Volume 9 Issue 1
Feb.  2024
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Amal Mlhem, Thomas Teklebrhan, Evenezer Bokuretsion, Basim Abu-Jdayil. Development of sustainable thermal insulation based on bio-polyester filled with date pits[J]. Journal of Bioresources and Bioproducts, 2024, 9(1): 74-89. doi: 10.1016/j.jobab.2023.12.004
Citation: Amal Mlhem, Thomas Teklebrhan, Evenezer Bokuretsion, Basim Abu-Jdayil. Development of sustainable thermal insulation based on bio-polyester filled with date pits[J]. Journal of Bioresources and Bioproducts, 2024, 9(1): 74-89. doi: 10.1016/j.jobab.2023.12.004

Development of sustainable thermal insulation based on bio-polyester filled with date pits

doi: 10.1016/j.jobab.2023.12.004
More Information
  • Corresponding author: E-mail address: Babujdayil@uaeu.ac.ae (B. Abu-Jdayil)
  • Available Online: 2023-12-26
  • Publish Date: 2024-02-01
  • Date palm pit (DPP)-filled poly (-hydroxybutyrate) (PHB) composites were prepared, evaluated, and characterized to determine their thermal insulation ability. Thermal conductivity values ranged between 0.086 and 0.100 W/(m·K). At a maximum filler concentration (50% (w)), the specific heat capacity and thermal diffusivity were 1 183 J/(kg·K) and 0.068 9 mm2/s, respectively. The DPP increased the thermal stability, and the highest compressive strength obtained was 80 MPa at 30% filler content. The PHB-DPP composites exhibited promising water absorption (less than 6%) and tensile strength (6–14 MPa). Date-pit-based PHB composites could be used in sustainable building engineering and cleaner production.

     

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  • Abas R.A., 2005. Experimental studies of the thermal diffusivities concerning some industrially important systems. 0976-0976.
    Abu-Jdayil B., Al-Malah K., 2008. Jordanian clay-based heat insulator composites: mechanical properties. J. Reinf. Plast. Compos. 27, 1559–1568. doi: 10.1177/0731684407087371
    Abu-Jdayil B., Hittini W., Mourad A.H., 2019a. Development of date pit-polystyrene thermoplastic heat insulator material: physical and thermal properties. Int. J. Polym. Sci. 2019, 1697627.
    Abu-Jdayil B., Mourad A.H.I., Hussain A., 2016. Investigation on the mechanical behavior of polyester-scrap tire composites. Constr. Build. Mater. 127, 896–903. doi: 10.1016/j.conbuildmat.2016.09.138
    Abu-Jdayil B., Mourad A.H., Hittini W., Hassan M., Hameedi S., 2019b. Traditional, state-of-the-art and renewable thermal building insulation materials: an overview. Constr. Build. Mater. 214, 709–735. doi: 10.1016/j.conbuildmat.2019.04.102
    Abu-Jdayil B., Mourad A.H.I., Hussain A., Al Abdallah H., 2022. Thermal insulation and mechanical characteristics of polyester filled with date seed wastes. Constr. Build. Mater. 315, 125805. doi: 10.1016/j.conbuildmat.2021.125805
    Abu-Jdayil B., Barkhad M.S., Mourad A. -H.I., Iqbal M.Z., 2021. Date palm wood waste-based composites for green thermal insulation boards. J. Build. Eng. 43, 103224. doi: 10.1016/j.jobe.2021.103224
    Adebayo T.S., Ullah S., Kartal M.T., Ali K., Pata U.K., Ağa M., 2023. Endorsing sustainable development in BRICS: the role of technological innovation, renewable energy consumption, and natural resources in limiting carbon emission. Sci. Total Environ. 859, 160181. doi: 10.1016/j.scitotenv.2022.160181
    Al Abdallah H., Abu-Jdayil B., Iqbal M.Z., 2022. Improvement of mechanical properties and water resistance of bio-based thermal insulation material via silane treatment. J. Clean. Prod. 346, 131242. doi: 10.1016/j.jclepro.2022.131242
    Al Marri M.G., Al-Ghouti M.A., Shunmugasamy V.C., Zouari N., 2021. Date pits based nanomaterials for thermal insulation applications-towards energy efficient buildings in Qatar. PLoS One 16, e0247608. doi: 10.1371/journal.pone.0247608
    Al-Absi R.S., Khan M., Abu-Dieyeh M.H., Ben-Hamadou R., Nasser M.S., Al-Ghouti M.A., 2023. The recovery of strontium ions from seawater reverse osmosis brine using novel composite materials of ferrocyanides modified roasted date pits. Chemosphere 311, 137043. doi: 10.1016/j.chemosphere.2022.137043
    Al-Mawali M., Al-Habsi N., Rahman M.S., 2021. Thermal characteristics and proton mobility of date-pits and their alkaline treated fibers. Food Eng. Rev. 13, 236–246. doi: 10.1007/s12393-020-09257-6
    Arioz O., Karasu B., Kaya G., Arslan G., Tuncan M., Tuncan A., Korkut M., Kıvrak S., 2008. A preliminary research on the properties of lightweight expanded clay aggregate. J. Aust. Ceram. Soc. 44, 23–30.
