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.

The potential of biopolymers for packaging application is often limited due to their poor processability. In this study, the effect of commonly used plasticizers on the properties of different cast biopolymer films is investigated. This enables a valuation of the potential of different biopolymers as packaging materials and an estimation of the effectiveness of plasticizers for certain biopolymer systems. Polysaccharides (corn starch and alginate) and plant proteins (wheat gluten and pea protein) were tested as film materials. To improve the processability by decreasing the brittleness of these cast biopolymer films, glycerol (Gly), sorbitol (Sor), and triethanolamine (TEA) were added as plasticizers. The structural, mechanical, and barrier properties to water vapor and oxygen were characterized in order to study the effectiveness of the plasticizers and their respective influence on the film properties. The mechanical results show there was a plasticizing effect with all the plasticizers, but the influence on the barrier properties depends on the specific plasticizer: While glycerol (Gly) leads to an increase in water vapor and oxygen permeability (OP), Sor leads to almost constant, and TEA even to decreased OP of the biopolymer films. Therefore, careful selection of the plasticizer allows biopolymer films with improved processability and high or low permeabilities to be manufactured

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A mathematical model describing the water content-dependent release of an antimicrobial agent (allyl isothiocyanate (AITC)) from a bio-based film to the packaging headspace was implemented. The system was characterised experimentally by assessing release kinetics and diffusivities. The model was validated by comparing simulations to experimental data. In spite of the high complexity of the system coupling moisture and antimicrobial diffusion within the packaging material and then release into headspace, the presented model provides a good enough reproduction of experimental conditions. A sensitivity study conducted on the model showed that the release kinetics of the antimicrobial agent were the most influential parameters, and that the diffusivity of moisture and AITC within the film have negligible impact. The model was then used to demonstrate the efficiency of such packaging for shelf-life optimization as it successfully inhibited the growth of bacteria. This work provides a framework that can be used for decision support systems

The incorporation of salt in a polymer matrix could potentially achieve a humidity-regulating film system of high porosity for packaging applications. In this study, sodium chloride (NaCl) powder was used as a model substance for humidity-regulating fillers in polypropylene films. A polypropylene homopolymer was extrusion-blended with NaCl at concentrations of 0.03, 0.06, 0.12, and 0.24 g NaCl·g film-1. Films were produced and were subsequently oriented mono and biaxially. At stretching ratios (SRs) of between 2 and 25 a porosity of 20% v/v to 50% v/v was achieved. The porosity positively correlated with the SR. An empirical model based on ellipsoids that approximated the correlation between the SR and the porosity was developed. This correlation offers a basis for further studies on other salt-polymer systems that have undergone differing orientation processes