High flexural modulus of PLA composites for FDM 3D printing using multifunctional octaspherosilicates

doi:10.21203/rs.3.rs-3759173/v1

Download PDF

Research Article

High flexural modulus of PLA composites for FDM 3D printing using multifunctional octaspherosilicates

https://doi.org/10.21203/rs.3.rs-3759173/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

This work extends prior investigations into creating a new nanocomposite using modified silsesquioxanes and spherosilicates. These modifiers are used as additives to PLA to manage its properties specifically for FDM 3D printing. Following the chemical composition and the ratio of functional groups, the miscibility and reactivity of the additives in the polymer matrix, their effect on the rheology and mechanical properties of the material, and the water contact angle of the surface can be controlled. The most important aspect is achieving better melting of the material during printing, which, combined with the appropriate printing parameters, can ultimately produce more robust objects with fewer voids and discontinuities.

spherosilicate

polylactic acid

FDM

3D printing

POSS

silsesquioxane

Designing and manufacturing components in the past has never been as simple and easily accessible as it is today. In recent years, the development of new technologies has made the design process much shorter. Additive technologies, commonly called 3D printing, have played a significant part in this. In the last ten years, more than forty thousand scientific articles have been published, and more than sixty thousand patent applications were filed on 3D printing alone, according to the Scopus database. One of the best-growing branches of 3D printing is the technology of incremental deposition of polymeric materials, particularly the Fused Deposition Modeling (FDM) technique. The FDM 3D printing process automatically creates objects from thermoplastic polymer materials based on digital models prepared in 3D modeling software. The material, in the form of a filament, is inserted into the print block, subjected to temperature, and then applied layer by layer to form the final object in three-dimensional space XYZ [1]. Thanks to the simple technical solutions used in FDM 3D printers, they are an affordable tool available to many consumers, especially in the manufacturing sector, as the cost of purchasing the apparatus is relatively small concerning the time it takes to produce an object and go from concept to a tangible physical part with virtually unlimited shapes. The use of 3D printing is expanding, constantly expanding into new areas of application, including biomedical engineering [2], the construction industry [3], art and education [4], or even 3D printed electronics components [5]. This entails improving existing materials and creating new solutions to make objects for special applications.

FDM 3D printing, like any other technology, has certain limitations resulting from the manufacturing method, such as the surface roughness, porosity occurring in the structure of printed objects, limiting their tightness, insufficient mutual strength of adhesion between individual layers of printouts affecting the strength of objects, or voids caused by the lack of filling of individual layers due to difficulties in feeding the material. The correct execution of objects also depends on the type of material used. The most used materials in 3D FDM printing include PLA [6], PETG [7], ABS [8], and more specialized polymers such as TPU [9], PEEK [10], PA12 [11], and a number of their composites. Among the defects resulting from the material used, we can distinguish: the buckling of objects caused by thermal shrinkage of the polymer, defects related to moisture in the materials, or those caused by not using the appropriate printing conditions, which are necessary when printing from more demanding materials [12]. Despite continuous advances in technical solutions in the construction of printers, the elimination of some process defects is not possible by improving hardware parameters, which is why several attempts to modify the properties of polymeric materials can be found in the literature [13]. Various types of natural and synthetic fiber [14], [15], as well as mineral powder fillers, are utilized to modify polymeric materials to influence parameters such as strength and tribological wear resistance or impart special physical properties. In the literature, powder fillers such as metal oxides (e.g., TiO2) are used as a coloring agent [16] and metal carbides are described. Du Y. et al. employed tungsten carbide to confer electroconductivity to PLA [17], Samoylenko D.E. et. al utilized CaC2 derived from industrial waste, which reduces processing shrinkage during printing and enhances strength properties [18]. In our previous work [19], on the other hand, we addressed the design of new polymeric materials by modifying them with spherosilicates containing different functional groups in their structure. Multiwalled oligomeric silsesquioxanes are hybrid organic-inorganic compounds with nanometer sizes and the general formula [RSiO_3/2]n, in which R can be a hydrogen atom or an organic group (alkyl, aryl, etc.). For application reasons, and because of their well-defined spatial structure, the most interesting subgroups are the T₈-caged silsesquioxanes, especially the subgroup of spherosilicates, which have additional siloxane bridges in their structure to separate the functional groups from the cube-core. The use of silsesquioxanes as modifiers of polymer properties is well documented in the literature [20]. Due to their specific properties resulting from their hydride inorganic-organic structure, not even a large addition of them can significantly shape new functionalities of modified materials, which are strictly dependent on the number and type of functional groups contained in the molecule of its derivatives.

