{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T01:15:28Z","timestamp":1778548528936,"version":"3.51.4"},"reference-count":47,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2024,2,1]],"date-time":"2024-02-01T00:00:00Z","timestamp":1706745600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Project \u201cAgenda ILLIANCE\u201d","award":["C644919832-00000035|Project n\u00ba 22"],"award-info":[{"award-number":["C644919832-00000035|Project n\u00ba 22"]}]},{"name":"Project \u201cAgenda ILLIANCE\u201d","award":["UIDB\/00481\/2020"],"award-info":[{"award-number":["UIDB\/00481\/2020"]}]},{"name":"Project \u201cAgenda ILLIANCE\u201d","award":["UIDP\/00481\/2020"],"award-info":[{"award-number":["UIDP\/00481\/2020"]}]},{"name":"PRR\u2014Plano de Recupera\u00e7\u00e3o e Resili\u00eancia","award":["C644919832-00000035|Project n\u00ba 22"],"award-info":[{"award-number":["C644919832-00000035|Project n\u00ba 22"]}]},{"name":"PRR\u2014Plano de Recupera\u00e7\u00e3o e Resili\u00eancia","award":["UIDB\/00481\/2020"],"award-info":[{"award-number":["UIDB\/00481\/2020"]}]},{"name":"PRR\u2014Plano de Recupera\u00e7\u00e3o e Resili\u00eancia","award":["UIDP\/00481\/2020"],"award-info":[{"award-number":["UIDP\/00481\/2020"]}]},{"DOI":"10.13039\/501100001871","name":"TEMA","doi-asserted-by":"publisher","award":["C644919832-00000035|Project n\u00ba 22"],"award-info":[{"award-number":["C644919832-00000035|Project n\u00ba 22"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"TEMA","doi-asserted-by":"publisher","award":["UIDB\/00481\/2020"],"award-info":[{"award-number":["UIDB\/00481\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"TEMA","doi-asserted-by":"publisher","award":["UIDP\/00481\/2020"],"award-info":[{"award-number":["UIDP\/00481\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Natural fiber composites (NFC) are eco-friendly alternatives to synthetic polymers. However, some intrinsic natural fillers\u2019 properties hinder their widespread implementation as reinforcement in polymeric matrices and require further investigation. In the scope of this study, the thermal, rheologic, mechanical (tension and flexural modes), and morphological properties, as well as the water absorption and dimensional stability of the NF polypropylene (PP)-based injection molded composites reinforced with rice husk (rh) and olive pits (op) of 20 wt.% and 30% wt.%, respectively, were investigated. The results suggest that the higher content of the rice husk and olive pits led to a similar reduction in the melt flow index (MFI), independent of the additive type compared to virgin polypropylene (PPv). The melting and crystallization temperatures of the PPrh and PPop composites did not change with statistical significance. The composites are stiffer than the PP matrix by up to 49% and possess higher mechanical strength in the tension mode at the expense of decreased ductility. PPrh and PPop have a superior flexural modulus in the bending mode, while the flexural strength improvement was accomplished for the PP30%rh. The influence of the fibers\u2019 distribution in the bulk of the parts on their mechanical performance was confirmed based on a non-localized morphology evaluation, which constitutes a novelty of the presented research. The dimensional stability of the composites was improved as the linear shrinkage in the flow direction was decreased by 49% for PPrh and 30% for PPop, positively correlating with an increase in the filler content and stiffness. PPop was less susceptible to water sorption than PPrh due to fibers\u2019 composition and larger surface-to-area volume ratios.<\/jats:p>","DOI":"10.3390\/ma17030696","type":"journal-article","created":{"date-parts":[[2024,2,1]],"date-time":"2024-02-01T09:43:22Z","timestamp":1706780602000},"page":"696","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Sustainable Polypropylene-Based Composites with Agro-Waste Fillers: Thermal, Morphological, Mechanical Properties and Dimensional Stability"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2150-6241","authenticated-orcid":false,"given":"Tatiana","family":"Zhiltsova","sequence":"first","affiliation":[{"name":"Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"TEMA\u2014Centre for Mechanical Engineering and Automation, University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"LASI\u2014Intelligent Systems Associate Laboratory, 4800-058 Guimar\u00e3es, Portugal"}]},{"given":"J\u00e9ssica","family":"Campos","sequence":"additional","affiliation":[{"name":"Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"Andreia","family":"Costa","sequence":"additional","affiliation":[{"name":"OLI-Sistemas Sanit\u00e1rios, S.A. Travessa de Mil\u00e3o, Esgueira, 3800-314 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6190-1238","authenticated-orcid":false,"given":"M\u00f3nica S. A.","family":"Oliveira","sequence":"additional","affiliation":[{"name":"Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"TEMA\u2014Centre for Mechanical Engineering and Automation, University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"LASI\u2014Intelligent Systems Associate Laboratory, 4800-058 Guimar\u00e3es, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,2,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1080\/1023666X.2016.1148316","article-title":"Mechanical and Morphological Properties of Injection-Molded Rice Husk Polypropylene Composites","volume":"21","author":"Aridi","year":"2016","journal-title":"Int. J. Polym. Anal. Charact."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"20180198","DOI":"10.1520\/JTE20180198","article-title":"Dynamical Mechanical Properties of Polypropylene Composites Filled with Olive Pit Particles","volume":"47","year":"2019","journal-title":"J. Test. Eval."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1298","DOI":"10.1007\/s11595-018-1967-9","article-title":"Physical and Mechanical Properties of PP Composites Based on Different Types of Lignocellulosic Fillers","volume":"33","author":"Erdogan","year":"2018","journal-title":"J. Wuhan Univ. Technol. Sci. Ed."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"107135","DOI":"10.1016\/j.compositesb.2019.107135","article-title":"Mechanical, Thermal, Viscoelastic Performance and Product Application of PP-Rice Husk Colombian Biocomposites","volume":"176","author":"Salinas","year":"2019","journal-title":"Compos. Part B Eng."},{"key":"ref_5","unstructured":"(2023, December 03). Made in EU. Rice: Sustainable EU Rice. Available online: https:\/\/www.sustainableeurice.eu\/sustainable-rice\/."},{"key":"ref_6","unstructured":"Fundacao Francisco Manuel dos Santos (2023, November 25). PORDATA, the Database of Contemporary Portugal. Available online: https:\/\/www.pordata.pt\/en\/portugal\/olive+production+\u2013+mainland+portugal-3362."},{"key":"ref_7","unstructured":"Genieva, S.D., Turmanova, S.C., and Vlaev, L.T. (2011). Cellulose Fibers: Bio- and Nano-Polymer Composites: Green Chemistry and Technology, Springer."},{"key":"ref_8","first-page":"319","article-title":"12 State-of-the-Art Applications of Natural Fiber Composites in the Industry","volume":"Volume 5","author":"Campilho","year":"2015","journal-title":"Natural Fiber Composites"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Mallick, P.K. (2017). Polymer Matrix Composites: Processing and Applications, CRC Press.","DOI":"10.1201\/9781315157252"},{"key":"ref_10","unstructured":"Berzin, F., and Vergnes, B. (2021). Fiber Reinforced Composites, Elsevier."},{"key":"ref_11","unstructured":"Thomas, S., and Jose, S. (2022). Wool Fiber Reinforced Polymer Composites, Elsevier Science."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1169","DOI":"10.1177\/0731684407087759","article-title":"Recent Development in Natural Fiber Reinforced Polypropylene Composites","volume":"28","author":"Malkapuram","year":"2009","journal-title":"J. Reinf. Plast. Compos."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Sperling, L.H. (2005). Introduction to Physical Polymer Science, Wiley.","DOI":"10.1002\/0471757128"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1016\/j.compositesb.2014.07.010","article-title":"A Comparison of Processing and Performance for Lignocellulosic Reinforced Polypropylene for Injection Moulding Applications","volume":"67","author":"Burgstaller","year":"2014","journal-title":"Compos. Part B Eng."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1002\/pc.24614","article-title":"Characterization of Dimensional Stability in Flax Fiber Reinforced Polypropylene Composites","volume":"40","author":"Davis","year":"2019","journal-title":"Polym. Compos."