Humidity regulation

Salt Containing Films. Novel humidity regulating polymer composite films contain salts such as calcium chloride and sodium chloride as active substances. These reversibly absorb water vapor. Due to that property they can stabilize the relative humidity in their environment. In packaging related applications undesired effects of humidity can be avoided thereby

Influence of plasticizers on the mechanical and barrier properties of cast biopolymer films

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

Gas permeabilities of polyurethane films for fresh produce packaging: Response of O2 permeability to temperature and relative humidity

Thermoplastic shape memory polyurethane (SMPU) polymers were synthesized, cast to films, and their gas barrier properties were characterized. In addition, performance of an optical method was assessed by measuring oxygen permeability (PO2) of the films. PO2 of the SMPU film was at least two times higher than that of low density polyethylene (LDPE and increased at higher relative humidity. Permselectivity (PCO2/PO2) of the SMPU film was 15, which is approximately three times higher than for LDPE. The film absorbed circa 18% water vapor at 98% relative humidity. The optical method agreed very well (maximum 20% deviation) with a standard carrier gas method in PO2 measurement. Overall our results show that SMPU is an attractive polymer for fresh produce packaging

A mathematical model for tailoring antimicrobial packaging material containing encapsulated volatile compounds

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

Water Repellence and Oxygen and Water Vapor Barrier of PVOH-Coated Substrates before and after Surface Esterification

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 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

Identification of polybutene-1 (PB-1) in easy peel polymer structures

Polybutene-1 (PB-1) is dispersed via extrusion in polyethylene (PE) based sealing layers to achieve ‘easy peel’ properties. PB-1 forms islands there. During opening of packagings with such sealing layers, cohesive fracture occurs within the sealed area along these PB-1 islands. The aim of this study was to find suitable methods for the identification of PB-1 in such PE based sealing layers. For this investigation PE-LD films with 3, 6, 9, 12 and 15 wt.-% PB-1 were extruded. FTIR spectroscopy and FTIR microscopy are suitable methods to identify low concentrations PB-1 in PE-LD layers in opposite to GC-FID and DSC. Raman spectroscopy is a suitable method to distinguish PB-1 from PE-LD

Labbag® - a versatile bag-based cultivation system for expansion, differentiation and cryopreservation of human stem cells

Novel approaches in regenerative medicine and tissue engineering are highly promoted by human induced pluripotent stem cells. Typical workflows include the expansion, differentiation and/or cryopreservation of these cells. Often, the differentiation, cytotoxicity tests or disease modelling rely on multicellular aggregates. Here, we present the novel bag-based system “Labbag®” to address workflows required for these applications. As a unique feature, the Labbag® provides a chemical spot pattern to allow the formation of several hundreds of hanging droplets within a few seconds with standard laboratory equipment. In this study, we describe the general concept of the Labbag® and show aggregate formation of stem cells as first stem cell workflow successfully transferred