The mobility sector is at a crucial point of transformation, with increasing pressure to reduce the environmental footprint of vehicles and meet sustainability targets set by global and local regulations. In the European Union, passenger cars are responsible for around 16% of total CO2 emissions, prompting the European Commission to set a target of reducing greenhouse gas emissions by 55% by 2030 (compared to 1990), culminating in the sector’s carbon neutrality by 2050 [1].
In automobile production, several factors influence emissions reduction, including the materials used in their production, as well as the dimensions and weight of vehicles. Regarding vehicle weight reduction, replacing conventional metals with lighter materials has become a solution. At the heart of this transformation, polymers play a fundamental role due to their unique properties, such as lightness, specific stiffness, and chemical resistance, which are essential for vehicle efficiency and safety. Plastic materials have been widely used in automobiles for decades, currently constituting 50% of the car’s total volume, representing 8% of its total weight [2]. However, sustainability remains a significant challenge, as most conventional plastics still come from fossil sources, raising environmental concerns. In this context, the development of solutions that integrate more durable, recyclable, biodegradable, and bio-based polymers to replace fossil plastics, as well as the incorporation of natural fibers, is essential to meet the demands for greener and more sustainable mobility. Furthermore, in the context of more sustainable mobility, it is important to mention the contribution of these materials to the development of electric mobility solutions, where they are used in critical components related to the storage of electrical energy in batteries or in pressure cylinders for the storage of compressed hydrogen.
From a product development perspective, more important than simply replacing materials or incorporating natural fibers, is ensuring that the product will meet the needs for which it is being developed. It is crucial to ensure compliance with requirements from various perspectives, namely functional, decorative, and economic. A product that contains 1% or 99% recycled material in its composition, however aesthetically appealing it may be, but fails mechanical or thermal tests, for example, is not a useful product. The magic of product development lies in being able to transform the most diverse needs and problems into concrete and achievable requirements, and reconciling them so that the final solution fulfills its functions.
In terms of design, optimizing geometry, combined with material design, is essential for developing an efficient, sustainable, and functional product. Achieving the stringent safety standards required in the mobility sector and developing products that maintain the same characteristics as metal products requires various design techniques, including the implementation of Generative Design tools. Generative Design is a 3D CAD capability that uses artificial intelligence algorithms to create optimal designs based on a set of product requirements and specifications entered by designers and/or engineers. This allows for concepts that strike an ideal balance between weight and mechanical strength, reduced material use, and optimized geometry, taking into account the manufacturing process and the material. Furthermore, it reduces design time compared to traditional methods, exploring a variety of product ideas and experiences, including those that are unimaginable. These ideas and concepts can draw inspiration from nature, using biomimicry, which replicates natural forms, functions, and processes to optimize form, structure, and movement. With this approach, we can achieve performance and safety while reducing emissions and fuel consumption and increasing efficiency and aerodynamics. Additionally, the combination of natural patterns, colors, and textures can create unique and appealing designs for consumers. Even during the product development process, it is increasingly important to consider the modularity of components. With a focus on sustainability, components should be disassembled and replaceable, as well as reusable, thus contributing to the production and consumption model known as the circular economy.
PIEP’s Product Design and Development (PDD) department has the expertise to consider these different approaches to develop a more sustainable product.
On the other hand, incorporating functionality into merely decorative parts in the mobility sector allows for added value and innovations in the scientific and technological fields. A simple example is the replacement of cables, wires, and mechanical buttons with capacitive sensors on the steering wheel and dashboard of vehicles, to control the multimedia system, air conditioning, and interior lighting. These capacitive buttons can be integrated directly into the surface of polymeric parts through technologies such as Laser Direct Structuring (LDS) and In-Mold Electronics (IME). The great advantage is using curved surfaces and benefiting from all the geometric freedom this provides. A major challenge in using this technology is false touch detection, since if the user bumps into the sensor area, the capacitive touch is detected by the system, resulting in a false command. To remedy this problem, one proposed solution is to integrate a pressure sensor with the capacitive sensor. This way, only capacitive touches, along with a minimum force detected by the sensor, are interpreted as an effective command by the user.