    Arora N.K., 2018. Environmental sustainability: necessary for survival. Environ. Sustain. 1, 1–2. doi: 10.1007/s42398-018-0013-3
    Avecilla-Ramírez A.M., del Rocío López-Cuellar M., Vergara-Porras B., Rodríguez-Hernández A.I., Vázquez-Núñez E., 2020. Characterization of poly-hydroxybutyrate/luffa fibers composite material. BioResources 15, 7159–7177. doi: 10.15376/biores.15.3.7159-7177
    Barkhad M.S., Abu-Jdayil B., Iqbal M.Z., Mourad A.H.I., 2020. Thermal insulation using biodegradable poly(lactic acid)/date pit composites. Constr. Build. Mater. 261, 120533. doi: 10.1016/j.conbuildmat.2020.120533
    Benchouia H.E., Guerira B., Chikhi M., Boussehel H., Tedeschi C., 2023. An experimental evaluation of a new eco-friendly insulating material based on date palm fibers and polystyrene. J. Build. Eng. 65, 105751. doi: 10.1016/j.jobe.2022.105751
    Cabeza L.F., Castell A., Medrano M., Martorell I., Pérez G., Fernández I., 2010. Experimental study on the performance of insulation materials in Mediterranean construction. Energy Build. 42, 630–636. doi: 10.1016/j.enbuild.2009.10.033
    Chin C.O., Yang X., Paul S.C., Wong L.S., Kong S.Y., 2020. Development of thermal energy storage lightweight concrete using paraffin-oil palm kernel shell-activated carbon composite. J. Clean. Prod. 261, 121227. doi: 10.1016/j.jclepro.2020.121227
    Christian S.J., Billington S.L., 2011. Mechanical response of PHB- and cellulose acetate natural fiber-reinforced composites for construction applications. Compos. B Eng. 42, 1920–1928. doi: 10.1016/j.compositesb.2011.05.039
    da Silva Moura A., Demori R., Leão R.M., Crescente Frankenberg C.L., Campomanes Santana R.M., 2019. The influence of the coconut fiber treated as reinforcement in PHB (polyhydroxybutyrate) composites. Mater. Today Commun. 18, 191–198. doi: 10.1016/j.mtcomm.2018.12.006
    de Koning G.J.M., Scheeren A.H.C., Lemstra P.J., Peeters M., Reynaers H., 1994. Crystallization phenomena in bacterial poly [(R)-3-hydroxybutyrate]: 3. Toughening via texture changes. Polymer 35, 4598–4605. doi: 10.1016/0032-3861(94)90809-5
    Faruk O., Bledzki A.K., Fink H.P., Sain M., 2014. Progress report on natural fiber reinforced composites. Macromol. Mater. Eng. 299, 9–26. doi: 10.1002/mame.201300008
    García Sánchez G.F., Guzmán López R.E., Gonzalez-Lezcano R.A., 2021. Fique as a sustainable material and thermal insulation for buildings: study of its decomposition and thermal conductivity. Sustainability 13, 7484. doi: 10.3390/su13137484
    García M.A., Martino M.N., Zaritzky N.E., 2000. Lipid addition to improve barrier properties of edible starch-based films and coatings. J. Food Sci. 65, 941–944. doi: 10.1111/j.1365-2621.2000.tb09397.x
    Getachew A., Woldesenbet F., 2016. Production of biodegradable plastic by polyhydroxybutyrate (PHB) accumulating bacteria using low cost agricultural waste material. BMC Res. Notes 9, 509. doi: 10.1186/s13104-016-2321-y
    Ghazanfari A., Emami S., Panigrahi S., Tabil L.G., 2008. Thermal and mechanical properties of blends and composites from HDPE and date pits particles. J. Compos. Mater. 42, 77–89. doi: 10.1177/0021998307086212
    Goli E., Parikh N.A., Yourdkhani M., Hibbard N.G., Moore J.S., Sottos N.R., Geubelle P.H., 2020. Frontal polymerization of unidirectional carbon-fiber-reinforced composites. Compos. A Appl. Sci. Manuf. 130, 105689. doi: 10.1016/j.compositesa.2019.105689
    González-López J.R., Juárez-Alvarado C.A., Ayub-Francis B., Mendoza-Rangel J.M., 2018. Compaction effect on the compressive strength and durability of stabilized earth blocks. Constr. Build. Mater. 163, 179–188. doi: 10.1016/j.conbuildmat.2017.12.074
    Graupner N., Müssig J., 2011. A comparison of the mechanical characteristics of kenaf and lyocell fibre reinforced poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) composites. Compos. A Appl. Sci. Manuf. 42, 2010–2019. doi: 10.1016/j.compositesa.2011.09.007
    Gunning M.A., Geever L.M., Killion J.A., Lyons J.G., Higginbotham C.L., 2013. Mechanical and biodegradation performance of short natural fibre polyhydroxybutyrate composites. Polym. Test. 32, 1603–1611. doi: 10.1016/j.polymertesting.2013.10.011
    Gupta M.K., Singh R., 2019. PLA-coated sisal fibre-reinforced polyester composite: water absorption, static and dynamic mechanical properties. J. Compos. Mater. 53, 65–72. doi: 10.1177/0021998318780227
    Hassan A., Muhammad Rafiq M.I., Zainal Ariffin M.I., 2019. Improving thermal and mechanical properties of injection moulded kenaf fibre-reinforced polyhydroxy-butyrate composites through fibre surface treatment. BioResources 14, 3101–3116. doi: 10.15376/biores.14.2.3101-3116
    Hassan A., Salleh N.M., Yahya R., Sheikh M.R.K., 2011. Fiber length, thermal, mechanical, and dynamic mechanical properties of injection-molded glass-fiber/polyamide 6, 6: plasticization effect. J. Reinf. Plast. Compos. 30, 488–498. doi: 10.1177/0731684410397898
    Hittini W., Abu-Jdayil B., Mourad A.H., 2021. Development of date pit–polystyrene thermoplastic heat insulator material: mechanical properties. J. Thermoplast. Compos. Mater. 34, 472–489. doi: 10.1177/0892705719847242
    Hosokawa M.N., Darros A.B., da Silva Moris V.A., de Paiva J.M.F., 2016. Polyhydroxybutyrate composites with random mats of sisal and coconut fibers. Mat. Res. 20, 279–290. doi: 10.1590/1980-5373-mr-2016-0254
    Huner U., 2018. Effect of chemical surface treatment on flax-reinforced epoxy composite. J. Nat. Fibres. 15, 808–821. doi: 10.1080/15440478.2017.1369207
    Jerman M., Černý R., 2012. Effect of moisture content on heat and moisture transport and storage properties of thermal insulation materials. Energy Build. 53, 39–46. doi: 10.1016/j.enbuild.2012.07.002
    Jin X., Wang W.Y., Xiao C.F., Lin T., Bian L.N., Hauser P., 2016. Improvement of coating durability, interfacial adhesion and compressive strength of UHMWPE fiber/epoxy composites through plasma pre-treatment and polypyrrole coating. Compos. Sci. Technol. 128, 169–175. doi: 10.1016/j.compscitech.2016.03.026
    Kaliappan S., Velumayil R., Natrayan L., Pravin P., 2023. Mechanical, DMA, and fatigue behavior of Vitis vinifera stalk cellulose Bambusa vulgaris fiber epoxy composites. Polym. Compos. 44, 2115–2121. doi: 10.1002/pc.27228
    Khoukhi M., Dar Saleh A., Mohammad A.F., Hassan A., Abdelbaqi S., 2022. Thermal performance and statistical analysis of a new bio-based insulation material produced using grain puffing technique. Constr. Build. Mater. 345, 128311. doi: 10.1016/j.conbuildmat.2022.128311
    Kolak M.N., Oltulu M., 2023. Investigation of mechanical and thermal properties of new type bio-composites containing camelina. Constr. Build. Mater. 362, 129779. doi: 10.1016/j.conbuildmat.2022.129779
    Korjenic A., Petránek V., Zach J., Hroudová J., 2011. Development and performance evaluation of natural thermal-insulation materials composed of renewable resources. Energy Build. 43, 2518–2523. doi: 10.1016/j.enbuild.2011.06.012
