Cells analyses, mechanical and thermal stability of extruded polylactic acid/kenaf bio-composite foams Nur Adilah Abu Hassan a , Sahrim Ahmad a,b , Ruey Shan Chen a,b,⇑ , Dalila Shahdan a a Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor D. E., Malaysia b Materials Science Programme, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor D. E., Malaysia highlights  Polylactic acid/kenaf fiber bio-composites were foamed with exothermic ADC.  The gas decomposition of ADC is more efficient at a lower extrusion temperature (P2).  The increasing ADC loading has reduced the density and mechanical strength.  The increased number of foam cells has reduced the water resistance properties. article info Article history: Received 20 June 2019 Received in revised form 20 November 2019 Accepted 15 December 2019 Keywords: Polymer composites Biopolymer Biodegradable polymers Reinforcement Mechanical properties abstract Kenaf fiber (KF), polylactic acid (PLA) and azodicarbonamide (ADC) foaming agent were mixed evenly at two different extrusion temperatures via extrusion and followed by hot–cold pressing. The effects of two extrusion temperature profiles (P1:175, 180, 185, 170 °C and P2: 165, 170, 175, 160 °C) and the loadings of ADC (1–5 phr) on the morphological structure, and physical, tensile and thermal properties of foamed PLA/KF bio-composites were investigated. Results revealed that the tensile and water resistance proper- ties of the foamed PLA bio-composites decreased with the increasing of ADC loadings and the number of foamed cells in the PLA/KF bio-composite foams. The P2 extrusion temperature profile appeared as more suitable blending temperature with the production of uniform porous structured bio-composite foams which having lower density and higher mechanical strength. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Construction is one of the industrial fields that consumes signif- icant global resources which unfortunately caused negative impacts to the surrouding environment. Consequently, there are increasing efforts have been made to establish sustainable building design in order to minimise the severe impacts induced from con- struction [1]. In term of material selection, bio-based polymers are potential candidates to substitute as high as 90% of the petroleum– based of industrial polymers with the estimated increasing pro- duction from 0.36 million tons (in 2007) to 3.45 million tons by 2020 [2]. In the path of developing new polymers with a marked environmental focus, polylactic acid (PLA) could be one of the promising candidates to replace current commodity polymers [3]. PLA is a biodegradable thermoplastic polymer that is fully green and compostable via enzymatic degradation [4]. From the aspect of material performance, it is well-established that PLA shows favorable mechanical strength as compared to poly(ethy- lene), poly(propylene) and poly(styrene) (PS). PLA possesses good processability, excellent electrical resistivity and high dielectric breakdown strength over a temperature from room temperature to 343 K [5]. Nevertheless, the PLA has several disadvantages which are its high brittleness, low toughness and impact strength, hydrophilic- ity, and weak performance at high temperature and humidity, which limiting its utilization in various industrial applications [6,7]. To partially overwhelm these drawbacks, the reinforcement of PLA with low cost natural fibers has been implemented [8,9]. The use of natural fibers in bio-composites provides the advan- tages such as low density per unit volume, compostable and ease of recyclability, high availability from renewable resources as well as better thermal stability, mechanical and acoustic insulation properties [10,11]. Recent literature has reported the development of PLA-based green composite materials using natural fibers such https://doi.org/10.1016/j.conbuildmat.2019.117884 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor D. E., Malaysia. E-mail address: chen@ukm.edu.my (R.S. Chen). Construction and Building Materials 240 (2020) 117884 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat