Additive manufacturing technologies are being increasingly adopted in the manufacturing industries due to their capabilities in producing complex geometries without the need for special tools. Material extrusion (MEX-TRB/P) is a popular additive manufacturing technology due to its simple operation. However, optimization of various process parameters remains a challenge, as incorrect combinations can lead to reduced dimensional accuracy and incapacitated mechanical properties of the fabricated parts. Given that the MEX-TRB/P process relies on the heating and cooling of thermoplastic materials, understanding the role of temperature is critical to optimizing the MEX-TRB/P printed parts. This article reviews existing research on the effects of process parameters, specifically those that are temperature sensitive, on the mechanical properties of the printed parts. The review first classified the process parameters into temperature sensitive and non-temperature sensitive process parameters. Then, the influence of temperature on the bonding quality and material properties is investigated, and a relationship between the thermal conditions and mechanical properties of 3D printed parts is established. This review also summarizes experimental and numerical methods for investigating temperature evolution during printing. This study aims to provide a deep understanding of the optimization of temperature-sensitive process parameters and their role in enhancing the mechanical properties of MEX-TRB/P-printed parts.

In this study, tensile test specimens were fabricated using a material extrusion 3D-printer at various printing temperatures to evaluate the development of physical bonds within the same layer as well as in between previous layers. The tensile test specimens were fabricated using PLA material, with printing temperatures ranging from 180 °C to 260 °C. Experimental investigations were conducted to investigate the dimensional accuracy and physical appearance of the parts across printing temperatures. Uniaxial tensile tests were conducted at a strain rate of 1 mm/min and repeated five times for each variable in accordance with the ASTM D638-14 standard. Results showed that increasing the printing temperatures yielded parts with better tensile properties. An approximate difference of 40% in tensile strength was observed between specimens fabricated under the two most extreme conditions (180 °C and 260 °C). The changes in tensile properties were attributed to bonding mechanisms related to interlayer bonding strength and a reduction in voids within the internal geometry. Analysis of the fracture surface using scanning electron microscopy (SEM) revealed fewer and smaller voids within the internal geometry for parts printed at higher temperature. The percentage area of voids reduced significantly when the printing temperature was increased from 180 °C to 220 °C. The tensile properties continuously improved with the printing temperature, with parts printed at 220 °C exhibiting the highest dimensional accuracy. The findings offer insight into the impact of the printing temperature on both the external physical bonds between printed roads, affecting the physical appearance and dimensional accuracy, and the internal bonds, affecting the tensile properties of the fabricated parts.

Nitrate removal or denitrification, involves reduction of nitrate into nitrogen and oxygen. The use of nanoparticles zero valent metals for denitrification receives great attention as they have been proven to be effective and environmentally safe. In this work, the nanoparticles were prepared by reducing the metals salts, dissolved in a mixed solution of water and ethanol, using sodium borohydrate. The nitrate reduction reaction took place in an ambient environment – room temperature, neutral pH and aerobic condition. Results from the experiments carried out showed that nitrate has been successfully reduced up to a maximum of 40% in all the samples without an increase in the pH of the solution, a strong indication that ammonia was not produced. As for the study on the reactivity of the recycled NZVI, the samples synthesized with 4:1 (v/v) ethanol/water and using 9: 1 (v/v) ethanol/water, the reactivity of the iron is similar to the fresh NZVI for the first two hours of the study.

The main objective of this paper is to reduce the amount of external heat penetrating the building wall, hence reducing the cooling load requirements and eventually the electricity consumption. Expanded polystyrene and wood sawdust were chosen as filler material to reduce the thermal conductivity in perforated bricks because both are commonly found waste products with good potential due to their lightweight, low thermal conductivity and high specific heat. It was found that bricks with polystyrene recorded the lowest temperature change. Although sawdust has a much higher thermal conductivity, the temperature change is almost similar to that of polystyrene. This could be attributed by the higher density of wood, which means more mass are occupying the same volume of space. Hence, the paper found that thermal conductivity, specific heat capacity and density of the filler material can influence the effective thermal conductivity of the perforated brick.

Material extrusion (MEX) 3D-printed parts are primarily used for prototyping rather than functional components due to lower mechanical strength. To address this limitation and promote sustainability, current work explores the reinforcement of plant-based polylactic acid (PLA) with pineapple leaf fibre (PALF). An in situ approach was proposed to embed continuous PALF within the middle layer of a 3D-printed component during the MEX process. An experimental investigation was conducted to evaluate the impact performance of composites produced via this new fabrication method. To optimize the fibre–matrix interface, an alkaline treatment was applied to the natural fibre, enhancing interfacial adhesion. Neat PLA, along with two types of PALF-reinforced PLA composite, were printed with both single-strand and three-strand fibre configurations. Fracture surfaces were analyzed under a digital microscope and a scanning electron microscope (SEM) to correlate morphological characteristics with the impact strength. The results showed that the impact strength of the three-strand treated PALF-PLA composite (3 PALF-PLA) surpassed that of neat PLA by 2.71% due to reduced porosity. In contrast, the one-strand PALF-PLA composites exhibited lower performance compared to neat PLA due to the presence of the fibre gap caused by the mid-print pause. Treated fibres consistently outperformed untreated ones due to their rougher surface morphology resulting from alkaline treatment. The results demonstrate that the combination of alkaline treatment and continuous fibre reinforcement significantly enhances energy absorption of 3D-printed MEX parts and offers a sustainable pathway for 3D-printed MEX parts.