Reactive extrusion of lignocellulose-polyester biocomposites
Doktorsavhandling, 2024
The development of biodegradable and recyclable composites based on renewable resources can mitigate the effects of plastic pollution and the depletion of fossil fuels. A biocomposite consists of a matrix strengthened with fibres, and in this work, biodegradable polyesters have been blended with lignocellulosic derivatives, and reactive processing strategies have been developed to tackle the drawbacks of poor lignocellulose dispersion and poor adhesion of the lignocellulose to the polymer matrix. Reactive melt processing combines melt compounding with chemical reactions, and herein it has been explored to tune the interface of biocomposites and improve their performance. Three different ways of strengthening the polymer-lignocellulose interface have been investigated involving (a) modification of the polymer matrix, (b) modification of the lignocellulose, and (c) the addition of a third component.
The first approach was a peroxide-initiated branching/crosslinking carried out with water-assisted feeding of the lignocellulose. Crosslinking led to the formation of a uniform hybrid polymer-lignocellulose network that developed creep resistance and heat-shrinkage in the matrix. The mechanical recycling and industrial composting of crosslinked poly(butylene adipate-co-terephthalate) (PBAT)-pulp fibre biocomposites were successfully verified.
In the second category, the grafting of epoxidized bio-sourced oils onto industrial lignin was investigated as a way to plasticize the lignin and promote its miscibility with polyesters. Deformable and tough PBAT-modified lignin blends were prepared and shaped by film-blowing, to be subsequently mechanically recycled or industrially composted. The cellulose was also modified by in-situ polymerization of bio-sourced ethylene brassylate to graft the polymer from the cellulose surface. Ring-opening polymerization was achieved by organic and enzymatic catalysis, which showed that grafting from is an effective method of achieving nanocellulose dispersion and consequent stress transfer with the matrix.
In the third approach, amphiphilic diblock copolymers with two different tail lengths were designed to mediate the interface between cellulose nanofibrils and PBAT. In an aquatic environment, the cationic anchor block was effectively adsorbed onto the negatively charged nanofibrils, promoting their dispersion, while the longer tail block favoured entanglement with the matrix and deformation of the biocomposites.
This thesis contributes to the understanding of biocomposite interfaces, paving the way for future investigations, and proposes sustainable alternatives for the industrial replacement of commodity plastics.
The first approach was a peroxide-initiated branching/crosslinking carried out with water-assisted feeding of the lignocellulose. Crosslinking led to the formation of a uniform hybrid polymer-lignocellulose network that developed creep resistance and heat-shrinkage in the matrix. The mechanical recycling and industrial composting of crosslinked poly(butylene adipate-co-terephthalate) (PBAT)-pulp fibre biocomposites were successfully verified.
In the second category, the grafting of epoxidized bio-sourced oils onto industrial lignin was investigated as a way to plasticize the lignin and promote its miscibility with polyesters. Deformable and tough PBAT-modified lignin blends were prepared and shaped by film-blowing, to be subsequently mechanically recycled or industrially composted. The cellulose was also modified by in-situ polymerization of bio-sourced ethylene brassylate to graft the polymer from the cellulose surface. Ring-opening polymerization was achieved by organic and enzymatic catalysis, which showed that grafting from is an effective method of achieving nanocellulose dispersion and consequent stress transfer with the matrix.
In the third approach, amphiphilic diblock copolymers with two different tail lengths were designed to mediate the interface between cellulose nanofibrils and PBAT. In an aquatic environment, the cationic anchor block was effectively adsorbed onto the negatively charged nanofibrils, promoting their dispersion, while the longer tail block favoured entanglement with the matrix and deformation of the biocomposites.
This thesis contributes to the understanding of biocomposite interfaces, paving the way for future investigations, and proposes sustainable alternatives for the industrial replacement of commodity plastics.
