Correlating molecular and crystallization dynamics to macroscopic fusion and thermodynamic stability in fused deposition modeling; a model study on polylactides

Srinivas, Varun; Hooy-Corstjens, Catharina S. J. van; Harings, Jules

doi:10.1016/j.polymer.2018.03.063

Cited by 69 publications

(77 citation statements)

References 45 publications

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“…As a matter of fact, Conditions 1, 3, 4, and 5 possess very similar degrees of crystallinity after the third zone due to the fact that they all experience a similar thermal history during the third zone with a T build plate of 110 • C. Findings by other authors support these trends [43][44][45][46][47]. The large difference in melting enthalpy between Condition 6 using LMWPA and the conditions printed with HMWPA illustrates the substantial effect of a decrease in molecular weight on the total degree of crystallinity that is developed over the course of the FFF process, already demonstrated in the literature for PLA [30]. Applying the correction for reflection originating from the nozzle of the print head onto the simulated thermal profile has very little influence on the eventual melting enthalpies for both Conditions 1 and 6, as can be seen in Figure 10, for both monitored layers.…”

Section: Approximation Of Thermal Profiles and Simulation In Fscsupporting

confidence: 71%

“…As a consequence, the development of interlayer strength and crystallization will become time-dependent [26,27]. Thermal monitoring of the FFF process to extract the non-isothermal temperature profile of a printed layer has been extensively reported in the literature, either by utilizing a thermocouple [28][29][30] or through infrared (IR) thermography [31][32][33][34][35][36][37][38]. Other authors have successfully attempted to model the temperature profiles within consecutively deposited layers [32,[39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

“…A slower print speed is also suggested to contribute to a higher degree of crystallinity. For PLA, both a high L-enantiomeric purity and low molecular weight have been shown to greatly intensify crystallization kinetics, indicating the possibility to alter crystallization during FFF on a molecular level [30].…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Crystallinity Development during Fused Filament Fabrication through Fast Scanning Chip Calorimetry

et al. 2019

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Although semi-crystalline polymers are associated with considerably better mechanical properties and thermal stability compared to their amorphous counterparts, using them as feedstock for Fused Filament Fabrication still poses some major challenges. Hence, the development of printed part crystallinity during printing should be fully understood in order to control the developed weld strength, as well as part shrinkage and warpage. Infrared thermography was utilized to record the thermal history of deposited layers while printing a single-layer wall geometry, employing two PA 6/66 copolymers with distinct molecular weights as feedstock. Print settings were varied to establish which settings are essential to effectively monitor final part crystallinity. The resulting temperature profiles were simulated in a Fast Scanning Chip Calorimetry device that allows for the rapid heating and cooling rates experienced by the printed polymer. Both liquefier temperature and print speed were found to have very little influence on the total attained crystallinity. It became apparent that the build plate, set at a temperature above the polymer’s glass transition temperature, imposes a considerable annealing effect on the printed part. A reduced molecular weight was observed to enhance crystallinity even more strongly. The presented methodology proves that Fast Scanning Chip Calorimetry is an effective tool to assess the impact of both print parameters and feedstock characteristics on the crystallization behavior of semi-crystalline polymers over the course of printing.

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Section: Approximation Of Thermal Profiles and Simulation In Fscsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

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Assessment of Crystallinity Development during Fused Filament Fabrication through Fast Scanning Chip Calorimetry

et al. 2019

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“…At this nonequilibrium transition, a metastable phase is formed, yet the crystallization potential of the material is not exhausted. Moreover, variation in the thermal characteristics occurs between different strands, though the degree of crystallinity of the polymer at the top and side strands is usually lower due to faster cooling and that of the bottom layers is determined by the build platform temperature, that is, higher temperature favors obtaining higher crystallinity . In order to complete the crystallization of PLA, either in pure form or constituting the matrix of a composite, that is, to increase the crystallinity degree of the material processed by various thermal and solvent methods, a subsequent annealing treatment may be required …”

Section: Introductionmentioning

confidence: 99%

Enhancement of Mechanical Properties of FDM‐PLA Parts via Thermal Annealing

Wach

Wolszczak

Adamus-Włodarczyk

2018

Macro Materials & Eng

172

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The objective of this study is to investigate the possibility of enhancing mechanical properties of poly(lactic acid) (PLA) samples processed by a rapid manufacturing (RM) technique by increasing PLA crystallinity degree via thermal annealing. The samples are manufactured by fused deposition modeling (FDM) at different temperatures and subsequently evaluated by three‐point bending flexural and tensile tests. The polymer processed at 215 °C is thermally annealed over its glass transition temperature in order to increase the degree of crystallinity to the maximum attainable level as measured by the differential scanning calorimetry and confirmed by X‐ray diffraction. The increase in the degree of crystallinity of FDM‐PLA enhances flexural stress of the samples by 11–17%. The study also demonstrates applicability of radiation sterilization for FDM‐PLA parts. Therefore, thermal annealing might be introduced into a standard RM technology of PLA, particularly for sterilizable customized implants, to efficiently improve their mechanical properties.

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“…Because of the stacking process of cylindrical filaments, there is an inevitable range of corrugated structures (such as wavy shapes) on the surface of printing specimens . The layer thickness of the corrugated structure (shown in the XZ plane of Figure c) determines the product appearance quality and is a key factor in the forming process.…”

Section: Resultsmentioning

confidence: 99%

Preparation and Rheological and Mechanical Properties of Poly(butylene succinate)/Talc Composites for Material Extrusion Additive Manufacturing

Zhou

Xia²,

Liu

et al. 2019

Macro Materials & Eng

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In this paper, poly(butylene succinate) (PBS) with a low melting point and a similar performance to polyethylene is employed as a printing material; talc is introduced into the matrix to enhance the melt strength of pure PBS during printing. The PBS/talc composite 3D printing filament is prepared by melt extrusion, and the thermal, mechanical, morphological, and rheological properties of the composites are investigated. The results show that the addition of talc to PBS leads to an increase in crystallization temperature. In addition, the tensile and flexural strengths of the injection‐molded specimens increase when the talc concentration increases. However, the mechanical properties of the printed specimens exhibit an opposite variation trend due to their distinct forming process. The printing temperature is 135 °C, which is far lower than those of commercial grade polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) printing filaments. Scanning electron microscopy (SEM) images show that increasing the talc concentration creates better printed formability and well‐organized fracture surface structures. By comparing printed fishbones, the results suggest that the presence of talc leads to a good printing performance with the composite. Furthermore, the rheological results reveal that η*, G′, and G″ are enhanced by the addition of talc.

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Correlating molecular and crystallization dynamics to macroscopic fusion and thermodynamic stability in fused deposition modeling; a model study on polylactides

Cited by 69 publications

References 45 publications

Assessment of Crystallinity Development during Fused Filament Fabrication through Fast Scanning Chip Calorimetry

Assessment of Crystallinity Development during Fused Filament Fabrication through Fast Scanning Chip Calorimetry

Enhancement of Mechanical Properties of FDM‐PLA Parts via Thermal Annealing

Preparation and Rheological and Mechanical Properties of Poly(butylene succinate)/Talc Composites for Material Extrusion Additive Manufacturing

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