Thermal, mechanical, morphological and aesthetical properties of rotational molding PE/pine wood sawdust composites

This research addresses the importance of pine wood sawdust granulometry on the processing of medium-density polyethylene (MDPE)/wood composites by rotational molding and its effects on the morphological, mechanical and aesthetical properties of parts, aiming to contribute for the development of sustainable wood polymer composites (WPC) for rotational molding applications. Pine wood sawdust was sieved (1000 µm) and analyzed for its physical, morphological and thermal characteristics. Rotational molded parts were produced with matrix/wood ratios from 90/10 to 70/30 wt% considering different wood granulometries. As a natural material, wood changed its color during processing. Granulometries below 500 µm presented better sintering, homogeneity and less part defects. Furthermore, 300–500 µm favored the impact resistance (1316 N), as irregular brick-shaped wood was able to anchor to PE despite the weak interfacial adhesion observed. The increase of wood content from 10 to 30% reduced the impact properties by 40%, as a result of a highly porous structure formed, revealing sintering difficulties during processing. WPC parts of differentiated aesthetics and functionalities were achieved by rotational molding. A clear relationship between wood granulometry and WPC processing, structure and properties was identified.Financial support of the Project RoTMI-Rotomolding Technology and Materials Innovations (POCI-01-0247-FEDER-33095), cofinanced by the European Regional Development Fund (FEDER) through the Operational Program for Competitiveness and Internationalization (POCI) under the “Portugal 2020” framework; to the Portuguese Foundation for Science and Technology (FCT) through the National Funds References UIDB/05256/2020 and UIDP/05256/2020 provided to IPC

Improving cork polymer composites for the automotive industry

[Excerpt] The pressure imposed by legislations and treaties to adopt more sustainable and eco-friendly alternative materials is rising. Therefore, the use of cork-polymer composites (CPC) in the automotive industry could bridge the difficulties they have complying with the environmental laws and the need of giving a second life to the cork industrial wastes. From the cork processing, residues are generated, also called cork subproducts, with granulometries that wouldn’t be possible to use in other cork typical applications. With the purpose of implementing a circular economy model and reduce the waste that would be generated in normal conditions by burning or by throwing the cork residues in a landfield, the investigation and the development of new products involving these residues are taking place. [...

Application of DMAIC method in an industrial case study

Purpose. In the present work DMAIC methodology is implemented in a Portuguese enterprise. The main goal is to reduce the percentage of non-conformities in an injection molded part for the automotive industry, through the elimination of defects that appear after painting. Design/methodology/approach. The DMAIC method was adopted to find an optimal set of factors that reduce the existing non-conformities. Along the five DMAIC phases, different quality tools were implemented to identify the root causes of the problem and to develop an action plan to reduce defects and minimize the process variability. Findings. In the application of this method, teamwork and brainstorming were essential for satisfactory results in a short period of time. A key finding is that the analysis of the possible causes that gave rise to the problem must be carried out separately, in order to easily identify the changes that created a significant improvement in the process. Research limitations/implications. The project is not fully completed since some of the improvement actions are being implemented. Originality/value. This paper describes a practical application of DMAIC methodology that contributed to reduce part defects and improve the production process of a Portuguese company.The authors would like to acknowledge Fehst Componentes, Lda. for providing physical, technical and human resources and to be strongly involved on the development of this study; to the founds provide by National Funds through FCT - Portuguese Foundation for Science and Technology, References UIDB/05256/2020 and UIDP/05256/2020

Circularity micro-indicators for plastic packaging and their relation to circular economy principles and design tools

