| Titre : | Synthesis and characterization of composites: thermoplastic/lignocellulosic fibers from the Biskra region |
| Auteurs : | Nedjla Debabeche, Auteur ; Boussehel Hamida, Directeur de thèse ; Oum Kelthoum Kribaa, Directeur de thèse |
| Type de document : | Thése doctorat |
| Editeur : | Biskra [Algérie] : Faculté des Sciences Exactes et des Sciences de la Nature et de la Vie, Université Mohamed Khider, 2023 |
| Format : | 1 vol. (131p.) / ill., couv. ill. en coul / 30 cm |
| Langues: | Anglais |
| Langues originales: | Anglais |
| Mots-clés: | Palm petiole fibers, Linear low-density polyethylene, Chemical treatment, Natural weathering Morphological, Mechanical, Dynamic mechanical. |
| Résumé : |
This study's main goal was to make an eco-friendly composite from palm petiole fibers that could be used as fillers in a linear low-density polyethylene (LLDPE) matrix with a loading of 15–25 wt% and to look into how the composites age naturally. To achieve this main objective, lignocellulosic fibers were prepared using successive treatments on the fiber surface (NaOH, hydrogen peroxide, and acetic anhydride). The NaOH pretreatment aimed to overcome the recalcitrance of lignocellulosic biomass. FTIR showed that pretreatment with NaOH helped the peroxide hydrogen treatment of NaOH-petiole fibers to break down biomass without separating it into different parts. This made it possible to get micrometric-sized lignocellulosic fibers. These lignocellulosic fibers that have been extracted are hydrophilic, which means that the hydroxyl groups in the fibers interact with water molecules. The hydrophilic nature of these lignocellulosic fibers often results in poor compatibility with hydrophobic polymeric matrices. Surface modification is therefore necessary to make them more hydrophobic and compatible with the hydrophobic matrices. For this reason, we treated the lignocellulosic fibers with acetic anhydride, which is used to modify the surface of the fibers and make them more hydrophobic. The scanning electron microscopy (SEM) results showed that the enhanced interfacial adhesion between the fibers and the matrix makes treated composites more rigid and more homogeneous, which means that the fibers are distributed more uniformly. The tensile modulus and flexural strength were all enhanced by adding 15-25% of untreated palm petiole fibers, while the tensile strength was decreased. Palm-petiole fiber composites' storage modulus increased, and the acetylated-alkali fiber (FNA) reinforced LLDPE composite showed the highest storage modulus. Loss modulus increased when palm petiole fibers were strengthened. The Tan delta of composites made from palm petiole fibers was low initially but expanded with fiber addition. After exposing the LLDPE/PPF composites to natural aging, we observed, by IRTF, the formation of several oxidation products, an increase in the crystallinity rate, and Young's modulus. Furthermore, the SEM images clearly show that the degradation is severe with aging. We concluded that successive treatments improve the performance of the palm petiole fiber and have the potential to create a new type of sustainable and eco-friendly material for various applications. |
| Sommaire : |
List of figures List of table VII General Introduction General Introduction . 1 Reference 4 Part I: General Review of the Literature Chapter I : Fibrous Materials I.1. Generality of lignocellulosic fibers ....... 7 I.2. Morphology of natural cellulosic fibers ........... 7 I.3. Lignocellulosic composition ..... 8 I.4. Date palm ... 10 I.5. Properties and uses of natural fibers.. 12 I.6. Lignocellulose modification ......... 13 a.Mechanical treatment 13 b.Chemical treatment .... 13 c.Chemical functionalization . 16 d.Pretreatment combination .. 17 Reference 19 Table of contents Chapter II : Composite Materials II.1. Generality of composite materials 23 II.2. Bio-composite materials 24 II.3. Polyethylenes (PE) . 25 II.4. Cellulose fiber-reinforced composite materials . 26 II.5. Properties of cellulose fiber-reinforced composites 27 a.Fiber aspect ratio b. Fiber volume fraction c. Fiber orientation d. Fiber dispersion ....28 e.Fiber/matrix interface adhesion ................ 28 f.Fibers type .. 28 II.6. Processes for composite materials ............................... 29 a.Extrusion and injection molding .............................. 29 b.Compression molding ......................................... 30 Reference ............................................................ 31 Chapter III : Degradation Of Biocomposite III.1. Degradation of biocomposites ............... 34 III.2. Natural weathering ................................... 34 III.2.1. Visual Changes Due to Natural Weathering ....................... 36 III.2.2. Process of water absorption by composites .................................. 37 III.2.3. Effect of Natural Weathering on Composite Structure ...................... 