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"296","DOI":"10.1177\/0892705711423289","article-title":"Assessment of Long-Term Water Absorption in Natural Fiber Reinforced Thermoplastic Composites Influenced by Filler Rate and Compatibilizer Treatment","volume":"26","author":"Kord","year":"2013","journal-title":"J. Thermoplast. Compos. Mater."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"15261","DOI":"10.1080\/15440478.2022.2121354","article-title":"Effect of Compatibilizer on the Properties of Areca-Fiber Reinforced Polypropylene Composites","volume":"19","author":"Venkatachalaiah","year":"2022","journal-title":"J. Nat. Fibers"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1016\/S0266-3538(02)00225-7","article-title":"Durability of Bamboo-Glass Fiber Reinforced Polymer Matrix Hybrid Composites","volume":"63","author":"Thwe","year":"2003","journal-title":"Compos. Sci. Technol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1007\/BF03218594","article-title":"Thermal and Dynamic-Mechanical Characterization of Rice-Husk Filled Polypropylene Composites","volume":"17","author":"Rosa","year":"2009","journal-title":"Macromol. Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"675","DOI":"10.1080\/1023666X.2016.1207006","article-title":"Investigating Morphological and Performance Deterioration of Injection-Molded Rice Husk\u2013Polypropylene Composites Due to Various Liquid Uptakes","volume":"21","author":"Aridi","year":"2016","journal-title":"Int. J. Polym. Anal. Charact."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"279","DOI":"10.1016\/j.compositesb.2013.08.028","article-title":"Characterization and Biodegradability of Polypropylene Composites Using Agricultural Residues and Waste Fish","volume":"56","author":"Nourbakhsh","year":"2014","journal-title":"Compos. Part B Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"65","DOI":"10.4028\/www.scientific.net\/KEM.733.65","article-title":"Effects of Olive Pit and Almond Shell Powder on Polypropylene","volume":"733","year":"2017","journal-title":"Key Eng. Mater."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Jurado-Contreras, S., Navas-Martos, F.J., Rodr\u00edguez-Li\u00e9bana, J.A., Moya, A.J., and La Rubia, M.D. (2022). Manufacture and Characterization of Recycled Polypropylene and Olive Pits Biocomposites. Polymers, 14.","DOI":"10.3390\/polym14194206"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"8470","DOI":"10.15376\/biores.11.4.8470-8482","article-title":"Characterization of Rice Husk-Incorporated Recycled Thermoplastic Blend Composites","volume":"11","author":"Chen","year":"2016","journal-title":"BioResources"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Kufel, A., and Kuciel, S. (2019). Basalt\/Wood Hybrid Composites Based on Polypropylene: Morphology, Processing Properties, and Mechanical and Thermal Expansion Performance. Materials, 12.","DOI":"10.3390\/ma12162557"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1177\/00219983211050705","article-title":"A Review of Applications of CT Imaging on Fiber Reinforced Composites","volume":"56","author":"Gao","year":"2021","journal-title":"J. Compos. Mater."},{"key":"ref_27","unstructured":"(2000). Determination of the Melt Mass-Flow Rate (MFR) and the Melt Volume-Flow Rate (MVR) of Thermoplastics (Standard No. ISO 1133-1997)."},{"key":"ref_28","unstructured":"(2018). Plastics\u2014Differential Scanning Calorimetry (DSC)\u2014Part 3: Determination of Temperature and Enthalpy of Melting and Crystallization (Standard No. ISO 11357-3:2018)."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Ehrenstein, G.W., Riedel, G., and Trawiel, P. (2004). Thermal Analysis of Plastics, Hanser Publishers.","DOI":"10.3139\/9783446434141.fm"},{"key":"ref_30","unstructured":"(2012). Plastics\u2014Determination of Tensile Properties\u2014Part 1: General Principles (Standard No. ISO 527-1)."},{"key":"ref_31","unstructured":"(2003). Plastics Determination of Flexural Properties (Standard No. ISO 178: 2001)."},{"key":"ref_32","unstructured":"(2013). Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement (Standard No. D792-13)."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"117744","DOI":"10.1016\/j.molliq.2021.117744","article-title":"Viscosities and Densities of Different Alcohols (1-Propanol, 2-Propanol, 1-Pentanol and 2-Pentanol) at High Pressures","volume":"344","author":"Moreau","year":"2021","journal-title":"J. Mol. Liq."