lignin
pulp fibres
reactive extrusion
biocomposites
crosslinking
ethylene brassylate
nanocellulose
biodegradable materials
FB-Salen, Kemigården 1, Chalmers
Opponent: Professor Manjusri Misra, University of Guelph, Canada
Författare
Angelica Avella
Chalmers, Industri- och materialvetenskap, Konstruktionsmaterial
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Reusable, Recyclable, and Biodegradable Heat-Shrinkable Melt Cross-Linked Poly(butylene adipate-co-terephthalate)/Pulp Biocomposites for Polyvinyl Chloride Replacement
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Lignin valorization in thermoplastic biomaterials: from reactive melt processing to recyclable and biodegradable packaging
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Artikel i vetenskaplig tidskrift
Avella, A.; Rafi, A.A.; Deiana, L.; Mincheva, R.; Cordova, A.; Lo Re, G. Organo-mediated ring-opening polymerization of ethylene brassylate in reactive extrusion with cellulose nanofibrils
Deiana, L.; Avella, A.; Rafi, A.A.; Mincheva, R.; De Winter, J.; Lo Re, G.; Cordova, A. In-situ enzymatic polymerization of ethylene brassylate mediated by artificial plant cell walls in reactive extrusion
Avella, A.; Telaretti Leggieri, M. R.; Alexakis, A. E.; Malmström, E.; Lo Re, G. Design of extruded nanostructured composite via decoupling of the cellulose nanofibril/poly(butylene adipate-co-terephthalate) interface
Plaster, eller mer korrekt polymera material, är vanligt förekommande i vår vardag och används till många produkter. Lämpligheten av den relativt omfattande användningen av polymera material har under senare år också diskuterats allmänt, bland annat problem med nedskräpning och användningen av råolja för tillverkning av syntetiska plaster. I sammanhanget finns stort intresse av nya förnyelsebara polymera material med liknande funktionella egenskaper som kan ersätta syntetiska plaster och därmed undvika eller åtminstone reducera miljömässiga nackdelar. Polymera kompositer är här av särskilt intresse, exempelvis material sammansatta av en polymer matris och en eller flera tillsatser, syftande till att i något avseende nå bättre egenskaper än hos endera komponenten självt. I föreliggande arbete har bionedbrytbara polymerer matriser använts, blandade med träbaserade tillsatser. Sådana biokomposter är ofta förstärkta med träbaserade komponenter, syftande till en ökning av både styvhet och styrka men också till att öka andelen förnyelsebart i materialet. Ett välkänt allmänt problem ned träförstärkta polymera kompositer är att de träbaserade komponenterna har dålig kompatibilitet med den polymera matrisen, vilket vanligen minskar den avsedd förstärkning av kompositen. För att förbättra kompatibiliteten har vi i föreliggande arbetet undersökt möjligheter att använda bearbetningsmetoden benämnd reaktiv extrudering, vilket är en metod som inkluderar kemiska reaktioner samtidigt som komponenter smälts och blandas under extrudering. Vårt specifika syfte med reaktiva extrudering var att åstadkomma kemisk och fysikalisk bindning mellan de träbaserade komponenterna och den polymera matrisen, för att därmed förbättra egenskaperna. Ett flertal kemiska reaktioner studerades vid reaktiv extrudering och resulterande egenskaper hos materialet studerades. Till exempel hade massafiberbaserade biokompositer som reagerade via tvärbindning dubbelt så stor styvhet som den rena polymeren och fyra gånger högre töjning än icke-reagerade biokompositer. Dessutom gjorde tvärbindning det möjligt för biokompositen att krympa vid upphettning, en egenskap som behövs för vissa förpackningar. Även bionedbrytning vid kompostering och upprepad materialåtervinning studerades med några material.
Plastic is a common material useful in many different applications in our daily lives. However, the extent of its use has been debated in recent years, mainly because of environmental problems related to plastic pollution and the use of oil in its fabrication. New materials with characteristics similar to those of conventional plastics but without their environmental drawbacks are of interest. Polymer composites are a class of materials made of two or more components, a polymer matrix and fillers, combined to give better properties than those of the original components alone. In this work, the matrices used were biodegradable and they were mixed with renewable and biodegradable wood-based fillers called lignocelluloses. Lignocelluloses increase the stiffness and strength of biocomposites while also increasing their renewable content. Lignocelluloses are often not readily compatible with polymers, and this prevents the desired improvement of properties. To tackle this problem, ways of making lignocellulose and polymers more compatible through reactive extrusion, a method where chemical reactions are executed while melting and mixing the components, were investigated. The purpose of using reactive extrusion was to create chemical or physical links between the lignocellulose and the polymers, to achieve a better performance. Several chemical reactions were studied and the properties of the resulting materials were determined. For example, pulp fibre-based biocomposites reacted via crosslinking were twice as stiff as the polymer alone and the elongation was four times that of the non-reacted biocomposites. Crosslinking also enabled the biocomposite to shrink when heated, a property needed for some packaging. The biodegradation in compost and mechanical recycling through multiple extrusions were assessed for some of the materials.
Drivkrafter
Hållbar utveckling
Ämneskategorier
Materialteknik
Styrkeområden
Materialvetenskap
ISBN
978-91-8103-067-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5525
Utgivare
Chalmers
FB-Salen, Kemigården 1, Chalmers
Opponent: Professor Manjusri Misra, University of Guelph, Canada