Your Science Partner for Advanced and Innovative Packaging Solutions

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Materials Design

Troubleshooting

Surface Modification

Paper Labels

Liquid Packaging Board

Adhesion Improvement

Tactile Perception

Biodegradability Tests

Mechanical Testing

Recyclability Evaluation

Sterile Packaging

Food Packaging Optimization

Barrier Coatings

Oxygen Absorbers

Edible Coatings

Microbiological Quality

Life Cycle Assessments

Packaging SolutionsSP – your Science Partner in:• Materials design – including biomaterials - for advanced and innovative packaging solutions• Troubleshooting – for enhanced performance of products and processes

We have experience working with packaging materials in many different applications, ranging from liquid packaging board, barrier coatings and edible coatings in the food packaging field to other areas such as paper labels and sterile packaging. Technical cases are described on the following pages, illustrating some of the application areas in which we work and some of the services we provide regarding analyses, testing and assessments.

How can we work together with you – for Advanced and Innovative Packaging Solutions?We can collaborate with you in different ways, in e.g. contract work, EU projects, consortia projects with several industrial partners and in projects with some public funding from e.g Vinnova.

Contact persons:Marie Sjöberg, marie.sjoberg@sp.se Marie Ernstsson, marie.ernstsson@sp.se

*AKD = alkyl ketene dimer, a sizing agent to make paper more hydrophobic.

Paper labels based on water-based pressure sensitive adhesives (PSAs)

How can the parameters that cause performance loss be identified to improve the properties of the adhesive?

Examples • Adhesive properties such as tack and shear resistance – effect of ageing• Detect how different molecules in PSA paper labels migrate under ageing • Surfactant migration in water-based PSA film - effect on tack and shear resistance • Paper components migration - effect on tack and shear resistance

Paper components – migration from face paper to adhesive filmMigration of components in labels was detected by surface analysis techniques (AFM, XPS and ToF-SIMS), and correlated with the effect on adhesive properties - tack and shear resistance.

The example shows that the sizing agent AKD* can migrate from the face paper to the PSA-silicone interface in paper labels after ageing at high temperature. The presence of hard AKD domains at the adhesive surface results in a decrease in tack after ageing of labels.

PSA film in paper label.

The presence of AKD was confirmed by XPS and ToF-SIMS surface analysis. According to ToF-SIMS data shown in the graph, AKD signals are detected on the surface only for the paper label with AKD in the face paper. AKD in both hydrolyzed form as ketone but also some AKD wax are present at the PSA surface after ageing for 2 weeks at 50 ºC and 50% RH.

AFM phase images of the adhesive PSA surface for two paper labels, with no AKD (left) and with AKD in the face paper (right), after ageing for 2 weeks at 50 ºC and 50% RH. The AKD domains show up as bright (hard) areas in the AFM phase image (10 x 10 µm).

451, AKD ketone

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no AKD in face paper with AKD in face paper

479, AKD ketone

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533, AKD wax

Contact persons: Marie Ernstsson, marie.ernstsson@sp.seKenth Johansson, kenth.johansson@sp.seBirgit D. Brandner, birgit.brandner@sp.se

Troubleshooting for enhanced performance of products and processes

How choose a suitable surface analysis technique to get the wanted information?

Plastic surfaces – distinguish between polymers such as PE and PP

The XPS valence band spectra for fingerprinting of polyethylene (PE) and polypropylene (PP) show clear differences. Hence it is possible to separate between products made of PE or PP, while traditional XPS spectra are very similar (and show mainly carbon). XPS analysis including also valence band spectra is therefore very useful to determine the surface chemical composition of unknown polymers.

The Confocal Raman Microscopy map shows identification of three different polymer layers by comparing to Raman spectra of the different components. The advantage with Confocal Raman Microscopy for these types of samples is that there is no need to prepare cross-sections. Scale bar in map: 5 µm.

Plastic materials – identification of different polymer layers

PE PP

Surface modification for tailor-made surfaces

How can the surface chemistry be designed to achieve the wanted surface properties?