Plastic packaging, in the form of films, brought several advantages to the commercialization of products given its lightness and durability. It provided better ergonomics, ease of transport, increased shelf life, and easy handling and use. Despite that, plastic packaging is facing enormous sustainability concerns associated with the traditional practice of linear economy, combined with commonplace irresponsible handling by citizens since it is almost exclusively designed for single-use and its end-of-life (EOL) management is not planned for. To mitigate that, the circularity of plastic packaging must be more clearly studied and evaluated through approaches such as micro-level circular economy (CE) indicators. This paper focuses on the selection of relevant CE micro-indicators specifically for the plastic packaging sector among the plethora of indicators available. Relations are also established between CE micro-indicators and CE guiding principles, as well as the most prevalent Design for X (DfX) approaches, providing new insights into how these different aspects of sustainability can be linked together. Results show three micro-level indicators as the most relevant for circularity calculation in packaging, namely those termed ‘MCI’, ‘VRE’, and ‘CEIP’, because their methodology and approach address most of the CE guiding principles and DfX approaches relevant for the packaging sector. Finally, guidelines and good practices to promote circularity adoption in the plastic packaging sector are highlighted. This work can guide companies aiming to adopt CE micro-indicators in their practical implementation, overcoming the significant knowledge barrier that currently exists

Extrusion compounding of polyethylene with blowing agent

Cellular plastics are very attractive for the production of lightweight, structural and/or large dimension parts, e.g., boats, floaters, decks, etc. For their production, polymers and chemical blowing agents are either mixed or compounded prior to processing by injection or rotational moulding. It is essential to ensure good dispersion of the blowing agent in the polymeric matrix, and prevent its activation from occurring during compounding, i.e., an optimal processing window must be used. The aim of this work is to produce medium density polyethylene with Azodicarbonamide (MDPE/ADCA) masterbatches in pellet form for further processing by rotational moulding. For that purpose, a set of experimental procedures was conducted to evaluate the correct processing window without premature expansion during extrusion. Upon melt compounding of the masterbatch in pellets of different sizes, foamed parts were produced and characterized in terms of visual aspect, expansion ability and morphology.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No. 734205 – H2020-MSCA-RISE-201

Study of welding strengh in PVC profiles

Polyvinyl chloride, PVC, is one of the most widely produced and used plastic, being commonly used in civil industry due to its wide range of mechanical properties (from rigid to flexible), low cost, durability, and easy to assemble. Due to its good mechanical and thermal properties, PVC can be used to produce window and door frames, protecting the interior from the external actions, such as noise and temperature gradients. In order to achieve the final dimensions and geometry, previously extruded profiles must be cut and assembled, being the butt welding one of the most efficient techniques. This plastic welding method involves three main steps: i) pressing the parts to be joined against either side of a heated plate; ii) removing the plate when the parts are sufficiently molten and iii) pressing the components together and holding them until they are cooled. The amount of molten material, generated during the heating stage at an adequate heating time and the plate temperature, as well as the amount of material forced out from the joint during the pressing stage (joining displacement), have major influence in the final welding properties. Although the lack of information about the butt welding of PVC, previous studies with for others materials [1-3] showed that the welding strength can be optimized changing the plate temperature and/or joining displacement. The aim of this work was to study the influence of the plate temperature and the heating time in the welding strength of PVC profiles used in windows frames. The profiles were welded in an industrial butt welder machine, setting the plate temperature at 245ºC, 260ºC and 275ºC and the heating time at 15 and 20s. The mechanical properties were evaluated by mechanical bending tests, according to UNE-EN 514 standard and the welding strength was correlated with the morphology of the welded parts observed by optical microscopy. The results are showing that the increase of plate temperature and heating time increase the welding strength. However, the presence of impurities in the joint, such as trapped air or degraded material, as well as the joint alignment, can have a detrimental effect on the welding strength, as observed by the morphological analyses

Morphological aspects of injection-molded polypropylene with metallic pigments

Publicado em "ANTEC 2013 - Proceedings of the 71st Annual Technical Conference & Exhibition"Innovation, design freedom, cost and weight reduction are some factors for the replacement of metals by plastics. Plastics continue to offer attractive solutions for design engineers. The metallic effect obtained by incorporation of metal particles in polymers by injection molding has the advantage of eliminating post-processing techniques such as painting or metallization. Moreover, it reduces production costs and time to get a superior part quality. Nevertheless, undesired defects in the final appearance of parts are common, such as flow lines and weld lines. These defects occur due to inhomogeneous orientation and anisotropy of the metal particles. Very few studies are reporting the influence of metallic particles on the morphology development of PP parts. Therefore, this study is focused on the production of parts made of PP/metallic pigments (aluminum, bronze and copper) by injection molding in order to understand the influence of metallic particles on the aesthetic and morphological properties of the parts.ADI -American Dysautonomia Institut

