Thesis Title
Total Page：16
File Type：pdf, Size：1020Kb
DEGREE PROJECT, IN MACROMOLECULAR MATERIALS , SECOND LEVEL STOCKHOLM, SWEDEN 2015 Preparation and Properties of Starch – Lignosulfonate Blends for Food Packaging Applications EVA ÝR ÓTTARSDÓTTIR KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF CHEMICAL SCIENCE AND ENGINEERING Kungliga Tekniska hogskolan¨ 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 Abstract 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. ii Sammanfatting Efterfr˚aganp˚abioplast v¨axer st¨andigt p˚agrund av den ¨okande anv¨andingen av syn- tetiska plaster, deras icke milj¨ov¨anliga egenskaper och den l˚anga nedbrytningstiden. Denna avhandling unders¨oker m¨ojligheten att anv¨anda blandningar av st¨arkelse-lignosulfonat i livsmedelsf¨orpackningar. Potatisst¨arkelse och tv˚aolika typer av lignosulfonater med kalcium och natrium anv¨andes f¨oratt tillverka filmer genom formgjutning. Filmerna j¨amf¨ors med filmer med ren potatisst¨arkelse, med avseende p˚aderas mekaniska egenskaper och fuktabsorption. Karakterisering av filmerna genomf¨ors ¨aven med hj¨alp av svepelek- tronmikroskop, energir¨ontgenspektroskopi och ljusmikroskopi f¨oratt se interaktionen mel- lan potatisst¨arkelse och lignosulfonater. Dragproverna visar att ingen av lignosulfona- terna har mjukg¨orande e↵ekt p˚apotatisst¨arkelsefilmerna. Energir¨ontgenspektroskopin visade att lignosulfonaterna ¨arhomogent dispergerade i hela filmen b˚ade p˚aytan och i tv¨arsnittet. Fuktabsorptionstestet visade att upptaget av vatten inte minskar genom tillsats av lignosulfonater i potatisst¨arkelse-filmen. Fr˚andessa resultat kan man dra slut- satsen att det ¨arm¨ojligt att framst¨alla filmer fr˚anpotatisst¨arkelse och lignosulfonater i olika f¨orh˚allanden. Men potatisst¨arkelse: lignosulfonatfilmer ¨arinte ett h˚allbart alternativ f¨orlivsmedelsf¨orpackningar p˚agrund av sin spr¨odhet och h¨ogafuktupptagning. iii Acknowledgements 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¨oFabriker 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. iv Contents 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 4.3 Moisture absorption ............................... 16 v Contents 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 C Raw data from EDS 34 vi Chapter 1 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). 1 Introduction 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;