Examples• Surface cleaning and/or surface functionalization• Adhesion improvement• Surface modification of fillers/fibers for compatibility with the matrix • High or low energy surfaces – hydrophilic or hydrophobic• Superhydrophobic surfaces

Contact persons:Kenth Johansson, kenth.johansson@sp.se Marie Ernstsson, marie.ernstsson@sp.se

Water droplet with blue dye on a superhydrophobic paper surface. The water contact angle is higher than 150o.

Plasma surface modification is used to change the surface properties of a material. The color inside the reactor depends on from what gas the plasma is formed.

Contact persons:Marie Ernstsson, marie.ernstsson@sp.seKenth Johansson, kenth.johansson@sp.seViveca Wallqvist, viveca.wallqvist@sp.se

Adhesion improvement by understanding its mechanisms

How can the impact of surface properties on adhesion be explored at different length scales?

Examples• Adhesion force measurements over small areas, from micro-scale (μm) to nano-scale (nm) – AFM force mapping• Adhesion tests at macro-scale (cm) – peel tests • Surface chemical composition and structure of the surfaces after failure in adhesive joint – XPS and SEM• Determination of locus of failure – adhesional or cohesive• Detection of contaminations between surfaces - weak boundary layers • Wetting of surfaces – surface energetics of substrate

Pigment coated paper – surface propertiesTwo pigment coated papers were investigated for surface chemical composi-tion by XPS and adhesion measured on micro-scale by AFM force mapping. These techniques are used to explore the adhesion mechanism between dif-ferent samples, e.g. an extruded polymer and a paperboard. By measuring the adhesion at very small length scales (μm) the interference from for instance the plastic deformation, which is always present during macroscopic peel tests, will be minimized. Adhesion tests performed at macroscopic length scales (cm) should therefore be included for comparison and correlation.

AFM force mapping data for two pigment coated papersFrom AFM topography and adhesion force images it is possible to get average values of surface roughness and adhesion force. The pigment coated paper with calcium carbonate compared to kaolin clay has a higher surface roughness (rms values: 80 nm > 46 nm), and a higher adhesion force (4.1 nN > 2.9 nN).

Surface chemical composition as measured by XPS for two pigment coated papers with kaolin clay or calcium carbonate in the coating layer. XPS data shows that mainly carbon (C) and oxygen (O) and the pigment specific signals for clay (Si, Al) and calcium carbonate (Ca) were detected. In addition low amounts of the elements Na, S and N were found, most likely signals from additives such as surfactants used in e.g. the latex dispersion.

AFM topography images and adhesion force images over small areas 3 x 3 µm for the two pigment coated papers. Areas with higher adhesion appear as brighter in the adhesion force images. For ka-olin the flaky clay platelets are clearly visible, with latex and other organic components mainly found in between the platelets. For calcium carbonate the smaller pigment particles provide a rougher surface, with higher adhesion observed in some areas.

Topography – kaolin clay Adhesion force – kaolin clay

Topography – calcium carbonate Adhesion force – calcium carbonate

Right feeling of the packaging material

What physical properties are important for a desired tactile perception?

Examples• Tactile friction – the friction perceived between finger and sample • Surface roughness• Thermal conductivity• Surface chemical composition

Physical properties measured by instruments can be related to perception meas-urements by human subjects, e.g. how smooth or cool a sample is perceived. By identifying these relations it is possible to find the most important features, and their target quantities, to design the right feeling of a packaging material.

Correlation between finger friction coefficient and surface roughness (Ra in µm). The smoother pigment coated paper has a higher fric-tion than the rougher uncoated paper. The friction depended on the real contact area, and this was related to the perception of e.g. the coolness. Hence the smoother coated paper surface was perceived as cooler, while the rougher uncoated paper was perceived as warmer.

