Cut resistance of hybrid para-aramid fabrics for protective gloves

This paper deals with cut resistance of hybrid woven para-aramid fabrics tested according to the appropriate clause of EN 388 – “Protective Gloves against Mechanical Risks”. Abrasion, puncture and tear resistance properties of the fabrics were also measured. The experimental sample set was plain-woven fabrics made of hybrid yarns composed of staple para-aramid fibres with different core/sheath ratios of various filaments in their structure. The effects of core/sheath ratio and core filament type were investigated. The results revealed that decreasing core–sheath ratio of the hybrid yarns led to the increase in weight and thickness, resulting in improved cut, abrasion and puncture resistance properties. It was confirmed that cut resistance increased with the increase in thickness and weight of the fabric. Para-aramid/Dyneema® fabric had higher cut, abrasion and puncture resistance properties.     

Properties of self-compacting portland pozzolana and limestone blended cement concretes containing different replacement levels of slag

In order to reduce energy consumption and CO₂ emission, and increase production, cement manufacturers are blending or inter-grinding mineral additives such as slag, natural pozzolana, and limestone. This paper reports on the results of an experimental study on the production of self-compacting concrete (SCC) produced with portland cement (PC), portland pozzolana (PPC) and portland limestone (PLC) blended cements. Moreover, the effect of different replacement levels (0–45%) of ground granulated blast furnace slag (GGBFS) with the PPC, PLC, and PC cements on fresh properties (such as slump flow diameter, T ₅₀₀ slump flow time, V-funnel flow time, L-box height ratio, setting time, and viscosity) and hardened properties (such as compressive strength and ultrasonic pulse velocity) of self-compacting concretes are investigated. From the test results, it was found that it was possible to manufacture self-compacting concretes with PPC or PLC cements with comparable or superior performance to that of PC cement. Furthermore, the use of GGBFS in plain and especially blended cement self-compacting concrete production considerably enhanced the fresh characteristics of SCCs.     

Transport properties based multi-objective mix proportioning optimization of high performance concretes

In this study, multi-objective mix proportioning optimization of high performance concretes was performed. For this purpose, five factors; w/b ratio, total binder content (b), silica fume (SF) replacement ratio, fine to total aggregate ratio (s/a), and amount of superplasticizer (SP), were investigated to determine their effects on the transport and mechanical properties of high performance concrete. Slump, compressive strength, splitting tensile strength, modulus of elasticity, ultrasonic pulse velocity, water absorption, water penetration, and chloride ion penetration of mixtures were measured. Then, using mix proportion variables, mathematical formulations were obtained for the slump, mechanical and permeation properties via regression technique. To find out the best possible mix proportions for the simultaneous minimization of water absorption, water penetration and chloride ion penetration, a multi-objective optimization problem was defined and solved. In order to verify that the theoretically determined optimum mix proportions really minimized the transport properties of high performance concretes, an experimental study was conducted and it was observed that theoretically proposed optimum mix proportions can satisfy expected minimum permeation properties.     

Dispersion polymerization of L-lactide in supercritical carbon dioxide

Triblock (A-B-A) oligomers of ε-caprolactone (ε-CL) (A) and poly(ethylene glycol) with an average molecular weight of 400 (PEG400) (B) were synthesized with three different molecular weight in the range of 2–6 kDa by changing the ratio of PEG400/ε-CL. These oligomers were then used in dispersion polymerization of L-lactide in supercritical carbon dioxide (scCO₂) as stabilizers. 5% stabilizer in the polymerization recipe allowed synthesis of poly(L-lactide) (PLLA) in scCO₂ in the powder form with a weight average molecular weight of around 60 kDa with polymerization yields around 80%. Interestingly, there was almost no effect of stabilizer molecular weight on polymerization. L-lactide polymerization in scCO₂ without any stabilizer was also possible but both the PLLA molecular weight and polymerization yield were lower, and the product was as aggregates instead of powders. A stabilizer concentration of 5% in the polymerization recipe was found adequate. Further increases in the stabilizer load resulted lower molecular weights and lower yields.     