This paper discusses new materials obtained by modifying polylactide with octaspherosilicate (OSS) derivatives, containing functional methacrylate (MA) and trimethoxysilane (TMOS) groups, in different molar ratios for use in FDM 3D printing. The effect of multifunctional derivatives on the mechanical properties (tensile, flexural, impact) of objects printed from PLA composites was determined. The use of multifunctional organosilicon derivatives significantly changes the physicochemical characteristics and microstructure of polylactide during the printing process, as confirmed by microscopic observations. The transformations occurring in the material under the influence of the applied modifiers change the failure mechanics of the composite under different loading conditions.

Materials

The Polylactide (PLA) used, specifically the Ingeo 2003D grade, was acquired from NatureWorks in Minneapolis, MN, USA. The following reagents were used: Tetraethoxysilane (TEOS), chlorodimethylsilane, tetramethylammonium hydroxide (TMAH) 25 wt% methanol solution from ABCR, vinyltrimethoxysilane from Linegal Chemicals (Warsaw, Poland), allyl methacrylate, chloroform-d, 2 wt% Karstedt’s catalyst xylene solution from Merck (Poznan, Poland), P2O5 and toluene from Avantor Performance Materials Poland S.A. (Gliwice, Poland). Toluene was degassed and dried through a distillation process involving P2O5 under an argon atmosphere.

The procedure for synthesis of Octadecyl-trimethoxysilyl octaspherosilicate derivatives (OSS-2MA-6TMOS, OSS-4MA-4TMOS, OSS-6MA-2TMOS)

The methodology for the synthesis of octaspherosilicate compounds in accordance with the methodology described in our previous work was used in this work. [21]. The reaction temperature was kept below 60°C to mitigate the effects of allyl methacrylate polymerization. The obtained products were identical in appearance and spectroscopic characteristics to those obtained in the referenced work. The products are presented on the Fig. 1.

Fabrication of Filaments

Preparation of granulates

To homogenize the polymer and additives, a laboratory two-roll mill ZAMAK MERCATOR WG 150/280 was used. 500g of PLA was used in the process, heated until melting, and then the additive was added until a mixture was obtained with an additive concentration of 5.0% by weight (based on the weight of the entire system). The mixing was carried out at a roller temperature of 210°C for 15 min, until the composition was fully homogeneous. The resulting mixture was then granulated using a SHINI SG-1417-CE mill and dried at 55°C/24 hours. The obtained granulates with a concentration of 5% by weight. diluted with pure PLA to the final additive concentration of 0.10, 0.25, 0.50, 1.0, 1.5, 2.5% by weight, respectively. The obtained granulate was extruded on a FILABOT EX6 single-screw extruder and then dried for 24 hours at 40°C.

Extrusion of Filaments

Fibers with a diameter of 1.75 mm were extruded from granulates of various concentrations using a FILABOT EX6 single-screw extrusion device. The extrusion temperatures from the nozzle to the feed zone were respectively: 170°C, 195°C, 190°C, 60°C.

3D Printing (FDM)

Two types of samples were printed from the filaments obtained in this work using the FDM method: dumbbells and barbells, using a Prusa i3 MK3S + 3D printer. The dimensions of the samples were in accordance with the PN-EN ISO 527-2 and EN ISO 178 standards. Printing parameters are given in Table 1.

Table 1

Process parameters for sample printing.
Layer height	0.18 mm
Top layer height	0.27 mm
Shells	2
Top and bottom layers number	3
Bottom layers number	3
Infill density	100%
Fill angle	45°
Infill pattern	Rectilinear grid
Printing speed	60 mm/s
Idle speed	80 mm/s
Extruder temp.	220°C
Table temp.	60°C

Analyses

Nuclear Magnetic Resonance (NMR) spectra for ¹H, ¹³C, and ²⁹Si were conducted at 25°C using Bruker Ascend 400 and Ultra Shield 300 spectrometers. CDCl3 was used as the solvent, and chemical shifts are presented in ppm, referencing the residual solvent (CHCl₃) signals for ¹H and ¹³C.

Contact angle assessments were conducted using the sessile drop method at standard room temperature and atmospheric pressure, using a Krüss DSA100 goniometer. Three independent measurements were taken for each sample, each with a 5 µl water droplet, and the results were averaged to reduce the impact of surface inhomogeneities.

