Upcycling Humins via Esterification Reactions of Hydroxyl Groups: From Functional Powders to PLA Foams and Compatibilized Blends.

The valorization of humins side streams from bio-refineries holds significant economic and sustainability potential. One plausible strategy involves using them as building blocks to create new materials. However, humins pose conceptual challenges in their natural state due to their high viscosity, processing difficulties, and temperature sensitivity.

On the Difference in Mechanical Behavior of Glass Bead-Filled Polyamide 12 Specimens Produced by Laser Sintering and Injection Molding.

An increasing demand for additively manufactured polymer composites with optimized mechanical properties is manifesting in different industries such as aerospace, biomedical, and automotive. Laser sintering (LS) is an additive manufacturing method that has the potential to produce reinforced polymers, which can meet the stringent requirements of these industries. For the development of a commercially viable LS nylon-based composite material, previous research studies worldwide have focused on adding glass beads to the powder material with the goal to produce fully dense parts with properties more representative of injection molded (IM) thermoplastic composites.

On the gelation of humins: from transient to covalent networks.

Humins are a by-product of many acid-catalyzed biorefinery processes converting polysaccharides into platform chemicals. The valorization of humin residue to increase the profit of biorefinery operations and reduce waste is a field that is growing interest as the production of humins continues to increase. This includes their valorization in materials science.

Magnetic Self-Healing Composites: Synthesis and Applications.

Magnetic composites and self-healing materials have been drawing much attention in their respective fields of application. Magnetic fillers enable changes in the material properties of objects, in the shapes and structures of objects, and ultimately in the motion and actuation of objects in response to the application of an external field. Self-healing materials possess the ability to repair incurred damage and consequently recover the functional properties during healing.

Humins Blending in Thermoreversible Diels-Alder Networks for Stiffness Tuning and Enhanced Healing Performance for Soft Robotics.

Humins waste valorization is considered to be an essential pathway to improve the economic viability of many biorefinery processes and further promote their circularity by avoiding waste formation. In this research, the incorporation of humins in a Diels-Alder (DA) polymer network based on furan-maleimide thermoreversible crosslinks was studied. A considerable enhancement of the healing efficiency was observed by just healing for 1 h at 60 °C at the expense of a reduction of the material mechanical properties, while the unfilled material showed no healing under the same conditions.

The Extent of Interlayer Bond Strength during Fused Filament Fabrication of Nylon Copolymers: An Interplay between Thermal History and Crystalline Morphology.

One of the main drawbacks of Fused Filament Fabrication is the often-inadequate mechanical performance of printed parts due to a lack of sufficient interlayer bonding between successively deposited layers. The phenomenon of interlayer bonding becomes especially complex for semi-crystalline polymers, as, besides the extremely non-isothermal temperature history experienced by the extruded layers, the ongoing crystallization process will greatly complicate its analysis. This work attempts to elucidate a possible relation between the degree of crystallinity attained during printing by mimicking the experienced thermal history with Fast Scanning Chip Calorimetry, the extent of interlayer bonding by performing trouser tear fracture tests on printed specimens, and the resulting crystalline morphology at the weld interface through visualization with polarized light microscopy.

Boosting PLA melt strength by controlling the chirality of co-monomer incorporation.

Bio-based and degradable polymers such as poly(lactic acid) (PLA) have become prominent. In spite of encouraging features, PLA has a low melt strength and melt elasticity, resulting in processing and application limitations that diminish its substitution potential classic plastics. Here, we demonstrate a large increase in zero shear viscosity, melt elasticity, elongational viscosity and melt strength by random co-polymerization of lactide with small amounts, 0.

Viscoelastic cluster densification in sheared colloidal gels.

Many biological materials, consumer products and industrial formulations are colloidal suspensions where the suspending medium is itself a complex fluid, and such suspensions are effectively soft matter composites. At rest, the distortion of the microstructure in the suspending fluid by the particles leads to attractive interactions between them. During flow, the presence of a microstructure in the viscoelastic suspending medium changes the hydrodynamic forces due to the non-Newtonian and viscoelastic effects.

Influence of Carbon Nanoparticle Addition (and Impurities) on Selective Laser Melting of Pure Copper.

The addition of 0.1 wt % carbon nanoparticles significantly improved the optical absorption and flowability of gas-atomized copper powder. This facilitated selective laser melting (SLM) by reducing the required laser energy density to obtain 98% dense parts.

Stress Contributions in Colloidal Suspensions: The Smooth, the Rough, and the Hairy.

The collective properties of colloidal suspensions, including their rheology, reflect an interplay between colloidal and hydrodynamic forces. The surface characteristics of the particles play a crucial role, in particular, for applications in which interparticle distances become small, i.e.

Covalent organic frameworks for membrane separation.

Covalent organic frameworks (COFs), which are constructed from organic linkers, are a new class of crystalline porous materials comprising periodically extended and covalently bound network structures. The intrinsic structures and the tailorable organic linkers endow COFs with a low density, large surface area, tunable pore size and structure, and facilely-tailored functionality, attracting increasing interests in different fields including membrane separations. Exciting research activities ranging from fabrication strategies to separation applications of COF-based membranes have appeared.