Contact persons:Lisa, Skedung, lisa.skedung@sp.seLovisa Ringstad, lovisa.ringstad@sp.seMartin.Arvidsson, martin.arvidsson@sp.se

Tactile perception of printing paper

The contribution of the finger friction to tactile perception was investigated for a series of printing papers, both uncoated and pigment coated papers. Finger friction measurement - using a force sensor to measure the friction while moving a finger over a paper surface.

Coated paper Uncoated paper

Roughness

Friction

Biodegradability testing of packaging materials

For which materials can biodegradability testing be of interest?

Examples • Plastic films• Paperboard samples• Paper/pulp samples• Plastic and paper bags• Polymer samples – bio-based and others• Packaging materials of different kind

Biodegradability tests can be used to evaluate different materials. The biodegradation is performed by microorganisms in either water or in soil/compost. During the test the amount of carbon dioxide produced from the test material is followed as a function of time. This amount is then related to the theoretical amount of carbon dioxide that can be pro-duced from the test material (calculated from the measured total organic carbon - TOC – content). The biodegradability test is terminated when the plateau phase of biodegradation, often close to 100%, has been reached. The standard time for termination is 45 days, but the test can continue up to six months.

Biodegradable paper bag for collection of household waste.

Ref MCC powder

Compostable paper bag

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Result from biodegradability tests.Note! Different types of e.g. plastics and papers can both be easily biodegradable or not biodegradable at all. The diagram only shows examples of data that can be derived from biode-gradability tests. The compostable paper bag reached its plateau value 90 % biodegradability after ca 60 days. The plastic sample based on PLA (polylactic acid), produced from renewable sour-ces such as corn starch, reached 100 % biodegradability after ca 85 days. Included is also the result for a reference sample of microcrystalline cellulose (MCC) powder reaching its plateau value 100 % biodegradability after ca 60 days.

Biologicallydegradable

SP´s polymer waste treatment certification system, SPCR 141 based on EN 13432, consists of both test methods and criteria for acceptance. The intention with a certification system is to make it easier for producers to get an objective verification of material characteristics while the end users can use it as a waste management guide.

Contact persons:Catrin Lindblad, catrin.lindblad@sp.se Ignacy Jakubowicz, ignacy.jakubowicz@sp.se

The certification system can be used on materials and products for:• Industrial composting• Small scale (home) composting• Biological degradation after exposure to sunlight or heat

Mechanical properties of packaging materials

What mechanical properties are important to test and under what conditions?

Examples• Tensile, peel, impact and burst testing are important for packaging materials• Most tests can be run at different temperatures, from – 40 oC up to +200 oC• Tensile tests can be run from very low to very high speeds - ranging from μm/min to m/s

Tensile tests performed at very high speeds of deformation are important since these give information about a material in the high speed produc-tion lines in use today.

Accelerated ageing tests in different climates are available correspond-ing to both indoor and outdoor climates. Some examples are ageing in UV-exposure, heat, coolness and humidity. Many years of natural ageing can in this way be simulated in order to estimate the service life of dif-ferent products.

Results from tensile testing with typical stress – strain curves, here shown as tensile force vs elongation. Useful data from tensile testing are for example values of elongation at break, i.e. how much the sample can be strained before breaking. The results show more than 90% reduction in the elongation at break after ageing, due to the strong UV-degradation of the polymeric tape.

Contact persons:Erik Lindhagen, erik.lindhagen@sp.seJörgen Romild, jorgen.romild@sp.se

Accelerated ageing and tensile testing combined for detection of UV-degradation

Tensile testing of a commercial polymeric tape designed for indoor use. Since some outdoor exposure was expected in the application, it was of interest to find out the effect on the tape after exposure to an equivalent of three months of outdoor light (UV-exposure).

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Contact persons:Isabel Mira, isabel.mira@sp.seKenth Johansson, kenth.johansson@sp.se Marie Ernstsson, marie.ernstsson@sp.se Mats Stading, mats.stading@sp.seTim Nielsen, tim.nielsen@sp.se

Barrier coatings for food packaging

How can the barrier performance / surface properties of the coatings be enhanced?

