence and barrier properties were studied. For this purpose, different grades of polyvinyl alcohol (PVOH) were coated on regenerated cellulose films ("cellophane") and paper and then grafted with fatty acid chlorides. The PVOH grades varied in their degree of hydrolysis and average molecular weight. The surface was esterified with two fatty acid chlorides, palmitoyl (C16) and stearoyl chloride (C18), by chemical grafting. The chemical grafting resulted in water-repellent surfaces and reduced water vapor transmission rates by a factor OPEN ACCESSPolymers 2014, 6 2765 of almost 19. The impact of the surface modification was greater for a higher degree of hydrolysis of the polyvinyl alcohol and for shorter fatty acid chains. Although the water vapor barrier for palmitoyl-grafted PVOH was higher than for stearoyl-grafted PVOH, the contact angle with water was lower. Additionally, it was shown that a higher degree of hydrolysis led to higher water vapor barrier improvement factors after grafting. Furthermore, the oxygen permeability decreased after grafting significantly, due to the fact that the grafting protects the PVOH against humidity when the humidity is applied on the grafted side. It can be concluded that the carbon chain length of the fatty acid chlorides is the limiting factor for water vapor adsorption, but the grafting density is the bottleneck for water diffusing in the polymer.

Natural cellulose fibres have been employed for packaging applications for a long time. Their use, however, has been hampered by their high hydrophilicity and their moisture sensitivity. It has, thus, been proposed to circumvent this problem through the hydrophobic modification of their surface thanks to the use of molecular grafting approaches. * The authors are pleased to acknowledge the important contribution of Dr. David Guerin and Matthieu Schelcher from CTP (Centre Technique du Papier) in Grenoble for the fatty acids HPLC analysis.We are also indebted to the European Union for its financial support through the collaborative research program, Phycello (http://ec.europa.eu/research/industrial technologies/articles/article 387 en.html) and for a Marie Curie Grant to one of us. Brought to you by | University of Connecticut Authenticated Download Date | 5/26/15 11:19 PM reagent migration and reaction. Grafting densities were performed by using the HPLC technique.The results obtained through the use of this test allowed a better understanding of chromatogenic chemistry phenomenon and an identification of the main parameters which affect the process: the nature of the reagent, the temperature, the reaction time, the nature of the substrate, etc. We have more particularly shown that the diffusion and grafting yields were maximal for a specific temperature which increases with the boiling point and therefore with the chain length of the reagents. We have proposed that this temperature should correspond to a compromise between the diffusion and reactivity properties of the reagent, its evaporation and its degradation by hydrolysis.