Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
Doctoral thesis, 2023

Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces.

The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.

molybdenum disulfide

magnesium stearate

thermomechanical pulp

alkyl ketene dimer

friction

rheology

Lecture hall 10:an, Kemigården 4, Gothenburg
Opponent: Professor Mark Hughes

Author

Seyedehsan Hosseini

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry

Reducing friction between metal and thermo-mechanical pulp using alkyl ketene dimers and magnesium stearate Seyedehsan Hosseini, Roujin Ghaffari, Anette Larsson, Gunnar Westman, and Anna Ström

På grund av miljöhänsyn behöver vi minska användningen av plast och syntetiska polymerer. Det är därför forskare letar efter hållbara naturresurser som är lika kostnadseffektiva och starka som traditionella alternativ. En lovande kandidat är termomekanisk massa (TMP) fibrer. Dessa fibrer kommer från träd och är kostnadseffektiva att producera, produceras utan kemisk bearbetning och genererar högt utbyte, det vill säga små volymer av sidoströmmar genereras.

Det finns dock utmaningar. TMP-fibrer flödar inte under höga temperaturer, vilket syntetiska polymerer gör. På grund av detta tillsätter man ofta TMP till en matrix av syntetiska polymerer, vilket förbättrar flödesegenskaperna något, men tillsats av höga halter TMP gör produktion svår och energikrävande. Dessutom blandar TMP dåligt med syntetiska polymerer, vilket ytterligare komplicerar bearbetning. I det här arbetet undersöker jag om bearbetning av TMP och syntetiska polymerer kan förenklas genom tillsats av magnesium stearat (MgSt), molybdenum disulfide och alkyl keten dimer (AKD).

Resultaten visar att alla tillsatser förbättrade interaktionen mellan syntetiska polymeren och TMP-fibrerna. Dessutom visar resultaten att tillsatts av AKD till TMP-fibrer möjligen förenklar bearbetning av TMP med polypropylen, en syntetisk polymer. Resultaten visar också att friktionen mellan TMP och metall reduceras vid temperaturer relevanta för termisk bearbetning, om MgSt och AKD tillsätts. Reducerad friktion mellan metall och TMP kan potentiellt ha inverkan på helhetsbearbetning.

Subject Categories

Polymer Chemistry

Physical Chemistry

Paper, Pulp and Fiber Technology

Manufacturing, Surface and Joining Technology

Polymer Technologies

Textile, Rubber and Polymeric Materials

Materials Chemistry

Metallurgy and Metallic Materials

Organic Chemistry

Composite Science and Engineering

Driving Forces

Sustainable development

ISBN

978-91-7905-940-8

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5406

Publisher

Chalmers

Lecture hall 10:an, Kemigården 4, Gothenburg

Opponent: Professor Mark Hughes

More information

Latest update

10/23/2023