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1

Trabecular bone remodelling in the femur of C57BL/6J mice treated with diclofenac in combination with treadmill exercise

Lehmann Tomasz P., Wojtków Magdalena, Pruszyńska-Oszmałek Ewa, Kołodziejski Paweł, Pezowicz Celina, Trzaskowska Aleksandra, Mielcarek Sławomir, Szybowicz Mirosław, Nowicka Ariadna B., Nowicki Marek, Misterska Ewa, Iwańczyk-Skalska Ewa, Jagodziński Paweł, Głowacki Maciej

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 3

3--11

EN

Purpose: Analgesic treatment with diclofenac deteriorates bone structure and decreases biomechanical properties. This bone loss has been though to be reversed by training. The impact of exercise on bone treated with diclofenac (DF) has reminded elusive. In the present study, we assayed the combined impact of exercises and DF on mouse femur. Methods: The femur samples we obtained from 30 days treated C57BL/6J female mice. The training group ran on a horizontal treadmill at 12 m/min by 30 min a day (5% grade/slope). The group of ten mice treated with DF received the drug subcutaneously every day (5 mg/kg of body weight/day). The combined group ran on the treadmill and obtained DF. After 30 days, we sacrificed mice and studied their femurs using microcomputed tomography (µCT), dynamic mechanical analysis (DMA) and nanoindentation. Results: We observed that treadmill running and DF decreased trabecular bone volume and mineral density. Combined effect of training and DF was not additive. A significant interaction of both parameters suggested protective effect of training on bone loss provoked by DF. The femur cortical bone shell remained untouched by the training and treatment. The training and the DF treatment did not alter the storage modulus E’ significantly. The unchanged storage modulus would be suggesting on the unaltered bone strength. Conclusions: We concluded that even relatively short time of training with concomitant DF treatment could be protective on trabecular bone. Although viscoelastic properties of the entire femur were not modulated, femur trabecular tissue was thinned by treatment with DF and protected by training.

2

Evaluation of physical and dynamic mechanical properties of coconut husk ash (CHA) reinforced polyester composites

Ipilakyaa Tertsegha, Tuleun Livinus, Sule Terngu

Journal of Mechanical and Energy Engineering

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2020

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Vol. 4, No 4

315--324

EN

The evaluation of physical and dynamic mechanical analysis (DMA) properties was carried out on a developed Coconut Husk Ash Reinforced Polymer Composite. Sieve analysis of pretreated coconut husk ash was done to obtain 75 μm, 150 μm and 300 μm particles sizes. These particles were used at varying compositions of 5%, 10%, 15%, 20% and 25% as reinforcements for polyester composites. The catalyst and accelerator used were Methyl Ethyl Ketone Peroxide and Cobalt Naphthenate respectively. The densities of the evaluated composites made with 150 μm particles were found to be less dense with values ranging from 0.9792 g/cm3 to 1.2561 g/cm3 than those made with 75 μm and 300 μm. The results also show that the percentage water absorbed by samples increased, ranging from 0 to over 2000 E’/MPa for all percentage reinforcements of coconut husk ash, with an increase in the duration of immersion of the samples in distilled water. However, 25% reinforcement had better results for all particle sizes. There were obvious variations of storage modulus, loss modulus and mechanical loss factor with percentage weight of reinforcement, temperature and frequency. The composite with 15%reinforcement displayed better results. The composite shows promising results as a material for interior components in aerospace and automobile industries.

3

Dynamic mechanical characterization of epoxy composite reinforced with areca nut husk fiber

Muralidhar N., Kaliveeran Vadivuchezhian, Arumugam V., Srinivasula Reddy I.

Archive of Mechanical Engineering

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2020

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LXVII, nr 1

57--72

EN

Natural fiber polymer composites are gaining focus as low cost and light weight composite material due to the availability and ecofriendly nature of the natural fiber. Fiber composites are widely used in civil engineering, marine and aerospace industries where dynamic loads and environmental loads persist. Dynamic analysis of these composites under different loading and environmental conditions is essential before their usage. The present study focuses on the dynamic behavior of areca nut husk reinforced epoxy composites under different loading frequencies (5 Hz, 10 Hz and 15 Hz) and different temperatures (ranging from 28◦C to 120◦C). The effect of loading and temperature on storage modulus, loss modulus and glass transition temperature was analyzed. Increase in storage modulus is observed with increase in loading frequency. The storage modulus decreases with increase in temperature. The glass transition temperature of the composite is determined to be 105◦C. The elastic modulus calculated from the DMA data is compared with three point bending test

4

DMA analysis of the structure of crosslinked poly(methyl methacrylate)s

Barszczewska-Rybarek I. M., Korytkowska-Wałach A., Kurcok M., Chladek G., Kasperski J.

Acta of Bioengineering and Biomechanics

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2017

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Vol. 19, no. 1

47--53

EN

Purpose: This paper presents the study aimed at the development of crosslinked poly(methyl methacrylate)s (X-PMMA) of varied crosslink density and the investigation of the relationships between the polymer network structure and dynamic mechanical properties. Methods: A series of model X-PMMA networks were crosslinked by the introduction of: 1, 2, 5, 10 and 20% of triethylene glycol dimethacrylate (TEGDMA). The copolymerizations led to various glass-rubber relaxation properties of the polymer networks, as revealed by dynamic-mechanical analysis (DMA). Glass temperature (Tg) and storage modulus above the Tg ( ) Erubbery  were a sensitive function of network architecture. DMA data were used for calculating the network parameter (Mc), crosslink density (q) and its alternative measure – the degree of crosslinking (DX). Results: The viscoelastic properties as well as structural parameters calculated from those showed correlation with the amount of the crosslinker. The increase in TEGDMA content resulted in the Tg, q and DX increases, whereas Mc decrease. The possible incomplete conversion of double bonds was detected in the DMA analysis, which was confirmed by the degree of conversion (DC), measured by FTIR spectroscopy. Additionally, some amount of sol fraction was found by 1H NMR experiments. Conclusions: The structure-property relationships developed for the system presented in this work could be useful in tissue engineering, where X-PMMA is applied. The direct measure of storage modulus values before and above glass transition may serve as a simple and fast indicator of the X-PMMA crosslink density.

5

Storage and loss modulus investigations of magnetorheological elastomers

Skalski P., Dębek C.

Logistyka

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2015

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nr 3

4408--4412, CD 1

EN

In this paper, the magnetorheological elastomers (MREs) based on natural rubber were studied. Several MRE samples, with different weight percentages of carbon iron particles, were fabricated without applying a magnetic field. Their microstructures were observed by using an environmental scanning electron microscope (SEM), and their rheological measurements were carried out using ARES rheometer. The MR effect was investigated by changing the volume of carbon iron particles.

PL

W pracy zaprezentowano badania elastomerów magnetoreologicznych (MR) zbudowanych na kauczuku naturalnym. Kilka próbek elastomeru MR z różną zawartością cząstek pyłu karbonylkowego zostało wytworzonych bez obecnego pola magnetycznego. Struktura próbek została przedstawiona na podstawie zdjęć z mikroskopu elektronowego, a pomiary reologiczne zostały przeprowadzone na reometrze ARES. Efekt magnetoreologiczny został przebadany pod kątem wielkości zawartości pyłu karbonylkowego.

6

Mathematical model analysis of sample from polyurethane vibroinsulation mat

Dzikowska W.

Postępy w Inżynierii Mechanicznej

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2014

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nr 3(2)

13--20

EN

The paper presents further developments in mathematical modelling of vibroinsulation mats. There was proposed the introduction of new parameters for characterizing the properties of the mat. An attempt to analyze the model in terms of its dynamic properties resulting from the determination of frequency transfer function was made. In conclusion the methodology of the studies necessary to quantify the material constants model was described.

PL

W pracy zaprezentowano kolejny etap rozwoju modelu matematycznego poliuretanowej maty wibroizolacyjnej. Zaproponowano wprowadzenie nowych parametrów chrakteryzujących własności maty. Podjęto próbę analizy modelu ze względu na jego własności dynamiczne wynikające z określenia transmitancji częstotliwościowej. W podsumowaniu opisano metodykę badań koniecznych do ilościowego określenia stałych materiałowych modelu.

7

Dynamic Mechanical Properties of Artifcially Aged Double Base Rocket Propellant and the Possibilities for the Prediction of Their Service Lifetime

Matečić-Mušanić S., Sućeska M.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 2

225--244

EN

The ageing of double base (DB) rocket propellants, as a consequence of the chemical reactions and physical processes that take place over time, has a signifcant effect on their relevant properties, such as chemical composition and mechanical and ballistic properties. The changes to relevant properties limit the safe and reliable service life of DB rocket propellants. Accordingly, numerous research efforts have been undertaken to fnd reliable methods to measure the changes caused by ageing in order to assess the quality of DB rocket propellants at a given moment of their lifetime, and to predict their remaining service lifetime. In this work we studied the dynamic mechanical properties of DB rocket propellant artifcially aged at temperatures of 80, 85 and 90 °C, in order to detect and quantify changes in the dynamic mechanical properties caused by ageing, and to investigate the possibilities for the prediction of service lifetime. Dynamic mechanical properties were studied using a dynamic mechanical analyser (DMA). The results obtained have shown that ageing causes signifcant changes in the storage modulus (E´), the loss modulus (E˝) and the tan δ curves’ shape and position. These changes are quantifed by following some characteristic points on the E´-T, E˝-T, and tan δ-T curves (e.g. glass transition temperatures; storage modulus, loss modulus and tan δ at characteristic temperatures, etc.). It has been found that the monitored parameters are temperature and time dependent, and that they can be shown to be functions of the so called ‘reduced time of artifcial ageing’. In addition, it has been found that, on the basis of known changes in viscoelastic properties as a function of time and ageing temperature, and the known kinetic parameters of the ageing process, it is possible to calculate (determine) the change in the properties at any ageing temperature provided that the mechanism of the ageing process does not change. Unfortunately, the use of kinetic parameters obtained by artifcial ageing at high temperatures (above 60 °C) for the prediction of the propellant lifetime will not give reliable results, because the mechanisms of ageing at 85 °C and 25 °C are not the same.

8

Biodegradowalne biopolimery: materiały opakowaniowe

Mościcki L., Mitrus M.

Inżynieria Rolnicza

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2004

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R. 8, nr 5

215--221

PL

Z uwagi na narastające problemy związane z zagospodarowaniem odpadów opakowaniowych w wielu ośrodkach naukowych na całym świecie prowadzi się badania nad biodegradowalnymi materiałami opakowaniowymi. Duże nadzieje wiąże się z tzw. skrobią termoplastyczną. W niniejszej pracy publikowane są wyniki badań wybranych własności fizycznych ziemniaczanej skrobi termoplastycznej wytworzonej za pomocą techniki ekstruzji.

EN

Due to utilization problems with of solid packaging waste many scientific centres all over the world are busy with development of biodegradable packaging materials. So called thermoplastic starch (TPS) seems to be a perfect solution. Chosen results of the research of physical properties of the potato thermoplastic starch are presented in this paper.