The results this work, present a step forward of the industrial application of Bio composites in polypropylene reinforced with short Alfa fibers, in particular in the field of dental appliances.
International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 12, December 2019, pp 390-398 Article ID: IJMET_10_12_041 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=12 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication MORPHOLOGICAL AND THERMOMECHANICAL CHARACTERIZATION OF INJECTED BIO COMPOSITES WITH POLYPROPYLENE REINFORCED BY SHORT ALFA FIBERS Maryama Essajii Ecology and environment laboratory, Applied Microbiology team, Ben M’sik Faculty of Sciences, Hassan II University, Morocco Fatiha Rhrich Laboratory of odontological sciences, Oral biology team, Faculty of Dentistry, Hassan II University, Morocco Mariam Benhadou Laboratory of industrial management and energy and technology of plastics and composites ENSEM - Hassan II University, Casablanca Morocco Jamal Mouslim Ecology and environment laboratory, Applied Microbiology team, Ben M’sik Faculty of Sciences, Hassan II University, Morocco Abdellah Haddout Laboratory of industrial management and energy and technology of plastics and composites ENSEM - Hassan II University, Casablanca Morocco ABSTRACT Bio-composites based on natural fibers have aroused a lot of interest in various industrial fields, such as the medical field, in particular the dental field The socioeconomic and environmental aspects have their role in the development prospects of these products The results this work, present a step forward of the industrial application of Bio composites in polypropylene reinforced with short Alfa fibers, in particular in the field of dental appliances We applied different surface treatments to the obtained fibers, in order to promote their adhesion with the polypropylene matrix We have conducted an in-depth study for the definition and optimization of the industrial http://www.iaeme.com/IJMET/index.asp 390 editor@iaeme.com Maryama Essajii, Fatiha Rhrich, Mariam Benhadou, Jamal Mouslim and Abdellah Haddout, conditions for injection molding of the Bio composites produced We have highlighted the impact of surface treatment and injection molding conditions, such as mold temperature and injection speed: on the morphology as well as the thermo mechanical properties of the injected parts Key words: Bio-Composite, Polypropylene /short alfa fibers, alkaline treatment, injection molding, morphology, mechanical behavior Cite this Article Maryama Essajii, Fatiha Rhrich, Mariam Benhadou, Jamal Mouslim and Abdellah Haddout, Morphological and Thermo mechanical Characterization of Injected Bio Composites with Polypropylene Reinforced by Short Alfa Fibers International Journal of Mechanical Engineering and Technology, 10(12), 2019, pp 390-398 http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=12 INTRODUCTION Bio-composites based on vegetable fibers have an evident development in several activities with many industrial applications Plant fibers are sought after for several advantages: environmental, enduring development, economic and health techniques which industries could take advantage of: renewable raw material, biodegradability and carbon neutral balance, low density, energy saving, flexibility, low cost, recycling, no health problem for operators on the production lines [1-7] Bio composites based on Alfa fibers can find their applications in the health sector such as dentistry (in particular for mobile devices) or the automotive sector for applications such as interior door trim, cars roof boxes, bumpers However, technical obstacles exist during the processing of these fibers, in particular on specific technical developments Currently, the main areas of technical development of fibers and associated bio-materials are in improving the fibers properties by optimizing industrial process parameters [6] Alfa fibers are biological structures mainly composed of cellulose, hemicellulose and lignin [9] Unlike other fiber components which have an amorphous structure, cellulose has a largely crystalline structure Inside the fiber, the cellulosic chains are brought together in micro-fibrils which, when agglomerated, form fibrils, the angle which exists between these very structured elements and the axis of the fiber conditions the stiffness of the fiber [7-8] Alfa fibers have the following composition: 45% cellulose, 25% hemicellulose, 23% lignin, 5% wax and 2% ash At the structural level, observation by scanning electron microscopy shows that an alfa rod consists of bundles of fibers with lignin Their shape is a kind of tube whose section is not circular