HRP immobilized microporous Poly(styrene-divinylbenzene-polyglutaraldehyde) monolith for forced flow injected phenol biosensing

A colorimetric detection system based on horseradish peroxidase (HRP) immobilized microporous Poly(styrene-divinylbenzene-polyglutaraldehyde) monolith was developed for phenol biosensing. The incorporation of the aldehyde groups to the backbone of the microporous (90%) monolith was achieved by the polymerization of the continuous phase of a high internal phase emulsion. HRP was chemically immobilized onto the inner walls of the micropores of the monolith via the aldehyde groups. HRP immobilized microporous monolith (HRP-MM) was used as a biocatalytic cell under forced flow conditions in a flow injection system. A carrier stream containing 4-aminoantipyrine (4-AAP) as color reagent was flowed through the HRP-MM at various flow rates ranged between 0.1-15 mL min^-1. The analytical parameters of response time, detection limit and linear range varied at the range of 1-60 s, 1-250 μM, and 0.25-2 mM, respectively. The results showed that the most accurate phenol biosensing was obtained at the flow rate of 1 mL min^-1. The microarchitected structure of the monolith improved the mass transferring conditions for the enzymatic reaction due to the forced flow through the micropores. The detection system presented a satisfactory precision evaluated by relative standard deviation of 1.1% (n = 13) and recovery of 100% at the flow rate of 1 mL min^-1. The system showed 60% of its initial signal from 12th day up to the two months.     

The effect of anionic surfactant on the properties of polythiophene/chitosan composites

Polythiophene/chitosan (PT/Ch) composites and PT homopolymers were chemically synthesized in the presence of anthraquinone‐2‐sulfonic acid sodium monohydrate, ACS anionic surfactant. Conductivity, FTIR, SEM, TGA, and XRD measurements were used to study the properties of the composites. The effect of the ratio of the surfactant to the Ch onto structural and physical properties of the composites was also investigated. Our experimental data show that the properties of the composites depend on the amount of both surfactant and Ch used. The highest conductivity of 9.62 × 10^?3 S/cm^?1 was measured for the PT/Ch2 sample. When measurements were taken for PT/Ch/ACS samples with different Ch and surfactants content, the highest conductivity and initial decomposition temperature were recorded for the PT/Ch2/ACS10 sample as 3.49 × 10^?4 S/cm^?1, 223°C, respectively. POLYM. ENG. SCI., 54:2632–2640, 2014. © 2013 Society of Plastics Engineers     

Volatile compounds and proteolysis in traditional Beaten (Bieno sirenje) ewe's milk cheese

Beaten ewe's milk cheese is a traditional autochthonous type of cheese manufactured in Macedonia with a relatively high nutritional value and sensory characteristics. The objective of this study was to characterise the gross composition, proteolysis and volatile profiles of the cheese that is supplied from different retails. The ranges for gross composition were from 31.53% to 42.83% (w/w) for moisture, 41.99% to 50.98% (w/w) for fat‐in‐dry matter, 2.03% to 8.25% (w/w) for salt content and 20.74% to 33.35% (w/w) for protein. Proteolysis results showed various levels of soluble nitrogen ranged from 3.15 to 33.50 for water‐soluble nitrogen (WSN) and from 1.11% to 6.79% for nitrogen soluble in 12% trichloroacetic acid (TCA‐SN). The ranges for total free amino acids were from 1.65 to 8.06 mg Leu/g. Lower proteolysis was observed in the cheese samples due to high salt contents. In total, 65 volatile compounds were identified in Beaten cheese. As a conclusion, the variation of the peptide profile, electrophoresis and volatile contents of Beaten cheeses are due to the lack of standardised manufacture protocols.     

A preliminary study on the manufacturing aluminum–potassium feldspar metal matrix composite materials

This study reports the results of a preliminary study of manufacturing aluminum–potassium feldspar metal matrix composites including its castability and mechanical properties. The material was composed considering 0.25 %, 0.5 %, and 0.75 % additive ratios to examine the impact of the amount of potassium feldspar on the material and mechanical properties of the manufactured aluminum metal matrix composite material. Aluminum alloy (A356) was utilized as the matrix of the composition. The composite material was manufactured by the stir casting technique. The modulus of elasticity, yield strength, tensile strength, elongation, density, and quality index of the material parameters was taken into account to determine the materials′ practicality. The preliminary results indicated that potassium feldspar is a promising mineral to be utilized as an additive for aluminum metal matrix composites since it has a positive impact on mechanical properties. By optimizing the casting parameters, the positive aspects of the potassium feldspar may make the material more practical to be utilized in vast engineering applications.