The PDD areas, in addition to Advanced Manufacturing Processes – Polymers (PAFP), also have the technological capacity for the development and validation of these technologies, as well as their integration into other production processes.
Regarding material selection, the role of polymers in the current mobility landscape is growing, largely due to the increased demand for lightweight and durable materials. However, the increasing electrification of vehicles has generated the need for polymeric solutions that meet more specific requirements, particularly with regard to the growing demand for electromagnetic and thermal management properties [3]. Therefore, polymeric materials face increasing challenges in meeting industry expectations. To meet thermal management requirements, engineering and high-performance polymers that withstand higher temperatures have been increasingly used. Furthermore, fillers such as carbon fibers and metallic particles are being used to meet heat dissipation and thermal conductivity requirements, as well as to ensure protection against electromagnetic interference (EMI), a characteristic especially important for materials used in battery casings. Polymer composites reinforced with glass or carbon fibers are also widely used to ensure mechanical strength. However, this functionalization of polymers with different fillers requires compatibility between the different materials to ensure adhesion and the structural stability of the product. In addition to the growing research and development of polymeric materials that meet these requirements, there is also a growing concern for the use of more sustainable materials, thus driving the development of recycled and biodegradable polymers, aligned with global carbon emission reduction goals. Therefore, to remain at the forefront and a preferred material in the mobility sector, continuous innovation in polymeric materials is essential.
Regarding the development of new materials, biodegradable alternatives, such as PLA, are emerging as an essential solution for reducing the environmental impact of plastics. The challenge is ensuring that they offer adequate mechanical strength and performance for demanding applications, such as the automotive sector. The Vital project [4], for example, explores the recyclability of PLA, a widely used bio-based polymer, with a focus on improving the end-of-life management of these materials, a crucial issue for sustainability. Currently, bio-based thermoplastics (b-bTPs) are not yet adopted as part of ‘circular by design’ business models to replace fossil fuel-based solutions in thermoplastic processing value chains. This situation will only change when the cost and processability of b-bTPs become commercially viable. As b-bTP production capacity increases globally, expectations for a significant reduction in their prices are growing. However, even when the costs of b-bTPs are comparable to those of synthetic alternatives, there will still be processing challenges that need to be addressed to enable wider commercial acceptance. The Vital project explores the development of thermoplastic foaming processes, combined with intelligent digital control approaches, which will allow the processing of bio-based thermoplastics both on traditional processing equipment (such as foam injection molding and bead foaming) and on 3D printing equipment developed specifically for the project. This will enable a paradigm shift toward bio-based alternatives. The project addresses demonstration in sectors such as automotive, aeronautics, and electronics, with PIEP leading the injection molding line and the outreach activities of the Learning Factory.
Additionally, replacing petroleum-derived polymers with bio-based polymers (from renewable sources) is a promising strategy for reducing the carbon footprint of vehicles and promoting a greener economy. The ‘From Fossil to Forest’ (FF2F) Biocomposites project, for example, focuses on incorporating bio-based polymers into various applications, such as thermoforming and injection molding, reducing the use of fossil-based plastics and promoting more sustainable production. The development of sustainable materials emerges as an urgent solution, given that the production and consumption of fossil-based polymers contribute to the depletion of natural resources and global pollution. Projects like FF2F are crucial in this transition, aiming to replace fossil-based polymers with biodegradable and renewable solutions developed from forest biomass, such as cellulose. Led by Navigator Paper Setúbal, S.A. and the RAIZ research center, FF2F includes 27 entities in a consortium that ranges from research into new materials to the creation of prototypes for future industrial production. The project invests in innovative production processes that enable the design of a wide range of biodegradable products, from rigid and flexible products to 3D printing filaments and textile yarns. With six work areas defined within the Recovery and Resilience Plan (RRP), the project ensures that the replacement of fossil-based polymers with bio-based polymers does not compromise the economic efficiency or quality of the final products. The transition to bio-based alternatives represents an opportunity to reduce the industry’s environmental footprint and ensure the longevity of natural resources, while combining technological innovation with environmental responsibility.
