Designing Prepregnation and Fused Filament Fabrication Parameters for Recycled PP- and PA-Based Continuous Carbon Fiber Composites.

Continuous carbon fiber (cCF)-based 3D-printed polymer composites are known for their excellent flexural properties; however, the optimization of the overall process is still desired, depending on the material types involved. Here, the improved manufacturing of cCF-based composites is reported, considering virgin polyamide (PA) and postindustrial waste polypropylene (PP), and the parameters affecting the material properties are evaluated. Firstly, the prepregnation technique was optimized to manufacture cCF polymer filaments with various fiber-to-polymer ratios.

Playing with Low Amounts of Expanded Graphite for Melt-Processed Polyamide and Copolyester Nanocomposites to Achieve Control of Mechanical, Tribological, Thermal and Dielectric Properties.

Polyamide 11 (PA11) and copolyester (TPC-E) were compounded through melt extrusion with low levels (below 10%) of expanded graphite (EG), aiming at the manufacturing of a thermally and electrically conductive composite resistant to friction and with acceptable mechanical properties. Thermal characterisation showed that the EG presence had no influence on the onset degradation temperature or melting temperature. While the specific density of the produced composite materials increased linearly with increasing levels of EG, the tensile modulus and flexural modulus showed a significant increase already at the introduction of 1 wt% EG.

Carbon Nitride Grafting Modification of Poly(lactic acid) to Maximize UV Protection and Mechanical Properties for Packaging Applications.

Due to their biobased nature and biodegradability, poly(lactic acid) (PLA) rich blends are promising for processing in the packaging industry. However, pure PLA is brittle and UV transparent, which limits its application, so the exploration of nanocomposites with improved interfacial interactions and UV absorbing properties is worthwhile. We therefore developed and optimized synthesis routes for well-designed nanocomposites based on a PLA matrix and graphitic carbon nitride (g-CN; CN) nanofillers.

Solvent electrospinning amorphous solid dispersions with high itraconazole, celecoxib, mebendazole and fenofibrate drug loading and release potential.

In this work, the feasibility of ultra-high drug loaded amorphous solid dispersions (ASDs) for the poorly soluble itraconazole, mebendazole and celecoxib via solvent electrospinning in combination with poly(2-ethyl-2-oxazoline) and fenofibrate in combination with polyvinylpyrrolidone is demonstrated. By lowering the polymer concentration in the electrospinning solution below its individual spinnable limit, ASDs with a drug content of up to 80 wt% are obtained. This is attributed to drug-polymer interactions not being limited by default to hydrogen bonds, as also Van der Waals interactions can result in high drug loadings.

Multicomponent Acrylic Formulation Design for Corrosion Casting with Controlled Mechanical Properties.

Corrosion casting based on the curing of acrylic resins enables one to create casts as replicas of body systems, enhancing our knowledge of veterinary medicine. The identification of the optimal chemical formulations as well as the processing conditions, the delivery of good control during the liquid state and the excellent macroscopic properties during solidification and after use are remaining challenges. In the present work, based on the identification of more qualitative trends, it is demonstrated that multicomponent comonomer mixtures are interesting materials that can be used to expand the range of mechanical properties and can specifically result in a better balance between stiffness and flexibility while guaranteeing dimensional stability.

Molecular Pathways for Polymer Degradation during Conventional Processing, Additive Manufacturing, and Mechanical Recycling.

The assessment of the extent of degradation of polymer molecules during processing via conventional (e.g., extrusion and injection molding) and emerging (e.

Response-Surface-Methodology-Based Increasing of the Isotropic Thermal Conductivity of Polyethylene Composites Containing Multiple Fillers.

To optimize the thermal conductivity of high-density polyethylene, 15 hybrid filler composites containing either aluminum oxide, graphite, expanded graphite, carbon nanotubes or a combination of the former, have been studied using an extrusion-compression processing tandem. The experimental density of the cube-shaped specimens is substantially lower than the theoretical density calculated by the linear mixing rule, mainly for the composites with high filler contents. The morphology of the composites, as studied by scanning electron microscopy (SEM), highlighted a good dispersion quality and random orientation of the fillers in the test specimens but also revealed air inclusions in the composites, explaining the density results.

Toward More Universal Prediction of Polymer Solution Viscosity for Solvent-Based Recycling.

The viscosity of polymer solutions is important for both polymer synthesis and recycling. Polymerization reactions can become hampered by diffusional limitations once a viscosity threshold is reached, and viscous solutions complicate the cleaning steps during the dissolution-precipitation technique. Available experimental data is limited, which is more severe for green solvents, justifying dedicated viscosity data recording and interpretation.

