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This study investigated the flexural properties of unidirectional flax sliver reinforced polylactic acid by molding pressure and chitosan fiber addition. As a molding condition, the range of molding pressures was 1 MPa to 5 MPa. Molding was done using vacuum compression molding. The amount of added chitosan fiber was 5 wt.%. The chitosan fiber was applied to the flax sliver surface. After chitosan fiber addition, the flax sliver surface was observed using scanning electron microscopy (SEM). Static three-point flexural tests of the green composite were conducted at room temperature. As a result, the flexural strength and modulus of green composite increased with increased molding pressure. The flexural strength and the modulus of chitosan fiber with added green composite greatly decreased compared with those of green composite with no added chitosan fiber when the molding pressure was 5 MPa. SEM observations revealed many chitosan fibers on the flax sliver surface. The flexural properties of green composites were affected because matrix penetration among the flax fibers readily occurred at molding pressures. However, the flexural properties of the green composite with added chitosan fiber at a molding pressure of 5 MPa was lower than that of the green composite with no added chitosan fiber at a molding pressure of 5 MPa because matrix penetration between flax fibers was probably prevented by the chitosan fiber addition.

Edible films and coatings are thin layers, with a thickness of generally less than 0.3 mm, that are used for centuries to protect food products and to avoid the deterioration of their ingredients. While an edible coating is formed directly on the food surface by spraying, dipping or spreading techniques, an edible film is first produced by solvent casting, compression moulding or extrusion procedures and posteriorly implemented into the food products, being placed on or between food components. The food sector is the main consumer of packaging materials, with the edible films and coatings being mainly applied into meat and seafood, fruits and vegetables and dairy products. These packaging materials, normally formed by a cohesive structured biopolymer, additives and/or a solvent, can also be used as carriers of several active ingredients, like colourants, flavours, nutrients and antimicrobial and antioxidant compounds, which can prolong the shelf life, improve the organoleptic characteristics and enhance the nutritional value of the final product. Nowadays, due to health and environmental concerns, the use of natural antioxidant and antimicrobial sources, like natural extracts, is emerging in the packaging research sector, being widely applied as active ingredients in edible film and coating formulations. A wide range of studies revealed the comprehensive interests in edible films and coatings with functional properties. So, the main objective of this review is to cover the recent works on edible films and coatings, including the investigation of recent advances in the incorporation of active compounds, namely natural extracts, and the challenges and opportunities for future research.

Natural fiber‐reinforced composites have emerged as a promising alternative in various industries, including automotive, aerospace, construction, and civil engineering, owing to their eco‐friendly nature and favorable mechanical properties. However, challenges such as low thermal stability and high moisture absorption limit their widespread use. To overcome these limitations, surface modifications such as mercerization, benzoylation, silane treatment, and acetylation have been extensively explored. Hybrid composites (HCs), combining natural and synthetic fibers, offer a compelling solution by harnessing the unique properties of both materials. This review comprehensively examines the types of fibers and polymers utilized in HCs, along with various chemical treatments to enhance their properties. Additionally, a detailed analysis of different manufacturing processes for HCs is provided, including hand lay‐up, vacuum‐assisted resin transfer molding, autoclave molding, injection molding, and compression molding. Furthermore, this review highlights recent advancements in HCs and their applications. Significant outcomes include a deeper understanding of the synergistic effects between natural and synthetic fibers, improved mechanical and thermal properties, and enhanced applications in diverse industries. The potential of HCs as a sustainable and high‐performance material solution emphasizes the importance of ongoing research and innovation in this field to overcome existing challenges and unlock new possibilities for composite engineering. Highlights Surface modifications such as mercerization, benzoylation, and silane treatment enhance the properties of natural fibers in composite materials. Hybrid composites (HCs) offer unique advantages by combining natural and synthetic fibers, including improved thermal, mechanical, and damping properties. Various chemical treatments and manufacturing processes contribute to enhancing the properties and applications of HCs. Recent advancements in HCs have led to an improved understanding and utilization of composite engineering across multiple industries. The review discusses challenges, opportunities, and future prospects for HCs, emphasizing the need for ongoing research and innovation in this field. Natural fiber‐reinforced hybrid composites are emerging as eco‐friendly alternatives in different industrial applications for their favorable mechanical and thermal properties.

Tremendously negative effects have been generated in recent decades by the continuously increasing production of conventional plastics and the inadequate management of their waste products. This demands the production of materials within a circular economy, easy to recycle and to biodegrade, minimizing the environmental impact and increasing cost competitiveness. Bioplastics represent a sustainable alternative in this scenario. However, the replacement of plastics must be addressed considering several aspects along their lifecycle, from bioplastic processing to the final application of the product. In this review, the effects of using different additives, biomass sources, and processing techniques on the mechanical and thermal behavior, as well as on the biodegradability, of bioplastics is discussed. The importance of using bioplasticizers is highlighted, besides studying the role of surfactants, compatibilizers, cross-linkers, coupling agents, and chain extenders. Cellulose, lignin, starch, chitosan, and composites are analyzed as part of the non-synthetic bioplastics considered. Throughout the study, the emphasis is on the use of well-established manufacturing processes, such as extrusion, injection, compression, or blow molding, since these are the ones that satisfy the quality, productivity, and cost requirements for large-scale industrial production. Particular attention is also given to fused deposition modeling, since this additive manufacturing technique is nowadays not only used for making prototypes, but it is being integrated into the development of parts for a wide variety of biomedical and industrial applications. Finally, recyclability and the commercial requirements for bioplastics are discussed, and some future perspectives and challenges for the development of bio-based plastics are discussed, with the conclusion that technological innovations, economic incentives, and policy changes could be coupled with individually driven solutions to mitigate the negative environmental impacts associated with conventional plastics.

Petroleum-based polymers are used in a multitude of products in the commercial world, but their high degree of contamination and non-biodegradability make them unattractive. The development and use of polymers derived from nature offer a solution to achieve an environmentally friendly and green alternative and reduce waste derived from plastics. This review focuses on showing an overview of the most widespread production methods for the main biopolymers. The parameters affecting the development of the technique, the most suitable biopolymers, and the main applications are included. The most studied biopolymers are those derived from polysaccharides and proteins. These biopolymers are subjected to production methods that improve their properties and modify their chemical structure. Process factors such as temperature, humidity, solvents used, or processing time must be considered. Among the most studied production techniques are solvent casting, coating, electrospinning, 3D printing, compression molding, and graft copolymerization. After undergoing these production techniques, biopolymers are applied in many fields such as biomedicine, pharmaceuticals, food packaging, scaffold engineering, and others.

Long-fiber thermoplastic (LFT) materials are a versatile category of composite materials that can be directly compounded (LFT-D) in twin screw extruders and compression molded. Originating in the automotive sector, the LFT-D process is becoming increasingly attractive for other industries where low cycle times, lightweight performance and recyclability are required. The purpose of this work is to summarize mechanical properties and findings from the investigations into LFT-D process–microstructure–property relationships and present a design of experiments (DoE) study based on the current state of the art. Primary parameters from LFT-D compounding, screw speed, fiber roving amount and polymer throughput mp are chosen as DoE factors. Polyamide 6 (PA6) is reinforced with a glass fiber (GF) mass fraction wf between wf = 20% and wf = 60%. Tensile, flexural and impact properties are chosen as DoE output parameters, characterized and discussed in relation to the state of the art. The unique microstructure of LFT-D materials, especially the existence of a charge and flow area as well as the fiber migration, is considered in the discussion. All mechanical properties characterized have a linear relation to wf. This study demonstrates the interactive relationship between the main factors and wf, which significantly influences the mechanical properties. This dependence of wf on the DoE factors is accounted for in advanced response contour plots proposed in this work. Parameter recommendations for the screw speed are reported by ranges of wf and polymer throughput for the goal of maximum mechanical properties or low coefficient of variations. At wf < 30% a low screw speed is recommended to improve most mechanical properties as well as the coefficient of variation.

In this study, machine learning algorithms (MLA) were employed to predict and classify the tensile strength of polymeric films of different compositions as a function of processing conditions. Two film production techniques were investigated, namely compression molding and extrusion-blow molding. Multi-factor experiments were designed with corresponding parameters. A tensile test was conducted on samples and the tensile strength was recorded. Predictive and classification models from nine MLA were developed. Performance analysis demonstrated the superior predictive ability of the support vector machine (SVM) algorithm, in which a coefficient of determination and mean absolute percentage error of 96% and 4%, respectively were obtained for the extrusion-blow molded films. The classification performance of the MLA was also evaluated, with several algorithms exhibiting excellent performance.

The study reviewed crucial parameters in the compression molding process for biocomposites affecting the properties of short natural fiber-reinforced polymer composites. The evaluation of drying and compounding processes between the polymer and short natural fiber was an essential consideration before the compression molding of biocomposites. Meanwhile, the parameters of molding temperature, compression pressure, and duration appeared to be other crucial and significant considerations requiring attention. In this study, all significant considerations affecting the performance of biocomposites were highlighted to provide essential information in the compression molding process of natural fiber composites topic. The findings from the present study are expected to improve the performance of short natural fiber-reinforced polymer composites and be an alternative to conventional polymer in various engineering applications in the future.

Over the past decades, research has escalated on the use of polylactic acid (PLA) as a replacement for petroleum-based polymers. This is due to its valuable properties, such as renewability, biodegradability, biocompatibility and good thermomechanical properties. Despite possessing good mechanical properties comparable to conventional petroleum-based polymers, PLA suffers from some shortcomings such as low thermal resistance, heat distortion temperature and rate of crystallization, thus different fillers have been used to overcome these limitations. In the framework of environmentally friendly processes and products, there has been growing interest on the use of cellulose nanomaterials viz. cellulose nanocrystals (CNC) and nanofibers (CNF) as natural fillers for PLA towards advanced applications other than short-term packaging and biomedical. Cellulosic nanomaterials are renewable in nature, biodegradable, eco-friendly and they possess high strength and stiffness. In the case of eco-friendly processes, various conventional processing techniques, such as melt extrusion, melt-spinning, and compression molding, have been used to produce PLA composites. This review addresses the critical factors in the manufacturing of PLA-cellulosic nanomaterials by using conventional techniques and recent advances needed to promote and improve the dispersion of the cellulosic nanomaterials. Different aspects, including morphology, mechanical behavior and thermal properties, as well as comparisons of CNC- and CNF-reinforced PLA, are also discussed.

Luffa spp. is readily available and widely grown in Asia and Africa and is a rich source of natural fibres for composite development. This paper reviews research findings on Luffa fibres and their composites. The progress of research, novel findings that affect the paradigm of the research area, recent trends, knowledge gaps and future perspectives are evaluated. It was found that the average chemical composition of Luffa fibres ranges from 57–74% cellulose, 14–30% of hemicellulose, 1–22% of lignin and 0–12.8% of the other components. Luffa fibres were usually extracted by drying. Furthermore, the most common modification technique was found to be by alkali mercerisation. About 53% of the research studies made use of epoxy resins for their base polymer making it the most popular polymer type for Luffa fibre reinforced composites. The composites are fabricated usually by manual mixing and hand layup and the most common curing technique was found to be compression moulding (about 63% of the research studies). The mechanical, thermal, crystalline and other properties of the composites are also considered in this review. Further interesting areas suggested for future work include investigation of the effect of drying, more trials with L. acutangula and utilisation of multi-resin ternary systems. It is concluded that Luffa is a promising material for composite development and based on its favourable properties is likely to continue playing an important role for the years to come.