Abstract. Drying cellulose nanocrystals (CNCs) while maintaining their nanoscale dimensions is a ... more Abstract. Drying cellulose nanocrystals (CNCs) while maintaining their nanoscale dimensions is a major challenge for uses which require a dry form of the material. Three methods were examined here to dry CNC suspensions: (1) air drying, (2) freeze drying (FD), and (3) spray-drying (SD). The effect of drying methods on the morphology, thermostability, and surface energy of CNCs was evaluated using scanning electron microscopy, thermogravimetric analysis, and inverse gas chromatography. Air-drying formed solidly packed CNCs. FD formed ribbon-like structures of CNCs with nanoscale thicknesses. SD formed particles with a size distribution ranging from nanometers to several microns. Freeze-dried CNCs had a lower dispersion component of surface energy than air-dried and spray-dried CNCs. The drying methods do not significantly affect the onset temperatures of thermal degradation of CNCs. Spray-drying is proposed as a technically suitable manufacturing process to dry CNC suspensions.
Cellulose nanomaterials have attracted a great deal of interest as sustainable alternatives to no... more Cellulose nanomaterials have attracted a great deal of interest as sustainable alternatives to nonrenewable or fossil fuelderived materials, particularly in composite applications. Cellulose nanofibrils (CNF) are most often derived from wood sources through energy-intensive and costly mechanical fibrillation processes. In this study, recycled cardboard, referred to as old corrugated cardboard (OCC), was investigated as an alternate CNF source. OCC is a recycled material that can be obtained at one-tenth the cost of the commonly used bleached softwood Kraft pulp and can be refined to similar levels with nearly one-half of the energy consumption. Additionally, the distinct composition and morphology of OCCderived CNF provides a more favorable fiber−matrix interface and better reinforcement capabilities of the cellulose nanofibrils in polymer matrices, displaying an over 70% increase in tensile modulus at a loading of 40 wt % with no decrease in tensile strength. When paired with biobased poly(L-lactide) (PLLA), OCC-derived CNF is proven to be an attractive low-cost and low-energy reinforcing agent for sustainable, high performance nanocomposites.
Journal of Thermoplastic Composite Materials, 2019
The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fibe... more The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fiber–high-strength styrenic copolymer plastic composites (wood–plastic composites (WPCs)) was investigated on specimens preconditioned for 1 month under water immersion (distilled water (DW) and saltwater (SW)). These specimens were then tested in the same conditions for short-term creep and creep-recovery response using a submersible clamp. The short-term creep tests of WPC specimens (that are immersed in water as a function of different temperatures) have not yet been reported in previous studies. The objective of this study was to determine whether the hygrothermal creep response of WPC material evaluated through water immersion differs from the creep response published in the literature for other environmental exposure conditions. The experiments included measuring 30 min of creep and 30 min of creep recovery on the specimens immersed in SW and DW at two different levels of flexural str...
ABSTRACTThe uniform dispersion of cellulose nanofibers (CNFs) in non‐polar polymer matrices is a ... more ABSTRACTThe uniform dispersion of cellulose nanofibers (CNFs) in non‐polar polymer matrices is a primary problem to overcome in creating novel nanocomposites from these materials. The aim of this study was to produce CNF‐polyethylene (PE) nanocomposites by melt compounding followed by injection molding to investigate the possibility of using polyvinyl alcohol (PVA) to improve the dispersion of CNF in the PE matrix. The tensile strength of CNF‐ filled composites was 17.4 MPa with the addition of 5 wt % CNF–PVA, which was 25% higher than the strength of neat PE. The tensile modulus of elasticity increased by 40% with 5% CNF–PVA addition. Flexural properties also significantly increased with increased CNF loading. Shear viscosity increased with increasing CNF content. The elastic moduli of the PE/CNF composites from rheological measurements were greater than those of the neat PE matrix because of the intrinsic rigidity of CNF. Melt creep compliance decreased by about 13% and 45% for th...
