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Flexible packaging has many advantages in the food industry, arising from low weight, formability, multilayer complexity and cost. Heat sealing is a very efficient technique to close flexible food packaging. Currently, many thermoplastic materials are used in seal layers. A seal can be formed when these materials are heated and brought into contact; thereafter, polymer chains diffuse across the seal interface and entangle. Hydrogen bonds, polar and ionic interactions are molecular forces that can come into play, depending on the thermoplastic materials that are used in the seal layer. Bonds between identical polymers, referred to as autohesion, are formed in pouch applications (e.g., horizontal and vertical form-fill-seal packages). In lidding applications, the flexible film is sealed to a rigid cup, tray or bottle, whereby bonds can be formed between non-identical polymers because the materials are often provided by different suppliers. All heat seal technologies imply heating of seal layers but differ in the heating principle. In the food industry and in most scientific seal studies, the seals of mono-and multilayered packaging are mainly formed by conductive heating. Recently, the use of emerging technologies, such as ultrasonic and laser heating, is increasingly described in recent papers. Applied seals are characterized by strength after a specified cooling time. Immediately after heating, this strength is referred to as hot tack. A good seal performance is crucial to guarantee food safety and quality. Besides strength, tightness is important to prevent food degradation, caused by microorganisms and external gases, and to keep aromatic gases inside the package. This review aims to give a literature overview that can support stakeholders in the food industry to improve and optimize the material selection in flexible packaging , in order to obtain seals with desired tightness and strength. Heat seal studies on materials and seal technology of flexible food packaging, such as pouches and lidding films, are considered. Scientific data are categorized from a materials' perspective, based on chemical structure, which is revealed by chemical and thermal analysis. A majority of the seal studies is categorized in a first section on polyolefins as seal layers. The following sections describe the seal functionality of (i) ethylene copoly-mers, such as ionomers; and (ii) polyesters, such as poly (ethylene terephthalate), pol (lactic acid) and poly (butylene succinate). The role of plasticizers, fillers and other

Ethylene vinyl alcohol copolymer (EVOH) is one of the most commonly used barrier materials in a broad range of applications. Its outstanding gas barrier properties have already been widely investigated for oxygen (O2). However, EVOH is also gaining more attention as a barrier material against other gases and organic substances such as aromas, flavours, fuels, chemicals and even as a functional barrier. The objective of the research is to determine the barrier properties of EVOH against a selection of gases, i.e. O2 and nitrogen (N2) in varying conditions of relative humidity and temperature, and organic substances such as mineral oil saturated hydrocarbons (MOSH), mineral oil aromatic hydrocarbons (MOAH) and other non-intentionally added substances (NIAS). The permeation of the gases was determined by an online permeation setup based on the equal pressure method and consists of a permeation system connected to a gas chromatography (GC)-based detection system. A similar setup with GC-mass spectrometry (MS) was used for the organic substances. Additionally, an off-line method using a spiked donor taped on barrier and receptor were used to perform experiments modelling mineral oil migration from cardboard into foodstuff with EVOH acting as a functional barrier. The concentration of the mineral oil components was analysed by GC-MS. The research shows that EVOH is a multi-functional barrier against both gases such as O2 and N2, as well as a functional barrier against mineral oils. Three grades containing 32, 44 and 48 mol% ethylene show good O2 and N2 barrier properties and outperform other polymers such as polyethylene (PE), polypropylene (PP) and polyamide 6 (PA 6) by several orders of magnitude. Moreover, only 3 m EVOH containing 27 or 32 mol% ethylene is required as functional barrier against mineral oils and other NIAS migrating from paperboard to protect foodstuff with a shelf-life of over 2 years.

A method is presented to apply solid powder/granulate contamination (ground coffee, blood powder) in between the heat conductive seals of flexible packaging materials. A response surface method is tested and validated to optimize seal strength of heat conductive sealing with and without solid contamination. In this study, a maximal seal strength is defined as optimal. Using these methods, three typical packaging films with varying seal layer composition (metallocene LLDPE, plastomer and sodium ionomer) are maximized towards contaminated seal strength. Contamination caused a decrease in seal strength and narrowed down the process window (seal temperature and time combinations) in which at least 90% of the maximal strength is obtained. The influence of seal layer composition on the clean and solid (ground coffee, blood powder) contaminated seal performance (seal strength, process window and leak tightness) was evaluated. The film with the plastomer based seal layer outperformed the other films with respect to the width of the process window. It also reached a higher seal strength and a higher amount of leak tight seals (evaluated with the dye penetration test) after optimization. The hot tack test was evaluated as predictive test for the contaminated seal strength. The results of this study do not support an indicative relationship. Agentschap Innoveren & Ondernemen (VLAIO-TETRA nr. 150817)) and German government (German Federal Ministry for Economic Affairs and Energy (BMWi, IGF project no. 172 EBR))