The largest dimension of the tube section is approximately 200 µm [9-1 0] The hydrophilic nature of plant fibers is the cause of the lack of compatibility with the more hydrophobic polymer matrix Very few links exist between the “reinforcement” phase and the “matrix” phase This incompatibility causes poor dispersion of the fibers in the matrix and the formation of a heterogeneous material [11-1 2] The objective of this work is the mastery of the overall process of extracting alfa fibers and producing various formulations of thermoplastic bio-composites made of polypropylene (PP) reinforced with short Alfa fibers We were particularly interested in the study of the influence of fibers treatment conditions and the conditions of processing by injection on the microstructure and the behavior of mechanical strength of our bio-composites [13] http://www.iaeme.com/IJMET/index.asp 391 editor@iaeme.com Morphological and Thermo mechanical Characterization of Injected Bio Composites with Polypropylene Reinforced By Short Alfa Fibers We collected the ALFA plant from the Boulemane region in the High Atlas in Morocco Extracting Alfa fibers from raw stems is a multi-step process The structure of the stem is complex It needs multiple consecutive treatments in order to remove all of the non-cellulosic components We applied different surface treatments, on the fibers obtained, with Sodium hydroxide and Maleic Anhydride, in order to promote their adhesion with a polypropylene matrix MATERIALS AND EXPERIMENTAL TECHNIQUES 2.1 Materials The thermoplastic used in our composites is an isotactic polypropylene with a density of 0.902 g /cm3 and a melt flow index of 25g /10min at 230°C according to ISO1133 standard The Alfa fibers used have an average length of 2.3 mm We have added 4.5% maleic anhydride polypropylene to our blend Polypropylene modified with maleic anhydride (MA) which is a coupling agent composed of long polymer chains with an MA functional group grafted on extremity MAPP acts as a bridge between non-polar polypropylene and polar cellulose fibers The MA group binds to the surface of the cellulose by forming covalent or hydrogen bonds with the reactive OH groups on the surface of the cellulose and lignin The rest of the chain remains free and forms tangles with the chains of the PP polymer The fiber / thermoplastic polymer mixture, the coupling agent and the additives were extruded and granulated in our laboratory using an extruder, the screw profile of which is suitable for compounding bio-composites, according to a defined procedure 2.2 Injection molding of standard test sample We carried out this study using an industrial injection press with a closing force of 120 tones, fitted with a 35 mm diameter screw The injection machine is controlled by a microprocessor This system allows in particular the automatic adjustment of the press (mold closing force, the heating collars temperature, the barrel and the rheometer, ) and the adjustment of the injection cycle parameters (injection speed, holding pressure, holding time, cooling time, injection pressure, ) We studied the molding behavior of different formulations and defined the transformation conditions for each one Then we produced standardized tensile test pieces using a doublecavity of instrumented technical mold These are tensile test pieces defined according to ISO standard R527 The main injection parameters used are described in Table 1: Table 1: The main injection parameters Injection parameter Values Injection temperature 200 °C Mold temperature 35-50-70°C Ejection temperature 75°C Injection pressure 50MPa Holding pressure 45 MPa Holding time 6s http://www.iaeme.com/IJMET/index.asp 392 editor@iaeme.com Maryama Essajii, Fatiha Rhrich, Mariam Benhadou, Jamal Mouslim and Abdellah Haddout, Speed of screw rotation 60 -85 - 115 tours/min Injection speed 25 -35 - 55 mm/s Using an experimental design, we conducted an in-depth study for the definition and optimization of the injection molding conditions of the bio-composites produced We have determined the optimum processing parameters for our materials and we have manufactured standardized test pieces Then, we carried out on our test samples a series of analyzes and characterizations These tests have allowed us to better understand the interaction between the processing parameters and the characteristics of the parts made of bio-composites based on short Alfa fibers RESULTATS ET DISCUSSION 3.1 Morphological characterization We first carried out a series of morphological analyzes on the test pieces in order to validate the chosen injection parameters These tests were carried out using a reflection optical microscope