ABSTRACT This study is to investigate the reinforcing effects of fillers on mechanical and physic... more ABSTRACT This study is to investigate the reinforcing effects of fillers on mechanical and physical properties of foamed styrene-maleic anhy- dride (SMA) composites. According to the results, the best foaming was determined for starch reinforced SMA composite. The best result of expansion ratio was found as 22.75% to SMA/starch composites. Stereo light microscopy results demonstrated that the foamed cell distribution is heterogeneous and composed of two sec- tions. The minimum density was found as 0.64g/cm3 for foamed SMA/starch composites. Mechanical properties of all foamed com- posites were found to be low as compared to neat SMA composite.
There is considerable interest in the automotive industry towards light-weighting vehicles throug... more There is considerable interest in the automotive industry towards light-weighting vehicles through the application of new material technologies, and polymer matrix composites are of primary importance in meeting the goals of light-weighting. In addition, the application of renewable materials like wood and plant fibers is of interest in meeting sustainability goals and replacement of petroleum-derived feedstocks. This paper presents results of a study examining novel hybrid polypropylene composites using a combination of cellulose nanofibrils and talc for potential use in automobile applications. The composites were compounded using a laboratory scale co-rotating extrusion system, and test samples were prepared by injection molding tensile, flexure and impact test specimens. The tensile and flexural properties of the hybrid composites were determined using an Instron testing machine and the Izod impact strength was determined on Ceast Impact tester. Cellulose nanofibrils can replace...
Driven by the motive of minimizing the transportation costs of raw materials to manufacture wood–... more Driven by the motive of minimizing the transportation costs of raw materials to manufacture wood–plastic composites (WPCs), Part I and the current Part II of this paper series explore the utilization of an alternative wood feedstock, i.e., pellets. Part I of this study reported on the characteristics of wood flour and wood pellets manufactured from secondary processing mill residues. Part II reports on the physical and mechanical properties of polypropylene (PP)-based WPCs made using the two different wood feedstocks, i.e., wood flour and wood pellets. WPCs were made from 40-mesh wood flour and wood pellets from four different wood species (white cedar, white pine, spruce-fir and red maple) in the presence and absence of the coupling agent maleic anhydride polypropylene (MAPP). With MAPP, the weight percentage of wood filler was 20%, PP 78%, MAPP 2% and without MAPP, formulation by weight percentage of wood filler was 20% and PP 80%. Fluorescent images showed wood particles’ distrib...
Abstract Cellulose nanomaterials (CNMs) naturally exist in plant biomass. The success of extracti... more Abstract Cellulose nanomaterials (CNMs) naturally exist in plant biomass. The success of extraction of CNMs opened up a new era of using plant biomass for innovative industrial applications. Because CNMs are abundant, renewable, biodegradable, transparent, light weight and low in cost, they are ideal materials for large volume applications such as packaging, automotive, building and infrastructure. In many potential application areas, CNM-enabled products appear in a composite form, mostly polymer composites. The industrial-scale manufacturing of CNM/thermoplastic composites remains as a set of unsolved problems for academia and industry. A prime challenge in applications is the nanoscale dispersion of CNMs in thermoplastic matrices during melt processing. Both bench-scale and pilot-scale studies have been conducted to solve the dispersion issue of CNMs. In this article, research related to the dispersion of CNMs in thermoplastic matrices during melt processing were critically reviewed. All research papers were classified into three groups: chemically-aided dispersion, physically-aided dispersion and mechanically-aided dispersion. Numerous factors affect the CNM dispersion and the mechanical performance of its nanocomposites. There are material-related factors, including CNM types and forms, polymer matrices, surface modification, coupling agents, etc. Extrusion processing parameters also play a significant role, covering screw rotation speed, extrusion barrel temperature settings and screw design. In addition, the material-related factors interact with the processing-related factors. Understanding all factors and their interactions are important for moving CNM nanocomposites research a step further towards industrial-relevant production, which is the final ambitious goal of this manuscript.
The production of cellulose nanofibrils (CNFs) continues to receive considerable attention becaus... more The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution. Pretreating biomass by biological, chemical, mechanical, or physical means can render plant feedstocks more facile for processing and thus lower energy requirements to produce CNFs. CNFs from nonconventional fibrillation methods have been investigated for various applications, including films, composites, aerogels, and Pickering emulsifiers. Continued research is needed to develop protocols to standardize the characterization (e.g., degree of fibrillation) of the lignocellulosic fibrillation processes and resulting CNF products to make them more attractive to the industry for specific product applications.
