Preparation and Properties of Starch– Lignosulfonate Blends for FoodPackaging Applications

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Preparation and Properties of Starch

– Lignosulfonate Blends for Food

Packaging Applications

EVA ÝR ÓTTARSDÓTTIR

KTH ROYAL INSTITUTE OF TECHNOLOGY

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Preparation and Properties of

Starch - Lignosulfonate Blends for Food

Packaging Applications

Master Thesis by

Eva ´

Yr ´

Ottarsd´

ottir

Supervisors: Josefina L. Ho↵mann and Kristine Koch

Examiner: Minna Hakkarainen

A thesis submitted in fulfilment of the requirements for the degree of Master in Engineering

in

Macromolecular Materials

Department of Fibre and Polymer Technology June 2015

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The demand for bio-plastics is constantly growing, due to the increasing use of synthetic plastic, their non environmentally friendly properties and long degradation time. This thesis explored the possibility to use starch-lignosulfonate mixtures for food packaging. Films are prepared from potato starch and two di↵erent types of lignosulfonates, calcium and sodium respectively using mold casting. The films are compared to pure potato starch films in respect to their mechanical properties and moisture absorption. Characterization o↵ the films is also conducted using scanning electron microscopy, energy-dispersive X-ray spectroscopy and light microscopy to see the interaction between the potato starch and lignosulfonates. The tensile test reveals that neither of the lignosulfonates do have a plasticizing e↵ect on the potato starch films. The energy-dispersive X-ray spectroscopy conceded that the lignosulfonates are homogeneously dispersed throughout the film both on the surface and cross section. The moisture absorption test showed that the uptake of water does not decrease by adding lignosulfonates to the potato starch film. From these results it can be concluded that it is possible to produce films from potato starch and lignosulfonates in various ratios. But the potato starch:lignosulfonate films are not a viable option for food packaging due to their brittleness and high moisture uptake.

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Efterfr˚agan p˚a bioplast växer ständigt p˚a grund av den ökande användingen av syn-tetiska plaster, deras icke miljövänliga egenskaper och den l˚anga nedbrytningstiden. Denna avhandling undersöker möjligheten att använda blandningar av stärkelse-lignosulfonat i livsmedelsförpackningar. Potatisstärkelse och tv˚a olika typer av lignosulfonater med kalcium och natrium användes för att tillverka filmer genom formgjutning. Filmerna jämförs med filmer med ren potatisstärkelse, med avseende p˚a deras mekaniska egenskaper och fuktabsorption. Karakterisering av filmerna genomförs även med hjälp av svepelek-tronmikroskop, energiröntgenspektroskopi och ljusmikroskopi för att se interaktionen mel-lan potatisstärkelse och lignosulfonater. Dragproverna visar att ingen av lignosulfona-terna har mjukgörande e↵ekt p˚a potatisstärkelsefilmerna. Energiröntgenspektroskopin visade att lignosulfonaterna är homogent dispergerade i hela filmen b˚ade p˚a ytan och i tvärsnittet. Fuktabsorptionstestet visade att upptaget av vatten inte minskar genom tillsats av lignosulfonater i potatisstärkelse-filmen. Fr˚an dessa resultat kan man dra slut-satsen att det är möjligt att framställa filmer fr˚an potatisstärkelse och lignosulfonater i olika förh˚allanden. Men potatisstärkelse: lignosulfonatfilmer är inte ett h˚allbart alternativ för livsmedelsförpackningar p˚a grund av sin sprödhet och höga fuktupptagning.

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I would like to start of thanking my supervisors Kristine Koch and Josefina L. Ho↵mann for all the help and encouragement through out the project. Kristine without you I would properly still be in the lab in Uppsala trying to get it right, thanks for your patients and the time you took out of your day for discussions and help during my time at SLU. Josefina thanks for guiding me the right way within SP and helping me put the characterization part together and for always greeting me with a smile when I came running to your office for help. I also like to thank Hanna who was my supervisor for the first weeks of the project, thanks for your help and for introducing me to SP and the people there.

Secondly I like to thank all the people that helped me conduct experiments during my project. Rodrigo Robinson at SP in Stockholm thanks for all of your help with the SEM, EDS and the moisture adsorption as well as the time you took out of your busy schedule for discussions and speculations regarding the results, without you at least 3 sections of the thesis would not exist. Marie Ernstsson for your help in introducing me to the existing research and guiding me forward with my research. As well as checking up on me throughout my time at SP to see how it was going. Carolin Menzel thanks for all of your help and informative discussions during my time at SLU. Xi Yang I would like to thank you for helping me with the tensile testing and then the help you provided me during the analyses of the results.

A big thank you to Domsj¨o Fabriker AB and Borregaard LignoTech for the lignosulfonates used for the project.

Lastly I like to thank the other master students at SP for their encouragement, help, discussion, lunches and fikor during our time there. I want to thank my ”home-girls” here in Sweden for keeping me sane during the months of this theses by dragging me to the gym, discussing and cheering me on when I was doubting myself. I like to thank all my friends and my family back in Iceland for the support. Last but not least I like to thanks my rock, Birkir, for all of his help though my LaTex and Matlab troubles, discussions, encouragement and for being there for me when I needed him to.

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Abstract ii

Sammanfatting iii

Acknowledgements iv

Contents v

1 Introduction 1

1.1 Plastics: what are they and what are they made from? . . . 1

1.2 The history of plastics . . . 2

1.3 The environmental factors . . . 2

1.4 Bio-plastics . . . 3

1.5 Food packing . . . 4

1.6 Starch . . . 5

1.6.1 Potato starch . . . 5

1.6.2 Starch as a plastic material . . . 6

1.7 Lignosulfonates . . . 7

1.8 Potentials for starch/lignosulfonate blends as a food packing material . . . 7

2 Aim 9 3 Materials and methods 10 3.1 Materials . . . 10

3.2 Blend preparation . . . 10

3.3 Tensile test . . . 11

3.4 Moisture absorption . . . 12

3.5 Scanning electron microscopy (SEM) . . . 12

3.6 Energy-dispersive X-ray spectroscopy (EDS) . . . 12

3.7 Light microscopy . . . 12

4 Results and discussion 13 4.1 Optimization of the blend preparation method . . . 13

4.2 Mechanical properties . . . 14

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4.4 Surface morphology and film crystallinity . . . 17 4.5 Chemical element distribution . . . 19 4.6 Surface morphology and lignosulfonate distribution on the film surface . . . 21

5 Conclusions 23

6 Future research 24

A Raw data from tensile testing 29 B Raw data from moisture absorption test 33

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Introduction

1.1 Plastics: what are they and what are they made from?

Plastics are made from polymers that are mixed with other substances, called additives, to obtain the ideal material properties for the application at hand. These additives are for example plasticizers, fillers and flame retardants. Polymers are large molecules made up of many smaller units of molecules, called monomers. Figure 1.1 shows a simplified version of the transition from monomeric to polymeric structure (Saldivar-Guerra and Vivaldo-Lima, 2013). The name polymer comes from the Greek words; poli that means many and meros that means parts (Goodship, 2007).

