A new ‘Tailor-made’ methodology for the mechanical behaviour analysis of rubber-like materials: II. Application to the hyperelastic behaviour characterization of a carbon-black filled natural rubber vulcanizate

The purpose of this paper is the modelling of the mechanical behaviour of an elastomeric material, through detailed experimental and numerical procedures, specific to large strains. The experimental technique is based on in-plane kinematics measurements using a speckle extensometer, from which the whole two-dimensional field of in-plane displacements is obtained by a digital image processing [Polymer (2002)]. This part of the work concerns the identification of the constitutive equation for a carbon black natural rubber (NR) vulcanizate. We start by quoting some theoretical considerations relative to rubber elasticity and stress-softening effect, which is the counterpart of the filler reinforcement. Then, we describe the experimental procedure and present data for both non-preconditioned and preconditioned samples. Next, the identification of the constitutive law parameters using a minimization algorithm is driven. Finally, we present the validation of the constitutive model, by its implementation into the finite element code SYSTUS and the numerical simulation of the response of a double edge notched tensile (DENT) specimen.     

ACHEMA 2022: Membranes and Membrane Processes

Numerous companies working in the field of membrane development, membrane production, and membrane separation engineering were present at ACHEMA 2022. Compared to the last ACHEMA in 2018, there were fewer attending companies and only few new topics since development has been blocked partially by the pandemic situation and the subsequent restrictions of this years. Nevertheless, some new developments have been identified concerning process design as well as ceramic and polymeric systems.     

Dissolution,Transport and Reaction at a DICY/DGEBA Interface

The curing of an epoxy consisting of the solid hardener dicyandiamide (DICY) and the resin diglycidyl ether of bisphenol A (DGEBA) is studied in a system consisting of a tablet of DICY embedded in liquid DGEBA. Dissolution of DICY within the liquid DGEBA in combination with the transport of dissolved DICY from the tablet border into DGEBA and the chemical reaction of both reactants is studied by scanning Brillouin microscopy and infrared spectroscopy. Scanning Brillouin microscopy demonstrates the spatial and temporal evolution of the static and dynamic hypersonic properties in the course of curing in the vicinity of the DICY tablet. Infrared spectroscopy performed on epoxy pieces extracted from the final sample at different distances from the tablet surface give information about the spatial evolution of the curing process. The results achieved by both techniques are finally combined to yield a better understanding of the curing of DICY-based epoxies, which transform upon curing from strongly heterogeneous systems towards increasingly homogeneous systems.     

Steam Drying - Modelling and Applications

ABSTRACT

The concept of steam drying originates from the mid of the last century. However, a broad industrial acceptance of the technique has so far not taken place. The paper deals with modelling the steam drying process and applications of steam drying with in certain industrial sectors where the technique has been deemed to hove special opponunities.

In the modelling scction the mass and heat transfer proceases are described along with equilibrium, capillarity and sorption phenomena occurring in porous materials during the steam drying process. In addition existing models in the literslure are presented.

The applications discussed involve drying of fuels with high moisture contcna, cattle feed exemplified by sugar beet pulp. lumber. paper pulp. paper and sludges.

Steam drying is compared to flue gas drying of biofuels prior to combustion in a boiler. With reference to a current insrallation in Sweden. the exergy losses. as manifested by loss of co-generation cupacity. are discussed. The energy saving potentid when using steam drying of sugar beet pulp as compared to other possible plant configurations is demonstrated.

Mechanical vapour recompression applied to steam drying is analysed with reference to reponed dau from industriul plsnts. Finally. environmcntul advantages when using steam drying are presented.     

Thermal Degradation Kinetics of Carotenoids in Palm Oil

In the present work, a detailed study is performed for carotene thermal degradation in palm oil at four temperatures ranging from 170 to 230 °C. The heating process was carried out with injection of nitrogen, and the samples were collected every 20 min during a total heating period of 140 min. HPLC analysis was conducted to monitor the carotenoids and tocols variations over the heating time at each temperature. The experimental data were then compared to literature data concerning carotenoids thermal degradation. The thermal degradation kinetics of carotenoids in palm oil followed an order superior to 1. The dependence of constant rates with temperature obeyed the Arrhenius relationship. The activation energy for the carotenoids thermal degradation in palm oil was found to be 109.4 kJ/mol.     