This study revealed the effects of spraydried cellulose nanofibril (SDCNF) addition (3,10 and 30 ... more This study revealed the effects of spraydried cellulose nanofibril (SDCNF) addition (3,10 and 30 wt%) and maleic anhydride polypropylene (MAPP) coupling agent (2 wt%) on the mechanical properties of polypropylene (PP). Results indicated that the elastic moduli of the PP composites increased as the SDCNF content increased above 10 wt%. The addition of MAPP into the SDCNF/PP composites did not improve the elastic moduli. Flexural strength of PP was improved when the SDCNF content increased above 10 wt%, while the tensile strength of PP decreased as the SDCNF content increased. The addition of MAPP into the SDCNF/PP composites increased the strength of the composites when the SDCNF content was above 10 wt%. Without the addition of MAPP, the composite's impact strength did not exhibit a significant increase among the pure PP and SDCNF/PP composites. No significant differences in crystallinity or crystal forms were found in the pure PP and PP/MAPP/SDCNF composites. The spherulitic size of PP was reduced after adding SDCNF into the PP.
Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared u... more Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared using the electrospinning method. PVA/CNC mats were reinforced with weight concentrations of 0, 20 and 50% CNC (w/w) relative to PVA. Scanning electron microscopy was used to measure the fiber diameter, which ranged from 377 to 416 nm. Thermogravimetric analysis (TGA) confirmed the presence of CNC fibers in the mat fibers which were not visible by scanning electron microscope (SEM). Mechanical testing was conducted using ASTM D 638 on each sample group at 10 mm min−1. Neat PVA and PVA/CNC mats were heat treated at 170 °C for 2h hours, and the morphological structure was maintained with some fiber diameter reduction. Mechanical property results after heat treatment showed a decrease in tensile strength, an increase in tensile stiffness and a decrease in strain to yield (%). This effect was attributable to enhanced diffusion bonding of the mat fiber intersections. The CNC fibers also increa...
Journal of Thermoplastic Composite Materials, 2019
The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modifie... more The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modified wood under hygrothermal treatment was studied and modeled. Multiple three-point bending creep/recovery tests were carried out using a dynamic mechanical thermal analyzer (DMTA) equipped with a submersible clamp. WPC specimens with a 15-mm span were subjected to two initial applied stresses; 9% and 14% of the flexural strength in 30 min of creep and 30 min of creep recovery under the combined effects of temperature (25°C, 35°C, and 45°C) and water immersion (saltwater (SW) and distilled water). A dry condition WPC control was used to compare the hygrothermal effects with respect to the control conditions. The WPC material in this article exhibited a linear viscoelastic behavior under the effect of temperature, whereas a nonlinear viscoelastic behavior was observed under immersion conditions. A power law model is considered a useful model to describe the creep behavior of WPC specimens w...
Few commodity semi-crystalline thermoplastics in neat form are used in fused deposition modeling ... more Few commodity semi-crystalline thermoplastics in neat form are used in fused deposition modeling (FDM) because they experience dimensional instability (warping) during printing. In this study, a commercially available polypropylene (PP) filament for FDM processing was used to print tensile and flexural test samples. Three printing parameters were investigated: (1) extrusion temperature (200, 250 °C), (2) printing speed (45, 90 mm/s) and (3) layer height (0.1, 0.3 mm). Differential scanning calorimetry (DSC) showed that FDM printed PP samples had fewer α-crystals and more β-crystals than injectionmolded (IM) PP samples. Scanning electron microscopy (SEM) indicated that a higher extrusion temperature, slower printing speed and smaller layer height facilitated the molecular diffusion at the interfaces and created a smaller neck size within the printed parts. Density measurements showed that IM PP samples were denser than the FDM PP samples. No differences in density were found among the FDM PP samples. Compared to the IM PP, the mechanical properties decreased less for the PP printed at higher extrusion temperature (< 11.5%). The FDM PP parts had similar or even increased flexural modulus compared to the IM PP.