Examples• Tailor-make the formulation for the intended application• Integrate new functionalities by adding fillers, nanoclay, etc.• Optimize the processing technology• Enhance barrier properties of biopolymers – fillers / surface modification

Water repellency of starch-based barrier coatings In one study the water repellency of starch-based barrier coatings was improved by creating hydrophobic barrier layers using a combination of electrospun coating and a plasma deposited coating.

Barrier and tensile properties are important for barrier coatingsBarrier functionalities for example against gases such as oxygen, liquids and aroma compounds are of importance. Tensile tests provide data of tensile strength and strain (elongation), and are performed on free stand-ing barrier films prepared by casting the dispersion in a Petri dish.

Renewable barriers for dispersion coating on paperBarrier coatings made from renewable sources and applied on paper sub-strates by dispersion coating are challenging to develop. One reason is the high speed used in paper-coating lines, giving complex flow properties with e.g. high shear rates on the coating formulation. It is therefore impor-tant to adjust the coating formulation and fine tune its rheological prop-erties to make it possible to technologically apply the dispersions in high-speed paper-coating lines. Renewable barriers based on cereal protein and starch have been developed in a research project with many partners. The barrier coatings were evaluated and developed from laboratory scale up to pilot production, and real pouches were produced and packed with an oxidation sensitive food product. Both protein and starch-based barriers had oxygen barrier properties in the same range as fossil-based barriers such as EVOH. In another project, with focus on xylan-based oxygen bar-rier for liquid packaging board, the improved oxygen barrier properties at high surrounding relative humidity were obtained for barrier coated board produced both in laboratory scale and in pilot scale.

Schematic illustration of a starch-based barrier coating on paperboard.

Electrospun modified starch creates a thin mesh, onto which a hydrophobic layer is plasma deposited.

Plasma deposited coating

Starch coated paperboard

Electrospun starch coating

Deposition of electrospun layers of modified starch effectively increas-es the water repellency of starch pre-coated paper, changing the sur-face from hydrophilic to hydropho-bic. The water contact angle increas-es from ca. 45o to 140o. Scale bar in SEM image: 10 micrometer.

Plasma deposited coating onto electrospun fiber mats of modified starch succeeds in changing the hydrophobic surface into a superhydrophobic surface. The water contact angle is 171o.

171o±1

140o±1

Barrier film of a xylan dispersion cast in a Petri dish and shown together with a sheet of paperboard.

A protein barrier applied on paper using dispersion coating in the laboratory.

Pouch packed with an oxidation sensitive food product.

Oxygen absorbers for prolonged shelf-life

How can food quality be maintained and shelf-life extended?

Examples • Exposure to oxygen can have negative effects on many foods• Improved barrier properties of the packaging prevents oxygen from reaching the food• Modified atmosphere - low oxygen level - inside the packaging is beneficial for many foods• Oxygen absorber removes every oxygen molecule inside the packaging

Oxygen absorbers for higher quality and longer shelf-life of foodExposure to oxygen can cause off-flavor, color changes, loss of nutrients and microbial growth in foods. Therefore, it is beneficial with a low level of oxygen inside the packaging to prevent oxidation reactions. In this study the oxidation of cereals was investigated by measuring the hexanal content. The hexanal concentration is used as an indicator for oxidation since hexanal is produced during lipid oxidation. The results indicated that storage in air or in a modified atmosphere containing 2 % oxygen were not particularly beneficial for this product. However, the oxidation reactions were inhibited by the use of an oxygen absorber.

Contact person:Tim Nielsen, tim.nielsen@sp.se

The oxidation of cereals stored for six months in different atmospheres was investigated by analyzing the hexanal content. After storage large amounts of hexanal were observed in cereals kept in air or in a modified atmosphere containing 2% oxygen, while only very low levels of hexanal were detected in cereals stored in a packaging with an oxygen absorber.

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Oxygen absorber

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Edible coatings designed for fruit and vegetables

How can fruit and vegetable shelf-life be extended using edible coatings?

