High impact polypropylene (hiPP) is a multiphase polymer material widely used in applications such as the automotive industry. The morphology of hiPP plays a crucial role in determining its bulk mechanical properties. Imaging of the morphology, based on well-established methods like electron microscopy, provide important morphological information on rubber size distribution and dispersion and support our understanding of hiPP structure-property relations. However, it is crucial to explore the nanoscale viscoelastic properties and link those to compositional differences and interface formations in hiPP to further enhance our knowledge of the hiPP structure and mechanical properties relationship and to evaluate the influence of these aspects on materials performance.

In this contribution we discuss an advanced approach involving comprehensive hiPP morphology characterizations across different length scales, utilizing advanced atomic force microscopy (AFM) techniques, in combination with various microscopy tools. We aim to demonstrate the benefits of applying the AFM-based dynamic mechanical analysis (AFM-nDMA) [1] and Intermodulation AFM [2] supplemented by advanced data analysis tools as a new generation of methodologies capable of revealing nano-viscoelastic properties of different phases in hiPP. The characterized quantitative nano-viscoelastic properties of ethylene-propylene rubber (EPR) and PP matrix in hiPP facilitated a novel approach for identification of compositional variations in EPR, the skin-core morphology and the interface formation. The importance of the morphology and nano-viscoelastic properties information, obtained by combining AFM, electron microscopy imaging, and other thermal and microscopy techniques to start paving the way towards a better understanding of hiPP structure-properties relationships will be highlighted in this presentation.

Polyethylene terephthalate (PET) is one of the most recycled plastics worldwide [1-2]. Recycled PET (rPET) has been used for numerous applications such as carry bags, roofing materials, and sandwich honeycomb panels for automotive use.
The mechanical properties of the final structure depend amongst others upon the quality of the incoming raw material. One of the biggest challenges in rPET application is feedstock variability and contamination. PET collected from different sources may have differing molecular weight (MW), molecular weight distribution (MWD), and impurity contents. This will cause batch-to-batch variation, leading to differences in the properties of the end-product, if not carefully monitored and optimized.
Thermal and rheological characterization techniques can help fingerprint the polymer molecular architecture, and provide useful guidance to the optimization of processing conditions [3-4]. DSC Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA) and rheology are utilized in this study to guide the melt extrusion of rPET feedstocks from different sources.
Different rheological methods will help in:
- fingerprinting the molecular architecture (MW, MWD) of the feedstock resins
- monitor the polymer stability at the processing temperature
- optimize the processing conditions.
DSC provides accurate measurement on rPET’s crystallinity, in relation to the processing conditions. Crystallinity relates to the final material properties. Moreover DSC testing can help in deciding whether there is a need of adding nucleating agents to speed up the crystallization.
TGA provides important information about the thermal stability and lifetime performance of the rPET versus the virgin material.

The transition to a circular economy demands innovative recycling technologies to manage plastic waste effectively. Polyvinyl chloride (PVC) is particularly difficult to recycle due to its complex composition of polymers and (legacy) additives. Emerging physico-chemical recycling methods show promise in recovering high-quality reusable PVC, but their success relies on comprehensive characterization throughout the recycling process. Conventional analytical techniques, such as spectroscopic methods and solvent extraction, are often insufficient to fully profile the additives, impurities and polymer degradation states.
Centrifugal Partition Chromatography (CPC), a preparative liquid chromatography method, was adapted for pre-treated PVC waste using a novel biphasic solvent system (heptane, dimethyl sulfoxide and diethyl ketone). This approach enables the separation of compounds into distinct fractions, particularly additives and polymer, making it a valuable tool for recovering purified polymer containing no additives such as phthalates plasticizers or organophosphorus flame retardants, which are currently highly regulated. Coupled with advanced analytical techniques such as reversed-phase liquid chromatography-high-resolution mass spectrometry (RPLC-ESI-HRMS/MS) for additive fractions and nuclear magnetic resonance spectroscopy (H1 and C13 NMR) for polymer fractions, this approach ensures a thorough characterization of PVC waste.
The methodology, specifically the selection of the biphasic system for CPC in this novel application, was validated on model PVC feedstocks, applied to a pre-treated PVC waste, and be described in this presentation. This study highlights CPC’s potential as a dual-purpose tool: an advanced characterization method and a scalable purification process for high-purity polymer recovery. CPC could present an innovative solution for physical PVC recycling.