Figure 1.1: Simplified figure of the transition from many small molecules, monomers to one large molecule, polymer.

Most plastics made today come from fossil based raw materials. The polymers are syn-thesized chemically in the laboratory, thus they can di↵er in structure from the polymers found in nature, the biopolymers (Saldivar-Guerra and Vivaldo-Lima, 2013).

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1.2 The history of plastics

Even though biological polymeric materials have always been around in nature, the iden-tification of polymers was not made until 1861, when Thomas Graham dissolved organic compounds, such as cellulose, and observed that they could not penetrate trough fine filters without leaving residuals on it. He called these materials colloids. In the 19th century the evolution of colloid- and polymeric materials continued and in 1870 John Wesley Hyatt chemically modified cellulose to produce a new material he called Celluloid. Both these polymeric materials were made by using materials already existing in nature. It was not until 1907 that the first completely synthetic polymer, Bakelite, was synthesized by Leo Hendrik Baekeland. During and after the second world war mass production of poly-mers as plastic materials began and has been growing ever since (Halden, 2010, Powers, 1993). Synthetic fossil based polymeric materials are among the most used materials in the world and the second largest application field of petroleum; the annual production in 2013 reached 299 million tons (PlasticsEurope, 2014). The popularity of conventional fossil based plastics is due to their low production cost and versatility, as they are used in a wide spectra of applications, for example food packing, textiles and constructions materials (Mekonnen et al., 2013).

1.3 The environmental factors

Many of the plastics produced throughout the last century contain toxic additives that can be hazardous for the environment and human health (Lithner, 2011), thus precautions need to be made both during their production and to dispose of them correctly. Due to plastics versatile properties they are used for wide range of applications, not only to make plastic packaging and household products; they are also used to make for example textiles, fibers, coatings and foams, for many di↵erent applications all over the world (Lithner, 2011). With consumption comes waste. In a newly published paper by Jambeck et al., (2015) on plastic waste entering the ocean, 192 coastal countries were investigated and estimations about their waste drawn up. They estimated that 275⇥106 _{tons of plastic waste was}

generated in 192 countries and furthermore that 31.9_⇥106 tons were mismanaged in the coastal regions of these countries, resulting in, estimated, 4.8-12.7⇥106 _{tons of plastic}

entering the ocean in 2010 (Jambeck et al., 2015). Most of these plastics are synthetic fossil based plastics that do not degrade completely in nature, as microorganisms do not recognize them (Wolchover, 2011). This can result in small plastic fragments that spread all over the world that both animals and humans consume on daily bases through breathing and eating (Knoblauch and Environmental Health News, 2009). During the past years there has been an awakening among consumers, producers and governments concerning

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the environmental factors of plastic consumption. With this awakening, being “green” is a desirable factor, resulting in manufacturers drive to invest into research of degradable polymeric materials made from renewable resource (Lithner, 2011). Europe is today the largest consumer of biodegradable polymers, responsible for about half of the global total and as environmental factors are playing a big role in the customers’ choice of products, the request for bio-plastics is expected to increase and further research within the field is necessary (Bastioli and Magistrali, 2014). More environmentally friendly plastics are not only achieved by using a biodegradable material from a renewable resource as a raw material, but the final product properties should also be taken into consideration.

1.4 Bio-plastics

In respect to the environmental factors caused by synthetic fossil based plastics it is es-timated that the global production of bio-plastics will increase significantly in the next years, reaching approximately 3.5 million tons in 2020 (Mekonnen et al., 2013).

Plastics can be divided into four di↵erent groups, depending on the raw material they are obtained from (fossil- or bio-based) and if they are biodegradable or not, see Figure 1.2 (Mekonnen et al., 2013). In e↵ort for a plastic to be called a bio-plastic it needs to be either biobased or biodegradable, some bio-plastics even have both of these properties (see the color overlapping area in Figure 1.2).

Figure 1.2: Explanation of di↵erent plastics; based on their source and degradability. Figure remade according to the European Bioplastics webpage (European Bioplastics,

2014).

Many di↵erent renewable resources have been tried out for producing plastic materials, such as starch and cellulose (Augustine et al., 2013). In order to decrease the amount of synthetic fossil based polymers, bio-plastics are often used as fillers, in composites within a synthetic matrix and copolymerized with synthetic polymer (Baumberger, 2002). Di↵erent

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compounds obtained from biomass have also been mixed with each other in various ways to obtain the optimal plastic material for di↵erent applications. Starch has for example been mixed with a variety of di↵erent biomass compounds, such as cellulosic fibers, chitosan, lipids and cereal proteins to obtain a polymeric material with desirable properties (Ban et al., 2006, Baumberger, 2002). The main drawback of exploring bio-plastic has been the energy costs of the processes available to produce them. But in light of the uncertain future of crude oil as a raw material for polymer production and the demand for more environmental friendly polymers, these drawbacks become less important in light of the positive aspect of bio-plastic production (Belgacem and Gandini, 2008).

