1,721,100 research outputs found
The influence of post-industrial and post-consumer recycling during Fused Filament Fabrication of PETG
No full textFused Filament Fabrication (FFF) is a commonly used additive manufacturing technique in which
filament is extruded through a heated nozzle onto a heated printer bed. In this manner the desired part
is produced layer by layer. This technique benefits from its ability to create highly specific parts in small
amounts, which is not possible with conventional techniques such as injection molding. However, some
challenges still occur such as material choice, definition of the printer settings, as well as the
sustainability aspect.
As polyethylene terephthalate (PET) is a commonly recycled material, this could be an interesting option
for FFF. However, amorphous materials are desirable for 3D printing, as these materials are less
susceptible to shrinkage and consequently deformations. An amorphous alternative for PET, namely
PETG or polyethylene terephthalate glycol, is in this case a better option. Nowadays this material is
already used for 3D printing, however, assessment of its recyclability is needed to decide if this material
is a sustainable option for FFF. For this purpose, four PETG grades, namely a low viscosity, medium
viscosity, high viscosity and high mechanical properties grade were investigated.
Filament was produced from each grade and used for printing with a commercial Prusa i3 MK3s printer.
Printing temperatures were varied between 215 and 270 °C, whereas printing speeds were varied
between 10 and 100 mm/s. Post-industrial recycling was simulated by adding up to 40 weight% recycled
PETG content from the filaments inside new filament for each grade. To simulate post-consumer
recycling, PET water bottles were collected, cleaned and shredded, and added inside new PETG
filament by 40 weight%.
From the results could be concluded that higher printing temperatures and lower printing speeds have
a positive effect on the mechanical properties. The influence of post-industrial PETG waste was
neglectable for the medium viscosity, high viscosity and high mechanical properties grade. For the low
viscosity grade, 20% post-industrial recycled content increased the mechanical properties whereas 40%
decreased the product’s quality. The introduction of post-consumer PET waste had a negative effect on
all grades, especially on the high mechanical properties grade, while the high viscosity grade was the
most resistant to a decrease in qualit
Additive manufacturing sensor design for energy harvest and action recognition
No full textSelf-powered flexible devices with multiple sensing abilities have attracted great attention due
to their broad application in the Internet of Things (IoT). Various methods have been proposed
to enhance the cheaper-fast or electric performance of flexible devices; however, it remains
challenging to realize the display and accurate recognition of motion trajectories for intelligent
control. Here we present a fully self-powered 3D printable-triboelectric bimodal sensor based
on ultra-long micro-nanostructured silver nano-wires (AgNWs) and thermoplastic elastomer,
which can patterned-display the force trajectories. The deformable silver nanowires used as
stretchable electrodes make the stress transfer stable through the overall device to achieve
outstanding self-powered properties. Moreover, the roughness of the surface is enhanced by
treatment with sandpaper which endows the resulting device with significantly improved
triboelectric performances (voltage increases from 5 to 16 V). We observed that the 3D
printing-obtained composite exhibited exceptional self-powered performances and sensing
properties, enabling the development of a highly reliable machine learning-based motion
recognition. This advancement offers a promising approach for future IoT-era devices focused
on advanced action interaction and smart wearable electronics
Effect of multiflow vibration injection molding on the filler dispersion and thermal conductivity of polyethylene composites
No full textThermoplastic composites are emerging as promising alternatives for thermal management application,
especially in the development of next-generation electronics and heat exchangers. These materials offer
several advantages over traditional metals, including lower cost, reduced weight, and superior corrosion
resistance. However, their utilization depends on the possibility to improve their thermal conductivity
(TC). Achieving high TC in thermoplastic composites involves careful design of the material, such as
selecting appropriate filler types and shapes, and optimizing processing parameters like dispersion
quality and mixing. Although much research has already been done on the thermal conductivity of
thermoplastic composites, the majority of it is focused on the less economically relevant compression
molding, while injection molding remain less researched. Injection molding is a versatile, non-continuous
processing technique used for making products of different shapes and sizes. During the processing,
molten polymer or composite is pushed into a mold cavity. The flow causes orientation of the fillers
present in the polymer matrix, resulting in a material with anisotropic properties. More specifically, a
skin-core structure will be visible in the product, where filler will be strongly aligned with the flow direction
near the mold walls, while the center will show more random filler alignment, or alignment resembling
the flow front. This anisotropic behavior influences thermal conductivity and should be considered when
designing the composite material.