Examples• By increasing the abrasion resistance• By providing antimicrobial protection• By acting as a gas barrier and adjusting the internal gas atmosphere

Edible coatings on food products for extended shelf-lifeEdible coatings can be used to prolong the shelf-life of food products by moving one barrier functionality from the packaging to the product. An everyday example is the starch coating on French fries which prevents excessive fat uptake and provides crispiness. Another is the chocolate film on the inside of ice cream cones used to prevent humidity migration and the cone from turning soggy. Such edible coatings based on normal ingredients are applied in such a way that the perceived texture, aroma and taste are not influenced.

The example with bananas illustrates the positive effect a protective coating has on delaying the ripening of bananas. The other example is from a study with edible coatings used to extend the shelf-life of pears, thus improving long distance export.

Contact person:Mats Stading, mats.stading@sp.se

Bananas ripened for one week illustrates the drastic effect a thin maize protein coating has on delaying the ripening process. The protein coating acts by preventing ethane from reaching the banana and initiating ripening.

Pears coated with sorghum protein have twice the normal shelf-life. This is important during long-distance transport, for example from South Africa to Europe. As can be seen in the photo the protein coating on the pear is not visible.

Edible coatings designed for meat

What properties are important when characterizing edible coatings?

Examples• Visual appearance such as color, gloss and transparency• Microstructure• Barrier properties• Mechanical properties such as tensile and tear strength, and perforation resistance• Wetting behavior – contact angle measurements• Adhesion / friction

Friction and adhesion tests of coated meatThe example shows friction tests of coated meat samples performed at 4 oC. At this temperature the applied meat coating forms a transparent hydrogel. The friction force was found to be lower for coated than for uncoated meat, while the adhesion force was similar for the coated and uncoated meat.

Contact persons:Anna Hillerström, anna.hillerstrom@sp.se

The friction between two pieces of coated meat was measured at 4 oC using a sliding test. The photos show that the edible coating on the meat is transparent.

Microbiological challenges in packaging material and its process

How can microbiological knowledge be used in the food packaging field?

Examples • Evaluation of antimicrobial additives in a packaging material and its components• Troubleshooting of microbiologically generated problems – e.g. slime, spots and odors in processes and products • Quantification and identification of the dominating microorganisms in a packaging material and its components• Implementation of and training in quality management system ISO 22000

Identification of microorganisms in packaging materials, processes and food productsTailor-made packaging for food products is used so that the quality of the food can be maintained during its shelf-life. However, if a microbio-logically generated problem arises there may be a need to identify molds, yeasts and bacteria. For this purpose DNA-based techniques are available in the microbiology laboratory. The example shows results that are typical for a sample such as paper, pulp or paperboard using a method called PCR*-based TRFLP**.

Preparation of an experiment for identification of microbial communities.

Contact persons:Birgitta Bergström, birgitta.bergstrom@sp.seKlara Båth, klara.bath@sp.se

Results from community profiling – identification - of the dominating micro flora in a paper tissue sample using PCR-based TRFLP. The graph shows that of the total amount of microorganisms ca 55% is found in the three largest areas marked with blue. These correspond to the three dominating species of microorganisms found in the sample.

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*PCR = Polymerase Chain Reactions, a method to make a large number of copies of a desired DNA segment.

**TRFLP = Terminal Restriction Frag-ment Length Polymorphism, a method for profiling of microbial communities.

System perspective is essential for sustainable packaging

Which is the environmental impact of the packaging solution?

Examples • Life Cycle Assessment (LCA) of food products and processes• LCA of packaging solutions - environmental impact of the packaging itself including end-of-life scenarios• Development of novel packaging solutions - environmental coaching and assessment• Third part reviewer of performed LCAs

LCA of food products, processes and the packaging itselfThe most important parameter for sustainable packaging solutions is to give optimal protection and shelf life of the packed food so that the food is eaten and not wasted.