Principles and Guidelines for In-Line Viscometry in Cereal Extrusion.

In the food industry, extrusion cooking finds numerous applications thanks to its high productivity and nutrient retention. More specifically, cereal extrusion, e.g.

Setting the Optimal Laser Power for Sustainable Powder Bed Fusion Processing of Elastomeric Polyesters: A Combined Experimental and Theoretical Study.

Additive manufacturing (AM) of polymeric materials offers many benefits, from rapid prototyping to the production of end-use material parts. Powder bed fusion (PBF), more specifically selective laser sintering (SLS), is a very promising AM technology. However, up until now, most SLS research has been directed toward polyamide powders.

Combining Chromatographic, Rheological, and Mechanical Analysis to Study the Manufacturing Potential of Acrylic Blends into Polyacrylic Casts.

Polyacrylics have been considered for a broad range of material applications, including coatings, dental applications, and adhesives. In this experimental study, the casting potential of a group of (co)monomers belonging to the acrylic family has been explored to enable a more sustainable use of these polymer materials in the medical and veterinary science field. The individual contributions of each comonomer have been analyzed, the reaction conversion has been studied via gas chromatography (GC), the rheological behavior has been characterized via stress-controlled measurements, and the final mechanical properties have been obtained from tensile, flexure, and impact tests.

A Combined Experimental and Modeling Study for Pellet-Fed Extrusion-Based Additive Manufacturing to Evaluate the Impact of the Melting Efficiency.

To improve the product quality of polymeric parts realized through extrusion-based additive manufacturing (EAM) utilizing pellets, a good control of the melting is required. In the present work, we demonstrate the strength of a previously developed melt removal using a drag framework to support such improvement. This model, downscaled from conventional extrusion, is successfully validated for pellet-based EAM-hence, micro-extrusion-employing three material types with different measured rheological behavior, i.

Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art.

In recent decades, quantum chemical calculations (QCC) have increased in accuracy, not only providing the ranking of chemical reactivities and energy barriers (e.g., for optimal selectivities) but also delivering more reliable equilibrium and (intrinsic/chemical) rate coefficients.

Going Beyond the Carothers, Flory and Stockmayer Equation by Including Cyclization Reactions and Mobility Constraints.

A challenge in the field of polymer network synthesis by a step-growth mechanism is the quantification of the relative importance of inter- vs. intramolecular reactions. Here we use a matrix-based kinetic Monte Carlo (MC) framework to demonstrate that the variation of the chain length distribution and its averages (e.

State-Of-The-Art Quantification of Polymer Solution Viscosity for Plastic Waste Recycling.

Solvent-based recycling is a promising approach for closed-loop recovery of plastic-containing waste. It avoids the energy cost to depolymerize the plastic but still allows to clean the polymer of contaminants and additives. However, viscosity plays an important role in handling the polymer solutions at high concentrations and in the cleaning steps.

Computational prediction of the molecular configuration of three-dimensional network polymers.

The three-dimensional arrangement of natural and synthetic network materials determines their application range. Control over the real-time incorporation of each building block and functional group is desired to regulate the macroscopic properties of the material from the molecular level onwards. Here we report an approach combining kinetic Monte Carlo and molecular dynamics simulations that chemically and physically predicts the interactions between building blocks in time and in space for the entire formation process of three-dimensional networks.

The Transferability and Design of Commercial Printer Settings in PLA/PBAT Fused Filament Fabrication.

In many fused filament fabrication (FFF) processes, commercial printers are used, but rarely are printer settings transferred from one commercial printer to the other to give similar final tensile part performance. Here, we report such translation going from the Felix 3.0 to Prusa i3 MK3 printer by adjusting the flow rate and overlap of strands, utilizing an in-house developed blend of polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT).

Progress in Reaction Mechanisms and Reactor Technologies for Thermochemical Recycling of Poly(methyl methacrylate).

Chemical or feedstock recycling of poly(methyl methacrylate) (PMMA) by thermal degradation is an important societal challenge to enable polymer circularity. The annual PMMA world production capacity is over 2.4 × 10 tons, but currently only 3.

The Competition of Termination and Shielding to Evaluate the Success of Surface-Initiated Reversible Deactivation Radical Polymerization.

One of the challenges for brush synthesis for advanced bioinspired applications using surface-initiated reversible deactivation radical polymerization (SI-RDRP) is the understanding of the relevance of confinement on the reaction probabilities and specifically the role of termination reactions. The present work puts forward a new matrix-based kinetic Monte Carlo platform with an implicit reaction scheme capable of evaluating the growth pattern of individual free and tethered chains in three-dimensional format during SI-RDRP. For illustration purposes, emphasis is on normal SI-atom transfer radical polymerization, introducing concepts such as the apparent livingness and the molecular height distribution (MHD).

