The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Igor Krupa - One of the best experts on this subject based on the ideXlab platform.
-
advanced thermal energy systems based on Paraffin Waxes applicable in building industry
Qatar Foundation Annual Research Conference Proceedings Volume 2014 Issue 1, 2014Co-Authors: Patrik Sobolciak, Igor Krupa, Mustapha Karkri, Mariam Al Ali Al MaadeedAbstract:Thermal energy storage systems are crucial for reducing dependency on fossil fuels and minimizing CO2 emissions. The building sector is a major sector responsible for producing high levels of CO2 in most countries (including Qatar). Thermal energy storage can be accomplished either by using sensible heat storage or latent heat storage components. Latent heat storage is more attractive than sensible heat storage because of its high storage density with smaller temperature fluctuations.[1] The materials able to utilize latent heat which can undergo phase changes (usually solid to liquid changes) at relatively low temperatures, while absorbing or releasing high amounts of energy are called phase change materials (PCMs).[2] Most promising PCMs are Paraffin Waxes which contain saturated hydrocarbon mixtures. They are frequently used due to their numerous advantages such as high latent heat of fusion, negligible super-cooling, and chemical inertness.[3,4] In this contribution, thermal properties of the PCMs based on linear low density polyethylene (LLDPE), different types of Paraffin Waxes with melting points, 25 oC and 42 oC, and expanded graphite (EG) were characterized by unique transient guarded hot plate technique (TGHPT), which allow to identified thermal properties of large sized samples[5] in comparison with commonly used ifferential scanning calorimetry (DSC). It was confirmed that all prepared PCMs were able to store and release huge amount of thermal energy. The 25 % increase of capacity to store and release a thermal energy was observed by PCMs contains Paraffin wax with melting point 25 oC in comparison with Paraffin wax with melting point 42 oC. Also reproducibility of storage and release heat of the PCMs by repeating of heating and cooling process has been demonstrated. Moreover, the increase of the EG content in the PCMs led to the increase of thermal conductivity from 0.24 W/mK for PCMs without EG to 1.3 W/mK for PCMs contain 15 wt.% of EG. Additionally, life cycle assessment of prepared PCMs has been demonstrated to identify the effects of these new materials on the Qatar environment. Our results indicate that using of PCMs in building industry can reduce emission of CO2 up to 10%. Keywords: phase change materials; latent heat; storage and release energy; thermal conductivity; life cycle assessment Acknowledgement: This contribution was made possible by NPRP Grant # 4-465-2-173 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors References: [1]Soaresa N, Costab JJ, Gaspar AR, Santos P. Energy Build 59 (2013) 82-103. [2]Krupa I, Mikova G, Luyt A.S. Europ. Polym. J. 43 (2007) 4695-4705. [3]Kenisarin M, Mahkamov K. Renew. Sustain. Energy Rev. 11 (2007) 1913-1965. [4]Lachheb M, Karkri M, Albouchi F, Nasrallah S, Fois F, Sobolciak P. Composites: Part B 66 (2014) 518-525. [5]Karkri M, Boudenne A, Ibos L, Garnier B, Candau Y. High Temp.-High Press. 40 (2011) 61-84.
-
thermal conductivity and latent heat thermal energy storage properties of ldpe wax as a shape stabilized composite phase change material
Energy Conversion and Management, 2014Co-Authors: Abdelwaheb Trigui, Mustapha Karkri, Igor KrupaAbstract:Abstract Phase change material (PCM) composites based on low-density polyethylene (LDPE) with Paraffin Waxes were investigated in this study. The composites were prepared using a meltmixing method with a Brabender-Plastograph. The LDPE as the supporting matrix kept the molten Waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (Waxes) and the supporting matrix (LDPE) is a necessary property for effective energy storage. Therefore, this type Paraffin can be used in a latent heat storage system without encapsulation. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. In addition, a DSC analysis was carried out. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. Results indicate the performance of the proposed system is affected by the thermal effectiveness of phase change material and significant amount of energy saving can be achieved.