Thermogravimetric analysis (TG) was carried out carried out with a NETZSCH 209 F1 Libra gravimetric analyzer. Each sample, weighing 5 ± 0.2 mg, was extracted from the granules and positioned in Al₂O₃ crucibles. The measurements were performed under a nitrogen atmosphere (flowing at 20 mL/min) within the temperature range of 30 to 800°C (heating rate of 10°C/min). Additionally, the differential scanning calorimetry (DSC) was conducted using a NETZSCH 204 F1 Phoenix calorimeter. Samples weighing 6 ± 0.2 mg were cut from the granules and inserted into an aluminum crucible sealed with a pierced lid. The measurements were carried out under a nitrogen atmosphere within the temperature range of 20 to 200°C, with a heating rate of 10°C/min.

The influence of the modifier addition on the mass flow rate (MFR) was assessed.

The effect of the modifier addition on the mass flow rate (MFR) was also determined Measurements were conducted with an Instron plastometer (Ceast MF20 model), according to the ISO 1133 standard. The assessment temperature was maintained at 190 ± 0.5°C, and the piston load applied was 2.16 kg.

For mechanical tests, such as tensile and flexural strength tests, type 1B dumbbell samples were printed in accordance with the EN ISO 527:2012 and EN ISO 178:2006 standards. Mechanical properties tests were carried out on the INSTRON 5969 universal testing machine with a maximum load force of 50 kN. The travel speed for tension and bending measurements was 2 mm/min.

For tensile and flexural strength tests, the obtained materials were printed into type 1B dumbbell specimens by EN ISO 527:2012 and EN ISO 178:2006, respectively. Tests of the obtained specimens were performed on a universal testing machine INSTRON 5969 with a maximum load force of 50 kN. The traverse speed for tensile and for flexural measurements was set at 2 mm/min. The Charpy impact test was carried out in accordance with the ISO 179-1 standard (samples without notches). The tests were performed using an Instron Ceast 9050 instrument. Six measurements were made for each tested material.

The surface of the printed samples was examined using scanning electron microscopy (SEM). Compositional analysis was also carried out using SEM-EDS. The tests were performed on the Quanta FEG 250 (FEI) instrument; SEM at 5 kV and EDS at 30 kV.

The surface of the samples after printing and mechanical testing was examined on a Keyence VHX 7000 digital light microscope with a 100x1000 VH-Z100T lens and a VHX 7020 camera.

Rheology

All the compositions were studied by MFI method (Fig. 2), as it is a simple, straight-forward method of measuring the flowability of polymers under low shear forces. Interestingly, it was found not only that all the compositions showed MFI parameter higher than that of neat PLA, but also that for OSS-6MA-2TMOS, together with decreasing additive loading, melt flow index would increase, while for the other two additives, it would stay unchanged within the statistical deviation threshold (Fig. 8). These results seemed unusual, as on one hand, the polymerizing additive, due to particles formation, can be seen similarly to fillers, where their addition usually causes MFI to drop, especially with increasing loading. On the other hand, the non-polymerized monomers, as mentioned above, may play the role of dilutant for the molten PLA, therefore increasing MFI. That, however, should be visible, especially for OSS-2MA-6TMOS, and increase together with the additive loading, while being either minimal or non-observable for OSS-6MA-2TMOS. Therefore, other factors needed to be considered. Chaka et al. observed that when using aluminum silicate dihydrate as a filler for isotactic polypropylene for FDM, the MFI would slightly increase in comparison to neat iPP, however, this observation was not discussed in much detail [33]. Salavati and Yousefi studied PP composites for FDM as well, however, they used bentonite and cloister clays as fillers; they observed a significant drop of complex viscosity when either filler was used [34]. They explained that the filler particles restrict polymer entanglements in the polymer melt, those being responsible for increasing the melt viscosity, as well as the unentanglement being responsible for the shear thinning of many polymers. The effect of filler particles prohibiting the polymer chain entanglement was discussed in more detail by Wang et al. when investigating iPP composites with montmorillonite [35]. They also observed an increase of MFI up to 2% filler loading and explained the effect based on the oriented filler particles preserving the unentangled state of the polymer chains after the application of shear forces. Based on the presented findings, we suggest that OSS-6MA-2TMOS at low loadings forms particles able to inhibit PLA entanglement in a molten state, while at higher loadings the effects of particle agglomeration and excessive matrix fill emerge. On the other hand, the effect of MFI value staying constant for all the additives above 1% may be the plastifying effect of the non-polymerized OSS monomers countering the filler effect of the polymerized particles.