The aim of this research is to analyse the effect of multiflow vibration injection molding (MFVIM) on the
filler dispersion and thermal conductivity of polyethylene composites containing multiple fillers. A highdensity polyethylene (HDPE) matrix is considered, doped with 1.0 m% carbon nanotubes (CNT) in
combination with three fillers of varying shapes and sizes, i.e., aluminum oxide (Al2O3; sphere-shaped),
graphite (G; platelet-shape) and expanded graphite (EG; platelet-shape). Conventional injection molding
(CIM) is compared to MFVIM in which three and five melt flows are introduced, each for three different
filler combinations. Scanning electron microscopy (SEM) is used to observe the orientation and
dispersion of the fillers in the produced parts and thermal conductivity measurements are done in the
in-plane (IP) and through-plane (TP) direction. SEM images of these injection-molded samples revealed
clear differences between the CIM and MFVIM with three and five melt flows. For the TC measurements,
the IP conductivity was much higher than the TP conductivity due to orienting of the fillers in the direction
of the flow during processing. Differences in TC could also be distinguished between the CIM and
MFVIM, as the IP TC showed an increase up to 37% when five melt flows were introduced during
vibration injection molding compared to conventional injection molding
A preliminary study on the flow-induced crystallization phenomenon in 3D printing of polyvinylidene fluoride
No full textFused Filament Fabrication (FFF) is a widely used additive manufacturing (AM) technique, renowned
for its versatility, affordability, and ease of use. It involves the layer-by-layer deposition of extruded
thermoplastic filaments to build three-dimensional objects. In the context of high-performance semicrystalline polymers, FFF, which is also known as 3D printing, presents both opportunities and
challenges due to the unique properties of these materials. A notable opportunity lies in the ability to
orient and align polymer chains. During the 3D printing process, both the shear flow within the nozzle
and the velocity gradients induced by deposition can significantly deform the polymer microstructure.
This deformation, termed flow-induced crystallization (FIC), mitigates kinetic barriers to crystallization
and directs the resultant morphology. This phenomenon of enhanced oriented crystallization could be
crucial for the production of piezoelectric devices of Polyvinylidene fluoride (PVDF). PVDF is a
thermoplastic semi-crystalline polymer distinguished by its polymorphism, with multiple crystalline
phases that significantly impact its properties and applications. The piezoelectric effect of PVDF is
closely linked to the β-phase content, morphology, and alignment, all of which are influenced by
processing conditions. This study aims to investigate the potential and limitations of flow-induced
crystallization for producing PVDF specimens with high β-phase content.
A Design of Experiments (DoE) methodology was employed to examine the effects of two factors,
printing speed and extrusion temperature, on various response variables. These response variables
were identified through comprehensive characterization analyses. Post-printing, measurements such as
the total crystallinity and the melting temperature were obtained via differential scanning calorimetry
(DSC), while the β-phase percentage was assessed using Fourier Transform Infrared Spectroscopy
(FTIR).
ANOVA analysis of the DSC results indicated that extrusion temperature is the critical parameter,
positively influencing total crystallinity. Conversely, the melting temperature was found to increase as
the extrusion temperature decreased. Furthermore, statistical analysis of the FTIR results reinforced the
significance of extrusion temperature on the crystallization phenomenon, revealing that the β-phase
content increased with decreasing extrusion temperature. From these findings, it can be inferred that
low extrusion temperatures could decrease system entropy due to the alignment of polymer chains
induced by the material flow. Additionally, a combination of increased extrusion temperature and low
printing speed promotes the nucleation and growth of crystals. However, this condition diminishes the
likelihood of achieving a microstructure characterized by a high β-phase percentag
Comparative study on PA12 and PA11 degradation for HP multi jet fusion process
No full textAdditive Manufacturing (AM) indicate the production of customized parts in polymer, metal or ceramic
material by mean of a layer by layer build up. Typically, 25 kg of polymer powder is used for one print.