-
Thermal behaviour of low and high molecular weight Paraffin Waxes used for designing phase change materials
Thermochimica Acta, 2007Co-Authors: Adriaan S. Luyt, Igor KrupaAbstract:Abstract Two Waxes, a soft petroleum wax and a hard Fischer–Tropsch Paraffin wax, have been investigated to find the reasons for multiple endothermic peaks observed during heating in a DSC. DSC curves, molar mass distribution curves, and variable-temperature XRD results were compared, and it was confirmed that the first endothermic peak for the soft petroleum wax was due to a solid–solid transition, while the second endothermic peak was due to melting. However, for the hard Fischer–Tropsch Paraffin wax there was no evidence of a solid–solid transition, and it was concluded that the multiple endothermic peaks in this case were due to melting of different molar mass fractions.
-
phase change materials based on low density polyethylene Paraffin wax blends
European Polymer Journal, 2007Co-Authors: G Mikova, Igor Krupa, Adriaan S. LuytAbstract:Phase change materials, based on low-density polyethylene blended with soft and hard Paraffin Waxes respectively, were studied in this paper. DSC, DMA, TGA and SEM were employed to determine the structure and properties of the blends. The blends were able to absorb large amounts of heat energy due to melting of Paraffin wax, whereas the LDPE matrix kept the material in a compact shape on macroscopic level. The hard Paraffin wax was, however, much more miscible with LDPE because of co-crystallization than the soft Paraffin wax. LDPE blended with hard Paraffin wax degrades in just one step, while blends containing soft Paraffin wax degrade in two distinguishable steps. SEM showed completely different morphology for the two Paraffin Waxes and confirmed the lower miscibility of LDPE and soft Paraffin wax. DMA analyses demonstrated the toughening effect of the Waxes on the polymer matrix. This technique was also used to follow the thermal expansion as well as the dimensional stability of the samples during thermal cycling. The most visible expansion could be seen in the first cycle, probably due to a totally different thermal history of the sample. With further cycling the dimensions stabilized after two and four cycles for soft and hard Paraffin wax, respectively. Controlled force ramp testing on DMA confirmed poor material strength of the blends containing soft wax, especially at temperatures above wax melting.
-
polypropylene as a potential matrix for the creation of shape stabilized phase change materials
European Polymer Journal, 2007Co-Authors: G Mikova, Igor Krupa, Adriaan S. LuytAbstract:Abstract Phase change materials, based on isotactic polypropylene (PP) blended with soft and hard Fischer−Tropsch Paraffin wax respectively, were studied in this paper. DSC, DMA, TGA and SEM were used to determine the structure and properties of the blends. While Paraffin Waxes in the blend changed state from solid to liquid, the PP matrix kept the material in a compact shape. Strong phase separation was observed in both cases, which was more pronounced in the case of soft Paraffin wax. Despite the fact that both grades of Paraffin wax are not miscible with PP due to different crystalline structures, it was shown that the hard Fischer−Tropsch Paraffin wax is more compatible with PP than the soft one. Both Waxes plasticized the PP matrix. TGA showed that PP blended with the hard Fischer−Tropsch wax degrades in just one step, whereas blends containing soft Paraffin wax degrade in two distinguishable steps. SEM exposed a completely different morphology for the two Paraffin Waxes and confirmed the lower compatibility of PP and soft Paraffin wax. The soft and hard characters of the Waxes were manifested in the viscoelastic properties, where the blends containing soft Paraffin wax exhibited a lower elastic modulus than pure polypropylene, whereas the hard Fisher−Tropsch Paraffin wax solidified the matrix. However, both kinds of blends were able to sustain the dynamic forces applied by the DMA within five cycle runs implying good shape stability.
Adriaan S. Luyt - One of the best experts on this subject based on the ideXlab platform.
-
Thermal behaviour of low and high molecular weight Paraffin Waxes used for designing phase change materials
Thermochimica Acta, 2007Co-Authors: Adriaan S. Luyt, Igor KrupaAbstract:Abstract Two Waxes, a soft petroleum wax and a hard Fischer–Tropsch Paraffin wax, have been investigated to find the reasons for multiple endothermic peaks observed during heating in a DSC. DSC curves, molar mass distribution curves, and variable-temperature XRD results were compared, and it was confirmed that the first endothermic peak for the soft petroleum wax was due to a solid–solid transition, while the second endothermic peak was due to melting. However, for the hard Fischer–Tropsch Paraffin wax there was no evidence of a solid–solid transition, and it was concluded that the multiple endothermic peaks in this case were due to melting of different molar mass fractions.