Thermal analysis

DSC analysis of OSS additives confirmed their reactive nature causing their spontaneous curing polymerization. An exemplary DSC thermogram is presented on Fig. 3, where OSS-4MA-4TMOS was subjected to two heating cycles. During the first one, an exothermic event is visible with an onset at ~ 120℃ and a peak at 147℃. During the second cycle, no thermal effects are to be observed. Similarly, OSS-6MA-2TMOS showed the same polymerization onset, but due to larger share of methacrylate moieties, it had a peak at a higher temperature of 180℃, as during the initial curing polymerization, the monomers present in the system transform into oligomers of increasing molecular weight and viscosity, greatly side chain freedom of the remaining, unreacted methacrylic groups. interestingly, the reduction of chain freedom for OSS-6MA-2TMOS is so severe that during the second heating, further polymerization can be observed.

DSC of PLA and the compositions thereof with OSS compounds revealed that the effect of their addition to the polymer matrix is rather small and hardly different from one additive to another (Fig. 4, Table 2). The effect of lowered glass transition temperature may be explained based on three different phenomena - one is plasticisation of the polymer bulk by the remaining non-polymerized OSS monomers, as the effect is visible by increased MFI of all compositions (see section Rheology). In this case, the monomers act similarly to solvents for polymer film casting, where the small molecular additives affect the polymer entanglement and ordering and provide polymer plasticization [26]. This plasticization effect resulting in T_g reduction was observed earlier when studying PLA nanofibrillar networks modified with SSQ-8Cl [27]. The other reason may be the formation of an additional PLA layer of increased freedom at the PLA-polymerized OSS interphase if the attractive forces on the interphase are lower than those within bulk PLA. Such interphase phenomena affecting T_g of polymer composites and nanocomposites have been discussed earlier [28–31]. The third one may be the lowered entanglement of PLA chains, which will be discussed in more detail further. On the other hand, the effects of OSS addition on T_cc are somewhat less conclusive - for OSS-4MA-4TMOS and OSS-6MA-2TMOS no significant change in comparison to neat PLA can be observed, as the additives form rather large and poorly distributed agglomerates that do not affect the event of PLA cold crystallization. On the other hand, for OSS-2MA-6TMOS, the additive formed smaller and more distributed agglomerates, which reduced the chain mobility of PLA and therefore slightly increased the cold crystallization event temperature. This finding is similar to the previous one, where OSS limonene derivative was introduced into PLA [27]. The melting event temperature is similar in all cases, as it is mostly based on the properties of the bulk polymer itself. Small lowering of the melting temperature may be due to either plasticization effect or by presence of imperfect, metastable crystallites formed upon nucleation by particles of polymerized OSS [32].

Table 2

DSC data from the second heating cycle, PLA compositions at 2.5% additive loading
	Glass transition temperature, T_g [°C]	Cold crystallisation temperature, T_cc [°C]	Melting temperature, T_m [°C]
PLA neat	66.5	123.0	154.3
PLA/ OSS-2MA-6TMOS	62.3	126.4	152.6
PLA/ OSS-4MA-4TMOS	62.3	122.6	152.4
PLA/ OSS-6MA-2TMOS	62.3	121.9	152.5

Thermogravimetric analysis was applied to assess any possible impact of the additives on the thermal stability of the obtained composites. The standard parameters, i.e. T_5%, T_onset and T_max were recorded for that matter. Based on the obtained data (Fig. 5, Table 3), the additives did not affect the properties of bulk PLA. The reasons for such behavior may be that the additives are blended physically with the matrix, therefore not chemically changing the matrix polymer itself, and that they are polymerized into particles that show even more limited interaction with the polymer.

Table 3

Results of thermogravimetric analysis.
Sample name	5% mass loss, T_5% [°C]	Onset, T_onset [°C]	Maximum mass loss rate, T_max [°C]
PLA neat	339.4	354.1	371.5
PLA/ OSS-2MA-6TMOS	341.9	356.1	374.3
PLA/ OSS-4MA-4TMOS	339.4	352.1	370.0
PLA/ OSS-6MA-2TMOS	341.0	353.3	372.9

Contact Angle Measurements

The hydrophobic properties of the obtained PLA/OSS blends have been studied by a standard water contact angle (WCA) measurement method (Table 4). It is clear that up to 1.5% loading, none of the additives affected the material surface wetting to a statistically significant level. Only at 2.5%, small rise of hydrophobicity was observed. It was not, however, significantly different between particular OSS additives. As the studied additives were proven to polymerize and form particles within the polymer matrix, it suggests that the main reason behind the increased WCA values at 2.5% loading is of physical nature, that is, additional micro-roughness introduced by the polymerized additive. This theory is confirmed by the microscopy images of the surface of printed specimens in question, as rough surface of the extruded patterns is visible, accompanied by pores and spots of varying high at the highest loading.