1.5 Food packing

Food packaging can be divided into four di↵erent levels: 1.Primary package, 2. Secondary package, 3. Distribution package and 4. Unit load, each of the packaging levels has di↵erent requirement when it comes to its properties. The primary packaging is the one that comes into direct contact with the food; this level should protect the content from contamination. This contamination factor can vary from water, light, odor, gases to microorganisms such as bacteria. The secondary packaging should protect the product from physical damage that it could be subjected to during transportation or storing for example. (Soroka, 2009, Talja, 2007). The distribution packaging’s main purpose is to protect the product during transportation and to make it easier to handle. The unit load packaging is the packaging that groups of distribution packaging are packed in for mechanical handling, storage and shipping (Soroka, 2009). In order for primary packaging to protect the content from con-tamination it is very common that di↵erent packaging materials are layered together to get the optimal properties for the application at hand (Soroka, 2009). Barrier protection packaging is important in the food packing industry as movement of gases into or out of the package can lead to alterations to the product properties (for example smell and taste). Barrier packaging can both be designed to keep the desired gases inside the packaging or protect the product from unwanted outside gases getting in. Of the packaging materials available today only glass and metals provide absolute barrier to all gases and volatiles, but even if these materials have advantages in aspect of barrier properties they have many disadvantages in other aspects. Thus plastic materials are often the preferred option when it comes to picking a packaging material. All plastics have a measurable permeability but not all plastics have the same permeability to the same kind of gases. Thus it is important to study both the gases and the volatile properties as well as the plastic properties, when choosing a material for a certain application (Soroka, 2009). Bio-plastics do not have the potential to fulfill all the requirements for a food packing material, due to their somewhat

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poor mechanical properties and their tendency to adsorb water (Soroka, 2009). But fur-ther research gives valuable knowledge that could lead to a shift in bio-plastics potential to serve as a primary packaging material.

1.6 Starch

Starch can be found in most plants and it is the second most abundant biomass material found on earth (Bastioli and Magistrali, 2014). It can be found for example in the leaves, roots, shoots, fruits and seeds of plants. The largest sources of starch today are corn, wheat, tubers (potatoes) and roots (cassava). Corn supplies more than 80% of the total starch available in the world, while wheat supplies less than 8%; next comes potatoes and cassava (Bergthaller and Hollmann, 2014). In 2003 the worldwide potato starch production was 2.49 million tons and Europe is responsible for more than 60% of the worldwide production (Grommers and van der Krogt, 2009). The two main components that make up starch are amylose (mostly linear) and amylopectin (branched), see Figure 1.3. The highly branched amylopectin has a molecular weight varying from 2-7_⇥108 _{g/mol depending on the source}

it is obtained from (Bergthaller and Hollmann, 2014). The amylose molecular weight is significantly lower, it varies from 0.2-2_⇥106g/mol (Bastioli and Magistrali, 2014). Amylose and amylopectin are packed into granules, which vary in their size and shape depending on the source they are obtained from (Sabokatkin, 2011).

Figure 1.3: Schematic structures of a. amylopectin (branched) and b. amylose (linear)

Starch is a desirable candidate for making plastic material due to its abundance, world wide availability, low cost and promising film forming properties (Bastioli and Magistrali, 2014, Baumberger, 2002, Koch et al., 2014).

1.6.1 Potato starch

Potato tubers contain approximately 15-20 wt% starch. The starch obtained from potato tubers is considered very pure compared to starch obtained from many other sources, as additional materials such as lipids are not present in potato tubers. Potato starch (PS) is also unique in many other aspects. The starch granules vary in size and have a smooth/even

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Figure 1.4: Light microscopy photo of pure potato starch

surface, see Figure 1.4. PS contains relatively high amounts of covalently bound phosphates as well as con-taining long amylopectin chains and amylose with high molecular weight. All of these factors make PS a desir-able raw material for bio-plastic production in material science (Bertoft and Blennow, 2009).

1.6.2 Starch as a plastic material

One of the most explored biodegradable materials for

bio-plastic fabrication is starch, as it has been proven to have good thermoplastic prop-erties (Bastioli and Magistrali, 2014, Baumberger, 2002, Koch et al., 2014). Starch based plastics are already of great commercial interest. Starch was initially used as a filler in plastics. Later composites were made from starch and thermoplastic polymers obtained by using graft polymerization methods (Carvalho, 2013, Mitrus and Moscicki, 2001). But the materials obtained by these methods were not completely biodegradable, thus the in-vestigation of the potential for starch to act as the main polymer in plastic fabrication began (Mitrus and Moscicki, 2001). Thermoplastic starch (TPS) (first developed in the 1970’s (Av´erous and Halley, 2014)) was the answer to these demands. TPS is an amor-phous or semi-crystalline material, made from gelatinised or destructurised starch, mixed together with a plasticizer (Mitrus and Moscicki, 2001). But as starch partially dissolute in moist environments it does not have all of the properties equipped for food packaging. The moisture absorption and the brittleness of starch based materials is its main drawback (Ban et al., 2006). In e↵orts to improve the properties of a starch based polymeric mate-rial without e↵ecting the degradability, many di↵erent approaches have been taken, such as mixing and copolymerization, with cellulosic fibers, chitosan, lipids and cereal proteins (Ban et al., 2006, Baumberger, 2002, Koch et al., 2014, Menzel, 2014, Mitrus and Moscicki, 2001). Today there are several starch based plastics on the market, the biggest producer is Novamont with production capacity of 80_⇥103 _{tons, their starch based bio-plastic is}

called Mater-Bi®. The second largest producer is Solanyl Biopolymers Inc. with produc-tion capacity of 65_⇥103 tons, their starch based bio-plastic product is called Solanyl BP® (Laycock and Halley, 2014). Both these products have shown great potential to replace some traditional fossil based plastics as they are equipped for many di↵erent applications that rely on fossil based plastics (Laycock and Halley, 2014, Solanyl Biopolymers, n.d.).

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1.7 Lignosulfonates

Lignin is found in almost all woody trees, as it is the chemical compound that makes up the middle lamella in woody fibers and holds them together (Toledo and Kuznesof, n.d.). The lignin content can vary from 15-35% depending on the wood type. As wood is common globally, lignin is one of the most abundant biopolymers. In the sulfide pulping process dissolution of lignin is obtained by the action of bisulphite ions. The counter ion can be calcium, sodium, ammonium or magnesium. During the process lignin ether bonds are broken randomly, and a sulfonic group is introduced to make the fragments more wa-ter soluble, creating lignosulfonate (LS) (Henriksson, 2011, Qiu et al., 2010). This gives LS interesting properties as it is combination of a hydrophobic aromatic skeleton and the hydrophilic sulforic groups that are added during the process. Thus the LS can be used as interfacial additives in many processes (Qiu et al., 2010). The molecular weight of LS varies from 1_⇥103 _{to 1.5}_⇥105 _{g/mol or even higher depending on the type and from which}

raw material they are produced from (Lora, 2008). Due to LS complicated structure, wide range of raw materials and di↵erent processes to obtain them there are no approved draw-ings available of the structure, only proposed structures. About 1.2 million tons of LS are produced every year. This is about 10% of the total amount of lignin produced by pulping methods annually (Lauten et al., 2010). LS are mostly used today as plasticizers when making concrete, as less water can be used to make it resulting in stronger material without reducing its viscosity (Chen and Zhou, 2012). In this project two di↵erent lignosul-fonates will be used calcium-lignosulfonte (⇠4-6.5⇥104 _{g/mol) and natrium-lignosulfonate}

(estimated molecular weight information not available in literature).