-
phase change materials based on low density polyethylene Paraffin wax blends
European Polymer Journal, 2007Co-Authors: G Mikova, Igor Krupa, Adriaan S. LuytAbstract:Phase change materials, based on low-density polyethylene blended with soft and hard Paraffin Waxes respectively, were studied in this paper. DSC, DMA, TGA and SEM were employed to determine the structure and properties of the blends. The blends were able to absorb large amounts of heat energy due to melting of Paraffin wax, whereas the LDPE matrix kept the material in a compact shape on macroscopic level. The hard Paraffin wax was, however, much more miscible with LDPE because of co-crystallization than the soft Paraffin wax. LDPE blended with hard Paraffin wax degrades in just one step, while blends containing soft Paraffin wax degrade in two distinguishable steps. SEM showed completely different morphology for the two Paraffin Waxes and confirmed the lower miscibility of LDPE and soft Paraffin wax. DMA analyses demonstrated the toughening effect of the Waxes on the polymer matrix. This technique was also used to follow the thermal expansion as well as the dimensional stability of the samples during thermal cycling. The most visible expansion could be seen in the first cycle, probably due to a totally different thermal history of the sample. With further cycling the dimensions stabilized after two and four cycles for soft and hard Paraffin wax, respectively. Controlled force ramp testing on DMA confirmed poor material strength of the blends containing soft wax, especially at temperatures above wax melting.
-
polypropylene as a potential matrix for the creation of shape stabilized phase change materials
European Polymer Journal, 2007Co-Authors: G Mikova, Igor Krupa, Adriaan S. LuytAbstract:Abstract Phase change materials, based on isotactic polypropylene (PP) blended with soft and hard Fischer−Tropsch Paraffin wax respectively, were studied in this paper. DSC, DMA, TGA and SEM were used to determine the structure and properties of the blends. While Paraffin Waxes in the blend changed state from solid to liquid, the PP matrix kept the material in a compact shape. Strong phase separation was observed in both cases, which was more pronounced in the case of soft Paraffin wax. Despite the fact that both grades of Paraffin wax are not miscible with PP due to different crystalline structures, it was shown that the hard Fischer−Tropsch Paraffin wax is more compatible with PP than the soft one. Both Waxes plasticized the PP matrix. TGA showed that PP blended with the hard Fischer−Tropsch wax degrades in just one step, whereas blends containing soft Paraffin wax degrade in two distinguishable steps. SEM exposed a completely different morphology for the two Paraffin Waxes and confirmed the lower compatibility of PP and soft Paraffin wax. The soft and hard characters of the Waxes were manifested in the viscoelastic properties, where the blends containing soft Paraffin wax exhibited a lower elastic modulus than pure polypropylene, whereas the hard Fisher−Tropsch Paraffin wax solidified the matrix. However, both kinds of blends were able to sustain the dynamic forces applied by the DMA within five cycle runs implying good shape stability.
A S Luyt - One of the best experts on this subject based on the ideXlab platform.
-
thermal and mechanical properties of ldpe sisal fiber composites compatibilized with functionalized Paraffin Waxes
Journal of Applied Polymer Science, 2012Co-Authors: L P Nhlapo, A S LuytAbstract:The effect of maleic anhydride-grafted hard Paraffin wax (MA-g-wax) and oxidized hard Paraffin wax (OxWax), as possible compatibilizers, on the morphology, thermal and mechanical properties of LDPE/sisal fiber composites were examined. The differential scanning calorimetry (DSC) results show that sisal alone did not change the crystallization behavior of LDPE, while the two Waxes influenced the crystallization behavior of LDPE in different ways, whether mixed with LDPE alone or in the presence of sisal. The thermal properties seem to be influenced by the fact that the Waxes preferably crystallize around the short sisal fibers, and by the fact that the two Waxes have different compatibilities with LDPE. The TGA results show an increase in the thermal stability of the blends in the presence of the two Waxes, with LDPE/OxWax showing a more significant improvement. The presence of wax, however, reduced the thermal stability of the LDPE/sisal/wax composites. The presence of OxWax and MA-g-wax similarly influenced the tensile properties of the composites. Both Waxes similarly improved the modulus of the compatibilized composites, but in both cases the tensile strengths were worse, probably because of a fairly weak interaction between LDPE and the respective Waxes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
-
polypropylene as a potential matrix for the creation of shape stabilized phase change materials
European Polymer Journal, 2007Co-Authors: G Mikova, Igor Krupa, A S LuytAbstract:Abstract Phase change materials, based on isotactic polypropylene (PP) blended with soft and hard Fischer−Tropsch Paraffin wax respectively, were studied in this paper. DSC, DMA, TGA and SEM were used to determine the structure and properties of the blends. While Paraffin Waxes in the blend changed state from solid to liquid, the PP matrix kept the material in a compact shape. Strong phase separation was observed in both cases, which was more pronounced in the case of soft Paraffin wax. Despite the fact that both grades of Paraffin wax are not miscible with PP due to different crystalline structures, it was shown that the hard Fischer−Tropsch Paraffin wax is more compatible with PP than the soft one. Both Waxes plasticized the PP matrix. TGA showed that PP blended with the hard Fischer−Tropsch wax degrades in just one step, whereas blends containing soft Paraffin wax degrade in two distinguishable steps. SEM exposed a completely different morphology for the two Paraffin Waxes and confirmed the lower compatibility of PP and soft Paraffin wax. The soft and hard characters of the Waxes were manifested in the viscoelastic properties, where the blends containing soft Paraffin wax exhibited a lower elastic modulus than pure polypropylene, whereas the hard Fisher−Tropsch Paraffin wax solidified the matrix. However, both kinds of blends were able to sustain the dynamic forces applied by the DMA within five cycle runs implying good shape stability.