However, the produced part will contain only 20% of all the material leaving 20 kg of post-industrial
polymer waste[1]. It is of great environmental and economical concern the improvement of the process
circularity through understanding of the polymeric powder aging.
PA powder is the most commonly adopted for power bed techniques and, among them, PA12 and PA11
are the most popular for MJF[2]. An increased interest on PA11 has arisen in the later years due to its
bio-based origin[3]. However, PA11 powder undergoes severe discoloration during printing, which has
been linked mainly to thermo-oxidative degradation[4]. A solution was proposed in this study regarding
the possibility to switch to an inert atmosphere. This will allow multiple recycling cycle of the powder.
We compared vacuum-aged and air-aged samples, which was the key to a better understanding on the
aging process and the effect of this last. Color analysis was performed on PA11 and PA12 powder, both
aged in vacuum and in presence of air. This analysis was coupled with molecular analysis, through
FTIR, which proved the formation of chromophore groups in the air aged powder. Moreover, to better
understand the mechanism, GPC analysis was performed, showing that the chain scission mechanism
happens simultaneously with other types of chain recombination. Finally The effect on the flow
properties of the melt were investigated through rheological analysis
Enhancing biodegradable packaging : comparative analysis of HDPE/starch-based blends
No full textThe widespread utilization of polymeric materials, particularly in the packaging industry, is driven by
their excellent properties including lightweight and low cost (1,2). However, the environmental impact of
these petroleum-based plastics, mostly polyolefins, necessitates a shift towards biodegradable
alternatives. In this context, starch-based polymers rise as a promising alternative to traditional
petroleum-based polymers in the food packaging sector (1–3). Starch offers the advantage of being
inexpensive, renewable and biodegradable. It is however impossible to thermally process dry starch
granules by itself, since the decomposition temperature of native starch is lower than its melting
temperature (4). Nevertheless, when mixed with a gelatinizer and subjected to heat and shear, starch
undergoes a destructurization, leading to a homogeneous melt known as thermoplastic starch (TPS)
(3). Despite its poor mechanical properties, blending TPS with HDPE, and introducing compatibilizers,
could improve its performance.
In the present work, blends of HDPE and starch are systematically compared. Starch will initially be
applied in its native granule state and will be blended with HDPE, at concentrations of 2,5 – 5 – 10 wt%
starch. Subsequently in a second approach, starch will first undergo gelatinization in a twin screw
extruder utilizing glycerol as a plasticizing agent before blending it with HDPE in concentrations up to
50 wt%. In a final phase, a compatibilizer, ethylene vinyl alcohol (EVOH), will be introduced to enhance
the compatibility within the HDPE/TPS blend. The morphological, thermal and mechanical
characterization of the blends is assessed by scanning electron microscopy (SEM), differential scanning
calorimetry (DSC), melt flow index (MFI), and tensile- and impact tests.