in order to study the orientation, distribution and breakage of the fibers in several areas of the test piece: Injection threshold, medium, extremities and end of filling The morphological observations allowed evaluating the phenomenon of the Alfa fibers orientations in the polypropylene matrix, to observe the porosity defects on the injected composites and to evaluate the influence of the injection conditions on fiber agglomeration and the thickness of the molding skin During the flow of the composite in the mold cavity, each fiber moves and is oriented according to the constraints imposed by its environment: the matrix, the other fibers, the cavity walls, the mixture viscosity and the thermal gradient in the mold After solidification, we observe a complex orientation distribution which varies according to position in the part Thus, the overall observation of a sample cut from the thickness of the test piece shows the distribution and orientation of the fibers in different areas (Figure 1) The fibers have a random orientation in the skin followed by a layer where the fibers are oriented parallel to the direction of flow, and a middle zone where the alpha fibers are oriented in the direction perpendicular to the flow The thicknesses of the different layers vary greatly depending on the mold temperature and the injection speed Figure 1: Distribution and global fibers orientation in the thickness of the injected part Zone 1- At the extremities: the fibers are randomly oriented in the plane of the part, Zone 2- Shear zone: the fibers are oriented parallel to the flow direction, Zone 3- In the center: the fibers are oriented perpendicular to the flow direction http://www.iaeme.com/IJMET/index.asp 393 editor@iaeme.com Morphological and Thermo mechanical Characterization of Injected Bio Composites with Polypropylene Reinforced By Short Alfa Fibers 3.2 Mechanical characterization The relaxation tests were carried out using the LLOYD LR50K type apparatus on ISO 527 type specimens This machine is equipped with a thermostatically controlled chamber cooled by a circulation of nitrogen and possibly heated by an electrical resistance and air ventilation During each relaxation test, the constancy of the deformation is ensured by extensometers of high precision and the temporal evolution of the stress is recorded with an acquisition rate of points / second The relaxation tests were carried out throughout the experiment at controlled temperatures Tensile tests were carried out on standardized test pieces injected according to the conditions defined in table FIG shows the evolution of the stress at break of the polypropylene bio-composite reinforced with different levels of treated short Alfa fibers We can clearly see a change in the tensile behavior of the composite as a function of the fiber content, in particular a marked reduction in deformation as a function of the fiber content of Alfa, with an improvement in the breaking stress 40 35 Constraint (MPa) 30 10% 25 20 30% 15 10 0 0.01 0.02 0.03 0.04 0.05 Déformation(%) Figure 2: Evolution of the tensile behavior of polypropylene reinforced with different rates of short Alfa fibers (Mold temperature 35 °C) In Figure 3, we present the average values of the elasticity modulus as a function of the fiber content This increases greatly with the Alfa fibers rate http://www.iaeme.com/IJMET/index.asp 394 editor@iaeme.com Maryama Essajii, Fatiha Rhrich, Mariam Benhadou, Jamal Mouslim and Abdellah Haddout, 7000 Module (Mpa) 6000 5000 4000 3000 2000 1000 0 10 20 30 40 50 Fibers rate (%) Figure 3: Young's modulus of the injected parts as a function of the treated Alfa fibers rate Figure shows the variation of the strain at break depending on the fiber content, with or without coupling agent Graph’s Analysis shows that the elongation at break decreases when the fiber content increases and more markedly for fiber composites with coupling agent Figure 4: Deformation at break as a function of the Alfa fiber content (Mold temperature 35°C) In low fiber volume fractions, the effect of surface treatment on breaking strain is more marked For higher volume fractions, there is a slight influence of the coupling agent These results attest to an influence of the nature of the fiber treatments on the behavior of deformation at break and deformation at flow of bio composites This influence is much more marked by the presence of the coupling agent in low content of short Alfa fibers As the mold temperature increases, the modulus of elasticity and the breaking stress increase, while the elongation at break decreases This evolution can be explained by the decrease in thickness of the layer instantly