1.8 Potentials for starch/lignosulfonate blends as a food

packing material

Many types of biomass from agricultural resources have the potential of being good appli-cants for making more environmentally friendly materials, especially those that are pro-duced as non-useful byproducts in processes for other materials, such as lignosulfonates. In 1996 Baumberger et al.,(1997) first attempted to mix wheat starch and LS to obtain a plastic film with better mechanical and water adsorption properties. In their study they tested two di↵erent methods to produce plastic films as well as two di↵erent LS. From that study they concluded that plastic films could be obtained by mixing starch and LS in ratios from 90:10 to 70:30 in the present of a plasticizer (30%/dry starch), by using both extrusion molding or casting methods. Baumberger et al.,(1997) also concluded that LS

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did in fact have a plasticizing e↵ect on the starch films. Furthermore that LS did not sig-nificantly improve the water resistance of the starch film. But as the results from contact angle measurements indicated that the LS were still surface active these kinds of materials could be equip for products for short lifetime applications. Later Morais et al.,(2010) pub-lished an article where the thermally molded corn starch-glycerol-LS blends were studied in a ternary diagram. In that research the composition of all three components is referred to 100% (starch-glycerol-LS), were the glycerol acts as a plasticizer for the blend. In the paper LS content is varied from 10 to 60% with di↵erent content of starch/glycerol ratios. From the results obtained a ternary diagram was made to represent the films that were successfully made and mechanically tested. Morais et al.,(2010) concluded from the tensile tests conducted, that the stress decreased when mixing starch and Na-LS while the strain increased. Indicating that the material obtained from blending starch and LS was softer and more elastic than the pure starch film.

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Aim

The aim of this project was to investigate the e↵ects on plastic film properties upon blend-ing starch with two di↵erent lignosulfonates, calcium (Ca)- and sodium (Na)- lignosul-fonates respectively. The experimental condition needed to be optimized. Tensile- and moisture absorption tests were carried out to investigate the e↵ect of di↵erent lignosul-fonates on these properties. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and light microscopy were also carried out for further characteriza-tion.

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Materials and methods

3.1 Materials

Potato starch (_{⇠20% amylose, dry matter 89.6%) was provided by the Swedish University} of Agricultural Sciences (SLU), sodium-lignosulfonate (_{⇠9% sodium, dry matter 95.5%)} was kindly provided by Domsj¨o Fabriker AB (Sweden) and calcium-lignosulfonate (⇠5% calcium, dry matter 98.8%) was kindly provided by Borregaard LignoTech (Norway).

3.2 Blend preparation

PS and LS were mixed in vials in di↵erent concentrations, according to table 3.1 and 2⇥3 ml of ionized water was added to each vial so the total dry matter was 5% of the total amount of water. The vials were closed with screw caps and placed in a heating tray (Pierce Reacti-Therm III, heating stirring module), the heat was turned on and set to_{⇠95 C while} stirring. The blend was heated for 1 hour after it had reached _{⇠95 C, and thereafter let}

Table 3.1: Sample names for di↵erent concentrations of PS , Na-LS and Ca-LS

Sample name Potato Starch Ca-Lignosulfate Na-Lignosulfate

[%] [%] [%] 100 PS 100 0 0 2.5 Ca-LS 97.5 2.5 0 2.5 Na-LS 97.5 0 2.5 5 Ca-LS 95 5 0 5 Na-LS 95 0 5 10 Ca-LS 90 10 0 10 Na-LS 90 0 10

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cool down for approximately one minute. 11 ml (4⇥2.75 ml of the blend) were poured into a petri dish (8.7 cm diameter). The films were then dried at room temperature (23_{± 2 C} and 25± 3% relative humidity (RH)) for 24 hours and the petri dish was thereafter left partly closed with the lid until the film was completely dry. Figure 3.1 shows the steps taken in the blending, heating and casting method used. The sample names that are used throughout this report, can be seen in Table 3.1.

Lignosulfonate Starch +

Water

Cast into petri dish and dried Add water to

the mixture. Mix lignosulfonate

and starch together

The mixture was set to boil at 95°C for 1 hour, while stirring.

Figure 3.1: Blending, heating and casting method for PS:LS films. See concentrations of PS:LS ratios in table 3.1

3.3 Tensile test

Samples were prepared by cutting 8-10 50_{⇥5 mm samples for each concentration. The} samples were conditioned (23±1 C and 45± 2% RH) for 48 hours before conducting the tensile tests. The tensile tests were carried out on an INSTRON 5944 apparatus at KTH. The instrument clamps were set 2 cm apart, the samples were clamped in and dragged apart using a stretching speed of 5 mm/minute, the setup can be seen in Figure 3.2. For

Figure 3.2: A simplified illustration of the sample clamped into the tensile test apparatus

each PS:LS concentration and LS type 8-10 samples were tested. From these samples 3-5 with less than 10% standard deviation were chosen for further analyses.

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3.4 Moisture absorption

The moisture absorption test was preformed essentially according to the method described in Koch et al. (2014). Small samples (approximately 20_{⇥20 mm) were prepared for each} film concentration. The samples were brought to 4% RH by putting them into a moisture chamber containing drying stones that had been dried at 105 C for 2 hours. The samples were kept in the chamber until their weight decrease ceased (weight di↵erence less than 1%). The samples were then placed in a moisture chamber conditioned with a saturated salt solution of potassium sulfate (K2SO4), resulting in RH of 98%. The samples were

weighed again until the weight increase came to a stop (weight di↵erence less than 1%). A pure PS film was used as reference sample. All measurements were performed in triplicates.