A method is presented to apply solid powder/granulate contamination (ground coffee, blood powder) in between the heat conductive seals of flexible packaging materials. A response surface method is tested and validated to optimize seal strength of heat conductive sealing with and without solid contamination. In this study, a maximal seal strength is defined as optimal. Using these methods, three typical packaging films with varying seal layer composition (metallocene LLDPE, plastomer and sodium ionomer) are maximized towards contaminated seal strength. Contamination caused a decrease in seal strength and narrowed down the process window (seal temperature and time combinations) in which at least 90% of the maximal strength is obtained. The influence of seal layer composition on the clean and solid (ground coffee, blood powder) contaminated seal performance (seal strength, process window and leak tightness) was evaluated. The film with the plastomer based seal layer outperformed the other films with respect to the width of the process window. It also reached a higher seal strength and a higher amount of leak tight seals (evaluated with the dye penetration test) after optimization. The hot tack test was evaluated as predictive test for the contaminated seal strength. The results of this study do not support an indicative relationship. Flemish (Agentschap Innoveren & Ondernemen (VLAIO-TETRA nr. 150817)) and German government (German Federal Ministry for Economic Affairs and Energy (BMWi, IGF project no. 172 EBR))

VLAIO Baekeland & Kuraray EVAL Europe

Recent studies have shown advantages of ultrasonic sealing over heat conductive sealing, namely sealing through contamination, decreased energy consumption, no need for thick peel layers. Up to now there is no efficient systematic methodology to determine the optimal settings for the ultrasonic sealing of flexible films. Besides that, almost no literature is available about the specific permeation of the seal area in a package. In this study, seal strength, compaction and/or energy consumption are investigated as determining parameters in optimizing the ultrasonic sealing (USS) performance of flexible packaging films. These parameters are used to evaluate the ultrasonic seal performance of polyolefin monolayer and multilayer materials – 60 μm monolayer polyethylene (PE) and polypropylene (PP) polyolefin films, laminated films of 24 μm polyethylene terephthalate (PET) or oriented polyamide (OPA) with 40 μm PE seal layer. These materials are sealed with a 35 kHz ultrasonic sealer at 15 different settings of force, amplitude and time to calculate the optimum settings and to evaluate the ultrasonic seal performance. Besides that, the oxygen transmission rate (OTR) of ultrasonically sealed commercial pouches and flat films with and without the presence of a high barrier layer, ethylene vinyl alcohol (EVOH) or aluminum (Alu), in PET laminates with a PE sealing layer, is evaluated. This is measured with a Mocon OX-TRAN® device. The optimization method is validated and ready for implementation. Metallocene linear low density polyethylene with C6 branches (mLLDPE-C6) and random copolymer polypropylene (raco PP) are selected as ultrasonic best performing polyolefin monolayers because of respectively mainly a lower energy consumption and a broader seal window compared to other tested films. PET was selected as the best performing laminate for ultrasonic sealing because of the lower energy consumption compared to OPA laminates. Ultrasonic seal strengths of OPA and PET laminates were similar. Strong ultrasonic seals have no impact on the OTR. This is illustrated by the OTR-results of high barrier PET/Alu/PE pouches at normal and extreme ultrasonic settings, respectively 0.66±1.56x104 and 0.48±2.9x10-4 cc/package.day. This research is done within the IWT-TETRA project “ULTRASEAL: The potential of ultrasonic sealing in packages” funded by VLAIO.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) belongs to the family of biobased and biodegradable polyhydroxyalkanoates (PHA). Although the general properties of PHBHHx are very promising for packaging applications amongst other PHA, the crystallization rate is very slow. This research focuses on the modification of PHBHHx using nucleating agents and fillers to augment its applicability as potential food packaging material. PHBHHx is modified using talc, organomodified montmorillonite clay (OMMT), and unmodified and surface-modified zinc oxide (sZnO). The samples are compression molded and analyzed for their crystallization, thermal, dispersion, colorimetric, opacity, barrier and tensile properties. PHBHHx presents a moderate barrier for O2 (8 cm3 mm/m2 day atm) and CO2 (40 cm3 mm/m2 day atm) and a fairly low water vapor permeability (1.4 g mm/m2 day). The latter could be useful, e.g. to protect a moisture-sensitive inner oxygen barrier layer. Ultra-fine talc is identified as an efficient nucleating agent. The non-isothermal crystallization half-time reduces with 97% at 70°C by adding 2 wt% talc. The gas permeability coefficients of the talc-filled composites remain within the same range as virgin PHBHHx. The Young’s modulus increases with 13% at 2 wt% talc loading, whereas tensile strength and elongation at break remain fairly constant. Adding 10 wt% OMMT reduces the O2, CO2 and water vapor permeability coefficients by 47%, 42% and 37% respectively. Unfortunately, the nanocomposites are more brittle upon increasing OMMT concentrations, with a 44% reduction of the elongation at break at 10 wt%. Adding up to 5 wt% sZnO nanorods shows fine dispersions in PHBHHx, but does not significantly affect the gas permeability. The Young’s modulus increases with 7%, whereas the elongation at break reduces by 19%. Despite the opacity increases from 11.5 to 15.9% by adding 1 wt% sZnO, this modification provides UV shielding, which can be a valuable feature for food packaging. Additional research is necessary to further optimize and combine selected additives in PHBHHx.