Table 4

Water contact angle results
	Contact angle [°]
Concentration	0.1%	0.25%	0.5%	1%	1.5%	2.5%
PLA neat	74.7 ± 1,2
PLA/ OSS-2MA-6TMOS	70.9 ± 4.9	68.3 ± 4.4	74.4 ± 4.8	75.0 ± 5.2	75.8 ± 4.5	83.0 ± 4.9
PLA/ OSS-4MA-4TMOS	74.2 ± 2.6	72.8 ± 3.3	73.3 ± 2.3	73.0 ± 3.1	72.6 ± 4.5	86.8 ± 3.2
PLA/ OSS-6MA-2TMOS	77.8 ± 3.9	80.6 ± 4.3	78.7 ± 3.3	77.9 ± 4.8	68.3 ± 4.4	82.0 ± 4.7

Microscopic analysis of samples after 3D printing

Optical microscopy

The extruded filaments dedicated for FDM, made of the prepared PLA compositions with the obtained OSS additives, were studied under digital light microscope to assess the material homogeneity and structure at micro scale, and confirm the findings of the SEM-EDS. Under normal light conditions it was difficult to note any differences between the neat PLA and PLA/OSS blends, besides the less uniform fracture surfaces of the blends. However, when polarized light was applied for sample imaging, it revealed significant agglomerations of glass-like phase within all the PLA/OSS compositions, which can be attributed to the polymerized OSS compounds (Fig. 6). For OSS-4MA-4TMOS and OSS-2MA-6TMOS, these were not visible by SEM-EDS, as the agglomerates were surrounded by PLA saturated with well-dispersed additive, as it was suggested in our previous works [25]. It can also be seen that with the increasing number of methacrylate groups per molecule from OSS-2MA-6TMOS (Fig. 6D) to OSS-6MA-2TMOS (Fig. 6B), the size and quantity of the agglomerates formed by cured material does also increase, which is in line with SEM-EDS showing severe agglomeration in the latter system. At lower loadings, these agglomerations were also observable, to a lesser extent, however.

SEM-EDS

In order to test the miscibility of the used organosilicon compounds with PLA, SEM-EDS analysis of the obtained PLA/OSS compositions was performed, the results are shown in Fig. 7. At this scale, EDS allows for the detection of agglomerates and spots of polymer with no additive present and was previously used as a handy tool for assessing the compatibility of spherosilicate compounds with polymer matrices, including PLA [22, 23]. The results initially suggested that OSS-4MA-4TMOS and OSS-2MA-6TMOS provided rather satisfactory miscibility with PLA, while OSS-6MA-2TMOS underwent heavy agglomeration due to the reactive nature of methacrylate groups. These conclusions were further supplemented and revised after light microscopy studies, however (see section Optical microscopy). As OSS-6MA-2TMOS, OSS-4MA-4TMOS, and OSS-2MA-6TMOS all possess alkyl methacrylate groups in their molecular structure, they are prone to spontaneous, thermal polymerization, as well known for methyl methacrylate, where the reaction can be observed below 100°C and is rapid and repeatable above 120°C [24]. Meanwhile, the PLA/OSS blend preparation was performed at the temperature of 210°C, which can be considered well above the activation temperature for polymerization of the methacrylate compounds studied in this work. The highest share of methacrylate groups in OSS-6MA-2TMOS explains the agglomeration of the additive in PLA, as the reactive moieties cause polyaddition curing of the additive during processing, while the increased share of trimethoxysilyl groups provides better dispersion or solubility of the additives within PLA.

Mechanical analysis

Tensile tests were performed to investigate the effects of the additives on the mechanical properties of the obtained materials (Fig. 8–10). While at low loadings (0.10–0.25%), composites with OSS-2MA-6TMOS and OSS-4MA-4TMOS show tensile strength comparable to that of neat PLA, OSS-6MA-2TMOS addition up to 0.5% resulted in significant increase of both tensile strength (up to 69.9 ± 1.1 MPa at 0.1%) and elongation at break, the latter being also improved to lesser degree by the remaining additives. This effect may be linked to the improved flowability of PLA, as suggested by MFI. At higher loadings, all the mechanical parameters’ trends, besides elongation at break, become complex and their explanation is possible only based on sample microstructure analysis, as it is heavily influenced by the material flowability and homogeneity that OSS additives alter, in consequence affecting interlayer fusion and bonding, void formation during printing, and cracking, debonding and fracturing/necking under load, which we discussed in detail in a recent study [19]. At higher loadings, OSS-6MA-2TMOS application resulted in heavy heterogeneity of the PLA composites, which may be considered as structural discontinuities, however, void formation or delamination was less significant than at low loadings. This effect may explain the improved flexural strength (Fig. 9) or impact strength (Fig. 10). For the latter, the polymerized particles present may play the role of fracture propagation-inhibiting agent. For OSS-4MA-4TMOS, neither of the mechanical properties were satisfactorily improved, besides elongation at break, as observed for all the additives. The poor characteristics can be explained based on a variety of structural defects present in the printed samples, as severe delaminating was present, alongside heavy void formation and inconsistency of extrudate strand shape. Cracking was visible as well, meaning that the additive did not improve the impact strength of the bulk composite. Finally, OSS-2MA-6TMOS offered the most attractive mechanical properties of the resulting PLA composites, as, besides the mentioned tensile strength improvement at 0.1%, it showed an increase of both flexural strength and impact strength at higher loadings, most notably at 2.5%, where both properties were improved.