3.5 Scanning electron microscopy (SEM)

A SEM apparatus (Quanta Feg 250) was used to perform the SEM analysis to gain in-formation about the film surface morphology and crystallinity. The voltage range was set to 10.00 kV and the chamber pressure was 80 Pa. The films were inspected at various magnifications; 1000⇥, 500⇥ and 100⇥ respectively.

3.6 Energy-dispersive X-ray spectroscopy (EDS)

Parallel to the SEM analysis the EDS analysis was carried out using (Oxford X-MaxN), were the SEM figures at 100_{⇥ magnification were analyzed to gain information about} the chemical element distribution in the sample and see if the LS were homogeneously distributed throughout it.

3.7 Light microscopy

A light microscope (Nikon Eclipse Ni-U microscope, Tokyo, Japan) was used to check if the starch and lignosulfonates were homogeneously distributed in the samples and to gain information about the e↵ect of LS concentration on the film surface morphology. Furthermore the light microscope was used to make sure that the starch granules were successfully broken down by using the blend preparation method described in section 3.2.

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Results and discussion

4.1 Optimization of the blend preparation method

Finding the suitable methods for blend preparation, PS:LS ratio, heating time and tem-perature and drying conditions took several attempts, as the films should be somewhat flexible and whole so they could be used in conducting various tests during the study. Ini-tially the blend preparation method from a previous study was used (Baumberger et al., 1997). The first films made can be seen in Figure 4.1. This film recipe, drying conditions and boiling temperature/time resulted in very brittle films that broke during the drying time, so changes were made both on the recipe and the drying conditions to obtain a whole and less brittle films. At this stage it was obvious that the methods from the previous study did not work so a trial and error approach had to be taken to find the right blend preparation method. The drying condition was changed from the fume hood to a location outside the fume hood, resulting in less brittle and whole films. The LS content was also decreased from varying from 10-30 wt% to varying from 2.5-10% which was also found to produce better films.

Figure 4.1: The films produced by the initial recipe and method during the project. From left to right; 10%, 20% and 30% Ca-LS.

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The boiling temperature and the boiling time were also changed a couple of times before the best results were found. Finally the amount of solution poured into each petri dish and the size of the petri dishes was changed until the optimal thickness was found. The final film forming conditions can be found in Chapter 3, the films are displayed in Figure 4.2, where it can be seen that the Na-LS blends result in darker films compared to the films produced from Ca-LS. This is due to the fact that the Na-LS powder had a darker color than the Ca-LS powder. As the LS came from di↵erent suppliers this color di↵erence could be explained, for example, by di↵erent production methods or raw material used for the production. No information regarding these factors were provided by the suppliers, so no conclusions on the matter can be made. One can also see that the films containing 10% LS are broken, indicating that they are more brittle than the films containing less LS. Even if the films obtained from this blend preparation method were not perfect, they were still an improvement in comparison to the first film produced, using blend preparation methods from literature (Figure 4.1). The final films produced in this study were whole and the brittleness had been decreased significantly as they did not break into small pieces during the drying time, like the previous ones.

Figure 4.2: The final films, made by using the blend preparation method described in Chapter 3. 1. 100 PS, 2. 2.5 Ca-LS, 3. 2.5 Na-LS, 4. 5 Ca-LS,

5. 5 Na-LS, 6. 10 Ca-LS, 7. 10 Na-LS

4.2 Mechanical properties

The tensile tests were carried out in order to gain information on how the LS change the mechanical properties of the starch films. Figure 4.3 and Table 4.1 show both the stress and strain at break as a function of the lignosulfonate content, both for Ca-LS and Na-LS. For comparison the reference sample containing no LS is displayed in the graph. All the samples containing LS show a lower strain at break than the reference samples, while the

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stress at break does not display as a consistent slope. Even if these values vary depending on the content and the type of LS, they are within the error limits of each other, indicating that the type of lignosulfonate does not play an important role when it comes to the stress at break. These results indicate that the LS do not have a plasticizing e↵ect on the starch films as films containing both Ca-LS and Na-LS do not increase the strain at break and lower the stress at break, as expected if they were indeed more elastic soft plastics.

Figure 4.3: The e↵ect of Ca-LS (red o) and Na-LS (blue *) content on strain at break (—) and stress at break (- - -).

This is a surprising conclusions in light of the study conducted by Baumberger et al.,(1997) that concluded that the LS did in fact have a plasticizing e↵ect on the starch film. The main factor varying between these studies is the addition of a plasticizer (glycerol) to the mixture in Baumberger et al.,(1997) study. The results obtained from this master thesis could thus indicate that the interaction between LS and glycerol is of greater importance than the interaction between LS and starch. As Baumberger et al.,(1997) observed in their study the addition of LS did have a plasticizing a↵ect on the starch film in the present of glycerol as a plasticizer. Indicating that there is some kind of an interaction between the glycerol and LS that enhances the plasticizing e↵ect on the starch film. But at this stage it is not certain how these materials interact as more studies need to be conducted in e↵orts to do so. Additionally it is worth noting that Baumberger et al.,(1997) used wheat starch, while potato starch was used during this study. These starches di↵erentiate mainly by two factors. Firstly wheat starch contains lipids that are free or complex bound to the starch chains, secondly potato starch contains covalently bound phosphate groups, whereas wheat starch does not. There could be a possibility that the lipids could interact with the LS or that Na and Ca could interact with the phosphates. But it was consider unlikely

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that these interaction would explain the absence of plasticization. With that noted it can be seen that the stress at break for both Ca-LS and Na-LS does not change significantly compared to the reference sample containing no LS, this is a indication that the strength of the material network has not been a↵ected by the addition of LS. During the mechanical tests the thickness for each sample was measured. The mean values for each sample can also be found in Table 4.1. The di↵erence between the thicknesses varies _{±6.7 µm or 11%} from the mean value. This suggests that the casting method used for the films is good as the di↵erence in the film thickness is not significant.

Table 4.1: The average modulus (MPa), average tensile strain at beak (%), average tensile stress at break (MPa) and average thickness (µm) for di↵erent PS:LS concentrations and type of LS, Na-LS and Ca-LS respectively. The raw data from the tensile test can be

found in Appendix A.