Raman spectroscopy is a powerful, non-destructive tool for input qualification, real-time monitoring, and output assessment of polymer processes, offering direct insights into the chemistry governing processing parameters and product quality.
When integrated into the extrusion process, Raman spectroscopy enables in-line analysis of polymer transformations, enabling process optimization and continuous quality monitoring. In this contribution, we present results of live analysis of composition, crystallinity, and structural changes, depending on mechanical or thermal stress.
Combining Raman spectroscopy with rheometry or dynamic mechanical analysis (DMA) provides a comprehensive understanding of both, the chemical and mechanical properties of polymers during processing. We discuss results of in-situ monitoring of polymerization reaction kinetics [1,2], as well as thermally and mechanically induced changes [3]. The degree of polymerization can be followed up to the point of physical hardening and significantly beyond, e.g. to determine the time to reach final structural strength.
The dual approach is particularly valuable for studying polymer melts, reactive extrusion, and material degradation, allowing researchers and manufacturers to fine-tune formulations and processing conditions efficiently.
By enabling real-time feedback, Raman-rheometer integration enhances process control, reduces waste, and improves the overall performance of polymer-based products.

Fracture properties of 3D-printed materials are often evaluated using testing protocols and geometries derived from other materials [1,2]. However, these conventional methods result in unrepresentative geometries, unsuitable for thin elements, and frequently lead to unstable crack growth, limiting the utility of the data obtained. The absence of a reliable methodology for fracture testing of thin 3D-printed elements poses a critical challenge for many 3D printing applications.
To address this, a novel Hinged Rigid Beam [3] fracture experiment and data analysis framework are introduced to evaluate fracture properties of thin samples produced via Selective Laser Sintering. The setup places a test specimen between two high-stiffness beams connected by a hinge on one end and applies an opening displacement on the other. This unique configuration ensures stable crack growth and tensile stresses throughout the specimen, eliminating the risk of buckling in thin samples.
An analytical model, based on a rigid beam on elastic foundation approach, is developed to quantify fracture energy and behaviour. While the model aligns well with results for elastic-brittle materials, discrepancies arise for polyamide samples due to ductility and significant plastic deformation. To address this, a numerical Cohesive Zone Model is employed, providing insights into non-linear material behaviour and enabling the extraction of fracture toughness values through an inverse procedure.
The results highlight suitability of the setup to testing thin materials and a much higher sensitivity of fracture properties to process parameters compared to tensile properties, emphasizing their critical role in ensuring part reliability in 3D printing applications.

Airbags in automobiles are essential to saving lives and reducing injuries in an accident. These airbags are housed behind polymer panels which are strategically weakened so that they break during airbag deployment. The contact of the airbag fabric with the panel results in this fracture propagates along the line of weakness to form an opening door. Although the material tearing and fracture is crucial to correct airbag deployment, the fracture toughness of the panel polymer is typically not reported by material suppliers and relevant literature is scarce. Fracture tests were conducted following the ESIS TC4 procedure on two types of polymers typical for this application, thermoplastic elastomer (TPE) and thermoplastic polyolefin (TPO) polymers, supported by tensile and density tests. The fracture toughness, represented by J0.2 values, varied from 8.49 kJ/m2 to 11.41 kJ/m2. Scanning electron microscopy showed that the fracture toughness is influenced by the pattern of microfibrils formed during fracture initiation and propagation. These findings demonstrate the importance of fracture toughness in airbag systems and the wider automotive industry. Furthermore, this discovery is a pivotal step toward optimizing airbag structures and minimizing material usage based on fracture toughness values, ultimately enhancing safety and protection in automotive applications.