1,720,983 research outputs found
Study of the barrier properties of ethylene vinyl alcohol copolymers (EVOH) against gases and volatile substances using a newly developed permeation measurement system
No full textEthylene 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,
permeability data of EVOH against other gases and (semi-)volatile organic
compounds (VOC) is usually limited to dry conditions.
As the previously established methods to measure permeation through EVOH
were not all useful and adequate to test a broad selection of molecules in varying
conditions of relative humidity (RH) and temperature, a new approach was applied.
This research resulted in the development of two new hyphenated systems also
known as the Permeability EVOH Barrier Measurement Tool (PEBaMeT) systems:
the PEBaMeT-HPA (High Purity Analyzer) for the gas transmission rate (GTR)
measurement of permanent gases on one side and the PEBaMeT-GC-MS (gas
chromatography – mass spectrometry) for the permeation measurement of
(semi-)VOCs. Both systems consist of a permeation system connected to a GCbased detection system.
The permeation system of both systems is based on the equal pressure method
and allows humidification of the up- and downstream flows in the PEBaMeT-HPA.
In case of the PEBaMeT-GC-MS only the downstream flow can be humidified. The
permeation systems have temperature control, which allows operation from below
room temperature (i.e. 10°C) up to temperatures to approximately 120°C. The
systems have respectively four and three permeation test cells, which are
sequentially sampled by the detection system via a rotating multi-port switching
valve.
The detection system of the PEBaMeT-HPA is a GC equipped with two different
channels, each consisting of a pre- and main column for the separation of all
permanent gases, including noble gases (except for helium (He) and neon (Ne))
and low weight hydrocarbons. The system was validated with O2GTR
measurements on EVOH containing 32 mol% ethylene (EVOH32) and EVOH48
and nitrogen (N2)GTR measurements performed on EVOH32, EVOH44 and
EVOH48 and was demonstrated suitable for permeation measurements when
compared to those performed with previously established methods. The PEBaMeT-HPA was able to measure N2GTR values as low as 0.06 cm³/(m²·day·atm).
Arrhenius curves of the three EVOH grades at 0% RH showed good correlation
and are adequate to extrapolate the N2GTR to other temperatures and when
tested in varying RH at 35°C, the EVOH grades demonstrate an optimal barrier at
approximately 30% RH of 0.12, 1.3 and 2.3 cm³/(m²·day·atm) for 20 µm of
EVOH32, EVOH44 and EVOH48 respectively. Unfortunately, it was not possible to
generate reliable carbon dioxide (CO2)GTR values due to strong adsorption and
desorption processes of CO2 on stainless steel surfaces, led to consistently higher
CO2GTR values than those obtained with established methods. This can be
resolved by using aluminium permeation cells instead or the application of a
coating.
The PEBaMeT-GC-MS has three different sampling systems for the analysis by GCMS: an autosampler, sample loop and thermal desorption (TD) trap. Calibration
can be performed by the autosampler, whereas permeation is sampled on either
the sample loop or the TD trap. Trapping can be especially useful when the
components are below detection limit for direct injection by sample loop. By
increasing the trap time, the detectable permeation value is effectively lowered,
generating more accurate results. This was successfully demonstrated with an
iso-octane permeation experiment through a multilayer film containing 22 µmEVOH32. Direct injection with the sample loop resulted in a value below detection
limit for two of the three cells. However, by using the trap for a duration of 15
min, the permeation in all three cells was visible. Whereas previous studies using
the weight loss method were unable to attain a permeation value for pure isooctane through EVOH32, the measurements performed on the PEBaMeT-GC-MS
showed that the iso-octane permeability of a multilayer structure containing 22
µm EVOH32 ranges between 1.48 x 10-4 and 1.95 x 10-4 g·µm/(m²·day).
The PEBaMeT-GC-MS is equipped with three versatile permeation cells. Using
these cells in different configurations, the difference in permeation of vapour
phase versus liquid phase contact with the film samples was observed for both npentane and iso-octane. In both cases vapour phase contact led to higher
permeation values, most likely due to the free movement of the molecules. Lastly, the barrier properties of EVOH against mineral oil hydrocarbons (MOH)
migrating from recycled paperboard were benchmarked against other materials
such as polyamide (PA) and polyethylene terephthalate (PET) using different
state-of-the-art methods: (1) the taped donor/receptor method and (2) the online
permeation method. In general, 3 and 5 µm EVOH32 and 3 µm EVOH27
demonstrate good functional barrier against MOH migrating from recycled
paperboard.
