Materials Science Forum Vols. 636-637

Abstract: Potato starch (PS), also one amylose-rich starch (high amylose maize starch, HAMS) and one amlyopectin-rich starch (waxymaize starch, WMS) were used for the syntheses as raw materials. Starch acetates were synthesized by reaction with acetic acid anhydride and potassium carbonate as activator. Tests of thermoplastic processability of the starch acetates were performed by extrusion followed by injection molding to specimens. Glycerine triacetate (triacetin, TAc) was attached as plasticizer to starch acetate. For this system a processing procedure was acquired under variation of different parameters. Starch- and cellulose-based films containing inorganic luminescent quantum dots, namely europium doped yttrium vanadate (YVO4:Eu) and cerium and terbium doped lanthanum phosphate (LaPO4:Ce,Tb) as well as an organic laser dye (naphthaldiimide, LV 570) were prepared by tape casting and air brush technique. Under UV-light exposure, they show a bright fluorescence radiation depending on the incorporate dye or quantum dot.

Abstract: In this work, the shear modulus and strength of the acrylic adhesive 3M® DP 8005 was evaluated by two different methods: the Thick Adherend Shear Test (TAST) and the Notched Plate Shear Method (Arcan). However, TAST standards advise the use of a special extensometer attached to the specimen, which requires a very experienced technician. In the present study, the adhesive shear displacement for the TAST was measured using an optical technique, and also with a conventional inductive extensometer of 25 mm used for tensile tests. This allowed for an assessment of suitability of using a conventional extensometer to measure this parameter. Since the results obtained by the two techniques are identical, it can be concluded that using a conventional extensometer is a valid option to obtain the shear modulus for the particular adhesive used. In the Arcan tests, the adhesive shear displacement was only measured using the optical technique. This work also aimed the comparison of shear modulus and strength obtained by the TAST and Arcan test methods.

Abstract: Organofunctionalised silica materials are of great interest once they combine a high surface area and a narrow pore size distribution with the advantage of owing organic ligand properties. This paper describes the organofunctionalisation of an amorphous silica with 2-mercaptobenzimidazole. The characterization of such material was performed by elemental analysis (EA), IR spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC) and solid state 13C and 29Si NMR spectroscopy.

Abstract: This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.

Abstract: Properties of poly(ethylene terephthalate) track membrane (PET TM) exposed to an allyl alcohol radiofrequency plasma after pre-activation its surface in an oxygen plasma were studied. The influence of plasma treatment conditions on basic membrane characteristics, i.e. pore size and shape, wettability, and water permeability, was studied. It has been shown that the plasma treatment of membrane can significantly improve its performance characteristics.

Abstract: This paper describes a structure and electrotransport properties of poly(ethylene terephthalate) track membrane (PET TM) modified by plasma of thiophene. It is shown that the deposition of the polymer on the track membrane surface by plasma polymerization of thiophene in case of forming a semipermeable layer results in creation of composite nanomembrane having in electrolyte solutions of asymmetry of conductivity - a rectification effect. It is caused by presence in the membrane of two layers with various functional groups, and also by changing of the pore geometry. Such type membranes can be used for creation of chemical and biochemical sensors.

Abstract: In the present study biodegradable copolymers of ethylene vinyl acetate and polylactic acid were synthesized using transesterification reactions, the structure, morphology, mechanical properties and biodegradability of the produced materials were characterized. Ethylene vinyl acetate was modified with polylactic acid in an internal mixer using titanium propoxide as transesterification catalyst. The graft copolymers were characterized by elemental analysis, infrared spectroscopy, rheology, scanning electron microscopy and thermal analysis. Selective extractions for all copolymers were made, and the results indicate that a maximum of 25 % of EVA-g-PLA copolymer was synthesized by this method. Biodegradation tests were carried out using the standard ISO 14851 (1999), which specifies a method for determining the biochemical oxygen demand in a closed respirometer. This procedure allowed to synthesize biodegradable copolymers with mechanical properties similar to conventional polymers.

Abstract: Aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polydioxone (PDO) and others, have been commonly used in biodegradable products. Hydrolytic and/or enzymatic chain cleavage of these materials leads to α-hydroxyacids, which, in most cases, are ultimately assimilated in human body or in a composting environment. However, each of these has some shortcomings, in terms of mechanical properties and degradation time, which restrict its applications. The combination of these materials, by copolymerization or blending, enables a range of mechanical properties and degradation rates. These are extremely promising approaches which can improve or tune the original properties of the polymers. A composite solution of several materials with different degradation rates also enables tuning the rate of degradation of a device and the mechanical properties. After immersion of an aliphatic polyester device, diffusion occurs very rapidly compared to hydrolysis. Therefore, it is usually considered that hydrolysis of ester bonds starts homogeneously and has traditionally been modelled according to a first order kinetics. In this experimental study, fibres of PLA-PCL, PGA-PCL, PDO and PGA, with two different dimensions, were characterized in terms of their degradation rate under three different environments (water, NaCl and PBS) at constant temperature (37°C). Weights and mechanical properties were measured after six different degradation stages. Stages durations were different depending on materials, according to the predicted degradation times. As other thermoplastics, they are viscoelastic materials. In this experimental study mechanical properties of fibres were compared at different strain rates.

Abstract: The performance of parts produced by Free Form Extrusion (FFE) may be limited by poor mechanical properties, due to poor bonding between the individual extruded filaments. In this work, an analytical solution is proposed for the transient heat transfer during filament deposition, taking into account contacts between filaments. The developed code using Matlab® allows to study the influence of the main process variables during filament deposition and may assist the process optimization.

Abstract: The present study investigates the morphology of polyamide (PA6) and polypropylene (PP) blends in the presence of an organoclay during extrusion. Physical PA6 /PP blends and blends of PA6/PP and PP modified with maleic anhydride, both filled with a montmorillonite (MMT) modified alkyl ammonium organoclay, were prepared in a modular co-rotating twin screw extruder. Samples were collected along the extruder and analyzed by X-ray diffraction (XRD), oscillatory rheology, and scanning and transmission electron microscopy (SEM and TEM, respectively). Intercalation and some degree of clay exfoliation seem to have been achieved. Generally, the presence of the organoclay yields a finer dispersed phase along the extruder.