The role of microcrystalline structure on optical scattering characteristics of semi-crystalline thermoplastics and the accuracy of numerical input for IR-heating modeling

Boztepe, Sinan; Gilblas, Rémi; Almeida, Olivier de; Gerlach, Christian; Maoult, Yannick Le; Schmidt, Fabrice

doi:10.1007/s12289-017-1386-z

Cited by 9 publications

(18 citation statements)

References 36 publications

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“…Since two different heating units were used for heating the samples in the temperaturedependent transmittance and reflectance tests, the waiting time for reaching steady-state temperature at each consecutive temperature step was different. In addition, for the R λ i,∩ (T) tests, a thin piece of black metal plate was mounted between the heating unit and the PE sample as our previous studies showed that PE is highly semi-transparent [5,16]. Thanks to this step, the amount of radiation flux that is transmitted through the sample medium would not reflect back and received by the detector, which may avoid having an erroneous reflectance measurement.…”

Section: Test Methodology For Temperature-dependent Spectroscopic Meamentioning

confidence: 99%

“…This point is discussed further in Ref. [5] based on the comparison between the T λ i,r and T λ i,∩ of PE samples prepared in different thicknesses and analyzed at room temperature. It was observed that the amount of backscattered light flux may be negligible in comparison to ϕ λ s considering the same spectral range, presented in Fig.…”

Section: Temperature-dependent Thermo-optical Properties Of Pementioning

confidence: 99%

“…The PE polymer has a milky color at lower temperatures and becomes totally transparent after 120°C. The reason behind these changes is obviously related to crystalline structure evolutions since the optical scattering becomes weaker at higher temperatures, especially closer to the melting range of PE [5]. In addition, the comparisons between the T λ i,r (T) and T λ i,∩ of an identical PE sample indicates that the amount of scattered and transmitted light may not be negligible for optically heterogeneous semi-crystalline PE medium, otherwise its temperature-dependent absorption characteristics may be overestimated, due to underestimation of transmittance levels.…”

Section: Temperature-dependent Thermo-optical Properties Of Pementioning

confidence: 99%

“…As a consequence, the final temperature state at the end of the heating stage plays a major role for achieving a successful forming process with respect to the quality of a thermoformed part. Therefore, predictive model for accurate temperature distributions is crucially important whereas it is known that the crystalline structure of polymers introduces an optically heterogeneous medium which causes optical scattering phenomenon [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…Such a wavelength-dependent scattering behavior in semi-crystalline polymers was discussed in Refs. [4,5,12]. The common point that was stressed out in those studies is that the scattering behavior becomes weaker considering an increase in the wavelengths roughly between 0.5 μm and 2 μm, which lies in the visible (VIS) and near-infrared (NIR) ranges.…”

Section: Introductionmentioning

confidence: 99%

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A combined experimental and numerical approach for radiation heat transfer in semi-crystalline thermoplastics

Boztepe

Almeida

Gilblas

et al. 2019

International Journal of Thermal Sciences

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This paper proposes a novel experimental-numerical approach for radiation heat transfer in semi-crystalline thermoplastics. The proposed experimental and numerical approaches were analyzed here for the case of IR heating of linear polyethylene (PE). The challenges for radiation transport in semi-crystalline polymers may be categorized into the two main aspects: optical heterogeneity in polymer medium due to semi-crystalline nature and, semi-transparency in certain type of such polymers, like PE. In this study, we address the temperature dependence in the thermo-optical properties of semi-crystalline thermoplastics concerning its effect as a thermal radiation parameter for radiation heat transfer modeling of such type of polymers. The temperature dependence in the optical properties of PE, namely transmittance and reflectance characteristics, were experimentally analyzed under heating condition and, the temperature-dependent thermo-optical properties of PE was determined. The experimental analyses showed that the change in the thermo-optical properties under heating is related to change in the optical scattering behavior in PE medium since it is strongly affected by its crystalline structure. The radiation heat transfer model was built based on optically homogeneous medium assumption at which the change in the amount of radiative energy absorbed by the PE medium under heating was introduced without modeling how the light scatters inside of the medium. Thus, the effect of optical scattering on the absorption characteristics of PE under varying temperature was taken into account without modeling the spatial distribution of the scattered light intensity at microscopic level, which offers computationally cost-effective numerical solutions. The accuracy of the numerical model was analyzed performing IR heating experiments where IR thermography and thermocouples were employed for the surface temperature measurements. Due to the semi-transparent nature of PE, an experimental method was developed for IR thermography of PE and its accuracy was analyzed. The experimental-numerical comparisons showed that the temperature field on PE can be closely predicted using its temperature-dependent thermo-optical properties. Thanks to the adopted comparative case study, it was demonstrated how the temperature field predictions may deviate from the experimental thermal measurements due to the ignorance of this temperature dependence. Considering any type of monochromatic or polychromatic radiation source, the combined experimental-numerical approach proposed here may be adopted for temperature field predictions and non-invasive surface temperature measurements on the radiatively heated semi-crystalline thermoplastics.-* Corresponding author.

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Section: Test Methodology For Temperature-dependent Spectroscopic Meamentioning

confidence: 99%

Section: Temperature-dependent Thermo-optical Properties Of Pementioning

confidence: 99%

Section: Temperature-dependent Thermo-optical Properties Of Pementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A combined experimental and numerical approach for radiation heat transfer in semi-crystalline thermoplastics

Boztepe

Almeida

Gilblas

et al. 2019

International Journal of Thermal Sciences

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Heterogeneous Nucleation of High-Density Polyethylene Crystals on Graphene within Microdomains

Volchko

2023

Macromolecules

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In polymer processes, nucleating agents are often used to control the kinetics of crystallization, but their application remains largely a matter of trial and error. Thermodynamically, the efficiency of a nucleating agent can be quantified by the difference in substrate/crystal, crystal/melt, and substrate/melt interfacial energies, Δσ. In this work, the efficiency of graphene nanoplatelets (GNP) as nucleating agents for high-density polyethylene (HDPE) is investigated. HDPE nucleates and crystallizes rapidly, so Δσ can be especially difficult to measure experimentally. To overcome this difficulty, blends of HDPE+GNP are confined to microdomains so that crystallization becomes nucleation limited. Two methods of microdomain formation are employed. In the first, HDPE+GNP is melt-blended with an immiscible matrix of polystyrene (PS), and crystallization is characterized using differential scanning calorimetry (DSC); in the second, dispersions of HDPE+GNP in toluene are sprayed onto PS substrates, and crystallization is characterized with polarized optical microscopy (POM). Heterogeneous nucleation rates at several crystallization temperatures and for several GNP loadings were measured by these two methods and found to give excellent agreement across GNP loadings. The value of Δσ for HDPE+GNP is calculated to be 0.83 ± 0.18 erg/cm 2 . This value is only 2.8 times larger than that reported for HDPE nucleated heterogeneously on a HDPE fiber, a nearly ideal nucleating agent for HDPE, and much smaller than many of the best nucleating agents reported for other polymers. We conclude that GNP is an efficient nucleating agent for HDPE.

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Three-Dimensional Printing of a Tough Polymer Composite Gel Ink Reinforced with Chemically Modified Cellulose Nanofibrils Showing Self-Healing Behavior

Dalloul¹,

Mietner²,

Navarro³

2023

ACS Appl. Polym. Mater.

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Three-dimensional (3D) gel printing has significant potential for producing structurally accurate biomaterials based on complex biological tissues for use in regenerative biotechnology. The efficiency depends on the chosen gel printing device and the parameters used but also primarily on the selection of the gel ink.In the present study, the dimerizing functions in ureidopyrimidinone (UPy) were exploited to develop a gel ink. A composite gel ink was developed made out of a polymer consisting of UPy and di(ethylene glycol) ethyl ether (DEGEEA) functions and modified cellulose nanofibril-containing UPy groups (CNF-g-UPy) as print performance-enhancing additives. This resulted in a hyper-crosslinked network with superior mechanical strength compared to the matrix itself, with an increase of 3.7× in storage modulus and 2.8× in loss modulus. The CNF-g-UPy/UPy-DEGEEA gel ink exhibited shear-thinning properties and could therefore be extruded to form uniform strands with no merging and retain a relatively stable structure. The self-healing ability was demonstrated by the adhesion of two printed patterns after 2 min at 80 °C. The multiple cross-linkages and self-healing ability of the filaments, therefore, allow for stable printed structures. All of these findings point out the promising potential of such gel ink for many biotechnological applications.

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The role of microcrystalline structure on optical scattering characteristics of semi-crystalline thermoplastics and the accuracy of numerical input for IR-heating modeling

Cited by 9 publications

References 36 publications

A combined experimental and numerical approach for radiation heat transfer in semi-crystalline thermoplastics

A combined experimental and numerical approach for radiation heat transfer in semi-crystalline thermoplastics

Heterogeneous Nucleation of High-Density Polyethylene Crystals on Graphene within Microdomains

Three-Dimensional Printing of a Tough Polymer Composite Gel Ink Reinforced with Chemically Modified Cellulose Nanofibrils Showing Self-Healing Behavior

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