-
effect of cross linking on the thermal stability and molar mass distribution of Paraffin Waxes
Polymer Degradation and Stability, 2001Co-Authors: F M Mhlongo, A S Luyt, C G C E Van SittertAbstract:The influence of dicumyl peroxide (DCP) (5, 10 and 15% by mass) on the structure and thermal properties of two different Paraffin Waxes was investigated. For both Waxes an increase of gel content was observed for increasing DCP concentration. Gel permeation chromatography, however, showed a decrease in intensity of the main peak, and the development of a lower molar mass peak. Differences were observed between the DSC curves for the untreated and treated samples, but these could not, with certainty, be linked to either cross-linking or degradation. TGA curves showed two well-developed decomposition steps for treated samples, which is in line with the development of a second peak in the GPC chromatogram.
-
comparative thermoanalytical investigation of the cross linking behaviour of three different Paraffin Waxes in the presence of potassium persulphate
Thermochimica Acta, 1999Co-Authors: A S Luyt, K Ishripersadh, D N TimmAbstract:Abstract The cross-linking of three different Paraffin Waxes – a hard oxidised wax, a medium wax, and a hard wax with narrow molar mass distribution – in the presence of potassium persulphate (PPS) was investigated thermoanalytically. DSC and TG curves for untreated Waxes and Waxes treated with different amounts of PPS were obtained and the observations were compared with gel content data obtained through gravimetric analysis. Although initial indications were that cross-linking did occur, reheat curves of wax/PPS mixtures as well as gel content data showed that no cross-linking occurred. It was, however, found that PPS most probably decomposed into KHSO4 and that this decomposition gave rise to functionalisation of the Waxes.
-
comparative thermoanalytical investigation of the cross linking behaviour of three different Paraffin Waxes in the presence of dicumyl peroxide
Thermochimica Acta, 1999Co-Authors: A S Luyt, K IshripersadhAbstract:Abstract The cross-linking of three different Paraffin Waxes – a hard oxidized wax, a medium wax, and a hard wax with narrow molar mass distribution – in the presence of dicumyl peroxide (DCP) was investigated thermoanalytically. DSC and TG curves for untreated Waxes and Waxes treated with different amounts of DCP were obtained and the observations were compared with gel content data obtained through gravimetric analysis. It was found that all three Waxes cross-linked in the presence of DCP, with the extent of cross-linking increasing with increasing DCP : wax ratio. It was also clear that the higher melting fractions of the different Waxes preferably cross-linked. From the gel content data it seems as if the oxidized and higher molar mass Waxes tend to cross-link at a faster rate.
Tony Mcnally - One of the best experts on this subject based on the ideXlab platform.