Sample Average Average tensile Average tensile Average name modulus strain at break stress at break thickness

[MPa] [%] [MPa] [µm] 100 PS 1879.9 9.5212 45.024 56.0 2.5 Ca-Ls 2079.3 5.8048 43.633 60.6 2.5 Na-LS 2211.0 5.1231 47.679 62.9 5 Ca-LS 2385.3 5.6105 49.361 52.6 5 Na-LS 2048.4 5.5795 46.407 56.7 10 Ca-LS 2456.3 3.6924 49.401 49.5 10 Na-LS 2345.1 3.2905 48.261 55.0

4.3 Moisture absorption

The moisture absorption increases when LS are present in the film (Table 4.2). These results are in line with values found in literature (Morais et al., 2010), where starch films containing 72% starch, 18% glycerol and 10% LS showed increased moisture absorption

Table 4.2: Exact moisture absorption (%) values for each sample containing di↵erent PS:LS ratios and types of LS; Na-LS and Ca-LS respectively. Raw data can be found in

Appendix B

Sample name Moisture absorption [%] 100 PS 31 2.5 Ca-LS 34 2.5 Na-LS 36 5 Ca-LS 32 5 Na-LS 34 10 Ca-LS 32 10 Na-LS 38

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when exposed to higher RH. Where the moisture absorption behaviour for three di↵erent RH; 53%, 75% and 84% was investigated. The film moisture uptake increased from ap-proximately 5.5%, 15% to 25% for the three di↵erent RH. In this study the RH reached 98% and the highest moisture uptake was 38%, which is not a surprising value when com-pared to the ones in Morais et al.,(2010) study. Furthermore it is interesting to see that the curves behave in a similar way for samples; 100 PS, 2.5 LS and 5 LS. For the samples containing 10% LS there is a shift in the slope between the Ca-LS and Na-LS samples, but when taking into consideration the errorbars of the graph this shift comes less significant (Figure 4.4). Furthermore it was considered that for more accurate, reliable results, more replicas of each sample would be needed and at least two separate chambers to conduct tests in. This realization was not made until the end of the time frame of this project, thus they could not be conducted at that stage, but it is a interesting project for further research.

Figure 4.4: The moisture absorption as a function of di↵erent PS:LS ratios for both Ca-LS (o) and Na-LS (*).

4.4 Surface morphology and film crystallinity

Figure 4.5 shows the SEM figures for each concentration of Na-LS, Ca-LS and the reference sample. It can be seen that with increasing LS concentration the sample surface becomes rougher and more crystal-like structures are present. It has been reported that starch granules can have crystallinity varying from 15-45% depending on the plant species it is obtained from (Av´erous and Halley, 2014), but as the light microscopy figures in section 4.6 confirm that the starch granules have been successfully broken down these crystal

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Figure 4.5: SEM images of the film surface, for di↵erent LS concentrations. 1. 100 PS, 2. 2.5 Ca-LS, 3. 2.5 Na-LS, 4. 5 Ca-LS, 5. 5 Na-LS, 6. 10 Ca-LS, 7. 10 Na-LS

structures are mostly likely caused by a di↵erent factor. The crystal-like structures could be explained by some sort of a phase separation between the PS and LS as they become more visible with increasing amounts of LS, so these structures could in fact be phase separated LS on the surface. When comparing samples from di↵erent LS sources (2 vs. 3), (4 vs. 5) and (6 vs. 7) some di↵erences are present as Na-LS seems to have a more spherical shape on the surface while Ca-LS show more of an intertwined structure of chains of some sort. Like stated before it is hard to understand the interaction between the PS and LS as little is know about the structure of them. But as the main di↵erence between the films is the ion type and their concentration, it is likely that these ions interact in a di↵erent way with the starch, resulting in di↵erent structures on the film surface. At this

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stage these are only suggestions as further research would be needed to make conclusions on this matter.

4.5 Chemical element distribution

The chemical element distribution results obtained from the EDS analysis are presented in Table 4.3. The surface for each sample was scanned using the SEM images at 100_⇥ magnification and chemical element distribution of the surface was obtained. These results confirm that the LS content was successfully increased accordingly to the amount added in each case. Like suspected there is some di↵erence when the Ca-LS and Na-LS are

Table 4.3: Chemical element composition on the surface. The results from the EDS analysis. Weight percentage for carbon, oxygen, sulfur, calcium and sodium for each

sample. Raw data can be found in Appendix C

Sample name Carbon (C) Oxygen (O) Sulfur (S) Calcium (Ca) Sodium (Na) [wt%] [wt%] [wt%] [wt%] [wt%] 100 PS 52.8 47.2 - - -2.5 Ca-LS 51 48.7 0.1 0.1 -2.5 Na-LS 52.6 47.1 0.2 - 0.1 5 Ca-LS 52.5 46.9 0.3 0.2 -5 Na-LS 52 47 0.4 - 0.4 10 Ca-Ls 52.9 46.2 0.5 0.3 -10 Na-LS 50.5 47.7 0.9 - 0.8

compared, Na-LS have significantly more of sodium in the samples compared to calcium for the same concentration. This can be explained by the fact that the Na-LS contained 9% sodium while Ca-LS only contained 5% calcium (see materials and methods in chapter 3). Figure 4.6 displays the chemical distribution for sample 10 Na-LS, figure labelled 1 shows the layered color-code for all the elements present, while figures labelled 2 and 3 show Na and S respectively. From these figures one can see that the Na-LS are homogeneously distributed through the sample. Similar figures for the other samples can be found in Appendix C. For further investigation it was decided to look at the cross-section of the sample to see the distribution through the sample and to check if the weight di↵erence between the components played a role in the element quantity on the surface. The cross-section test was carried out on the 10 Ca-LS and 10 Na-LS samples, as they contained the larges amount of LS. The analysis showed that the distribution of LS trough the sample was homogeneous as the profile did not show a certain pattern (see figure 4.7). EDS cross section figure for sample 10 Ca-LS can be found in Appendix C. These results confirm that mixing LS with PS was successful using the blend preparation method used during this study. But if the conclusions made regarding the phase separation in section 4.4. were right it would be estimated that the chemical element distribution of sulfur would

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Figure 4.6: EDS analysis for sample 10 Na-LS. 1. Chemical element distribution for all elements (Carbon (C), Oxygen (O),Sulfur (S) and Sodium (Na)). 2. Chemical element

distribution for Sodium (Na) and 3. Chemical element distribution for Sulfur (S).

be higher on the surface of the films. These results contradict each other, so either the phase separation theory it not the right conclusion or the EDS is not the ideal instrument for conducting chemical element distribution in these kind of films. Without additional research it is hard to know for sure witch theory is most likely to be right.