The example clearly illustrates that the environmental impact from pro-duction of the packaging itself often is a minor contributor to the total carbon footprint of the product.

Contact person:Katarina Nilsson, katarina.nilsson@sp.se

The production of 1 liter of milk gives rise to 1 kg CO2 equivalents, the same impact as from the production of 22 milk cartons. In this example the climate impact from the packaging contributes only to a minor fraction, 4.5 %, of the total carbon footprint of the product.

SP Technical Research Institute of Sweden

Box 857, SE-501 15 Borås, Sweden Telephone: +46 10 516 50 00 • Telefax: +46 33 13 55 02 E-mail: info@sp.se • www.sp.se

Our capabilities and services in the field of packaging materials – some examples

• Consulting and troubleshooting• Development of materials with desired properties – including biomaterials• Food packaging optimization• Surface modification – treatment by plasma or corona, adsorption, grafting, etc. • Surface chemistry and topography analyses - e.g. XPS, ToF-SIMS, Raman, SEM, AFM• Tactile perception and tribology – e.g. friction and wear• Formulation of barrier coatings, edible coatings, inks, etc.• Functionalization – e.g. in barrier coatings by adding fillers• Barrier performance – e.g. oxygen and water vapor permeability• Printing and behavior of liquid inks (inkjet, flexography, etc.)• Mechanical properties at various temperatures – e.g. peel, tensile, impact and burst testing• Small-scale processing – micro compounder, extruder, press• Ageing tests (accelerated) – in different climates• Biodegradability test program • Polymer waste treatment certification system• Recyclability evaluation • Chemical bulk and thermal analyses• Indentification of off-odours caused by the packaging material• Microbiological and materials analyses• Evaluation of antimicrobial additives• Life cycle assessments of packaging solutions

Contact persons – for general questionsMarie Ernstsson Phone: +46 10 516 6043 E-mail: marie.ernstsson@sp.seAlexander Milanov Phone: +46 10 516 6627 E-mail: alexander.milanov@sp.se

Improvement of Water-based PSA Paper Labels by mastering the Interaction between Adhesive film, Paper Components and Release LinerMarie Sjöberg, Marie Ernstsson, et al.

Causes of Poor Adhesion between Polymer Films and Paper or PaperboardKenth Johansson, Marie Ernstsson

Improved Adhesion between PE Films and Paper or Paperboard – Influence of Surface Chemical and Physical PropertiesKenth Johansson, Marie Ernstsson

Finger Friction Measurements on Coated and Uncoated Printing PapersLisa Skedung, et al.

Kinetics of Abiotic and Biotic Degradability of LDPE Containing Prodegradant Additives and its Effect on the Growth of Microbial CommunitiesIgnacy Jakubowicz, Nazdaneh Yarahmadi

Effects of Reprocessing of Oxo-biodegradable and Non-degradable Polyethylene on the Durability of Recycled MaterialsIgnacy Jakubowicz, Jonas Enebro

XyloPackEurostars project E!7420 XyloPack with focus on xylan based oxygen barrier for liquid packaging board.Marie Ernstsson

Renewable Functional Barriers from Forest and Agricultural ProductsVinnova project with a focus on long-term and sustainable production of high quality food packaging for excellent moisture, water and gas barrier properties.Isabel Mira, Kenth Johansson, Agne Swerin, Mats Stading, Tim Nielsen

SmartFoamDevelopment of hemicellulose-based foams for packaging applicationsMats Stading, Katarina Nilsson

Pack correctly – optimization of packaging solutionsTim Nielsen

ENVIROPAKEU-INCO funded project using by-products from African cereals to enhance shelf-life of fruit and nutsMats Stading

MEATCOAT EU project with a focus on new, natural, antimicrobial, edible film for fresh meatAnna Hillerström

Microbiological status of paper and board Birgitta Bergström

EcoBioCap- ECOefficient BIOdegradable Composite Advanced Packaging Katarina Nilsson, Lilia Ahrné

Current and concluded projects in the field of packaging materials - some examples