-
shape stabilised phase change materials based on a high melt viscosity hdpe and Paraffin Waxes
Applied Energy, 2016Co-Authors: Pam Basheer, Yun Bai, Wei Sha, Tony McnallyAbstract:Shape stabilised phase change materials (SSPCMs) based on a high density poly(ethylene)(hv-HDPE) with high (H-PW, Tm=56–58°C) and low (L-PW, Tm=18–23°C) melting point Paraffin Waxes were readily prepared using twin-screw extrusion. The thermo-physical properties of these materials were assessed using a combination of techniques and their suitability for latent heat thermal energy storage (LHTES) assessed. The melt processing temperature (160°C) of the HDPE used was well below the onset of thermal decomposition of H-PW (220°C), but above that for L-PW (130°C), although the decomposition process extended over a range of 120°C and the residence time of L-PW in the extruder was <30s. The SSPCMs prepared had latent heats up to 89J/g and the enthalpy values for H-PW in the respective blends decreased with increasing H-PW loading, as a consequence of co-crystallisation of H-PW and hv-HDPE. Static and dynamic mechanical analysis confirmed both Waxes have a plasticisation effect on this HDPE. Irrespective of the mode of deformation (tension, flexural, compression) modulus and stress decreased with increased wax loading in the blend, but the H-PW blends were mechanically superior to those with L-PW.
-
Shape stabilised phase change materials based on a high melt viscosity HDPE and Paraffin Waxes
Applied Energy, 2016Co-Authors: Pam Basheer, Yun Bai, Wei Sha, Tony McnallyAbstract:Shape stabilised phase change materials (SSPCMs) based on a high density poly(ethylene)(hv-HDPE) with high (H-PW, Tm=56–58°C) and low (L-PW, Tm=18–23°C) melting point Paraffin Waxes were readily prepared using twin-screw extrusion. The thermo-physical properties of these materials were assessed using a combination of techniques and their suitability for latent heat thermal energy storage (LHTES) assessed. The melt processing temperature (160°C) of the HDPE used was well below the onset of thermal decomposition of H-PW (220°C), but above that for L-PW (130°C), although the decomposition process extended over a range of 120°C and the residence time of L-PW in the extruder was
C.j Choi - One of the best experts on this subject based on the ideXlab platform.
-
binder system for sts 316 nanopowder feedstocks in micro metal injection molding
Journal of Materials Processing Technology, 2007Co-Authors: Sugeng Supriadi, Eung Ryul Baek, C.j ChoiAbstract:Abstract The stainless steel (STS) 316 nanopowder (average particle size of 100 nm) were mixed with thermoplastic binder system to produce feedstock for micro-metal injection molding (μMIM) by using lost mold method. The combination of Paraffin Waxes, bee's Waxes, carnauba Waxes, ethylene vinyl acetate (EVA), polypropylene (PP) and stearic acid were chosen as binder systems with various formulations adopted to attain optimum feedstock properties. Three different kinds of binder systems of EVA-based, PP-based, and wax-based binder system were deeply investigated. It is found that the wax-based binder system performs the lowest viscosity and heat capacity as well as greater pseudo-plasticity than other binder systems. The feedstocks were injected into SU-8 micromold which was fabricated using photolithography technique. The feedstock which was mixed with wax-based binder system performed the smallest deformation. This result inferred that wax-based binder system is appropriate as binder materials for very fine metal powder applied in μMIM. In this paper we also demonstrated the application of nanopowder on sintering process and showed that the sintered part using nanopowder provides less surface roughness than one produced using micron-sized metal powder.
-
binder system for sts 316 nanopowder feedstocks in micro metal injection molding
Journal of Materials Processing Technology, 2007Co-Authors: Sugeng Supriadi, Eung Ryul Baek, C.j ChoiAbstract:Abstract The stainless steel (STS) 316 nanopowder (average particle size of 100 nm) were mixed with thermoplastic binder system to produce feedstock for micro-metal injection molding (μMIM) by using lost mold method. The combination of Paraffin Waxes, bee's Waxes, carnauba Waxes, ethylene vinyl acetate (EVA), polypropylene (PP) and stearic acid were chosen as binder systems with various formulations adopted to attain optimum feedstock properties. Three different kinds of binder systems of EVA-based, PP-based, and wax-based binder system were deeply investigated. It is found that the wax-based binder system performs the lowest viscosity and heat capacity as well as greater pseudo-plasticity than other binder systems. The feedstocks were injected into SU-8 micromold which was fabricated using photolithography technique. The feedstock which was mixed with wax-based binder system performed the smallest deformation. This result inferred that wax-based binder system is appropriate as binder materials for very fine metal powder applied in μMIM. In this paper we also demonstrated the application of nanopowder on sintering process and showed that the sintered part using nanopowder provides less surface roughness than one produced using micron-sized metal powder.
