Viscoelastic, Thermal, and Mechanical Properties of Melt-Processed Poly (ε-Caprolactone) (PCL)/Hydroxyapatite (HAP) Composites

Poly (ε-caprolactone) (PCL)/hydroxyapatite (HAP) composites represent a novel material with desired properties for various applications. In this work, PCL/HAP composites at low loadings were developed through melt-extrusion processing. The effects of HAP loading on viscoelastic, thermal, structural, and mechanical properties of PCL were examined. The morphological analysis revealed better dispersion of HAP at low loadings, while aggregation was noticed at high concentrations. The complex viscosity of the prepared composites increased with increasing concentration of HAP. In addition, a significant decrease in crystallinity was observed upon increase in HAP loading. However, the elongation at break increased with increasing the concentration of HAP, probably due to a decrease in crystallinity. The onset thermal degradation temperature of PCL was enhanced at low concentrations of HAP, whereas a decrease was observed at high loading. Overall, different degrees of HAP dispersion resulted into specific property improvement.

A new generation of cable grade poly(vinyl chloride) containing heavy metal free modifier

Many additives are used to improve the performance of cables in terms of increasing their flame retardancy, thermal stability, thermal conductivity, and other characteristics. Unfortunately, most of these additives contain heavy metals. Therefore, the main objective of this study is to introduce a material representing a new generation of environmentally friendly heavy metal-free stabilizers for cable grade poly(vinyl chloride) that can compete with traditional materials in terms of performance and distinctive properties. This unique additive is Oxydtron, a synthetic silicate or simply nanocement. The tests performed are rheological properties represented by a capillary rheometry analysis, limiting oxygen index, and volume resistivity. The most significant improvement in Bagley correction measurements was 14.61%; 18.13%; and 27.20% more than poly(vinyl chloride) basic formulation when using 5wt.% Oxydtron at 160 °C, 170 °C, and 180 °C, respectively. Also, the mean increases in relaxation time were 3.200 times, 8.825 times, and 12.458 times more than poly(vinyl chloride) basic formulation with 1wt.%, 3wt.%, and 5wt.% of Oxydtron, respectively. Furthermore, the Oxydtron lowered the value of the accompanying thermal gradient of the L.O.I test, reducing the heat-affected zone. The best result was with the extrusion processing method due to the uniformity of the processing conditions. However, the thermal gradient analysis showed residual heat stress in the test samples after cutting the burning layer and re-testing the samples again; this causes them to burn faster. This situation requires caution for designs that are exposed to high temperatures without burning. The optimum improvement in volume resistivity value was 14.71% and 38.24% more than poly(vinyl chloride) basic formulation after adding 5wt.% and 7wt.% of Oxydtron, respectively.

STUDY OF OILSEED MATERIAL RHEOLOGY DURING EXTRUSION PROCESSING

Определены параметры течения пластичной жидкости при экструзионной переработке масличных культур. В качестве экспериментального материала использовали мезгу, выходящую из жаровни и поступающую в экструдер. Вязкость измеряли на ротационном вискозиметре при избыточном гидростатическом давлении 981 Па. Высота слоя материала в измеряемой ячейке составила 38 мм. Скорость сдвига в процессе измерения варьировали от 1 до 10 рад/с. Проведены эксперименты по определению зависимости вязкости от масличности материала, напряжения и скорости сдвига, а также гидравлического давления на исследуемый материал. Анализ результатов эксперимента свидетельствует о наличии структурообразования материала, поступающего в экструдер. Полученные параметры инженерной модели позволяют прогнозировать реологию вязкопластичного течения в широком диапазоне скоростей сдвига в каналах шнекового пресса. The parameters of the flow of plastic liquid during the extrusive processing of oilseed material are defined. The pulp coming from the brazier and into an extruder was used as experimental material. The viscosity was measured with rotational viscometer under excessive hydrostatic pressure of 981 PA. The height of the layer of material in the measuring cell was 38 mm. Shear rate during the measurement ranged from 1 to 10 rad/s. The experiments to determine the dependence of viscosity on oil content material, pressure, and velocity shear, and hydraulic pressure on the oilseed material were carrying out. Analysis of the results of the experiment indicates the presence of structure formation of the material coming into the extruder.