Introduction Packaging integrity is critical for the purpose of food quality, food safety and consumer trust. In 58% of the cases, seal contamination is the main reason for defective packaging (Dudbridge, M.; Turner, R. (2009): Seal integrity and the impact on food waste. WRAP. ). In this research the effect of a channel leak in the seal area on the preservation of ham sausage is studied. Materials and methods A commercial food packaging barrier film (PET/PE-EVOH-PE 12/50) from Amcor Flexibles (Belgium) is sealed by heat conductive sealing into pouches. 40 three-sided seal pouches (15 x 20 cm), are studied in a food preservation test. In 20 of these pouches one channel leak with an approximate diameter of 50 µm is induced by adding, and after sealing, removing a human hair in the seal area. All 40 pouches are packed with sliced ham sausage and finally sealed under modified atmosphere. All samples are stored at 4°C with an alternating 12 hours of light and 12h of darkness. Each day of analysis three samples of each package (with and without channel leak) are tested on physicochemical parameters (gas mixture in the headspace, pH, water activity), microbial growth and chemical parameters (peroxide value, free fatty acid content). At the end of the test (after 29 days), the oxygen transmission rate (=OTR) of two flat films are determined using fluorescence sensor technology. These measurements are used to calculate the OTR of the pouches with and without channel leak. Results and conclusions The OTR of the pouches with a channel leak is approximately 6 times higher than the OTR of the intact film. An intact pouch has a calculated OTR of 0,035 ± 0,001 cc/day, the channel leak adds 0,176 ± 0,003 cc/day to this OTR. During the food preservation test the pouches with a channel leak have a higher O2-concentration in the headspace than those without a channel leak. After four days of storage, O2-concentrations were 0,50% for the pouches with channel leak and 0,10 % for the pouches without channel leak. Throughout the storage of 29 days, the O2-concentrations are never exceeding 1%. Moreover, there are no effects of the presence of a channel leak on pH, water activity, microbial growth, peroxide value and free fatty acid content of the packed ham sausage. In contrast to the pouches without channel leak, a discoloration of the ham sausage is however observed in the pouches with channel leak, possibly due to the interaction of the higher O2-concentration with light exposure. This could lead to rejection of the meat packages by consumers. IWT-VIS

Polyhydroxyalkanoates (PHA) are a family of biobased polymers that have received a great deal of attention the last few decades for certain applications, such as packaging, medical devices, and controlled drug-delivery systems. PHAs are polyesters, that can be produced by a variety of bacteria from a wide range of renewable organic substrates. These polyesters are biodegradable as well as biocompatible. Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) can be considered as a candidate for replacement of specific fossil-based polymers, due to its ductile nature and wider processing window, compared to poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), which are the two most investigated PHAs. The mechanical properties of PHBHHx have been compared to low-density polyethylene, with a possible application for packaging. Unfortunately, the crystallization rate of PHBHHx is very slow, even at low 3-hydroxyhexanoate content. Therefore, many efforts are actually devoted to solve this problem (e.g., by addition of a nucleating agent or selected microfillers or nanofillers). The doctoral research of dr. ing. Jens Vandewijngaarden at the University of Hasselt (Belgium) aimed at the characterization and modification of PHA for application as food packaging material. Focus was placed on the polymer PHBHHx with a 3-hydroxyhexanoate content of 10 mol%. The research, which was performed from 2012 to 2016, involved the effective characterization and pinpointing the major positive and negative properties. Several types of modification techniques were investigated in order to enhance the applicability of these materials.