Abstract. Drying cellulose nanocrystals (CNCs) while maintaining their nanoscale dimensions is a ... more Abstract. Drying cellulose nanocrystals (CNCs) while maintaining their nanoscale dimensions is a major challenge for uses which require a dry form of the material. Three methods were examined here to dry CNC suspensions: (1) air drying, (2) freeze drying (FD), and (3) spray-drying (SD). The effect of drying methods on the morphology, thermostability, and surface energy of CNCs was evaluated using scanning electron microscopy, thermogravimetric analysis, and inverse gas chromatography. Air-drying formed solidly packed CNCs. FD formed ribbon-like structures of CNCs with nanoscale thicknesses. SD formed particles with a size distribution ranging from nanometers to several microns. Freeze-dried CNCs had a lower dispersion component of surface energy than air-dried and spray-dried CNCs. The drying methods do not significantly affect the onset temperatures of thermal degradation of CNCs. Spray-drying is proposed as a technically suitable manufacturing process to dry CNC suspensions.
Cellulose nanomaterials have attracted a great deal of interest as sustainable alternatives to no... more Cellulose nanomaterials have attracted a great deal of interest as sustainable alternatives to nonrenewable or fossil fuelderived materials, particularly in composite applications. Cellulose nanofibrils (CNF) are most often derived from wood sources through energy-intensive and costly mechanical fibrillation processes. In this study, recycled cardboard, referred to as old corrugated cardboard (OCC), was investigated as an alternate CNF source. OCC is a recycled material that can be obtained at one-tenth the cost of the commonly used bleached softwood Kraft pulp and can be refined to similar levels with nearly one-half of the energy consumption. Additionally, the distinct composition and morphology of OCCderived CNF provides a more favorable fiber−matrix interface and better reinforcement capabilities of the cellulose nanofibrils in polymer matrices, displaying an over 70% increase in tensile modulus at a loading of 40 wt % with no decrease in tensile strength. When paired with biobased poly(L-lactide) (PLLA), OCC-derived CNF is proven to be an attractive low-cost and low-energy reinforcing agent for sustainable, high performance nanocomposites.
Journal of Thermoplastic Composite Materials, 2019
The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fibe... more The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fiber–high-strength styrenic copolymer plastic composites (wood–plastic composites (WPCs)) was investigated on specimens preconditioned for 1 month under water immersion (distilled water (DW) and saltwater (SW)). These specimens were then tested in the same conditions for short-term creep and creep-recovery response using a submersible clamp. The short-term creep tests of WPC specimens (that are immersed in water as a function of different temperatures) have not yet been reported in previous studies. The objective of this study was to determine whether the hygrothermal creep response of WPC material evaluated through water immersion differs from the creep response published in the literature for other environmental exposure conditions. The experiments included measuring 30 min of creep and 30 min of creep recovery on the specimens immersed in SW and DW at two different levels of flexural str...
ABSTRACTThe uniform dispersion of cellulose nanofibers (CNFs) in non‐polar polymer matrices is a ... more ABSTRACTThe uniform dispersion of cellulose nanofibers (CNFs) in non‐polar polymer matrices is a primary problem to overcome in creating novel nanocomposites from these materials. The aim of this study was to produce CNF‐polyethylene (PE) nanocomposites by melt compounding followed by injection molding to investigate the possibility of using polyvinyl alcohol (PVA) to improve the dispersion of CNF in the PE matrix. The tensile strength of CNF‐ filled composites was 17.4 MPa with the addition of 5 wt % CNF–PVA, which was 25% higher than the strength of neat PE. The tensile modulus of elasticity increased by 40% with 5% CNF–PVA addition. Flexural properties also significantly increased with increased CNF loading. Shear viscosity increased with increasing CNF content. The elastic moduli of the PE/CNF composites from rheological measurements were greater than those of the neat PE matrix because of the intrinsic rigidity of CNF. Melt creep compliance decreased by about 13% and 45% for th...