On the other hand, natural fibers such as cellulose are increasingly being integrated into composite materials, improving the lightness and mechanical strength of products while reducing their environmental impact. The Be Neutral New Generation (BEN-NG) project is investigating the incorporation of rice husk waste into polypropylene (PP) for use in automotive panels. This approach not only increases the sustainability of composites but also reuses natural materials and reduces the use of fossil-based plastics. Replacing fossil-based plastics with organic materials is a promising strategy for mitigating the environmental problems associated with traditional plastics. Biodegradable, compostable, and bio-based materials obtained from renewable sources such as plants and microorganisms offer more sustainable alternatives, aligned with the principles of the circular economy. The BEN-NG project aims for more sustainable mobility, with one of its main focuses being the incorporation of Carolino rice husks into polypropylene for the production of vehicle interior trim parts. This replacement of fossil-based polymers with natural, 100% biodegradable fibers represents a significant increase in the value of a byproduct that is currently frequently burned. However, the biggest challenge is ensuring that the resulting biocomposites meet the rigorous requirements of the automotive industry.
At the end of their life, thermoplastic recycling plays a crucial role in reducing plastic waste pollution and resource depletion. Used in various industries for their versatility and durability, thermoplastics have become a major cause of environmental problems when not managed properly. Recycling offers a sustainable solution to mitigate these concerns by diverting plastics from landfills, reducing the consumption of virgin resources, and mitigating the environmental impacts associated with their production. This practice not only conserves valuable materials but also promotes a circular economy, where thermoplastics can be reused and reprocessed, creating new products and minimizing environmental impact. However, reprocessing thermoplastics can lead to material degradation, resulting in a significant drop in molecular weight, which compromises its viscosity, strength, processability, and, consequently, the quality of the final product. In the automotive industry, which has high performance requirements, combating these consequences is essential. The Vital project at PIEP also includes a component dedicated to the recyclability of bio-based polymers, aiming to create a ‘Digital Twin’ of the recycling process and develop polymer compositions supplemented with functional additives. This approach allows for a more detailed study of the recycling process, creating alternatives for its optimization, while also enabling the development of materials that are more resistant to reprocessing.
When it comes to developing new materials, PIEP has a team – Extrusion, Compounding and Advanced Materials (ECMA) – trained in a wide range of approaches, including composition with recycled materials, bio-based alternatives, and the incorporation of a wide variety of fibers and particles from natural sources.
Among the various technologies for producing plastic parts, injection molding stands out, allowing for the reproduction of highly complex geometric shapes, allowing for the application of various surface finishes and decorative options, while ensuring tight dimensional tolerances. It is, therefore, the most widely used technology in the production of plastic parts for the automotive sector, from lighting systems to center consoles, bumpers, fenders, and pillars, among others. Innovative solutions for weight reduction through the use of lightweight materials continue to be developed in this sector. In this sense, the use of cellular plastic parts has become an alternative: foam injection molding allows for the production of parts with cellular structures by integrating expanding agents into the polymer. These agents expand due to temperature and pressure drops, creating voids in the material’s structure. This technology can be applied to a variety of thermoplastics. In addition to the reduced amount of material used, which results in a reduction in the weight of the parts and, consequently, of the car, this technique improves the impact resistance and acoustic insulation of the parts [5][6] and saves energy during the production process. In the automotive sector, PP is the most widely used plastic to produce components with expanded material, such as sun visors, door panels, car pillars, trunk interiors, as well as main consoles.