Extended Abstract In the food packaging industry there is a gaining interest in bioplastics to replace conventional plastics, such as PET, PP, etc., as packaging material. Although these new polymers show the advantages of being bio-based and/or biodegradable, it is still a challenge to produce bioplastics with similar properties to the conventional plastics. For food packaging material for example, it is important to maintain food quality. Therefore it is essential to enhance the gas barrier properties of these bioplastics. Recent studies show that gas barrier properties of polymers can be improved through use of polymer nanocomposites, a two-phase system of a polymeric matrix and dispersed inorganic nanoparticles. A limiting factor, however, is the dispersion of the nanoparticles into the polymer. A solution is to deposit the nanoparticles on the polymer surface instead. Here, nanoparticles were deposited at temperatures below 95°C on the surface of the bioplastic PHBV through chemical bath method, which allows low-cost and low deposition temperatures, to study the effect of ZnO nanolayers on the gas barrier properties. By means of XRD the formation of (002) oriented ZnO was confirmed, while Raman spectroscopy confirmed the chemical structure of the ZnO nanolayer. The influence of the deposition of ZnO layers on the properties of the PHBV bioplastic was investigated by means of differential scanning calorimetry and transmission spectrometry in the wavelength ranging from 200 nm to 800 nm and. The O 2 , CO 2 and water vapour permeability were measured at a controlled temperature of 10°C, 23°C and 38°C to determine the influence of temperature on the barrier properties. For the O 2 permeability these experiments were performed at a relative humidity of 0%, 40% and 80% to also determine the influence of humidity on the oxygen barrier, while for CO 2 and water vapour permeability the relative humidity was kept constant at 0% and 100% respectively. The temperature study showed an increase of the oxygen, carbon dioxide and water vapour permeability with increasing temperature. This is mostly due to an increased free volume in the polymer matrix, improved motion of the polymer segments and a higher energy level of the permeating molecules. It was observed that the deposition of ZnO nanoparticles decreases oxygen, carbon dioxide and water vapour permeability. Temperature dependent measurements show that the activation energy for permeability of pure PHBV is lower than that of PHBV with a ZnO nanolayer on top. The humidity study of the oxygen barrier showed that for pure PHBV the permeability is stable until 40% RH and then increases with 20% at 23°C and even with 45% at 38°C. This is due to the fact that PHBV will absorb moisture from the humid air, which will lead to an increase in free volume and higher permeability values. For the PHBV with ZnO nanolayer an opposite effect is observed. In the region of 0%RH to 40%RH the oxygen permeability increases with 15% at 23°C and 23% at 38°C while afterwards, in the

Biobased and biodegradable polyhydroxyalkanoates (PHAs) are currently gaining momentum. Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) polymer has a useful processing window for extrusion and injection molding of packaging, agricultural and fishery applications with required flexibility. Processing PHBHHx into fibers using electrospinning or centrifugal fiber spinning (CFS) can further broaden the application area, although CFS remains rather unexplored. In this study, PHBHHx fibers are centrifugally spun from 4-12 wt.% polymer/chloroform solutions. Beads and beads-on-a-string (BOAS) fibrous structures with an average diameter (ϕav) between 0.5 and 1.6 µm form at 4-8 wt.% polymer concentrations, while more continuous fibers (ϕav = 3.6-4.6 µm) with few beads form at 10-12 wt.% polymer concentrations. This change is correlated with increased solution viscosity and enhanced mechanical properties of the fiber mats (strength, stiffness and elongation values range between 1.2-9.4 MPa, 11-93 MPa, and 102-188%, respectively), though the crystallinity degree of the fibers remains constant (33.0-34.3%). In addition, PHBHHx fibers are shown to anneal at 160 °C in a hot press into 10-20 µm compact top-layers on PHBHHx film substrates. We conclude that CFS is a promising novel processing technique for the production of PHBHHx fibers with tunable morphology and properties. Subsequent thermal post-processing as a barrier or active substrate top-layer offers new application potential. This research was funded by the Special Research Fund (BOF) of Hasselt University, grant number BOF20DOC06. The authors acknowledge Prof, Wouter Marchal (Analytical&Circular Chemistry, IMO-IMOMEC,UHasselt) for providing access to the DSC and rheometer equipment and Prof Louis Pitet (Advanced Polymer Functionalization, IMO-IMOMEC, UHasselt) for access to the hot-press. Jorgo Merchiers is acknowledged for the initial work on centrifugal fiber spinning, equipment development, polymer solution preparation, fiber fabrication and characterization. Lieze Schruers is acknowledged for the preliminary work on testing polymer concentrations for PHBHHx fibers using CFS.

In an organic circular economy, biodegradable materials can be used as food packaging, and at end-of-life their carbon atoms can be recovered for soil enrichment after composting, so that new food or materials can be produced. Packaging functionality, such as mechanical, gas barrier, and heat-seal performance, of emerging biodegradable packaging, with a laminated, coated, monomaterial, and/or blended structure, is not yet well known in the food industry. This lack of knowledge, in addition to end-of-life concerns, high cost, and production limits is one of the main bottlenecks for broad implementation in the food industry. This study determines application areas of 10 films with a pragmatic approach based on an experimental broad characterization of packaging functionality. As a conclusion, the potential application of these materials is discussed with respect to industrial settings and food and consumer requirements, to support the implementation of commercially available, biodegradable, and, more specifically, compostable, materials for the identified food applications. ispartof: POLYMERS vol:14 issue:13 ispartof: location:Switzerland status: published