ABSTRACT This study is to investigate the reinforcing effects of fillers on mechanical and physic... more ABSTRACT This study is to investigate the reinforcing effects of fillers on mechanical and physical properties of foamed styrene-maleic anhy- dride (SMA) composites. According to the results, the best foaming was determined for starch reinforced SMA composite. The best result of expansion ratio was found as 22.75% to SMA/starch composites. Stereo light microscopy results demonstrated that the foamed cell distribution is heterogeneous and composed of two sec- tions. The minimum density was found as 0.64g/cm3 for foamed SMA/starch composites. Mechanical properties of all foamed com- posites were found to be low as compared to neat SMA composite.
There is considerable interest in the automotive industry towards light-weighting vehicles throug... more There is considerable interest in the automotive industry towards light-weighting vehicles through the application of new material technologies, and polymer matrix composites are of primary importance in meeting the goals of light-weighting. In addition, the application of renewable materials like wood and plant fibers is of interest in meeting sustainability goals and replacement of petroleum-derived feedstocks. This paper presents results of a study examining novel hybrid polypropylene composites using a combination of cellulose nanofibrils and talc for potential use in automobile applications. The composites were compounded using a laboratory scale co-rotating extrusion system, and test samples were prepared by injection molding tensile, flexure and impact test specimens. The tensile and flexural properties of the hybrid composites were determined using an Instron testing machine and the Izod impact strength was determined on Ceast Impact tester. Cellulose nanofibrils can replace...
Driven by the motive of minimizing the transportation costs of raw materials to manufacture wood–... more Driven by the motive of minimizing the transportation costs of raw materials to manufacture wood–plastic composites (WPCs), Part I and the current Part II of this paper series explore the utilization of an alternative wood feedstock, i.e., pellets. Part I of this study reported on the characteristics of wood flour and wood pellets manufactured from secondary processing mill residues. Part II reports on the physical and mechanical properties of polypropylene (PP)-based WPCs made using the two different wood feedstocks, i.e., wood flour and wood pellets. WPCs were made from 40-mesh wood flour and wood pellets from four different wood species (white cedar, white pine, spruce-fir and red maple) in the presence and absence of the coupling agent maleic anhydride polypropylene (MAPP). With MAPP, the weight percentage of wood filler was 20%, PP 78%, MAPP 2% and without MAPP, formulation by weight percentage of wood filler was 20% and PP 80%. Fluorescent images showed wood particles’ distrib...
Abstract Cellulose nanomaterials (CNMs) naturally exist in plant biomass. The success of extracti... more Abstract Cellulose nanomaterials (CNMs) naturally exist in plant biomass. The success of extraction of CNMs opened up a new era of using plant biomass for innovative industrial applications. Because CNMs are abundant, renewable, biodegradable, transparent, light weight and low in cost, they are ideal materials for large volume applications such as packaging, automotive, building and infrastructure. In many potential application areas, CNM-enabled products appear in a composite form, mostly polymer composites. The industrial-scale manufacturing of CNM/thermoplastic composites remains as a set of unsolved problems for academia and industry. A prime challenge in applications is the nanoscale dispersion of CNMs in thermoplastic matrices during melt processing. Both bench-scale and pilot-scale studies have been conducted to solve the dispersion issue of CNMs. In this article, research related to the dispersion of CNMs in thermoplastic matrices during melt processing were critically reviewed. All research papers were classified into three groups: chemically-aided dispersion, physically-aided dispersion and mechanically-aided dispersion. Numerous factors affect the CNM dispersion and the mechanical performance of its nanocomposites. There are material-related factors, including CNM types and forms, polymer matrices, surface modification, coupling agents, etc. Extrusion processing parameters also play a significant role, covering screw rotation speed, extrusion barrel temperature settings and screw design. In addition, the material-related factors interact with the processing-related factors. Understanding all factors and their interactions are important for moving CNM nanocomposites research a step further towards industrial-relevant production, which is the final ambitious goal of this manuscript.
The production of cellulose nanofibrils (CNFs) continues to receive considerable attention becaus... more The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution. Pretreating biomass by biological, chemical, mechanical, or physical means can render plant feedstocks more facile for processing and thus lower energy requirements to produce CNFs. CNFs from nonconventional fibrillation methods have been investigated for various applications, including films, composites, aerogels, and Pickering emulsifiers. Continued research is needed to develop protocols to standardize the characterization (e.g., degree of fibrillation) of the lignocellulosic fibrillation processes and resulting CNF products to make them more attractive to the industry for specific product applications.