PIEP integrates different consortia of development projects using foam injection molding. In the case of I&DPIIMIO (Figure 3), with GLN as the lead promoter, an automotive console display was developed through an alternative process, integrating different technologies: overmolding, In-Mould Decoration and Electronics (IMD and IME), and microcellular injection molding (MuCell). In addition to reducing the weight of the part, the production of the two plastic components was achieved in a single step, as well as the functionalization (electronics, scratch resistance) and decoration (color, high gloss, and piano black effect) of the final part. Additionally, the integration of printed electronics eliminates the need for mechanical buttons, reducing the number of components, the amount of material, and the number of processes associated with the production of these parts [7]. Vital, a European project that includes Tofas – a Turkish automotive company jointly owned by Stellantis (through Fiat Group Automobiles), aims to develop different processing solutions for cellular thermoplastic materials of biological origin. This includes the use of microcellular injection molding with the application of both thermoplastic materials and expanding agents of biological origin [4].
Figure 3 – I&DPIIMIO Project.
Alongside technologies focused on weight reduction, the application of more sustainable materials is also a trend to meet EU targets. Large plastics companies are transforming their materials by integrating recycled raw materials into technical materials used in the automotive industry. In addition to mechanical recycling, chemical recycling is becoming a reality, as it ensures compliance with the high requirements and technical specifications of these materials [8]. In this context, BASF has developed a chemical recycling technology, ChemCycling, using plastic that cannot be mechanically recycled, thus incorporating it into the chemical production line for new raw materials [9] [10]. Using this technology, Mercedes-Benz uses fiberglass-reinforced polyamide in the door handles of its EQE and S-Class models [9]. From the same company, Ultradur High Speed’s, produced using this new technology, is a material used by the Antolin Group, which, being highly fluid, allows the production of long, thin-walled parts through the injection molding process [10]. Another example is Covestro, which already produces polycarbonate (PC) grades for the injection molding process that contain post-consumer recycled material, including components for automotive lighting systems; the cycle is closed, since Covestro’s Makrolon line, for example, is widely applied to the automotive industry for molding components for lighting systems [11].
On the other hand, the production of plastics derived from renewable and bio-based sources, primarily through the mass-balanced process, has already resulted in a wide variety of commercially available materials. Examples include Covestro’s high-performance PC and DuPont’s Renewably Sourced materials, which contain materials from renewable sources and are used in the automotive industry by brands such as Ford, Fiat, and Toyota [12] [13]. In this context, the microcellular foam injection molding process in the Vital project uses only plastic materials from renewable sources. Going beyond currently available alternatives, the developed polylactic acid (PLA) must meet the UL 94 V 0 requirement and contain more than 85% renewable sources for the production of Lower B Pillars for the Fiat Doblo and Fiat Tipo models [14].
Additionally, PIEP has been helping companies adapt their materials and processes to meet EU targets. The contributions of the Advanced Manufacturing Processes – Polymers (PAFP) area include, on the one hand, the validation of new, more sustainable materials suitable for the injection molding process and, on the other, the integration of different technologies with the injection molding process to produce lighter, more functional, and decorative parts in a single step.
Alternatively, the production of automotive components where performance and durability are selection criteria has increasingly led to the use of polymer-based composite materials (PMCs). These materials consist of a thermoplastic or thermoset matrix reinforced with high-performance materials such as glass fibers, carbon fibers, or aramid (Kevlar). They offer stiffness and specific strength characteristics comparable to (or superior to) their metallic counterparts. Furthermore, they have high chemical resistance, are lighter, and are easy to process, even for complex geometries. Therefore, they are particularly used in the automotive sector for the production of exterior, decorative, and structural components, and, more recently, in more specialized components such as battery casings and fuel storage pressure vessels (COPVs). The composite materials market in the automotive sector is expected to double in the next decade, especially in emerging segments such as battery electric vehicles (BEVs), solar electric vehicles (SEVs), and fuel cell vehicles (FCVs) [15]). This growth involves not only the application of more efficient and sustainable composite materials but also the development and application of more competitive and sustainable processing technologies. It is worth noting that the application of composite materials in critical components is already common, sometimes accompanied by the integration of structural health monitoring systems.
