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Sobolciak P.,Qatar University | Abdelrazeq H.,Qatar University | Ouederni M.,Qatar Petrochemical Company QAPCO | Karkri M.,University Paris Est Creteil | And 2 more authors.
Polymer Testing | Year: 2015

Artificial aging of Shape Stabilized Phase Change Materials (SSPCM) based on linear low density polyethylene (LLDPE) and paraffin wax (W) modified with various amounts of expanded graphite (EG) was investigated and reported in this paper. It was found that EG not only strongly suppresses leakage of paraffin wax from the material over time but also significantly improves the photo oxidation stability. The increase in the melting point of wax incorporated within LLDPE matrix during aging was observed whereas the specific melting enthalpy of the paraffin wax decreased. This is mainly caused by the leakage of paraffin wax from the blends. The melting of neat LLDPE decreased during aging whereas its specific enthalpy of melting increased. Addition of EG led to the prolonged photo-oxidation stability of materials, as confirmed by Carbonyl Index measurements. © 2015 Elsevier Ltd. All rights reserved. Source

Sobolciak P.,Qatar University | Abdelrazeq H.,Qatar University | Ozerkan N.G.,Qatar University | Ouederni M.,Qatar Petrochemical Company QAPCO | And 4 more authors.
Applied Thermal Engineering | Year: 2016

Thermal characterization of phase change materials (PCMs) compose of linear low-density polyethylene (LLDPE), paraffin wax (W) with a melting point of 25 °C, and expanded graphite (EG), that are highly effective in thermal energy storage systems in the building industry, is reported. Thermal investigation of PCMs with various compositions of LLDPE, W and EG has been performed by nonconventional transient guarded hot plane technique (TGHPT) and compared with conventional differential scanning calorimetry (DSC) measurements. An excellent agreement in determination of thermal characteristics by both methods was found. The highest values of the total amount of stored energy, sensible heat for solid and liquid states (Qtotal, Qs(solid) and Qs(liquid), respectively) were found for the PCMs with composition LLDPE/W/EG = 40/50/10 and 35/50/15 w/w/w. Moreover, thermal conductivity and diffusivity of PCMs have been significantly improved by adding EG. Additionally, life cycle assessment was performed to evaluate the environmental impact of three different materials as glass wool, rock wool and PCM used with brick wall. © 2016 Elsevier Ltd Source

Hawari A.,Qatar University | Ramadan H.,Qatar University | Abu-Reesh I.,Qatar University | Ouederni M.,Qatar Petrochemical Company QAPCO
Journal of Environmental Management | Year: 2015

The treatment of spent caustic produced from an ethylene plant was investigated. In the case of neutralization alone it was found that the maximum removal of sulfide was at pH values below 5.5. The higher percentage removal of sulfides (99% at pH=1.5) was accompanied with the highest COD removal (88%). For classical oxidation using H2O2 the maximum COD removal percentage reached 89% at pH=2.5 and at a hydrogen peroxide concentration of 19mM/L. For the advanced oxidation using Fenton's process it was found that the maximum COD removal of 96.5% was achieved at a hydrogen peroxide/ferrous sulfate ratio of (7:1). © 2014 Elsevier Ltd. Source

Krupa I.,Qatar University | Nogellova Z.,Slovak Academy of Sciences | Spitalsky Z.,Qatar Petrochemical Company QAPCO | Malikova M.,Slovak Academy of Sciences | And 6 more authors.
Thermochimica Acta | Year: 2015

The preparation of Phase Change Materials (PCM) with improved thermal conductivity, based on linear low-density polyethylene (LLDPE), paraffin wax with a melting point of approximately 42 °C and expanded graphite as well as the investigation of their physical behavior is reported in this paper. The absorption of heat energy is realized by phase transitions in the wax structure, i.e., solid-solid transitions between different crystalline structures of wax and, primarily, by a solid-liquid transition. An estimate of the total heat energy that can be reversibly absorbed or released by the designed materials was determined using Differential Scanning Calorimetry (DSC). The improvement in the thermal conductivity of the polymeric materials was obtained by incorporating expanded graphite into the blends. Expanded graphite has a reinforcing effect on the PCM, resulting in an increase in the toughness (Young's modulus) Significant amounts of wax are leached from the samples, and a higher wax content also results in more wax leakage. Graphite significantly reduces the wax loss from the samples. © 2015 Elsevier B.V. All rights reserved. Source

Khanam P.N.,Qatar University | Almaadeed M.,Qatar University | Almaadeed S.,Qatar University | Kunhoth S.,Qatar University | And 5 more authors.
International Journal of Polymer Science | Year: 2016

The focus of this work is to develop the knowledge of prediction of the physical and chemical properties of processed linear low density polyethylene (LLDPE)/graphene nanoplatelets composites. Composites made from LLDPE reinforced with 1, 2, 4, 6, 8, and 10 wt% grade C graphene nanoplatelets (C-GNP) were processed in a twin screw extruder with three different screw speeds and feeder speeds (50, 100, and 150 rpm). These applied conditions are used to optimize the following properties: thermal conductivity, crystallization temperature, degradation temperature, and tensile strength while prediction of these properties was done through artificial neural network (ANN). The three first properties increased with increase in both screw speed and C-GNP content. The tensile strength reached a maximum value at 4 wt% C-GNP and a speed of 150 rpm as this represented the optimum condition for the stress transfer through the amorphous chains of the matrix to the C-GNP. ANN can be confidently used as a tool to predict the above material properties before investing in development programs and actual manufacturing, thus significantly saving money, time, and effort. © 2016 P. Noorunnisa Khanam et al. Source

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