Influence of Different Stabilization Systems and Multiple Ultraviolet A (UVA) Aging/Recycling Steps on Physicochemical, Mechanical, Colorimetric, and Thermal-Oxidative Properties of ABS.

Commercially mass-polymerized acrylonitrile-butadiene-styrene (ABS) polymers, pristine or modified by stabilization systems, have been injection molded and repeatedly exposed to ultravilolet A (UVA) radiation, mechanical recycling, and extra injection molding steps to study the impact of such treatments on the physicochemical, mechanical, colorimetric, and thermal-oxidative characteristics. The work focus on mimicking the effect of solar radiation behind a window glass as relevant during the lifetime of ABS polymers incorporated in electrical and electronic equipment, and interior automotive parts by using UVA technique. The accelerated aging promotes degradation and embrittlement of the surface exposed to radiation and causes physical aging, deteriorating mechanical properties, with an expressive reduction of impact strength (unnotched: up to 900%; notched: up to 250%) and strain at break (>1000%), as well as an increase in the yellowing index (e.

Improving Mechanical Properties for Extrusion-Based Additive Manufacturing of Poly(Lactic Acid) by Annealing and Blending with Poly(3-Hydroxybutyrate).

Based on differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, polarizing microscope (POM), and scanning electron microscopy (SEM) analysis, strategies to close the gap on applying conventional processing optimizations for the field of 3D printing and to specifically increase the mechanical performance of extrusion-based additive manufacturing of poly(lactic acid) (PLA) filaments by annealing and/or blending with poly(3-hydroxybutyrate) (PHB) were reported. For filament printing at 210 °C, the PLA crystallinity increased significantly upon annealing. Specifically, for 2 h of annealing at 100 °C, the fracture surface became sufficiently coarse such that the PLA notched impact strength increased significantly (15 kJ m).

Time-Dependent Differential and Integral Quantum Yields for Wavelength-Dependent [4+4] Photocycloadditions.

The [4+4] photocycloaddition of anthracene is one of most relevant photoreactions and is widely applied in materials science, as it allows to remote-control soft matter material properties by irradiation. However, highly energetic UV irradiation is commonly applied, which limits its application. Herein, the wavelength dependence of the photodimerization of anthracene is assessed for the first time, revealing that the reaction is induced just as effectively with mild visible light (410 nm).

Visualization and design of the functional group distribution during statistical copolymerization.

Even though functional copolymers with a low percentage of functional comonomer units (up to 20 mol%) are widely used, for instance for the development of polymer therapeutics and hydrogels, insights in the functional group distribution over the actual chains are lacking and the average composition is conventionally used to describe the functionalization degree. Here we report the visualization of the monomer distribution over the different polymer chains by a synergetic combination of experimental and theoretical analysis aiming at the construction of functionality-chain length distributions (FUNC-CLDs). A successful design of the chemical structure of the comonomer pair, the initial functional comonomer amount (13 mol%), and the temperature (100 °C) is performed to tune the FUNC-CLD of copoly(2-oxazoline)s toward high functionalization degree for both low (100) and high (400) target degrees of polymerization.

Modeling of Miniemulsion Polymerization of Styrene with Macro-RAFT Agents to Theoretically Compare Slow Fragmentation, Ideal Exchange and Cross-Termination Cases.

A 5-dimensional Smith-Ewart based model is developed to understand differences for reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization with theoretical agents mimicking cases of slow fragmentation, cross-termination, and ideal exchange while accounting for chain length and monomer conversion dependencies due to diffusional limitations. The focus is on styrene as a monomer, a water soluble initiator, and a macro-RAFT agent to avoid exit/entry of the RAFT leaving group radical. It is shown that with a too low RAFT fragmentation rate coefficient it is generally not afforded to consider zero-one kinetics (for the related intermediate radical type) and that with significant RAFT cross-termination the dead polymer product is dominantly originating from the RAFT intermediate radical.

Effect of Matrix and Graphite Filler on Thermal Conductivity of Industrially Feasible Injection Molded Thermoplastic Composites.

To understand how the thermal conductivity (TC) of virgin commercial polymers and their composites with low graphite filler amounts can be improved, the effect of material choice, annealing and moisture content is investigated, all with feasible industrial applicability in mind focusing on injection molding. Comparison of commercial HDPE, PP, PLA, ABS, PS, and PA6 based composites under conditions minimizing the effect of the skin-core layer (measurement at half the sample thickness) allows to deduce that at 20 m% of filler, both the (overall) in- and through-plane TC can be significantly improved. The most promising results are for HDPE and PA6 (through/in-plane TC near 0.