Additionally, the 3D printed samples after the Charpy impact testing were studied under the optical microscope (Fig. 11). The analysis reveals that, depending on the type and amount of the additive, the quality of the 3D printed samples changes significantly in terms of layer uniformness, interlayer fusion/delamination, void formation, and homogeneity within the extrudate phase. Neat PLA is characterized by an average print quality, where quite significant void formation can be seen, the voids showing some irregularities as well, and the interlayer fusion being limited, as the interlayer interphase is rather easily visible at the boundaries between any of the interconnected extrudate strands (Fig. 11A1, 11A2). Additionally, some delamination between the layers may be noted, which is a result of the mechanical load exerted on the sample during the impact test and therefore causing brittle failure not only in a plane perpendicular to the sample length and to the extrudate strands visualized on Fig. 11 (parallel to the direction of the force during the impact), but additionally in planes parallel to the sample length. OSS-6MA-2TMOS addition caused less uniform layer formation and material heterogeneity, and above 0.5% loading, severe inclusion of polymerized OSS agglomerated was observed and the blend became glassier in appearance (Fig. 11B3). Despite the uneven characteristics of the microstructure and the composite-like heterogeneity, the material at a higher loading of 1% showed less void formation or delamination. OSS-4MA-4TMOS behaved similarly to a limited extent, however, glassiness and material heterogeneity were less visible, and delamination and void formation were present at all loadings (Fig. 11C). The most interesting results were obtained for OSS-2MA-6TMOS, where even at the lowest loading, a reduction of void formation was noted (Fig. 11D1, 11D2). At 1% and above, material homogeneity and interlayer fusion were significantly improved, and instead of debonding, the fractures being present in random spots of the sample, with very little interlayer debonding/fracture, the microscopic images suggesting notch-initiated fracture in this case (Fig. 11D3). The smooth, uniform surface of the fracture confirms that OSS-2MA-6TMOS is characterized by the highest miscibility of the tested additives thanks to the high share of alkoxysilyl groups, which is in line with the finding of the last study [19].

This work was focused on the investigation of the applicability of functionalized spherosilicate compounds as processing additives for 3D printing-dedicated PLA blends. The additives were susceptible to thermal polymerization during PLA processing, therefore forming agglomerates and in consequence, producing composites with the matrix polymer. OSS-2MA-6TMOS, bearing the least number of polymerizable groups, showed good miscibility with PLA and significantly improved the microstructure of the 3D printed samples in terms of increasing interlayer fusion and decreasing void formation, in turn improving mechanical properties of the blend, such as tensile and flexural strength, or impact strength. Interestingly, the OSS-6MA-2TMOS, despite forming heavily agglomerated particles within PLA, also significantly improved the flexural strength of such obtained composite.

CRediT authorship contribution statement

Bogna Sztorch: Methodology and conceptualization, Formal analysis, Investigation, Data curation, Writing – original draft, Writing – review & editing, Supervision

Julia Głowacka: Formal analysis, Investigation, Writing – original draft

Eliza Romańczuk-Ruszuk: Formal analysis, Writing – review & editing,

Dariusz Brząkalski: Formal analysis, Investiation, Writing – original draft

Bogdan Marciniec: Validation, Writing – review & editing,

Robert E. Przekop: Validation, Writing – review & editing,

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Conflict of interest

The authors have no conflicts of interest to declare.

Ethical approval

There are no experiments utilizing human tissue in this publication.

Acknowledgments

This research was funded by the National Centre for Research and Development under the LIDER X project (LIDER/01/0001/L-10/18/NCBR/2019).