solidified during filling of the cavity when the mold temperature increases, and this result in a more developed microstructure of the final part and therefore better rigidity 3.3 Viscoelastic behavior of PP bio-composites/ short alfa fibers http://www.iaeme.com/IJMET/index.asp 395 editor@iaeme.com Morphological and Thermo mechanical Characterization of Injected Bio Composites with Polypropylene Reinforced By Short Alfa Fibers The thermo mechanical tests were carried out with a dynamic mechanical measuring device (DMTA) This measurement gives: the variation of the elastic modulus E’ and the viscous modulus E’’ as a function of the temperature at a given frequency, as well as the mechanical damping coefficient tgδ Regardless of the fiber content, the general shape of the curves is identical The fall in modulus E ’observed between -20 and 10 ° C can be attributed to the main relaxation of the chains associated with the glass transition phenomenon, and E’ continues to decrease until the melting temperature not visible here These curves clearly show the three zones which also characterize the viscoelastic behavior of the composites (Figure 5) Figure 5: Evolution of the dynamic elastic modulus E ' and the viscous modulus E'' and the tangent of the mechanical loss angle as a function of temperature of injected polypropylene reinforced with 30% of treated short alfa fibers (Mold temperature 70°C) Figure shows an increase in the dynamic elastic modulus E ’of the bio composite as a function of the rate of short alfa fibers This increase can be explained by the improvement in the stiffness of the polypropylene and a better transfer of the stress across the interface (from the matrix to the fibers) Figure 6: Evolution as a function of the temperature of the dynamic elasticity module E ' of the polypropylene bio-composite reinforced with different rates of short Alfa fibers treated (With coupling agent- Mold temperature 50°C) CONCLUSION We have carried out an in-depth study for the definition and optimization of industrial conditions for injection molding of bio composites made with polypropylene / short Alfa fiber http://www.iaeme.com/IJMET/index.asp 396 editor@iaeme.com Maryama Essajii, Fatiha Rhrich, Mariam Benhadou, Jamal Mouslim and Abdellah Haddout, We have determined the optimum processing parameters for our materials and manufactured standardized test pieces Morphological observations made it possible to analyze the behavior of Alfa fibers in flow along an injected part We have highlighted the fiber's distribution and orientation phenomena as a function of the parameters of processing by injection The mold temperature and the injection speed induce large changes in mechanical properties When the mold temperature increases, the values of the breaking stress and the elasticity modulus increase markedly The work carried out in this study represents a very important step towards understanding Alfa's strengths in the form of fibers, this qualities and this possibilities of becoming one of the most widely used fibrous plants in the bio-composites industry REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] Bodros E., Pillin I., Montrelay N et Baley C, Could biopolymers reinforced by randomly scattered flax fibre be used in structural applications, Composites Science and Technology, 67, 462-470, 2007 Sajjan Kumar Lal, Dr Hari Vasudevan; International Journal of Engineering Research and Development Volume 7, Issue 5, PP.35-39, June 2013 A Haddout M Benhadou, F Rhrich; Brevet: Matériaux composites base de fibres d’Alfa – déposé au Maroc 2014 Hajnalka H., Racz I et Anandjiwala R.D., Development of Hemp Fibre Reinforced Polypropylene; Polypropylene Composites Journal of Thermoplastic Composite Materials, 21(2), 165–174 https://doi.org/10.1177/0892705707083949 Brahim BS, Cheikh RB, Baklouti M The alfa fibres in composite materials Proceedings of ICCM-13 conference, 2001, Beijing,China Campos AR, Cunha AM, Cheikh RB 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Mouslim and Abdellah Haddout, Morphological and Thermo mechanical Characterization of Injected Bio Composites with Polypropylene Reinforced by Short Alfa Fibers International Journal of Mechanical... http://www.iaeme.com/IJMET/index.asp 393 editor@iaeme.com Morphological and Thermo mechanical Characterization of Injected Bio Composites with Polypropylene Reinforced By Short Alfa Fibers 3.2 Mechanical characterization The relaxation... Characterization of Injected Bio Composites with Polypropylene Reinforced By Short Alfa Fibers [13] [14] Beg M.D.H., Pickering K.L., (2008b), Mechanical performance of Kraft fibre reinforced polypropylene composites: