137Tolentino S. y Caraballo S. Simulación numérica del ujo de aire.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 21, Nº 82 Marzo 2017 (pp. 4-15)ISSN 2542-3401137137ISSN 2542-3401/ 1316-4821Agredo et al., Wax and Bentonite Blends for Prototyping IndustrialUNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 25, Nº 111 Diciembre 2021 (pp. 137-144)ISSN-e: 2542-3401, ISSN-p: 1316-4821Wax and bentonite blends for prototyping industrial clay development: preliminary resultsRecibido (13/09/21 ) Aceptado (10/10/21) Abstract: The automotive design process and the materials in the automotive industry in recent years has caused great interest to the industrial and academic sector. In this study was to evaluate the effect of the amount of bentonite on the thermal and rheological properties of the compound bentonite / parafn wax. Two bentonite ratios were used: parafn wax (40:60 and 30:70). The parafn was characterized by Fourier transform infrared spectroscopy (FTIR), the bentonite was characterized by means of x-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray uorescence (XRF). The bentonite/parafne wax composite was characterized by differential-scanning calorimetry (DSC) and rheology. The sample that contains a higher amount of bentonite shows a lower latent heat, and this could cause a greater heat transfer. Finally, the sample that has a lower amount of bentonite evidenced a lower viscosity, and it could be related to a lower interaction between the particles. The sample S1 due to its lower latent heat compared to S2 could represent an interesting alternative to develop prototyping clays. since these materials are characterized by their low working temperatures and easy malleability.Mezclas de cera y bentonita para el desarrollo de arcilla industrial de prototipado: resultados preliminares Resumen: El proceso de diseño automotriz y los materiales en la industria automotriz pen los últimos años ha despertado un gran interés en el sector industrial y académico. En este estudio se evaluó el efecto de la cantidad de bentonita sobre las propiedades térmicas y reológicas del compuesto bentonita / cera de parana. Se utilizaron dos proporciones de bentonita: cera de parana (40:60 y 30:70). La parana se caracterizó por espectroscopia infrarroja por transformada de Fourier (FTIR), la bentonita se caracterizó mediante difracción de rayos X (XRD), análisis termogravimétrico (TGA), uorescencia de rayos X (XRF). El compuesto de cera de bentonita / parana se caracterizó por calorimetría de barrido diferencial (DSC) y reología. La muestra que contiene una mayor cantidad de bentonita presenta un menor calor latente, y esto podría provocar una mayor transferencia de calor. Finalmente, la muestra que tiene menor cantidad de bentonita evidenció una menor viscosidad, y podría estar relacionado con una menor interacción entre las partículas. La muestra S1 debido a su menor calor latente en comparación con S2 podría representar una alternativa interesante para desarrollar arcillas de prototipado. ya que estos materiales S3 caracterizan por sus bajas temperaturas de trabajo y fácil maleabilidad.Andrés Felipe Agredo Orozcohttps://orcid.org/0000-0001-5302-6050aagredo@eat.edu.coUniversidad EAFITMedellín, Colombia Diego Andrés Acosta Maya https://orcid.org/0000-0001-8654-6116dacostam@eat.edu.coUniversidad EAFITMedellín, Colombia Carlos Arturo Rodríguez Arroyave https://orcid.org/0000-0001-9054-2564carodri@eat.edu.coUniversidad EAFITMedellín, Colombia Luis Fernando Sierra Zuluagahttps://orcid.org/0000-0002-0664-6254lsierraz@eat.edu.coUniversidad EAFITMedellín, Colombia doi: https://doi.org/10.47460/uct.v25i111.524Keywords: automotive, prototyping, latent heat, bentonite, paraffin.Palabras clave: automóvil, prototipado, reología, bentonita, parafina.
138Tolentino S. y Caraballo S. Simulación numérica del ujo de aire.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 21, Nº 82 Marzo 2017 (pp. 4-15)ISSN 2542-3401138138ISSN 2542-3401/ 1316-4821I.INTRODUCTIONRecently, the smart and connected car is creating a new ecosystem of opportunities and competition be-tween different companies. Driven by shared mobility, services, and feature upgrades, new business models could expand automotive revenue pools by about 30 percent, adding up to $1.5 trillion [1]–[3]Along with this appear new challenges that must be faced. From manufacturing issues, implementation, development of new technologies and the restructuring of automotive design processes. Being the automotive design process and the materials involved in the process of great interest to the industrial and academic sector [4], [5].Currently in the South American market there are not many local alternatives of Industrial and prototy-ping clays and its components. Our continent is com-mitted to importing different automotive clays from abroad, such as Chavant, STAEDTLER, Tools INT'L, among others. Therefore, the import prices are much higher due to their dimensions and weight. There are a number of international formulations and alternatives for these materials. However, south America falls short in these developments and there are not many alternati-ves in our markets. Consequently, is of great interest to generate local alternatives with competitive prices for the South American market.[6][7]Among the materials used to develop these com-pounds are parafn wax, bentonite, Calcium stearate and kaolin have value-added functions, for instance, mechanical properties, heat stability, lubrication, lling capabilities, low cost, among others. Kaolin provides tensile strength, tear strength, abrasion resistance, im-prove air retention, among other benets considering that if used it could affect the compound color. Kaolin is one of the best materials to improve surface smoothness for better print quality while being very cost efcient [8]–[10]. However, It is known that prolonged exposu-re to materials such as kaolin can cause structural and functional damage to the lungs and deterioration to the respiratory system [11]. In addition, sulfur compounds and other similar materials are avoided due to environ-mental and health implications. Exposure to these types of materials can cause health damage ranging from res-piratory problems, skin problems, among others [12].Otherwise, bentonite is a native, colloidal, hydrated, non-metallic mineral of the Smectite Group composed of montmorillonite. Bentonite have gained much atten-tion because of their high sorption properties, high sur-face area and high porosity. Bentonite its abundant in many countries and its cost remains signicantly low [13], [14]. Parafns are white, translucent, tasteless and odorless solids composed of hydrocarbons of high mo-lecular weight. parafns are the most promising phase change materials because they are available in a large temperature range, have higher heats of fusion, chemi-cal inertness, stability, and they are commercially avai-lable at very low cost [15]–[17].To the best of the authors knowledge and belief, the inuence of bentonite and parafne wax on thermal and rheological properties has not been studied. Accordin-gly, the main objective of this study was to evaluate the effect of bentonite: parafn wax ratio (40:60 and 30:70) on rheological and thermal properties of composite.II.DEVELOPMENTCar designs do not change radically from one mo-del to another. Aspects such as the number of wheels, the seating positions, etc., do not change, and this has allowed the industry to structure its design in the ma-nufacturing processes in a very compartmentalized and sequential way, with the participation of a number of specialized supplies. In 1927 General Motors ushered in a new era in the eld of automotive design thanks to their exibility in the process, and they developed the method to create designs on paper as various types of sketches, turning them into full-size orthogonal illustra-tions, using them to create templates, etc. [18]. For fu-ll-size or reduced-size three-dimensional models, clay enables car designers to present and model the geome-try of a car's body [19].Industrial clays became a modeling material prima-rily used in automotive design studios. It was developed as an industrial version of play dough or hobby clay and they are wax-based and generally contain sulfur, which gives most articial clays a distinctive odor. clay mo-dels are essential for nding new concepts and drafts; this material is used in augmented prototyping methods to analyze proposed designs [20].In recent years, computer-aided design technolo-gy has generated so much interest, but it has failed to completely displace clay-based prototyping. On the contrary, the industry has found a way to take advan-tage of both methodologies, the automotive industry in Japan performs simulations in computer-aided enginee-ring system before making the rst prototype in order to identify and eliminate problems in advance. This makes it possible to transition from the rst prototype to the production prototype quickly [21].Although prototyping clays continue to be used, the requirements have varied over the years. Some mate-rials used to make these materials are dangerous for the environment and people. This has caused interest in less polluting and economically accessible materials such as Agredo et al., Wax and Bentonite Blends for Prototyping IndustrialUNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 25, Nº 111 Diciembre 2021 (pp. 137-144)ISSN-e: 2542-3401, ISSN-p: 1316-4821
139Tolentino S. y Caraballo S. Simulación numérica del ujo de aire.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 21, Nº 82 Marzo 2017 (pp. 4-15)ISSN 2542-3401139139ISSN 2542-3401/ 1316-4821Agredo et al., Wax and Bentonite Blends for Prototyping Industrialbentonite and parafn to grow in recent years.III.METHODOLOGYA.Materials and methodsParafn waxes and bentonite technical grade were used. The characteristics of each material are summari-zed in table 1.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 25, Nº 111 Diciembre 2021 (pp. 137-144)ISSN-e: 2542-3401, ISSN-p: 1316-4821Table 1. material raw data sheet.Table 2. Formulation compositionMaterialParameterUnitSpecificationParaffin waxMelting point°C58-60Oil content%1.5 maxColorSaybolt>17 minBentonitehumidity%12 maxpH-10.5 maxSwellingmL23.inB.Methodology The parafn was crushed until a powder was obtai-ned using a plastic mill (POKSPC400). Different mix-tures of bentonite and parafn were prepared (see table 2). The quantities required for each of the formulations were weighed on a digital scale (JADEVER JWN-30K). The two components are heated to 80 ° C under continuous stirring during 10 minutes. The mixtures were placed in a container (30 cm x 30 cm x 30 cm) and stored at 23 ° C for 5 hours.NomenclatureMaterialWt.%S1Paraffin wax60Bentonite40S2Paraffin wax70Bentonite30C.Characterization Rotational rheometer AR 2000 ex (TA Instruments) was used to measure the viscosities of the formulations according to ASTM standard D4440-15. Additionally, the formulations were studied within the range of 56–70 °C. The melting temperatures and the latent heat sto-rage capacity of the bentonite / parafn formulations are measured by DSC analysis method according to ASTM D3418-15 standard. The equipment used was a differential scanning calorimeter with modulated hea-ting MDSC Q200 (TA Instruments). General operating conditions and results tables for each formulation will be presented below. The heating program used consists of raising the temperature from 10 °C to 90 °C, at a hea-ting rate of 10 ° C/min. Then, an isotherm was applied for 5 minutes, and the material was cooled to 10 °C/min. All the analysis was carried out under a nitrogen atmosphere (99.995%, 50 mL).IV. RESULTSThe gure 1 shows the FTIR analysis of the parafn sample used in this study. The band around 2953 cm-1, 2915 cm-1 and 2850 cm-1 correspond to C-H functional group [22]. The band around 1464 cm-1 and 1378 cm-1 is due to the vibration of the functional group -CH2 and -CH3, respectively [23]. The band around 720 cm-1 could be related to the vibration of the functional group CH2 [24]. These bands are characteristic for parafn wax [24].
140Tolentino S. y Caraballo S. Simulación numérica del ujo de aire.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 21, Nº 82 Marzo 2017 (pp. 4-15)ISSN 2542-3401140140ISSN 2542-3401/ 1316-4821Figure 1. FTIR analysis of parafn wax materialFigure 2. TGA analysis of bentoniteAgredo et al., Wax and Bentonite Blends for Prototyping IndustrialUNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 25, Nº 111 Diciembre 2021 (pp. 137-144)ISSN-e: 2542-3401, ISSN-p: 1316-4821The gure 2 shows the TGA analysis of commercial bentonite. The rst weight loss (11.3%) is evidenced up to 200 °C, and could be related to degradation of the water molecules present on the surface and in the ben-tonite intercalations [25]. Additionally, the weight loss (3.9%) between 350 °C and 800 °C corresponds to the degradation of organic material [26].The table 3 shows the chemical composition of ben-tonite obtained from X-ray uorescence (XRF). This material is mainly composed of SiO2 (50.8%), Al2O3 (16.8%) and Fe2O3 (7.9%). Additionally, bentoni-te shows other components in lesser amounts such as MgO, CaO, Na2O, TiO2 and K2O. The amount of the main components of bentonite used in this study are si-milar to those found by Rabie et al. [27].
141Tolentino S. y Caraballo S. Simulación numérica del ujo de aire.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 21, Nº 82 Marzo 2017 (pp. 4-15)ISSN 2542-3401141141ISSN 2542-3401/ 1316-4821Agredo et al., Wax and Bentonite Blends for Prototyping IndustrialTable 3. Chemical composition of bentoniteFigure 3. XRD analysis of bentoniteUNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 25, Nº 111 Diciembre 2021 (pp. 137-144)ISSN-e: 2542-3401, ISSN-p: 1316-4821BentoniteSiO2Al2O3Fe2O3MgOCaONa2OTiO2K2OOthersWt.%50.816.97.932.21.10.80.80.6The gure 3 shows the XRD analysis of the ben-tonite used in this study. The diffraction peaks at 6°, 17°, 20°, 35°, 73.8° corresponds to the montmorillonite [28], [29]. The peaks at 21 ° and 27 ° are related to the presence of silica [28]. The presence of kaolinite is con-rmed by the presence of diffraction peaks at 12°, 34°, 59° and 94° [29]. Additionally, the peaks at 34.9°, 56.6° and 50.2° are due to the presence of calcite [30], [31]. Finally, the peak at 28.2° is associated with the presence of feldspar [32].The gure 4 shows the DSC analysis for bentoni-te/parafn wax composite. All the materials show two peaks of phase change: The endothermic peak between 40 °C and 43 °C is related to the solid-solid phase chan-ge of the parafn [33]. The second peak is due to the solid-liquid phase change of the parafn, and corres-ponds to the main peak. The latent heat for S1 and S2 samples are 119.8 J/g (59.26 ° C) and 59.3 J/g (59.3 ° C), respectively. Li et al. [34] reported that the thermal conductivity of parafn is around 0.12 W /m K, while the conductivity of bentonite is around 1 W /m K. This suggests that the sample with a higher amount of ben-tonite (S1) shows a lower latent heat, and this could be related to a higher heat transfer caused by the bentoni-te. The latent heat of sample S1 is lower than sample S2, suggesting that less energy is needed to melt the compound, and could be benecial in the prototyping process.
142Tolentino S. y Caraballo S. Simulación numérica del ujo de aire.UNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 21, Nº 82 Marzo 2017 (pp. 4-15)ISSN 2542-3401142142ISSN 2542-3401/ 1316-4821Figure 4. DSC analysis of bentonite/parafn wax composite. (a) S1 sample,( b) S2 sampleFigure 5. Rheological properties of bentonite/parafn wax composite, (a) S1 sample, (b) S2 sampleAgredo et al., Wax and Bentonite Blends for Prototyping IndustrialUNIVERSIDAD, CIENCIA y TECNOLOGÍA Vol. 25, Nº 111 Diciembre 2021 (pp. 137-144)ISSN-e: 2542-3401, ISSN-p: 1316-4821abThe gure 5 shows the effect of shear rate on visco-sity of composites. The gure 5a y 5b correspond to S1 y S2, respectively. All samples show a shear-thinning behavior, which consists in the reduction of the appa-rent viscosity with increasing shear rate. As the shear rate increases, the weak bonds between particles are broken and the viscosity decreases. In addition, in the sample F5 that has a lower concentration of bentonite, a lower viscosity is evidenced, and it could be related to a lower interaction between the particles [35]. Fina-lly, by increasing the temperature it is possible that the phase change of the compound occurs and the viscosity is reduced.abV.CONCLUSION This study evaluated the effect of bentonite/parafn wax on thermal and rheology properties for prototyping industrial clay. Sample S1 shows less latent heat com-pared to sample S2, and this could be related to a higher amount of bentonite. The bentonite could be increasing the heat transfer of S1 sample. In addition, the S2 sam-ple exhibit a lower viscosity, and it could be related to a lower interaction between the particles. The sample S1 could be represent an interesting alternative to develop prototyping clays, since evidenced a low working tem-perature. VI.ACKNOWLEDGEMENTWe thank the ICIPC and the EAFIT university re-search area for the support of this work.REFERENCES[1]X. Ferràs-Hernández, E. Tarrats-Pons, and N. Ari-many-Serrat, “Disruption in the automotive industry: A Cambrian moment,” Bus. Horiz., vol. 60, no. 6, pp. 855–863, 2017, doi: 10.1016/j.bushor.2017.07.011.[2]O. Heneric, G. Licht, S. Lutz, and W. Urban, “The Europerean Automotive Industry in a Global Con-text,” Eur. Automot. Ind. Move, pp. 5–44, 2005, doi:
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