38 III.2.4. Effect of Natural Weathering on Thermal Properties ....................... 38 III.2.5. Effect of Natural Weathering on Mechanical Properties ....... 39 Reference 40 Part II: Experimental Study Chapter I : Materials and Methods I.1. Materials 45 I.1.1. Vegetable fibers .......................................... 45 I.1.2. Resin Linear low-density polyethylene ................................ 45 I.2. Methods ............................................................................ 46 I.2.1. Preparation of petiole fiber ....................................... 46 I.2.2. Chemical modification of palm petiole fibers ........................... 46 a.1st Treatment: Alkaline ............................ 46 b.2nd Treatment: Hydrogen peroxide ................ 47 c.3rd Treatment: Acetylation ........................................... 48 I.2.3. Mechanical modification of petiole fiber ....................... I.2.4. Elaboration of composites ....................................... 49 a.Extrusion of Linear low-density polyethylene/Petiole fibers .............. 49 b.Compression molding .............................. 51 I.2.5. Natural weathering test Chapter II : Techniques of Characterization II.1. Fourier Transform Infrared Spectrometry (FTIR) .. 55 Table of contents II.2. Scanning electron microscopy (SEM) ...................................... 56 II.3. Differential Scanning Calorimetry (DSC)/Thermogravimetric analysis (TGA) .......... 56 II.4. Dynamic mechanical analysis (DMA) ............... II.5. Tensile test ...................................... 58 II.6. Three-point bending .............................. 60 II.7. Hardness ........................................... 61 Reference ............................ 63 Part III: Results and discussion Chapter I : Characterization of the Palm Petiole Fibers I.1. FTIR Spectroscopy ...................................................... 66 I.2. Morphological characterization (SEM) .............................................. 68 I.3. Thermal analysis ........................................................... 70 I.3.1. Thermogravimetric analysis (ATG/DTG) ...................... 70 I.3.2. DSC analysis ............................................ 73 Reference ......................................... 75 Chapter II : Characterization of the Composites Elaborates II.1. Morphological characterization (SEM) ................................... 78 a.Load Effect .............................. 78 b.Treatment effect ................................ 79 II.2. Thermogravimetric analysis (ATG/DTG) ...................... 82 Table of contents a.Load Effect ................................ 82 b.Treatment effect .................. 84 II.3. Mechanical Properties ..................................... 88 II.3.1. Tensile testing ................................... 88 II.3.1.1. Tensile strengh ..................... 88 a.Load Effect .......................................... b.Treatment effect .................................................... 89 II.3.1.2. Young’s modulus ........................... Load Effect 90 b.Treatment effect ....................... 91 II.3.2. Flexural testing ................................. 93 II.3.2.1. Flexural strength ............. 93 a.Load Effect ..................... b.Treatment effect ...................................... 93 II.3.2.2. Flexural modulus ................................ 95 a.Load Effect ............................. 95 b.Treatment effect ........................... 96 II.4. Dynamic mechanical analysis (DMA) ..................... 97 II.4.1. Storage modulus (E') ............................................ 97 a. Load Effect ......................... 97 b.Treatment effect ................... 98 II.4.2. Loss modulus (E") .................. 99 a.Load Effect ............. 99 b.Treatment effect ... 100 II.4.3. Tan Delta ..... 101 a.Load Effect ........... 101 b.Treatment effect ... 102 Table of contents II.5. Hardness ... 104 a.Load Effect b. Treatment effect 105 Reference 107 Chapter III : Characterization of Composite After Natural Weathering III.1. Effect of natural weathering on the visual appearance (color) ..............14 III.2. Effect of natural weathering on weight loss ................ 115 III.3. Effect of natural weathering on the morphological structure ( 116 III.4. FTIR Spectroscopy . 119 III.5. Effect of natural weathering on the mechanical Properties . 125 III.5.1. Tensile testing . 125 III.5.1.1. Tensile strength . 125 III.5.1.2. Young’s modulus .. 126 Reference .................... 127 General Conclusion General Conclusion ......... 131 Appendices |
| Type de document : | Thése doctorat |
| En ligne : | http://thesis.univ-biskra.dz/id/eprint/6396 |
Disponibilité (1)
| Cote | Support | Localisation | Statut |
|---|---|---|---|
| TCH/109 | Théses de doctorat | bibliothèque sciences exactes | Consultable |