    Krishnaprasad R., Veena N.R., Maria H.J., Rajan R., Skrifvars M., Joseph K., 2009. Mechanical and thermal properties of bamboo microfibril reinforced polyhydroxybutyrate biocomposites. J. Polym. Environ. 17, 109–114. doi: 10.1007/s10924-009-0127-x
    Kumar A., Staněk K., Ryparová P., Hajek P., Tywoniak J., 2016. Hydrophobic treatment of wood fibrous thermal insulator by octadecyltrichlorosilane and its influence on hygric properties and resistance against moulds. Compos. B Eng. 106, 285–293. doi: 10.1016/j.compositesb.2016.09.034
    Lee S.G., Choi S.S., Park W.H., Cho D., 2003. Characterization of surface modified flax fibers and their biocomposites with PHB. Macromol. Symp. 197, 89–100. doi: 10.1002/masy.200350709
    Lee S.Y., Kang I.A., Doh G.H., Yoon H.G., Park B.D., Wu Q.L., 2008. Thermal and mechanical properties of wood flour/talc-filled polylactic acid composites: effect of filler content and coupling treatment. J. Thermoplast. Compos. Mater. 21, 209–223. doi: 10.1177/0892705708089473
    Li D., Lv L., Chen J.C., Chen G.Q., 2017. Controlling microbial PHB synthesis via CRISPRi. Appl. Microbiol. Biotechnol. 101, 5861–5867. doi: 10.1007/s00253-017-8374-6
    Lu N., Oza S., 2013. Thermal stability and thermo-mechanical properties of hemp-high density polyethylene composites: effect of two different chemical modifications. Compos. B Eng. 44, 484–490. doi: 10.1016/j.compositesb.2012.03.024
    Marques B., Almeida J., Tadeu A., António J., Santos M.I., de Brito J., Oliveira M., 2021. Rice husk cement-based composites for acoustic barriers and thermal insulating layers. J. Build. Eng. 39, 102297. doi: 10.1016/j.jobe.2021.102297
    McAdam B., Fournet M.B., McDonald P., Mojicevic M., 2020. Production of polyhydroxybutyrate (PHB) and factors impacting its chemical and mechanical characteristics. Polymers 12, 2908. doi: 10.3390/polym12122908
    Mehrez I., Hachem H., Gheith R., Jemni A., 2023. Optimization of mortar/Agave americana fibers composite behavior based on experimental design. J. Nat. Fibres. 20: 2152149. doi: 10.1080/15440478.2022.2152149
    Melendez-Rodriguez B., Torres-Giner S., Aldureid A., Cabedo L., Lagaron J.M., 2019. Reactive melt mixing of poly(3-hydroxybutyrate)/rice husk flour composites with purified biosustainably produced poly(3-hydroxybutyrate- co-3-hydroxyvalerate). Materials 12, 2152. doi: 10.3390/ma12132152
    Melo J.D.D., Carvalho L.F.M., Medeiros A.M., Souto C.R.O., Paskocimas C.A., 2012. A biodegradable composite material based on polyhydroxybutyrate (PHB) and carnauba fibers. Compos. B Eng. 43, 2827–2835. doi: 10.1016/j.compositesb.2012.04.046
    Mlhem A., Abu-Jdayil B., Iqbal M.Z., 2023. High-performance, renewable thermal insulators based on silylated date palm fiber–reinforced poly(β-hydroxybutyrate) composites. Dev. Built Environ. 16, 100240. doi: 10.1016/j.dibe.2023.100240
    Mlhem A., Abu-Jdayil B., Tong-Earn T., Iqbal M., 2022. Sustainable heat insulation composites from date palm fibre reinforced poly(β-hydroxybutyrate). J. Build. Eng. 54, 104617. doi: 10.1016/j.jobe.2022.104617
    Moura A., Bolba C., Demori R., Lima L.P.F.C., Santana R.M.C., 2018. Effect of rice husk treatment with hot water on mechanical performance in poly(hydroxybutyrate)/rice husk biocomposite. J. Polym. Environ. 26, 2632–2639. doi: 10.1007/s10924-017-1156-5
    Nabili A., Fattoum A., Passas R., Elaloui E., 2016. Extraction and characterization of cellulose from date palm seeds (Phoenix dactylifera L. ). Cellul. Chem. Technol. 50, 1015–1023.
    Norvaišienė R., Griciutė G., Bliūdžius R., Ramanauskas J., 2013. The changes of moisture absorption properties during the service life of external thermal insulation composite system. Mater. Sci. 19: 103–107.
    Oliver-Ortega H., Julián F., Espinach F.X., Méndez J.A., 2023. Simulated environmental conditioning of PHB composites reinforced with barley fibres to determine the viability of their use as plastics for the agriculture sector. Polymers 15, 579. doi: 10.3390/polym15030579
    Panneerdhass R., Gnanavelbabu A., Rajkumar K., 2014. Mechanical properties of Luffa fiber and ground nut reinforced epoxy polymer hybrid composites. Procedia Eng. 97, 2042–2051. doi: 10.1016/j.proeng.2014.12.447
    Papadopoulos A.M., 2005. State of the art in thermal insulation materials and aims for future developments. Energy Build. 37, 77–86. doi: 10.1016/j.enbuild.2004.05.006
    Raza M., Abu-Jdayil B., 2023. Synergic interactions, kinetic and thermodynamic analyses of date palm seeds and cashew shell waste co-pyrolysis using Coats–Redfern method. Case Stud. Therm. Eng. 47, 103118. doi: 10.1016/j.csite.2023.103118
    Reis K.C., Pereira L., Melo I.C.N.A., Marconcini J.M., Trugilho P.F., Tonoli G.H.D., 2015. Particles of coffee wastes as reinforcement in polyhydroxybutyrate (PHB) based composites. Mater. Res. 18, 546–552. doi: 10.1590/1516-1439.318114
    Rodríguez E., Francucci G., 2016. PHB coating on jute fibers and its effect on natural fiber composites performance. J. Compos. Mater. 50, 2047–2058. doi: 10.1177/0021998315601203
    Salim A.M., Abu Dabous S., 2022. SWOT analysis of solar photovoltaic systems in public housing projects in the united Arab emirates. Proceedings of the 2022 Advances in Science and Engineering Technology International Conferences (ASET). Dubai, United Arab Emirates. IEEE, 1–6.
    Salleh F.M., Hassan A., Yahya R., Lafia-Araga R.A., Azzahari A.D., Nazir M.N.Z.M., 2014. Improvement in the mechanical performance and interfacial behavior of kenaf fiber reinforced high density polyethylene composites by the addition of maleic anhydride grafted high density polyethylene. J. Polym. Res. 21, 439. doi: 10.1007/s10965-014-0439-y
    Santos E.B.C., Barros J.J.P., de Moura D.A., Moreno C.G., de Carvalho Fim F., da Silva L.B., 2019. Rheological and thermal behavior of PHB/piassava fiber residue-based green composites modified with warm water. J. Mater. Res. Technol. 8, 531–540. doi: 10.1016/j.jmrt.2018.05.005
    Sheng X.W., Xiao S.M., Zheng W.Q., Sun H.Z., Yang Y., Ma K.L., 2023. Experimental and finite element investigations on hydration heat and early cracks in massive concrete piers. Case Stud. Constr. Mater. 18, e01926.