Patents: The results of this publication have been patented with Polish patent application no. P.445359

Kristiawan RB, Imaduddin F, Ariawan D, et al (2021) A review on the fused deposition modeling (FDM) 3D printing: Filament processing, materials, and printing parameters. Open Eng 11:639–649. https://doi.org/10.1515/eng-2021-0063
Ahangar P, Cooke ME, Weber MH, Rosenzweig DH (2019) Current Biomedical Applications of 3D Printing and Additive Manufacturing. Appl Sci 9:1713. https://doi.org/10.3390/app9081713
Wu P, Wang J, Wang X (2016) A critical review of the use of 3-D printing in the construction industry. Autom Constr 68:21–31. https://doi.org/10.1016/j.autcon.2016.04.005
Chen Y-H, Chang P-L (2018) 3D printing assisted in art education: Study on the effectiveness of visually impaired students in space learning. In: 2018 IEEE International Conference on Applied System Invention (ICASI). IEEE, Chiba, pp 803–806
Jian JR, Kim T, Park JS, et al (2017) High performance 3D printed electronics using electroless plated copper. AIP Adv 7:035314. https://doi.org/10.1063/1.4979173
Mushtaq RT, Iqbal A, Wang Y, et al (2023) Advancing PLA 3D Printing with Laser Polishing: Improving Mechanical Strength, Sustainability, and Surface Quality. Crystals 13:626. https://doi.org/10.3390/cryst13040626
Valvez S, Silva AP, Reis PNB (2022) Optimization of Printing Parameters to Maximize the Mechanical Properties of 3D-Printed PETG-Based Parts. Polymers 14:2564. https://doi.org/10.3390/polym14132564
Saenz F, Otarola C, Valladares K, Rojas J (2021) Influence of 3D printing settings on mechanical properties of ABS at room temperature and 77 K. Addit Manuf 39:101841. https://doi.org/10.1016/j.addma.2021.101841
Rodríguez-Parada L, de la Rosa S, Mayuet PF (2021) Influence of 3D-Printed TPU Properties for the Design of Elastic Products. Polymers 13:2519. https://doi.org/10.3390/polym13152519
Oladapo BI, Zahedi SA, Ismail SO, Omigbodun FT (2021) 3D printing of PEEK and its composite to increase biointerfaces as a biomedical material- A review. Colloids Surf B Biointerfaces 203:111726. https://doi.org/10.1016/j.colsurfb.2021.111726
Vidakis N, Petousis M, Velidakis E, et al (2022) Multi-functional polyamide 12 (PA12)/ multiwall carbon nanotube 3D printed nanocomposites with enhanced mechanical and electrical properties. Adv Compos Mater 31:630–654. https://doi.org/10.1080/09243046.2022.2076019
Wickramasinghe S, Do T, Tran P (2020) FDM-Based 3D Printing of Polymer and Associated Composite: A Review on Mechanical Properties, Defects and Treatments. Polymers 12:1529. https://doi.org/10.3390/polym12071529
Przekop RE, Gabriel E, Pakuła D, Sztorch B (2023) Liquid to Fused Deposition Modeling (L-FDM)—A Revolution in Application Chemicals to 3D Printing Technology—Mechanical and Functional Properties. Appl Sci 13:8462. https://doi.org/10.3390/app13148462
Lee CH, Padzil FNBM, Lee SH, et al (2021) Potential for Natural Fiber Reinforcement in PLA Polymer Filaments for Fused Deposition Modeling (FDM) Additive Manufacturing: A Review. Polymers 13:1407. https://doi.org/10.3390/polym13091407
Heidari-Rarani M, Rafiee-Afarani M, Zahedi AM (2019) Mechanical characterization of FDM 3D printing of continuous carbon fiber reinforced PLA composites. Compos Part B Eng 175:107147. https://doi.org/10.1016/j.compositesb.2019.107147
Sztorch B, Głowacka J, Hanuszewska A, et al (2022) Modified titanium dioxide for 3D printing applications [in:] Advances in biomedical engineering. https://doi.org/10.24427/978-83-67185-49-3_13
Du Y, Chen J, Liu X, et al (2018) Flexible n-Type Tungsten Carbide/Polylactic Acid Thermoelectric Composites Fabricated by Additive Manufacturing. Coatings 8:25. https://doi.org/10.3390/coatings8010025
Samoylenko DE, Rodygin KS, Ananikov VP (2023) Sustainable application of calcium carbide residue as a filler for 3D printing materials. Sci Rep 13:4465. https://doi.org/10.1038/s41598-023-31075-z