Enzymatic hydrolysis of polyester based coatings

The potential of two hydrolytic enzymes, namely a lipase from Thermomyces lanuginosus (TlL) and a cutinase from Humicola insolens (HiC) for hydrolysis of the phthalic acid backbone based polyester coatings was assessed. Two phthalic acid/trimethylolpropane based model substrates resembling the structure of the polyester backbone of coatings were synthesized. Out of both enzymes, only the cutinase was able to hydrolyze both model substrates while the larger substrate was hydrolyzed at a lower rate. The cutinase was also able to hydrolyze a coating (alkyd resin) both in suspension and as dried film. LC–MS analysis of the hydrolysis products released from the coating revealed the presence of oleic acid, its monoglyceride, phthalic acid and 2-((3-((2-((2,3-dihydroxypropoxy)carbonyl)benzoyl)oxy)-2-hydroxypropoxy)carbonyl)benzoic acid. These results indicate that the enzyme was able to hydrolyze the polyester backbone as well as to release fatty acid side chains. Consequently, enzymatic hydrolysis has a potential for the removal of coatings, their recycling or their functionalization.     

Dendrimers or Nanoparticles as Supports for the Design of Efficient and Recoverable Organocatalysts?

The Jørgensen–Hayashi catalyst [(S)‐α,α‐diphenylprolinol trimethylsilyl ether] was grafted onto the surface of two different supports: phosphorus dendrimers (generations 1 to 3) and magnetic, polymer‐coated cobalt/carbon (Co/C) nanobeads. These new supported catalysts displayed high activities and selectivities in the Michael additions of a wide range of aldehydes to different nitroolefins. Moreover, the dendrimer of the third generation displayed excellent recycling abilities since it could be recovered and reused in 7 consecutive runs without loss of activity.     

Chemical inhibitors when timing is critical: a pharmacological concept for the maturation of T cell contacts

Cellular signal transduction proceeds through a complex network of molecular interactions and enzymatic activities. The timing of these molecular events is critical for the propagation of a signal and the generation of a specific cellular response. To define the timing of signalling events, we introduce the combination of high-resolution confocal microscopy with the application of small-molecule inhibitors at various stages of signal transduction in T cells. Inhibitors of Src-family tyrosine kinases and actin dynamics were employed to dissect the role of the lymphocyte-specific tyrosine kinase Lck in the formation and maintenance of T cell receptor/CD3-dependent contacts. Anti-CD3epsilon-coated coverslips served as a highly defined stimulus. The kinetics of the recruitment of the yellow fluorescent protein-tagged signalling protein ZAP-70 were detected by high-resolution confocal microscopy. The analysis revealed that at 5 min after receptor engagement, Lck activity was required for maintenance of contacts. In contrast, after 20 min of receptor engagement, the contacts were Lck-independent. The relevance of the timing of inhibitor application provides a pharmacological concept for the maturation of T cell-substrate contacts.     

Break on through to the other side-biophysics and cell biology shed light on cell-penetrating peptides

Cell-penetrating peptides (CPPs) have become widely used vectors for the cellular import of molecules in basic and applied biomedical research. Despite the broad acceptance of these molecules as molecular carriers, the details of the mode of cellular internalization and membrane permeation remain elusive. Within the last two years endocytosis has been demonstrated to be a route of uptake shared by several CPPs. These findings had a significant impact on CPP research. State-of-the-art cell biology is now required to advance the understanding of the intracellular fate of the CPP and cargo molecules. Owing to their presumed ability to cross lipid bilayers, CPPs also represent highly interesting objects of biophysical research. Numerous studies have investigated structure-activity relationships of CPPs with respect to their ability to bind to a lipid bilayer or to cross this barrier. Endocytosis route only relocates the membrane permeation from the cell surface to endocytic compartments. Therefore, biophysical experiments are key to a mechanistic molecular understanding of the cellular uptake of CPPs. However, biophysical investigations have to consider the molecular environment encountered by a peptide inside and outside a cell. In this contribution we will review biophysical and cell-biology data obtained for several prominent CPPs. Furthermore, we will summarize recent findings on the cell-penetrating characteristics of antimicrobial peptides and the antimicrobial properties of CPPs. Peptides of both groups have overlapping characteristics. Therefore, both fields may greatly benefit from each other. The review will conclude with a perspective of how biophysics and cell biology may synergize even more efficiently in the future.