This study revealed the effects of spraydried cellulose nanofibril (SDCNF) addition (3,10 and 30 ... more This study revealed the effects of spraydried cellulose nanofibril (SDCNF) addition (3,10 and 30 wt%) and maleic anhydride polypropylene (MAPP) coupling agent (2 wt%) on the mechanical properties of polypropylene (PP). Results indicated that the elastic moduli of the PP composites increased as the SDCNF content increased above 10 wt%. The addition of MAPP into the SDCNF/PP composites did not improve the elastic moduli. Flexural strength of PP was improved when the SDCNF content increased above 10 wt%, while the tensile strength of PP decreased as the SDCNF content increased. The addition of MAPP into the SDCNF/PP composites increased the strength of the composites when the SDCNF content was above 10 wt%. Without the addition of MAPP, the composite's impact strength did not exhibit a significant increase among the pure PP and SDCNF/PP composites. No significant differences in crystallinity or crystal forms were found in the pure PP and PP/MAPP/SDCNF composites. The spherulitic size of PP was reduced after adding SDCNF into the PP.
Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared u... more Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared using the electrospinning method. PVA/CNC mats were reinforced with weight concentrations of 0, 20 and 50% CNC (w/w) relative to PVA. Scanning electron microscopy was used to measure the fiber diameter, which ranged from 377 to 416 nm. Thermogravimetric analysis (TGA) confirmed the presence of CNC fibers in the mat fibers which were not visible by scanning electron microscope (SEM). Mechanical testing was conducted using ASTM D 638 on each sample group at 10 mm min−1. Neat PVA and PVA/CNC mats were heat treated at 170 °C for 2h hours, and the morphological structure was maintained with some fiber diameter reduction. Mechanical property results after heat treatment showed a decrease in tensile strength, an increase in tensile stiffness and a decrease in strain to yield (%). This effect was attributable to enhanced diffusion bonding of the mat fiber intersections. The CNC fibers also increa...
Journal of Thermoplastic Composite Materials, 2019
The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modifie... more The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modified wood under hygrothermal treatment was studied and modeled. Multiple three-point bending creep/recovery tests were carried out using a dynamic mechanical thermal analyzer (DMTA) equipped with a submersible clamp. WPC specimens with a 15-mm span were subjected to two initial applied stresses; 9% and 14% of the flexural strength in 30 min of creep and 30 min of creep recovery under the combined effects of temperature (25°C, 35°C, and 45°C) and water immersion (saltwater (SW) and distilled water). A dry condition WPC control was used to compare the hygrothermal effects with respect to the control conditions. The WPC material in this article exhibited a linear viscoelastic behavior under the effect of temperature, whereas a nonlinear viscoelastic behavior was observed under immersion conditions. A power law model is considered a useful model to describe the creep behavior of WPC specimens w...
Few commodity semi-crystalline thermoplastics in neat form are used in fused deposition modeling ... more Few commodity semi-crystalline thermoplastics in neat form are used in fused deposition modeling (FDM) because they experience dimensional instability (warping) during printing. In this study, a commercially available polypropylene (PP) filament for FDM processing was used to print tensile and flexural test samples. Three printing parameters were investigated: (1) extrusion temperature (200, 250 °C), (2) printing speed (45, 90 mm/s) and (3) layer height (0.1, 0.3 mm). Differential scanning calorimetry (DSC) showed that FDM printed PP samples had fewer α-crystals and more β-crystals than injectionmolded (IM) PP samples. Scanning electron microscopy (SEM) indicated that a higher extrusion temperature, slower printing speed and smaller layer height facilitated the molecular diffusion at the interfaces and created a smaller neck size within the printed parts. Density measurements showed that IM PP samples were denser than the FDM PP samples. No differences in density were found among the FDM PP samples. Compared to the IM PP, the mechanical properties decreased less for the PP printed at higher extrusion temperature (< 11.5%). The FDM PP parts had similar or even increased flexural modulus compared to the IM PP.
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