Figure 4.7: Cross section EDS analysis for sample 10 Na-LS. 1. SEM image of the cross section at 1000_{⇥ magnification, 2. chemical element distribution for Sodium (Na) and 3.}

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4.6 Surface morphology and lignosulfonate distribution on

the film surface

Figure 4.8 shows the light microscopy photos obtained for each PS:LS ratio and for the two di↵erent types of LS. As can be seen the films containing Ca-LS, Figures 2, 4 and 6 have a lighter color than the films containing Na-LS, Figure 3, 5 and 7. This is caused by the fact that the Na-LS powder had a darker color than the Ca-LS powder, resulting in darker color of the film. The color di↵erence of the powders is unknown, but as they are obtained from separate suppliers di↵erence in processing methods or raw materials could be the cause of it. There is also a di↵erence from one picture to another in the vertical direction,

Figure 4.8: Light microscopy figures of the film surface, for di↵erent LS concentrations. 1. 100 PS, 2. 2.5 Ca-LS, 3. 2.5 Na-LS, 4. 5 Ca-LS, 5. 5 Na-LS, 6. 10 Ca-LS, 7. 10

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displaying increasing Ca-LS and Na-LS content. The film surface roughness becomes finer and the ”hills” and ”valleys” are not as obvious in Figures 6 and 7 as in Figures 2 and 3, this could indicate like stated in section 4.4, that there is a phase separation between the PS and LS resulting in small spherical structures that could be misinterpret as crystals on the film surface. From these films it can also be seen that the PS granules are no longer present that suggests that the PS was successfully broken down during the blend preparation. Here, like before some di↵erences between the Ca-LS and Na-LS could be explained by the di↵erence in Na and Ca percentage in each of the samples, but further research is necessary to make conclusions regarding the matter.

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Conclusions

The main conclusions drawn from this study is that films can be obtained by casting of PS:LS mixtures with ratios varying from 97.5:2.5 to 90:10, were usable films could not be obtained for ratios greater than 90:10. The tensile tests carried out on the di↵erent PS:LS films during this study did not show that LS have a plasticizing e↵ect on the PS. SEM, EDS and light microscopy confirmed that the LS were homogeneously distributed throughout the film, but indications of phase separation between the PS and LS were present in the SEM and light microscopy images obtained. Furthermore blending LS with PS does not decrease the moisture absorption of the PS film. So these films would not be accepted as conventional food packaging materials. But with some improvements and further investigation and studies, suggested in Chapter 6, the PS:LS films could become a better option in the run of becoming the next bio-plastic for food packaging purposes.

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Future research

While conducting this study many interesting questions came up that were not possi-ble to investigate further within the time frame for the project. To get a better insight to the PS:LS films one could prepare films containing only PS:LS blends and compare them with PS:LS:plasticizer films to see how the properties change between these films to gain a better understanding of how the LS interact upon blending with these materials. LS:glycerol mixture could also be added to a di↵erent material lacking a plasticizer to see if the same plasticizing e↵ects are obtained in other material as for starch like Baumberger et al.,(1997) concluded. Future researchers could also continue with improving the blend preparation method used in this study by changing di↵erent variables such as drying con-dition, concentration and molding methods for example. In order to gain a more even, whole and flexible film. Furthermore a wider range of test and analyzing methods could be conducted. For example water-vapor-transmission test, contact angle test and dynamic mechanical thermal analysis, as the films made for this thesis did not have the potential to be tested with these methods due to their brittleness and size. More chemical element distribution analysis could also be carried out to conclude if the EDS is in fact a suitable apparatus to measure these kind of films. Further analysis on each component could also be conducted, such as SEC and NMR to see the raw material properties and from there gain a better understanding of the components as a network. It could also be interesting to use the same quantities of Na in the Na-LS and Ca in the Ca-LS to see if the SEM and light microscopy figures would look the same between the two components aside from the color di↵erence. Another interesting factor would be to look at LS+plasticizer interaction alone, without any starch interrupting, to gain information of how these two materials interact.

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Raw data from tensile testing

0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 8 Specimen # 1 2 3 4 5 6 7 8 Modulus (Automatic) (MPa)

Tensile strain at Break (Cursor)

(%)

Tensile stress at Break (Cursor) (MPa) 1 1951.65042 10.36215 47.59965 2 1877.09961 12.62359 48.55628 X 3 2009.59667 6.04117 42.04818 4 1812.60111 13.90572 50.32421 X 5 1272.73260 7.34779 32.26197 X 6 1948.84436 6.33132 39.20000 7 1733.40421 9.87293 43.65737 8 1888.71127 8.41588 46.10752 Standard Deviation 82.94990 2.20383 2.52446 Maximum 1951.65042 13.90572 50.32421 Minimum 1733.40421 8.41588 43.65737 Mean 1852.69333 11.03605 47.24901 Tensile extension at Break (Cursor) (mm)

Load at Break (Cursor) (N) 1 2.07506 14.51789 2 2.52516 15.05245 X 3 1.20844 13.03494 4 2.78344 11.07133 X 5 1.48350 8.87204 X 6 1.26666 8.62400 7 1.97494 13.97036 8 1.68347 12.91011 Standard Deviation 0.44126 1.57431 Maximum 2.78344 15.05245 Minimum 1.68347 11.07133 Mean 2.20841 13.50443 Page 1 of 1

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0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 9 10 11 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 10 Specimen # 1 2 3 4 5 6 7 8 9 10 Modulus (Automatic) (MPa)

(%)

Tensile stress at Break (Cursor) (MPa) 1 2121.37235 6.78403 49.34270 2 2222.10112 6.45370 45.86472 3 2103.39871 7.74599 48.75343 4 2101.58528 4.45705 37.30994 5 2210.42212 2.83336 39.99858 6 2055.14133 4.70561 43.19898 7 2133.23877 10.70540 47.84422 8 2014.96708 5.33149 39.55968 9 2016.34568 2.91555 35.65447 10 1839.54558 3.91378 33.98767 Standard Deviation 110.27578 2.41939 5.63958 Maximum 2222.10112 10.70540 49.34270 Minimum 1839.54558 2.83336 33.98767 Mean 2081.81180 5.58460 42.15144 Tensile extension at Break (Cursor) (mm)