    Singha A.S., Thakur V.K., 2009. Synthesis and characterization of short Saccaharum cilliare fibre reinforced polymer composites. E J. Chem. 6, 34–38. doi: 10.1155/2009/176072
    Sinsukudomchai P., Aht-Ong D., Honda K., Napathorn S.C., 2023. Green composites made of polyhydroxybutyrate and long-chain fatty acid esterified microcrystalline cellulose from pineapple leaf. PLoS One 18, e0282311. doi: 10.1371/journal.pone.0282311
    Smith M.K.M., Paleri D.M., Abdelwahab M., Mielewski D.F., Misra M., Mohanty A.K., 2020. Sustainable composites from poly(3-hydroxybutyrate) (PHB) bioplastic and agave natural fibre. Green Chem. 22, 3906–3916. doi: 10.1039/d0gc00365d
    Song W., Yang Z.X., Zhang S.B., Fei B.H., Zhao R.J., 2023. Properties enhancement of poly(β-hydroxybutyrate) biocomposites by incorporating surface-modified wheat straw flour: effect of pretreatment methods. Int. J. Biol. Macromol. 232, 123456. doi: 10.1016/j.ijbiomac.2023.123456
    Stec A.A., Hull T.R., 2011. Assessment of the fire toxicity of building insulation materials. Energy Build. 43, 498–506. doi: 10.1016/j.enbuild.2010.10.015
    Torres-Giner S., Montanes N., Fombuena V., Boronat T., Sanchez-Nacher L., 2018. Preparation and characterization of compression-molded green composite sheets made of poly(3-hydroxybutyrate) reinforced with long pita fibers. Adv. Polym. Technol. 37, 1305–1315. doi: 10.1002/adv.21789
    Valente B.F.A., Silvestre A.J.D., Neto C.P., Vilela C., Freire C.S.R., 2021. Effect of the micronization of pulp fibers on the properties of green composites. Molecules 26, 5594. doi: 10.3390/molecules26185594
    Ventura H., Claramunt J., Rodríguez-Pérez M.A., Ardanuy M., 2017. Effects of hydrothermal aging on the water uptake and tensile properties of PHB/flax fabric biocomposites. Polym. Degrad. Stab. 142, 129–138. doi: 10.1016/j.polymdegradstab.2017.06.003
    Vicente D., Proença D.N., Morais P.V., 2023. The role of bacterial polyhydroalkanoate (PHA) in a sustainable future: a review on the biological diversity. Int. J. Environ. Res. Public Health 20, 2959. doi: 10.3390/ijerph20042959
    Vitorino M.B.C., Cipriano P.B., Wellen R.M.R., Canedo E.L., Carvalho L.H., 2016. Nonisothermal melt crystallization of PHB/babassu compounds. J. Therm. Anal. Calorim. 126, 755–769. doi: 10.1007/s10973-016-5514-7
    Wang W., Yang R.X., Li T., Komarneni S., Liu B.J., 2021. Advances in recyclable and superior photocatalytic fibers: material, construction, application and future perspective. Compos. B Eng. 205, 108512. doi: 10.1016/j.compositesb.2020.108512
    Waters C.L., Janupala R.R., Mallinson R.G., Lobban L.L., 2017. Staged thermal fractionation for segregation of lignin and cellulose pyrolysis products: an experimental study of residence time and temperature effects. J. Anal. Appl. Pyrolysis 126, 380–389. doi: 10.1016/j.jaap.2017.05.008
    Wu C.S., 2006. Assessing biodegradability and mechanical, thermal, and morphological properties of an acrylic acid-modified poly(3-hydroxybutyric acid)/wood flours biocomposite. J. Appl. Polym. Sci. 102, 3565–3574. doi: 10.1002/app.24817
    Ye H.R., Zheng G.Y., Zuo S.D., Yu Q.H., Xia C.L., Sheng Y.Q., Shi Y., Wang D.X., Li J.Z., Ge S.B., 2023. Lightweight, bacteriostatic and thermally conductive wood plastic composite prepared by chitosan modified biointerfaces. Appl. Surf. Sci. 615, 156313. doi: 10.1016/j.apsusc.2022.156313
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