The results of the mechanical tests, tensile strength in particular, reveal that adding a compatibilizer is
not enhancing the strength of the material as depicted by the tensile strength results in Figure 1. This
can be explained by the SEM-images (Figure 2) that show a pronounced droplet morphology for the
HDPE/TPS (+EVOH) blends, leading to a brittle material with low tensile strength, whereas blends with
native starch show less but bigger droplets. Therefore it can be concluded that blends with native starch
are favorable when the starch content is lower than 10wt%, taking in mind the processing steps and
economical aspect. When >10wt% starch is required, HDPE/TPS are preferred since EVOH is not
enhancing the properties to a great extent and represents an additional chemical input
A preliminary study on the flow-induced crystallization phenomenon in 3D printing of polyvinylidene fluoride
No full textFused Filament Fabrication (FFF) is a widely used additive manufacturing (AM) technique, renowned for its versatility, affordability, and ease of use. It involves the layer-by-layer deposition of extruded thermoplastic filaments to build three-dimensional objects. In the context of high-performance semicrystalline polymers, FFF, which is also known as 3D printing, presents both opportunities and challenges due to the unique properties of these materials. A notable opportunity lies in the ability to orient and align polymer chains. During the 3D printing process, both the shear flow within the nozzle and the velocity gradients induced by deposition can significantly deform the polymer microstructure. This deformation, termed flow-induced crystallization (FIC), mitigates kinetic barriers to crystallization and directs the resultant morphology. This phenomenon of enhanced oriented crystallization could be crucial for the production of piezoelectric devices of Polyvinylidene fluoride (PVDF). PVDF is a thermoplastic semi-crystalline polymer distinguished by its polymorphism, with multiple crystalline phases that significantly impact its properties and applications. The piezoelectric effect of PVDF is closely linked to the β-phase content, morphology, and alignment, all of which are influenced by processing conditions. This study aims to investigate the potential and limitations of flow-induced crystallization for producing PVDF specimens with high β-phase content. A Design of Experiments (DoE) methodology was employed to examine the effects of two factors, printing speed and extrusion temperature, on various response variables. These response variables were identified through comprehensive characterization analyses. Post-printing, measurements such as
the total crystallinity and the melting temperature were obtained via differential scanning calorimetry (DSC), while the β-phase percentage was assessed using Fourier Transform Infrared Spectroscopy (FTIR). ANOVA analysis of the DSC results indicated that extrusion temperature is the critical parameter, positively influencing total crystallinity. Conversely, the melting temperature was found to increase as the extrusion temperature decreased. Furthermore, statistical analysis of the FTIR results reinforced the significance of extrusion temperature on the crystallization phenomenon, revealing that the β-phase content increased with decreasing extrusion temperature. From these findings, it can be inferred that
low extrusion temperatures could decrease system entropy due to the alignment of polymer chains induced by the material flow. Additionally, a combination of increased extrusion temperature and low printing speed promotes the nucleation and growth of crystals. However, this condition diminishes the likelihood of achieving a microstructure characterized by a high β-phase percentage
Enhancing thermal conductivity of ABS and short carbon fibre composites : influence of processing techniques on carbon fibre orientation
No full textPolymer composites play a significant role in the transition to a sustainable future due to their exceptional
material properties. By adding fillers to a matrix, thermal properties can be improved, allowing for
broader application of lightweight materials. This study focuses specifically on acrylonitrile butadiene
styrene (ABS) in combination with 15 w% short carbon fibres (sCF), which form a composite with
improved thermal conductivity. Although most research has focused on compression moulding, this
study examines other relevant techniques including extrusion-fused filament fabrication (FFF) and
injection moulding. To ensure superior material properties, the adhesion between the matrix and the
fibre is investigated, by comparing the compatibility between the matrix and untreated fibres, and matrix
and fibres that have undergone a surface treatment with nitric acid. Based on optical microscopy and
SEM, it could observed that fewer air voids were visible in the pellet with the treated fibre. Consequently,
the treated fibre showed significantly better adhesion to the matrix. The SEM images showed that the
treated fibres did not have increased surface roughness. Therefore, the improvement is due to the
formation of functional groups. Furthermore, the fibre length distribution of the untreated and treated
fibre after compounding showed that the treated fibre underwent less fibre breakage then the untreated
fibres, as a result of the improved adhesion protecting the fibres. The improvement in thermal
conductivity measured by the Transient Plane Source (TPC) method, is mainly influenced by fibre
orientation and not by fibre length, as the fibre length distributions for the three processing techniques
did not show significant differences. In contrary to literature, compression moulding resulted in
anisotropic properties due to high pressure and low temperature, which aligned the fibres and increased