Load at Break (Cursor) (N) 1 1.35825 16.03638 2 1.29159 14.21806 3 1.55016 14.38226 4 0.89184 11.56608 5 0.56681 13.39952 6 0.94163 11.44773 7 2.14153 13.63560 8 1.06669 12.26350 9 0.58331 12.12252 10 0.78328 8.66686 Standard Deviation 0.48406 2.03361 Maximum 2.14153 16.03638 Minimum 0.56681 8.66686 Mean 1.11751 12.77385 Page 1 of 1

Figure A.2: Raw data from the tensile testing, 97,5% PS and 2,5% Ca-LS

0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 9 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 10 Specimen # 1 2 3 4 5 6 7 8 9 10 Modulus (Automatic) (MPa)

(%)

Tensile stress at Break (Cursor) (MPa) X 1 2330.47554 4.29106 49.73512 X 2 2425.16066 --- ---3 2107.24137 6.83185 44.93464 X 4 2256.36029 4.45507 46.57747 X 5 2150.02245 4.91459 49.46740 6 1717.66942 7.98784 49.12732 X 7 1688.03597 4.12266 43.89028 X 8 1686.94591 1.79159 21.71962 9 1859.02547 8.32778 45.78651 10 1990.96260 7.91542 48.00218 Standard Deviation 168.07149 0.64802 1.93757 Maximum 2107.24137 8.32778 49.12732 Minimum 1717.66942 6.83185 44.93464 Mean 1918.72471 7.76572 46.96266 Tensile extension at Break (Cursor) (mm)

Load at Break (Cursor) (N) X 1 0.85847 13.42848 X 2 --- ---3 1.36659 10.78431 X 4 0.89166 13.27458 X 5 0.98353 15.08756 6 1.59984 14.98383 X 7 0.82500 14.92269 X 8 0.35841 8.14486 9 1.66669 17.85674 10 1.58334 18.96086 Standard Deviation 0.13011 3.64921 Maximum 1.66669 18.96086 Minimum 1.36659 10.78431 Mean 1.55412 15.64644 Page 1 of 1

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0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 10 Specimen # 1 2 3 4 5 6 7 8 9 10 Modulus (Automatic) (MPa)

(%)

Figure A.4: Raw data from the tensile testing, 95% PS and 5% Ca-LS

0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 9 10 11 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 10 Specimen # 1 2 3 4 5 6 7 8 9 10 Modulus (Automatic) (MPa)

(%)

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0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 8 9 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 10 Specimen # 1 2 3 4 5 6 7 8 9 10 Modulus (Automatic) (MPa)

(%)

Tensile stress at Break (Cursor) (MPa) 1 2368.79246 2.20649 36.50090 2 --- 0.24926 5.39545 3 2979.34386 4.45534 58.46554 4 2317.33005 3.62251 44.99366 5 2801.51805 3.65949 58.77793 6 2541.62011 2.87363 49.41739 7 3024.83086 2.33128 49.01024 8 2509.90091 4.58109 53.79142 9 1797.07744 4.41332 41.15236 10 2572.59600 --- ---Standard Deviation 375.65982 1.40898 16.33001 Maximum 3024.83086 4.58109 58.77793 Minimum 1797.07744 0.24926 5.39545 Mean 2545.88997 3.15471 44.16721 Tensile extension at Break (Cursor) (mm)

Load at Break (Cursor) (N) 1 0.44166 8.39521 2 0.04987 1.32188 3 0.89166 13.73940 4 0.72488 10.79848 5 0.73322 15.87004 6 0.57497 9.88348 7 0.46650 9.31195 8 0.91678 12.64098 9 0.88322 13.99180 10 --- ---Standard Deviation 0.28201 4.27816 Maximum 0.91678 15.87004 Minimum 0.04987 1.32188 Mean 0.63142 10.66147 Page 1 of 1

Figure A.6: Raw data from the tensile testing, 90% PS and 10% Ca-LS

0 10 20 30 40 50 60 0 1 2 3 4 5 Te ns ile s tr es s (M Pa ) Tensile strain (%) Specimen 1 to 9 Specimen # 1 2 3 4 5 6 7 8 9 Modulus (Automatic) (MPa)

(%)

Tensile stress at Break (Cursor) (MPa) 1 1756.87247 3.53924 41.19965 2 2301.90944 3.99696 48.86724 3 2775.68065 0.91586 21.42907 4 2514.21921 3.08165 53.69941 5 1959.79535 1.78063 25.64522 6 2146.98058 0.91573 18.32899 7 2300.75497 2.87877 45.42382 8 2190.64044 2.91472 40.69516 9 2417.98393 3.58036 52.61749 Standard Deviation 299.93874 1.14801 13.51464 Maximum 2775.68065 3.99696 53.69941 Minimum 1756.87247 0.91573 18.32899 Mean 2262.75967 2.62266 38.65623 Tensile extension at Break (Cursor) (mm)

Load at Break (Cursor) (N) 1 0.70838 13.59588 2 0.80006 10.99513 3 0.18328 5.67870 4 0.61678 13.42485 5 0.35813 6.28308 6 0.18328 5.40705 7 0.58322 12.71867 8 0.58341 11.19117 9 0.71663 16.31142 Standard Deviation 0.22984 3.94314 Maximum 0.80006 16.31142 Minimum 0.18328 5.40705 Mean 0.52591 10.62288 Page 1 of 1

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Raw data from moisture

absorption test

Table B.1: Raw data from the moisture absorption test

Sample name Weight of dry sample Weight of wet sample Moisture absorption RH:4% RH:98% [g] [g] [%] 100 PS 0.062 0.081 31 2.5 Ca-LS 0.034 0.045 34 2.5 Na-LS 0.042 0.057 36 5 Ca-LS 0.033 0.044 32 5 Na-LS 0.035 0.047 34 10 Ca-LS 0.056 0.073 32 10 Na-LS 0.043 0.060 38

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Raw data from EDS

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Figure C.2: Raw date from the EDS analysis , 97,5% PS and 2,5% Ca-LS

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Figure C.4: Raw date from the EDS analysis, 95% PS and 5% Ca-LS

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Figure C.6: Raw date from the EDS analysis, 90% PS and 10% Ca-LS

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Figure C.8: Cross section EDS analysis for sample 10 Ca-LS. 1. SEM image of the cross section at 1000_{⇥ magnification, 2. chemical element distribution for Calcium (Ca) and}