Quantifying the dispersion quality of partially aggregated colloidal dispersions by high frequency rheology.

An important parameter for the performance of nanomaterials is the degree by which the nanoparticles are dispersed in a matrix. Optical microscopy or scattering methods are useful to characterise the state of dispersion, but are not generally applicable to all materials. Electron microscopy methods are laborious in preparation and typically offer only quantitative information on a very local scale.

Poly(alanine): Structure and Stability of the D and L-Enantiomers.

High-performance, biobased materials can potentially be manufactured from polymerized α-amino acids (α-polypeptides). This paper reports on the synthesis, structure, and properties of both polyalanine enantiomers (PLAla and PDAla). The molecular structure of the polypeptide chains, their molecular weight, and polydispersity were investigated by (1)H NMR, MALDI-TOF, and size-exclusion chromatography.

Simultaneous Synchrotron WAXD and Fast Scanning (Chip) Calorimetry: On the (Isothermal) Crystallization of HDPE and PA11 at High Supercoolings and Cooling Rates up to 200 °C s(-1).

An experimental setup, making use of a Flash DSC 1 prototype, is presented in which materials can be studied simultaneously by fast scanning calorimetry (FSC) and synchrotron wide angle X-ray diffraction (WAXD). Accumulation of multiple, identical measurements results in high quality, millisecond WAXD patterns. Patterns at every degree during the crystallization and melting of high density polyethylene at FSC typical scanning rates from 20 up to 200 °C s(-1) are discussed in terms of the temperature and scanning rate dependent material crystallinities and crystal densities.

Transient interfacial tension and morphology evolution in partially miscible polymer blends.

The influence of molecular weight asymmetry across an interface on the transient behavior of the interfacial tension is investigated for two different polymer combinations, polybutadiene (PBD)/polydimethylsiloxane (PDMS) and polybutene (PB)/PDMS. This choice ensures a minor diffuse interface using the first combination and a very diffuse interface in the latter case. Measurements of the interfacial tension as a function of time are carried out using a pendent/sessile drop apparatus at different temperatures ranging from 0 degrees C to 80 degrees C.

RheoDSC: a hyphenated technique for the simultaneous measurement of calorimetric and rheological evolutions.

A newly developed hyphenated technique is presented combining an existing rheometer and differential scanning calorimeter into a single experimental setup. Through the development of a fixation accessory for differential scanning calorimeter (DSC) crucibles and a novel rotor, the simultaneous measurement is performed inside the well-controlled thermal environment of a Tzero DSC cell. Hence, the evolution of thermal and flow properties of a material can be simultaneously measured using steady or oscillatory shear measurements and regular or modulated temperature DSC measurements.

Effect of confinement on droplet breakup in sheared emulsions.

The breakup of Newtonian droplets in a Newtonian matrix during shear flow is investigated in a counterrotating parallel plate device. For bulk conditions, the critical capillary number for breakup is known to be only determined by the viscosity ratio. Here, we show that the critical capillary number is also affected by the degree of confinement: for low viscosity ratios, confinement suppresses breakup, whereas for high viscosity ratios, confinement promotes breakup.

Structure development in confined polymer blends: steady-state shear flow and relaxation.

In this work, the structure development in immiscible polymer blends in confined geometries is systematically investigated. Poly(dimethylsiloxane)/poly(isobutylene) blends with a droplet-matrix structure are subjected to simple shear flows. The confined environment is created by using a Linkam shearing cell in which the gap is systematically decreased to investigate the transition from "bulk" behavior toward "confined" behavior.

Direct evidence for breakup of liquid fibrils via Rayleigh instabilities in model polymer blends in step-up experiments.

Droplet breakup in immiscible polymer blends after a sudden substantial increase in shear rate is studied using small-angle light scattering experiments. During the breakup of the fibrils, secondary streaks are visible in the scattering pattern, which indicate the occurrence of Rayleigh instabilities. A high-resolution camera allows quantitative determination of the evolution of the wavelength of the disturbances during the disintegration process.

Interfacial tension of aqueous biopolymer mixtures close to the critical point.

Proteins and polysaccharides, being the main constructional materials in many biological structures, have a limited compatibility in aqueous media. At sufficiently high concentrations, they form water-in-water emulsions. Interfacial tension is an important parameter in such systems since it is a controlling factor in the morphology development during processing.

Effect of shear flow on the phase behavior of an aqueous gelatin-dextran emulsion.

A rheo-optical methodology, based on small angle light scattering and transmitted light intensity measurements, has been used to study in situ and on a time resolved basis the shear induced morphology in ternary two-phase water-gelatin-dextran mixtures. Emulsions close to the binodal line as well as far from it have been investigated. It is shown that above a critical shear rate, shear-induced mixing occurs at the length scales probed by the laser light.