Figure 4 – Examples of automotive components produced with reinforced composite materials: a) BMW i3’s structure reinforced with carbon fiber composites [16], b) battery box for electric cars from Mitsubishi Chemical Group [17], c) door panel for Nissan GTR R35 in carbon fiber [18] and d) type IV pressure tanks for the storage of compressed hydrogen [19].
The search for more efficient, lower-cost, and environmentally sustainable solutions has been a key pillar for the research and development of new composite materials. In this sense, two of the major development focuses involve the use of more sustainable and bio-based reinforcement materials (such as flax and hemp fibers) and the replacement of conventional thermosetting matrices with thermoplastic matrices of fossil or biological origin. These thermoplastic matrices are intrinsically recyclable, unlike thermosetting matrices. The major challenge in applying these materials is to find equivalent solutions in terms of thermomechanical properties, service performance, reliability, and durability, without compromising their environmental sustainability and circularity [20].
In this context, PIEP’s Advanced Manufacturing Processes – Composites (PAFC) team has been involved in several projects aimed at using more environmentally sustainable materials. One of the projects within the field of mobility and energy transition toward cleaner and more sustainable energy sources is the HI_MOV Interreg project. Its main objective is to establish a cross-border ecosystem that promotes the emerging value chain around green hydrogen in the Galicia-Northern Portugal Euroregion, specifically its use in sustainable mobility applications (with zero-emission vehicles). To achieve this objective, the HI_MOV consortium involves partners from various technology centers (CTAG, EnergyLab, PIEP, CEiiA), universities (UMinho, UPorto, USC), territorial groups (AECTGNP), companies (Petrotec Group), and public administrations (INEGA-Xunta de Galicia) who collaborate in four complementary areas of work: hydrogen observatory; ecosystem strengthening and training; development of technological solutions; and pilot tests with a demonstration effect [21]. PIEP and the University of Minho are strategic partners in the development of a pressure vessel for storing compressed hydrogen gas at 700 bar, produced with composite materials (also known as COPV, from the English Composite Overwapped Pressure Vessel) with a thermoplastic matrix.
The PAFC team is also working on developing the composite casing that encloses the internal reservoir (thermoplastic) and is responsible for supporting the mechanical stresses caused by the COPV’s internal pressurization, induced by hydrogen in its gaseous state. To this end, the use of advanced composite materials with high mechanical performance is essential to ensure good performance without compromising their safe use over their lifetime. The team’s work will thus include material selection and characterization, the study and development of winding patterns, structural simulations, and, finally, experimental validation of the COPV produced by filament winding. In parallel, the casing will also integrate sensors to monitor the reservoir’s structural integrity and performance throughout its life cycle. The project’s main challenge will be the selection of thermoplastic-based materials processable by filament winding that meet technical requirements, such as service conditions (pressure and temperature) and hydrogen permeability, and offer a cost-effective relationship.
The paradigm shift in the automotive sector to meet EU-imposed targets for reducing greenhouse gas emissions, whether through the use of cleaner, more sustainable fuels or the reuse and recovery of plastic materials, preventing them from being sent to landfills or incinerated, is an increasingly prevalent reality. To this end, PIEP has been working on research and development of new mobility solutions, particularly in the automotive sector, exploring various fields of intervention, from the composition of new materials to the incorporation of bio-based materials and the development of innovative manufacturing technologies that enable a reduction in the amount of material used (whether through the implementation of new designs or process improvements). Therefore, it is expected that the use of lighter, more efficient, durable, and sustainable plastic components and parts, from the perspective of their recyclability, will be the path forward to meet the EU’s targets.
Authors:
Cátia Araújo, Catarina Rebelo, Daniel Reis, Filipa Carneiro, Leonor Calado, Luciano Rietter, Mariana Marques, Paulo Antunes, Pedro Abreu, Rafael Santos, Rosária Ferreira, Sílvia Cruz
PIEP – Centre for Innovation in Polymer Engineering
Article originally published in InterPLAST magazine.
