High Purity Glass Forms by a Colloidal Sol-Gel Process

Novara Technology (NTECH) has developed its own process for bulk silica glass based on Sol-Gel chemistry. The process is characterized by its thermomechanical ideal isotropy of the aerogel and the glass it forms. Remarkable glass properties are: ultrapurity up to 1 ppb or better for single metal contaminant, optical compatibility with high-temperature treatments up to 2000°C, precision mouldability without intrinsic dimensional limitations.The process, that makes large use of the fumed silica Aerosil® in combination with TEOS, is characterized by the synthesis of monolithic material, i.e. a chemically manufactured body with shape and dimensions defined at reaction time, when the whole material is generated as a unit. Process implementation was achieved with the operation of a pilot plant. The road to industrialization besides volume scale-up, readily achieved for the chemical and hypercritical drying sector of the plant, was focused on getting a cost effective procedure.     

Effect of the melt flow index of an HDPE matrix on the properties of composites with wood particles

Composites of wood waste and high-density polyethylene (HDPE) resins and different melt flow index (MFIs) was development in this work. Therefore, it was possible to assess their effect on the mechanical, thermal, and morphologic properties of these composites. The formulations were prepared using a twin-screw extruder, and the MFI, tensile strength, flexural strength, and impact strength of the composites were analyzed. Additionally, the thermal properties were evaluated by differential scanning calorimetry (DSC). Finally, structural analyses using optical microscopy (OM) and scanning electron microscopy (SEM) were performed to assess the particles’ dispersion, distribution, and adhesion to the polymer matrix. The results indicated that composites from HDPE resins with a lower MFI yielded a better dispersion of the wood waste. During processing was observed, reduce the MFI and better dispersion of the polymer matrix, which positively influenced some of the mechanical properties analyzed in the study.     

Evaluation of interlaminar fracture toughness and dynamic mechanical properties of nano TiO2 coated flax fibre epoxy composites

In this study, fibre modification technique is performed by coating nano titanium dioxide (TiO₂) particles on flax fibres. The fibre surface is treated with silane coupling agents and coated with nanoparticles at weight percentage 0.2, 0.4, 0.6 and 0.8% to develop chemical bonding at the fibre matrix interface. The improved interface is evaluated by performing Mode I, Mode II interlaminar fracture toughness (ILFT), and Dynamic mechanical analysis (DMA). The results indicate that the fibre modified composites with 0.4 wt % and 0.6 wt % coating shows 37% and 24% improvement in Mode I and Mode II ILFT values respectively. The storage modulus from the DMA analysis also exhibits improvement for the fibre modified composites. SEM analysis explains the changes in the fracture mechanism. FTIR analysis provides the details on the fibre coating by nanoparticles.     

Preparation of cassava starch-based superabsorbent polymer using a twin-roll mixer as reactor

Cassava starch-based superabsorbent polymer was successfully synthesized using a new technology that based on modification of a Haake twin-roll mixer as reactor. The cassava starch was first gelatinized then modified by grafting under external shear stress in the reactor. The torque and temperature curves as a function of time can reflect the variations in the reactor and also offer some information about the copolymerization reaction. The advantages of this system include starch modification can be carried out(1) with high starch concentration,(2) under controlled time and(3) smaller amount of sample(60 g) required. The technology provides useful guides for reactive extrusion. The starch grafted composites were characterized by Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(NMR) and thermal gravimetric analysis(TGA). The TGA was also used for determining the percentage of grafting ratio. The results show that the cassava starch has been successfully grafted with acrylamide then crosslinked by N,N′-methylene-bisacrylamide using this reactor. The ultimate water absorbent capacity of the cassava-based superabsorbent polymer impacted by various pH values illustrated that the acid and basic solutions inhibit the ability of imbibing water. Additionally, gel properties of the cassava-based superabsorbent polymer were investigated. It can be concluded that the structure of cassava gel is stable, while the three dimensional network of cassava-based superabsorbent polymer is rigid but its structure could not resist external force effectively and everlastingly since G′ was decreased with increasing amplitude.     

Synthesis and reactions of 3-alkylsulfanyl-1,3-dihydro-2,1-benzisothiazole 2,2-dioxides

Alkyl- and arylsulfanylation of 1,3-dihydro-2,1-benzisothiazole 2,2-dioxides (benzosultams) 1a-c and pyridosultam 1d with dialkyl and diaryl disulfides provides dithioacetals of 2-aminobenzaldehydes 6-13. 1,3-Dimethylbenzosultam 19 with disulfides forms 3-alkyl(aryl)sulfanyl-1,3-dimethylbenzosultams 20-22 that undergo thermal extrusion of SO₂ followed by a [1,5] sigmatropic hydrogen shift in the intermediate aza-ortho-xylylene leading to 1-arylvinyl sulfides 24-26. Tandem alkylation-sulfanylation of benzo- and pyridosultams 1a-d with 4-bromobutyl thiocyanate gives tetrahydrothiopyrano-spiro-benzosultams 27-30 that, after extrusion of SO₂ and [1,5] hydrogen shift, form 2-aryl-5,6-dihydro-4H-thiopyrans 32-35. Alkylation of pyridosultam 1d with 3-chloropropyl thiocyanate leads directly to 2-pyrido-3,4-dihydrothiophene derivative 37.     

Injection Moulding of Parts with Microstructured Surfaces for Medical Applications

m2M-systems (micro-to-Macro) are parts with lateral dimensions of macroscopic scale and structures on the surface in the dimension of microns. The microstructure on the surface has a specific function depending on the intended purpose of the parts. With the use of m2M-systems new methods of medical diagnostics are possible. Nowadays for the realisation of such parts mainly planar methods known from microelectronics and their standard materials silicon and glass are used. An alternative is to make m2M-systems by injection moulding of plastics which lowers the manufacturing costs. In order to get an acceptable replication of the microstructure the use of special moulding techniques is necessary. The results of investigations in the variotherm moulding process and the requirements for the injection moulding machine are described in this paper.