},{"key":"ref_34","unstructured":"(2014). Standard Test Method of Measuring Shrinkage from Mold Dimensions of Thermoplastics (Reapproved 2014) (Standard No. D955\u221208)."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"671","DOI":"10.1038\/nmeth.2089","article-title":"NIH Image to ImageJ: 25 Years of Image Analysis","volume":"9","author":"Schneider","year":"2012","journal-title":"Nat. Methods"},{"key":"ref_36","unstructured":"(2010). Standard Test Method for Water Absorption of Plastics (Reapproved 2010) (Standard No. D570\u221298)."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"12014","DOI":"10.1088\/1757-899X\/368\/1\/012014","article-title":"Effect of Fiber Loading on Mechanical and Water Absorption Capacity of Polylactic Acid\/Polyhydroxybutyrate-Co-Hydroxyhexanoate\/Kenaf Composite","volume":"368","author":"Ismail","year":"2018","journal-title":"IOP Conf. Ser. Mater. Sci. Eng."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1016\/S1672-6529(14)60107-4","article-title":"Morphological, Structural, Thermal and Tensile Properties of High Density Polyethylene Composites Reinforced with Treated Argan Nut Shell Particles","volume":"12","author":"Essabir","year":"2015","journal-title":"J. Bionic Eng."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"101271","DOI":"10.1016\/j.rineng.2023.101271","article-title":"A Comprehensive Review of Natural Fibers and Their Composites: An Eco-Friendly Alternative to Conventional Materials","volume":"19","author":"Elfaleh","year":"2023","journal-title":"Results Eng."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1016\/0272-8842(92)90102-J","article-title":"Distribution of Silica in Rice Husks and Its Effect on the Formation of Silicon Carbide","volume":"18","author":"Crishnarao","year":"1992","journal-title":"Ceram. Int."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"424","DOI":"10.1016\/j.matdes.2012.11.025","article-title":"A Review on the Degradability of Polymeric Composites Based on Natural Fibres","volume":"47","author":"Azwa","year":"2013","journal-title":"Mater. Des."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"314","DOI":"10.1016\/j.conbuildmat.2019.03.009","article-title":"Effect of Specimen Thicknesses on Water Absorption and Flexural Strength of CFRP Laminates Subjected to Water or Alkaline Solution Immersion","volume":"208","author":"Zhang","year":"2019","journal-title":"Constr. Build. Mater."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"7480S","DOI":"10.1177\/1528083720974424","article-title":"Water Absorption Behavior of Cellulosic Fibres Polymer Composites: A Review on Its Effects and Remedies","volume":"51","author":"Sahu","year":"2020","journal-title":"J. Ind. Text."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1641","DOI":"10.1177\/0892705715583175","article-title":"Properties of Kapok Husk-Filled Linear Low-Density Polyethylene Ecocomposites: Effect of Polyethylene-Grafted Acrylic Acid","volume":"29","author":"Chun","year":"2016","journal-title":"J. Thermoplast. Compos. Mater."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"882","DOI":"10.1177\/0892705718815536","article-title":"High Loading Rice Husk Green Composites: Dimensional Stability, Tensile Behavior and Prediction, and Combustion Properties","volume":"33","author":"Chen","year":"2020","journal-title":"J. Thermoplast. Compos. Mater."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Kordi, M., Farrokhi, N., Pech-Canul, M.I., and Ahmadikhah, A. (2023). Rice Husk at a Glance: From Agro-Industrial to Modern Applications. Rice Sci., in press.","DOI":"10.1016\/j.rsci.2023.08.005"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"23924","DOI":"10.1021\/acsomega.1c02932","article-title":"Wooden Polymer Composites of Poly(Vinyl Chloride), Olive Pits Flour, and Precipitated Bio-Calcium Carbonate","volume":"6","author":"Althobaiti","year":"2021","journal-title":"ACS Omega"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/17\/3\/696\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T13:52:57Z","timestamp":1760104377000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/17\/3\/696"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,2,1]]},"references-count":47,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2024,2]]}},"alternative-id":["ma17030696"],"URL":"https:\/\/doi.org\/10.3390\/ma17030696","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,2,1]]}}}