Overall it can be stated that the development and validation of the two
hyphenated systems was successful and that both systems can be used for their
respective applications.Ethyleen vinyl alcohol copolymeer (EVOH) is een van de meest gebruikte barrière
materialen in een breed gamma aan applicaties. De uitstekende gas barrière
eigenschappen zijn reeds uitgebreid onderzocht voor zuurstof (O2). Maar,
permeabiliteit data voor EVOH tegen andere gassen en (semi-) vluchtige
organische stoffen (VOS) is doorgaans beperkt tot droge condities.
Omdat de reeds beschikbare methoden om permeatie te meten door EVOH niet
allen nuttig en geschikt waren om een brede selectie aan moleculen te testen bij
variërende condities van relatieve vochtigheid (RV) en temperatuur, werd een
nieuwe aanpak toegepast. Dit onderzoek leidde tot de ontwikkeling van twee
nieuwe samengestelde systemen, deze worden ook wel de Permeability EVOH
Barrier Measurement Tool (PEBaMeT) systemen genoemd: de PEBaMeT-HPA
(High Purity Analyzer) voor de gas doorlaatbaarheid (GTR) metingen van
permanente gassen aan één kant en de PEBaMeT-GC-MS (gaschromatografie –
massa spectrometrie) voor de permeatie metingen van (semi-)VOS aan de andere
kant. Beide systemen bestaan uit een permeatie systeem geconnecteerd met een
GC-gebaseerd detectiesysteem.
Het permeatie system van beide systemen is gebaseerd op de gelijke druk
methode en maakte bevochtiging van zowel de up- en downstream flows in de
PEBaMeT-HPA. In het geval van de PEBaMeT-GC-MS is het enkel mogelijk om de
downstream te bevochtigen. De permeatiesystemen hebben temperatuur controle,
dit maakt het mogelijk om te meten onder kamertemperatuur (d.w.z. 10°C) en
bij temperaturen tot ongeveer 120°C. De systemen hebben respectievelijk vier
en drie peremeatie cellen, die sequentieel geanalyseerd worden door het
detectiesysteem via een roterende multi-positie kraan.
Het detectiesysteem van de PEBaMeT-HPA is een GC uitgerust met twee
verschillende kanalen, elk bestaande uit een voor- en een hoofdkolom voor de
scheiding van alle permanente gassen, inclusief nobele gassen (met uitzondering
van helium (He) en neon (Ne)) en laagmoleculaire koolwaterstoffen. Het systeem
werd gevalideerd met O2GTR metingen op EVOH met 32 mol% ethyleen (EVOH32)
en EVOH48 en met stikstof (N2)GTR metingen op EVOH32, EVOH44 en EVOH48,
en werd geschikt bevonden voor permeatie metingen in vergelijking met reeds eerder ontwikkelde methoden. Met de PEBaMeT-HPA konden waarden van 0.06
cm³/(m²·day·atm) nog gemeten worden. Arrhenius curves van de drie EVOH
types bij 0% RV gaven goede correlatie en bleken bruikbaar om de N2GTR te
extrapoleren naar andere temperaturen, en bij het testen in variërende RV bij
35°C, werd een optimale barrière gemeten voor de verschillende EVOH types bij
ongeveer 30% van 0.12, 1.3 en 2.3 cm³/(m²·dag·atm) voor 20 µm EVOH32,
EVOH44 and EVOH48 respectievelijk. Helaas was het niet mogelijk om
betrouwbare koolstofdioxide (CO2)GTR waarden te bekomen door de adsorptie en
desorptie processen van CO2 op roestvrij staal, dit leidde tot consistent hogere
CO2GTR waarden dan deze bekomen met reeds geëvalueerde methoden. Dit
probleem kan verholpen worden door het gebruik van aluminium permeatie cellen
of het aanbrengen van een coating.