Sztorch B, Brząkalski D, Głowacka J, et al (2023) Trimming flow, plasticity, and mechanical properties by cubic silsesquioxane chemistry. Sci Rep 13:14156. https://doi.org/10.1038/s41598-023-40784-4
Kausar A (2017) State-of-the-Art Overview on Polymer/POSS Nanocomposite. Polym-Plast Technol Eng 56:1401–1420. https://doi.org/10.1080/03602559.2016.1276592
Raszewski Z, Brząkalski D, Jałbrzykowski M, et al (2022) Novel Multifunctional Spherosilicate-Based Coupling Agents for Improved Bond Strength and Quality in Restorative Dentistry. Materials 15:3451. https://doi.org/10.3390/ma15103451
Brząkalski D, Sztorch B, Frydrych M, et al (2020) Limonene Derivative of Spherosilicate as a Polylactide Modifier for Applications in 3D Printing Technology. Molecules 25:5882. https://doi.org/10.3390/molecules25245882
Brząkalski D, Przekop RE, Dobrosielska M, et al (2020) Highly bulky spherosilicates as functional additives for polyethylene processing—Influence on mechanical and thermal properties. Polym Compos 41:3389–3402. https://doi.org/10.1002/pc.25628
Fenouillot F, Terrisse J, Rimlinger T (1998) Thermal Polymerization of Methyl Methacrylate at High Temperature. Int Polym Process 13:154–161. https://doi.org/10.3139/217.980154
Brząkalski D, Przekop RE, Sztorch B, et al (2020) Silsesquioxane Derivatives as Functional Additives for Preparation of Polyethylene-Based Composites: A Case of Trisilanol Melt-Condensation. Polymers 12:2269. https://doi.org/10.3390/polym12102269
Kong D, Yang M, Zhang X, et al (2021) Control of Polymer Properties by Entanglement: A Review. Macromol Mater Eng 306:2100536. https://doi.org/10.1002/mame.202100536
Frydrych M, Sztorch B, Brząkalski D, et al (2022) Silsesquioxane-Doped Electrospun Nanofibrillar Membranes for Separation Systems. Polymers 14:3569. https://doi.org/10.3390/polym14173569
Mayes AM (2005) Softer at the boundary. Nat Mater 4:651–652. https://doi.org/10.1038/nmat1470
Bansal A, Yang H, Li C, et al (2005) Quantitative equivalence between polymer nanocomposites and thin polymer films. Nat Mater 4:693–698. https://doi.org/10.1038/nmat1447
Ash BJ, Schadler LS, Siegel RW (2002) Glass transition behavior of alumina/polymethylmethacrylate nanocomposites. Mater Lett 55:83–87. https://doi.org/10.1016/S0167-577X(01)00626-7
Emamy H, Kumar SK, Starr FW (2020) Structural Properties of Bound Layer in Polymer–Nanoparticle Composites. Macromolecules 53:7845–7850. https://doi.org/10.1021/acs.macromol.0c01465
Mofokeng JP, Luyt AS, Tábi T, Kovács J (2012) Comparison of injection moulded, natural fibre-reinforced composites with PP and PLA as matrices. J Thermoplast Compos Mater 25:927–948. https://doi.org/10.1177/0892705711423291
Chaka KT (2022) Fused deposition modeling of polypropylene-aluminium silicate dihydrate microcomposites. E-Polym 22:87–98. https://doi.org/10.1515/epoly-2022-0014
Salavati M, Yousefi AA (2019) Polypropylene–clay micro/nanocomposites as fused deposition modeling filament: effect of polypropylene-g-maleic anhydride and organo-nanoclay as chemical and physical compatibilizers. Iran Polym J 28:611–620. https://doi.org/10.1007/s13726-019-00728-0
Wang K, Liang S, Deng J, et al (2006) The role of clay network on macromolecular chain mobility and relaxation in isotactic polypropylene/organoclay nanocomposites. Polymer 47:7131–7144. https://doi.org/10.1016/j.polymer.2006.07.067

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

High flexural modulus of PLA composites for FDM 3D printing using multifunctional octaspherosilicates

Status:

Version 1

Abstract

Figures

Introduction

Experimental

Materials

The procedure for synthesis of Octadecyl-trimethoxysilyl octaspherosilicate derivatives (OSS-2MA-6TMOS, OSS-4MA-4TMOS, OSS-6MA-2TMOS)

Fabrication of Filaments

Preparation of granulates

Extrusion of Filaments

3D Printing (FDM)

Analyses

Results and Discussion

Rheology

Thermal analysis

Contact Angle Measurements

Microscopic analysis of samples after 3D printing

Optical microscopy

SEM-EDS

Mechanical analysis

Conclusions

Declarations

References

Additional Declarations

Status:

Version 1