Circularity micro-indicators applied to plastic parts: the materials perspective

The use of polymeric materials has increased exponentially in recent decades in all application areas. However, currently, most plastic products are designed and manufactured without careful consideration of their end-of-life management. As a result, the generated waste presents a large diversity of different polymers (often including harmful additives), which are discharged in landfills, posing problems for sustainable and environmentally friendly waste management, and draining valuable finite resources. Thus, it is urgent to change the plastic sector regarding the way products are conceived, and to promote, through strategies of the circular economy, the recovery of plastic materials to produce new products. To make this possible, there is a need to inform plastic manufacturers about circular economy concepts and provide knowledge and tools that allow them to measure the circularity of their products. In recent years, circularity micro-indicators have been proposed as a type of tool addressing this issue; however, they vary in scope, breadth, and the perspective they take on the overall life cycle of the product. Additionally, among the plethora of such circularity micro-indicators, the materials used in the product and how the material is handled at the end-of-life stage are only relevant in some cases. As such, this paper aims to identify circular micro-indicators that are relevant to plastic products and consider the origin of their polymeric materials (virgin, recycled, biodegradable, compostable, or derived from renewable sources) for evaluating product circularity. Within the scope of decision making, these circularity micro-indicators can help project development teams to determine if the selected materials contribute to overall product sustainability. In addition, we identify—from the materials perspective—some guidelines and good practices that help maximize product circularity and accelerate the implementation of the circular economy in the plastics sector

Effect of reprocessed PPS on the mechanical performance of injection molded parts

[Excerpt] In the automotive industry, there is an increasing demand for the recyclability of the materials that are used in the parts. This demand has a special focus in the composite materials currently being used, such as those based on thermoplastic polymers, given their recycling capability. One of the thermoplastic polymers used for automotive applications is the Polyphenylene Sulfide (PPS) mainly because of its great chemical resistance and high temperature resistance, but also due to its low viscosity, which permits PPS to be molded with high loads of fillers, such as glass fibers and minerals. [...]Project 46091–Better Plastics, financed by Portugal 2020 and European Union, through FEDER-Fundo Europeu de Desenvolvimento Regional. Portuguese Foundation for Science and Technology (FCT) funding to IPC, through projects UIDB/05256/2020 and UIDP/05256/2020

Structure evolution during deformation of novel polymer systems based on poly(ethylene terephthalate) reinforced with inorganic particles

Inorganic particles have been incorporated into poly(ethylene terephthalate), PET, matrix with the aim of offering some aesthetic effects to the standard transparent beverage packaging. To assess to the effect of different type of inorganic particles (with different interaction with the polymeric matrix) in the deformation behaviour of PET composites, particles such as aluminium, bronze, nanoclay, graphite and mica, were used. Two types of processing methods, ensuring a good mixing, were adopted for the composite preparation: i) melt-blending in an asymmetric batch mini-mixer followed by compression and ii) melt-blending in a twin screw extruder followed by injection moulding. The structural and mechanical behaviours of neat PET and its composites were evaluated during uniaxial stretching at temperatures above the glass transition temperature, Tg, namely at 85, 90, 95, 100 ºC, using a standard tensile stretching machine equipped with an environmental chamber. This study aims at understanding the deformation behaviour of the materials at temperatures found in conventional transformation methods used for packaging. To interpret the structural evolution occurring in the samples, off-line techniques such as DSC, WAXD and SEM were used. A detailed structural evolution was accomplished by applying different stretching ratios to the samples up to a maximum of 5x. Injection moulded samples were also characterized for their mechanical properties at room temperature in order to assess the materials behaviour in service. From all particles studied the PET/Aluminium and PET/Bronze composites are the ones showing the best combination of aesthetic effects, deformation behaviour and final mechanical properties. Comparing to neat PET, their general properties are the same during the deformation process making the new materials suitable for conventional processing techniques. It was found that both particles offer superior molecular mobility to PET at room temperature. In other words, these composites present a higher deformation capacity, however its elastic modulus and tensile strength at yield are slightly reduced