De PEBaMeT-GC-MS heeft drie verschillende bemonsteringssystemen voor de
analyse via GC-MS: een autosampler, een sample loop en een thermische
desorptie (TD) trap. Kalibratie kan uitgevoerd worden via de autosampler, terwijl
permeatie bemonsterd wordt door de sample loop of de TD trap. Trappen kan
vooral nuttig zijn wanneer de concentratie van de component onder detectielimiet
ligt bij een directe injectie via de sample loop. Door de trap tijd te verhogen, kan
de detecteerbare permeatie waarde effectief verlaagd worden, dit leidt tot meer
betrouwbare resultaten. Dit werd succesvol gedemonstreerd met een iso-octaan
experiment door een multilaag structuur met 22 µm-EVOH32. Directe injectie via
de sample loop gaf een permeatie waarde onder detectielimiet voor twee van de
drie cellen. Maar door gedurende 15 min te trappen, werd de permeatie in alle
drie de cellen zichtbaar. Waar er bij vorige studies via de gravimetrische methode
niet in geslaagd werd om een waarde voor de permeatie van pure iso-octaan door
EVOH32 te meten, tonen de metingen met de PEBaMeT-GC-MS aan dat de
permeabiliteit van een multilaag structuur met 22 µm EVOH 32 voor iso-octaan
tussen 1.48 x 10-4 en 1.95 x 10-4 g·µm/(m²·dag) ligt.
De PEBaMeT-GC-MS is uitgerust met drie veelzijdige permeatie cellen. Door deze
cellen in verschillende configuraties te gebruiken, kon het verschil in permeatie
van dampfase t.o.v. vloeibaar fase contact met de film stalen vastgesteld worden
voor zowel n-pentaan als iso-octaan. In beide gevallen gaf dampfase contact hogere permeatiewaarden, dit is waarschijnlijk door de vrije beweging van de
moleculen.
Ten slotte werden de barrière-eigenschappen van EVOH tegen minerale oliën
(MO), die uit gerecycleerd karton migreren, vergeleken met die van andere
materialen zoals polyamide (PA) en polyethyleentereftalaat (PET) d.m.v.
verschillende state-of-the-art methoden: (1) de taped donor/receptor methode
en (2) de online permeatie methode. In het algemeen kan geconcludeerd worden
dat 3 en 5 µm EVOH32 en 3 µm EVOH27 goede barrière vertonen tegen MO die
uit gerecycleerd karton migreren.
Globaal kan worden gesteld dat de ontwikkeling en validatie van de twee
samengestelde systemen succesvol was en dat beide systemen kunnen worden
gebruikt voor hun respectievelijke toepassingen en hiermee de functionaliteit van
EVOH in diverse, nieuwe domeinen onderzocht kan worden wat de marktvraag
naar EVOH kan vergroten
Evaluation of the functionality of compostable bioplastics in food applications
No full textAs the focus in the food packaging industry changes more and more towards a sustainable and circular economy, food producers face challenges to make their packaging either reusable, recyclable or compostable. Over ten years of research on bioplastics have led to a variety of new materials for diverse applications. In 2021 the total global production of bioplastics was 2.41 million tonnes of which roughly 65% are biodegradable and over half of these materials are used in food packaging. While there is still some scepticism towards bioplastics due to dubious labelling (biodegradable vs. compostable), potential contamination of the recycling stream and the high cost of low volumes, the market and application range for bioplastics is expected to increase to 7.59 million tonnes by 2026. However, the functionality or the applicability of bioplastics as food packaging has not been widely investigated and in-depth research is necessary to promote the speedy implementation of these materials in new applications. In the past the emphasis was always on bioplastics based on materials such as polylactic acid (PLA), cellulose and starch. But in the past years new materials have become commercially available, such as polyhydroxyalkanoates (PHA), polybutylene succinates (PBS) and blends made of compostable bioplastics, also used as papercoatings. In the context of the Belgian TETRA (Technology Transfer) project “BIO-FUN”, a new generation of commercially available biodegradable plastics was evaluated for its seal performance, gas- and water vapour transmission rate, and mechanical properties to gain more insight in employment of these different materials in food packaging applications. After this broad screening was conducted, several case studies were launched to perform an in-depth analysis with a specific food application in mind. In this presentation these case studies are highlighted.VLAIO and members of the supervisory group of BIO-FU
Evaluation of the functionality of compostable bioplastics in food applications
No full textAs the focus in the food packaging industry changes more and more towards a sustainable and circular economy, food producers face challenges to make their packaging either reusable, recyclable or compostable. Over ten years of research on bioplastics have led to a variety of new materials for diverse applications. In 2021 the total global production of bioplastics was 2.41 million tonnes of which roughly 65% are biodegradable and over half of these materials are used in food packaging. While there is still some scepticism towards bioplastics due to dubious labelling (biodegradable vs. compostable), potential contamination of the recycling stream and the high cost of low volumes, the market and application range for bioplastics is expected to increase to 7.59 million tonnes by 2026. However, the functionality or the applicability of bioplastics as food packaging has not been widely investigated and in-depth research is necessary to promote the speedy implementation of these materials in new applications. In the past the emphasis was always on bioplastics based on materials such as polylactic acid (PLA), cellulose and starch. But in the past years new materials have become commercially available, such as polyhydroxyalkanoates (PHA), polybutylene succinates (PBS) and blends made of compostable bioplastics, also used as papercoatings. In the context of the Belgian TETRA (Technology Transfer) project “BIO-FUN”, a new generation of commercially available biodegradable plastics was evaluated for its seal performance, gas- and water vapour transmission rate, and mechanical properties to gain more insight in employment of these different materials in food packaging applications. After this broad screening was conducted, several case studies were launched to perform an in-depth analysis with a specific food application in mind. In this presentation these case studies are highlighted.VLAIO and members of the supervisory group of BIO-FU
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Cardboard Packaging with Ethylene Vinyl Alcohol Copolymer (EVOH) as a Functional Barrier against Mineral Oil Migration.
No full textIn 2012 a scientific opinion on the potential health risks of mineral oil contamination in food was published by the European Food Safety Authority (EFSA). Recycled cardboard is viewed as the
main cause for this contamination and the packaging industry had been confronted with this problem. Regulation (EC) No 1935/2004 states that food contact materials will not transfer any constituent to food in quantities that can endanger human health. Additionally, all plastic materials mus t comply with Commission Regulation (EU) No 10/2011, which contains a positive list of allowed substances and their specific migration limit into food. Non-authorised substances can only be used when a functional barrier separates them from the food, which limits the migration of these substances to below a given detection limit. However, no harmonized regulation exists for paper and cardboard packaging materials. The industry is looking for possible functional barriers against mineral oils and methods to determine their
functionality. Due to its outstanding barrier properties, ethylene vinyl alcohol copolymer (EVOH) is one of the key
materials of interest. To evaluate its barrier performance against mineral oil, the breakthrough time was determined. A donor paper material spiked with a known concentration of mineral oils, was placed against the functional barrier and the transferred substances were extracted from a PE receptor material
at regular intervals. This study shows that a multilayer film with 4.4 μm EVOH containing 32 mol% ethylene can compete with 20 μm polyamide (PA) and 12 μm (PET), as it shows only 1% breakthrough after 84 days at 60°C, which translates into a shelf life of over 10.6 years at room temperature. EVOH is a very suitable functional barrier for preventing mineral oil migration. More detailed research is ongoing to determine the efficacy of the barrier properties in specific packaging concepts.VLAIO Baekeland mandate & Kuraray EVAL Europe n
A study of the barrier properties of ethylene vinyl alcohol copolymers using gas chromatography
No full textEthylene 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
Cardboard Packaging with Ethylene Vinyl Alcohol Copolymer (EVOH) as a Functional Barrier against Mineral Oil Migration.
No full textIn 2012 a scientific opinion on the potential health risks of mineral oil contamination in food was published by the European Food Safety Authority (EFSA). Recycled cardboard is viewed as the
main cause for this contamination and the packaging industry had been confronted with this problem. Regulation (EC) No 1935/2004 states that food contact materials will not transfer any constituent to food in quantities that can endanger human health. Additionally, all plastic materials mus t comply with Commission Regulation (EU) No 10/2011, which contains a positive list of allowed substances and their specific migration limit into food. Non-authorised substances can only be used when a functional barrier separates them from the food, which limits the migration of these substances to below a given detection limit. However, no harmonized regulation exists for paper and cardboard packaging materials. The industry is looking for possible functional barriers against mineral oils and methods to determine their
functionality. Due to its outstanding barrier properties, ethylene vinyl alcohol copolymer (EVOH) is one of the key
materials of interest. To evaluate its barrier performance against mineral oil, the breakthrough time was determined. A donor paper material spiked with a known concentration of mineral oils, was placed against the functional barrier and the transferred substances were extracted from a PE receptor material
at regular intervals. This study shows that a multilayer film with 4.4 μm EVOH containing 32 mol% ethylene can compete with 20 μm polyamide (PA) and 12 μm (PET), as it shows only 1% breakthrough after 84 days at 60°C, which translates into a shelf life of over 10.6 years at room temperature. EVOH is a very suitable functional barrier for preventing mineral oil migration. More detailed research is ongoing to determine the efficacy of the barrier properties in specific packaging concepts.VLAIO Baekeland mandate & Kuraray EVAL Europe n
- …
