Extrusion processes are widely used in industries that aim to produce advanced solutions for increasingly sophisticated demands in the plastic, food, and pharmaceutical sectors. Though the process has been in use since the 1930s, limited information is available on the analytical computation of extrusion. Generally, production has been carried out based on empirical experience and trial-and-error approaches. The development of industrial operations is, however, best addressed by modelling the processes involved, and the flow of polymer melts and fibers in extruders has been subjected to some previous studies. Also included an overview of design of a die as well as challenges in sheet/film production. This article systematically and critically reviews the literature related to the process design, machine design, process parameters, flow models, and flow analysis of extrusion with a focus on modelling the extrusion of composite materials.

Reuse of materials is a significant global goal that contributes to sustainable development. Polymer-specific plastic identification from the waste stream is examined in this study to achieve environmentally optimistic reuse of plastic material in secondary applications. Two diverse waste streams, 86.11 kg of construction and demolition waste (CDW) plastic and 57.74 kg of mechanically sorted plastic, were analyzed by using a handheld tool whose identification technology was based on the near-infrared spectrum. The study indicates a significant effect of human and single fraction on manual separation. The polymer composition in the plastic waste stream varied depending on the source, but the most common plastic grades, polypropylene (PP) and polyethylene (PE), were represented in every waste stream. The waste stream also included unidentified and unfavorable wastes, which indicates that identification of the plastic fractions is needed and more studies should be done in this field in the future.

The requirements for the recycling of construction and demolition waste are tightening, and companies in the waste business have improved their performance to comply with new legislation. Construction and demolition waste includes various recyclable materials, such as metals, plastics and wood. However, effective material recovery requires functional and reliable technology for sorting in order to separate waste fractions into useful secondary materials or applications. This paper concerns the mechanical sorting efficiency of construction and demolition waste with a commercial mechanical sorting equipment consisting of a roller screening and an air separation unit. Sorting ability is studied with pre-sorted and crushed test material. Sieve analysis of pre-sorted test material is used to define particle size distribution before sorting. The quality criteria of construction and demolition waste vary greatly, depending on a number of factors which pose a challenge to the operation of the sorting system. The studied sorting equipment was found to be reliable for producing nine different fractions from pre-sorted and crushed material mixtures. The requirements for the purity level of the fractions and the profitability of utilization define the number of fractions to be sorted cost-efficiently. Typically, a compromise between cost and purity level has to be found.

The aviation industry is facing the challenge of reducing fossil fuels and emissions. Fuel efficiency is improved by making efficient powerplant systems and lighter aircraft. Modern passenger aircraft utilize polymeric and polymeric composite materials to achieve lighter structures without compromising strength. The European Union already has legislation to prevent landfilling and to increase the use of recyclable materials in the automotive industry. While older-generation aircraft, made mainly from metallic materials, are easily dismantled and recycled into other uses, such a process does not yet exist for aircraft made from composite materials. In the coming years, the industry will have to answer the question of how retired polymeric composite aircraft structures are to be recycled. One solution to increase the life cycle of polymeric and polymeric composite parts would be closed-loop recycling. In this paper, a perspective of the closed-loop recycling of polymeric aircraft parts is discussed. The technical aspects of recyclability and the different business models for the remanufacture of a finger pinch shroud certified for use in Airbus A350-900 passenger aircraft are investigated. The results show that closed-loop recycling is possible for polymeric aircraft parts. Future studies could include studying an LCA between virgin and recycled materials for a certain part.

Ecological concerns and the impending depletion of fossil fuels are driving the development of new bio-based, green products. Natural fibers are used increasingly as a filler or reinforcement in commercial thermoplastics due to their low cost, high specific properties and renewable nature. Agricultural byproducts and wastes are excellent alternative materials to supplement or substitute wood material as a reinforcement in composites.This comparative study focuses on the effects of the substitution of wood fiber with agro-basedfiber (barley straw) on the mechanical and physical properties of natural fiber/polypropylene composites. The studied mechanical properties are flexural strength and modulus, Brinell hardness and Charpy impact strength. Water absorption and thickness swelling are studied as physical properties. Generally, the research resultsindicate that almost all the studied properties weakened significantlyas woodwas substituted with barley straw.Ofmechanical properties, the major decrease wasobserved in hardness.However, the use of barley straw slightlyimproved impact strength.The moisture-related properties, water absorption and thickness swelling,which have a great impact on the durability of a composite material, weakened significantly.

In recent years, the growing interest in the development of 3D printing has focused more specifically on the utilization of eco-friendly, biodegradable and recycled materials. This paper presents the effect of the addition of cellulose filler on the tensile properties of filaments used in 3D printing. Cellulose-filled thermoplastic composite filaments were extruded from virgin polylactic acid (PLA), recycled acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polyvinylchloride (PVC), and the effect of cellulose filler on the tensile properties of composite filaments was measured. The results revealed that the tensile properties of recycled thermoplastic filaments weakened remarkably whereas the tensile properties of the filament made of virgin PLA slightly improved. However, despite the differences in the results, it was found that cellulose-filled thermoplastic composite filaments can be produced as feedstock used in 3D printing.