the in-plane thermal conductivity to 1.737 ± 0.045 W/(m∙K) compared to the thermal conductivity of ABS
(0.1818 ± 0.0004 W/(m∙K)), while the through-plane conductivity decreased to 0.053 ± 0.007 W/(m∙K)
due to entrapped voids in the material. For single screw extrusion followed by FFF, the fibres were
aligned in the flow direction due to the shear forces present, resulting in an increased thermal
conductivity of 1.532 ± 0.018 W/(m∙K). In the through-plane direction, a decrease of 0.166 ± 0.002
W/(m∙K) was observed due to the weak adhesion between the layers. Finally, injection moulding showed
the smallest increase in thermal conductivity in the in-plane direction, due to the less alignment of the
fibres in the core layer, where shear is minimal. It should be noted that the in-plane thermal conductivity
at the end of the 1A tensile test bar showed a greater increase, namely 1.126 ± 0.013 W/(m∙K), whereas
at the gate the in-plane thermal conductivity was 0.999 ± 0.003 W/(m∙K). However, it shows the greatest
in-crease in through-plane thermal conductivity, namely 0.199 ± 0.001 W/(m∙K), which is more important
for most applications such as a heat exchanger
Increased impact toughness of mass polymerized ABS by tuning polymer orientation via vibration injection moulding
No full textIn many sectors, stretching from house hold appliances to the automotive industry, acrylonitrile
butadiene styrene (ABS) is applied for its promising material properties. More recent developments in
the industrial production process of this polymer have provided improved stability of the raw material by
using a continuous polymerization process, called mass polymerization. The ABS polymer resulting from
this process, named mABS, is however slightly different in morphological characteristics as it rather
mimics high impact polystyrene (HIPS) than the more conventional used emulsion polymerized ABS
(eABS). These morphological characteristics make mABS more prone to processing related deviations
in part performance and final product morphology. Hence, this research covers the effect of flow induced
orientation on impact performance of mABS parts. To emphasize the effect of orientation, parts were
produced using regular injection moulding and compared to specimens made by the novel method of
vibration injection moulding, which applies a much higher amount of shear during processing and thus
increased orientation within the final product.
Impact specimens were cut from platelet samples in the parallel and perpendicular direction respective
to the flow path. Differences in morphological orientation of the rubber phase were determined via
scanning electron microscopy (SEM) imaging. A distinct layered structure, providing increased
orientation, was observed for the vibration injection moulded samples. This higher orientation caused a
higher resistance against impact deformation applied in the perpendicular direction. For impact applied
parallel to the oriented rubber phase however, no difference for increased orientation was established.
This research could therefore draw similar conclusions as found in research covering performance of
HIPS. It can thus be concluded that a higher degree of orientation within mABS parts can positively
contribute to part performance, depending on the direction of deformation.
Comparing mABS to the more conventional eABS, it should be stressed that anisotropy after processing
mABS is indeed high. This might cause altered product performance upon altering the used ABS type
without considering process adaptations
Mechanical characterisation and fibre morphology analysis in ABS and short carbon fibre composites : influence of different polymer processing techniques
No full textPolymer composites have attracted considerable interest due to their potential to enhance mechanical
properties of polymers or advanced applications. Yet, challenges exist including complex mechanical
behaviour and poor affinity between reinforcement material and polymer matrix. This study investigates
the influence of various processing methods on the mechanical properties of acrylonitrile butadiene
styrene (ABS) reinforced with 15 wt% short carbon fibres (sCF), focusing mainly on fibre morphology.
By analysing injection moulding (IM), fused filament fabrication (FFF) and compression moulding (CM),
this research aims to elucidate the relationship between the processing method, fibre orientation and
mechanical properties. Improved affinity is achieved through nitric acid surface treatment. Scanning
electron and optical microscopy are used to analyse the morphology, revealing insights into void
presence and fibre roughness, length, distribution and orientation. Additionally, mechanical properties
are assessed through impact, tensile and flexural tests. Significant differences in morphology among
ABS/sCF composites produced by different methods are revealed. Microscopy images show that in IM
parts, fibres are highly aligned in the shear layer but exhibit a more varying orientation in the core, with
minimal voids. FFF parts exhibit excellent sCF alignment but show voids between different layers,
whereas CM parts display varying fibre orientations and small air inclusions. These differences notably
affect the mechanical properties. Test bars produced via IM demonstrate superior stiffness, tensile
strength and tensile strain at break, followed by FFF (which shows very high impact strength), while CM
parts exhibit the least favourable properties, partly due to their isotropic nature and random sCF
orientation. These outcomes can be immediately linked to the resulting morphologies. The findings of
this work highlight the critical role of processing methods and fibre morphology in determining composite
performance
- …
