Equilibrium Modulus Of Elasticity Research Articles

Structure, morphology, thermal, and sorption characteristics of epoxidized natural rubber conjugated spent coffee via one‐pot synthesis

AbstractThe present work highlights the preparation of the epoxidized natural rubber conjugated spent coffee biocomposites (ENR‐g‐SC) via one‐pot synthesis to control petroleum oil spills. The structural determination of the spent coffee grafted epoxidized natural rubber (ENR‐g‐SC) was confirmed through FTIR and 1H‐NMR spectroscopic analyses. The thermal performance, tensile tests, and morphological properties of the synthesized (ENR‐g‐SC) biocomposites were performed. The data revealed that ENR‐g‐SC biocomposite with 20 phr of spent coffee (SC) exhibited the highest tensile properties due to maximal chemical linkages of spent coffee and epoxide groups in ENR. The epoxidized natural rubber conjugated spent coffee copolymers were evaluated as oil sorbers for oil absorbency applications in chloroform, toluene, and 10% crude petroleum diluted with toluene. The data revealed that the oil absorbency increased slightly with chloroform or toluene instead of 10% crude oil diluted with toluene. Furthermore, swelling and network parameters including the maximum oil absorbency (Qmax), swelling rate constant (k), polymer‐solvent interaction (χ), effective crosslink density (ύe), equilibrium modulus of elasticity (GT), and average molecular weight between crosslinks (Mc) and theoretical crosslink density (ύt) were determined, and correlated to the efficiency of the synthesized epoxidized natural rubber conjugated spent coffee.

Adsorbent biopolymers based on Couroupita guianensis

Introduction: A biopolymer oil sorbent was produced, aiming to remove oil spills from the sea. More than 80% of the world's energy matrix is still fossil fuels, which meet the energy demands but can potentially harm the environment during its production and processing or through its use (1-6). For this reason, a biopolymer obtained from renewable raw material, the pulp of Couroupita guianensis, a plant native to the Brazilian Amazon region and Atlantic Forest, as well as in other regions of the planet. The motivation of the present work is to synthesize high-density composite packing and absorption composites using the formed biopolymer. The effect of packing density, type, and amount of binder on porous properties as well as thermal conductivity were studied. The biopolymer showed various magnetics nanoparticles contents incorporated into synthesized materials. Methods: In this work, fractions of Couroupita guianensis pulp were prepared and mixed with toluene diisocyanate and tin octanoate. The biopolymer characteristics were prepared with the insertion of maghemite nanoparticles into a polymer matrix, aiming to make the removal of the polymer material containing petroleum from the water surface easier. This study used FTIR spectroscopy (Fourier Transform Infrared Spectroscopy) to assess the biochemical changes. The prepared materials were tested to absorb crude oil. In addition, swelling and mesh parameters including maximum oil absorption (Qmax), swelling kinetics rates, solvent-polymer interaction (χ), effective cross-linking density (ν℮), equilibrium modulus of elasticity (GT) and average molecular weight between cross-links (Mc) were verified and correlated with the absorption efficiency of the synthesized material. Results & Discussions: The FTIR spectrum of the pulp peaks at 3155.54, 2985.81, 1743.65, 1442.75, 1242.16, 1049.28, 933.55, 848.68, 786.96 and 702.09 cm -1 correspond to the functional groups such as carboxylic acids (O–H stretch), alkenes (C–H stretch), carboxylic acids (C=O stretch), aromatics (C–C stretch (in–ring)), alcohols, carboxylic acids, and esters, respectively. The stigmatic tissue; x400 of the sample showing canals equal in number to the carpels; x40.-10. The efficiency of the extract was also confirmed by microscopic visualization. The kinetic curves of ions sorption on modified cellulose phytochemicals of Couroupita guianensis at pH 7 shows that sorption equilibrium in heterogenic system ion–metal–sorbent was attained in 40–60 min. The oil and composite were magnetically removed, and the mass of the oil residue could be determined by gravimetry. In addition, tested materials presented an average cure degree equal to (99.1 ± 0.2)%, which means that, after an oil extraction by solvents, the sorbers can be reused, as proved by three additional tests, which showed that oil removal capability remained the same. Conclusions: Couroupita guianensis fruit extract was presented as a novel bio reductor agent, useful for instant green synthesis of oil-sorbent composite. The addition of magnetic nanoparticles into the polymer matrix allowed the production of a magnetic composite, which possesses a good magnetic force. One single gram of the best material was able to remove 15 g of oil from the water. This result can be improved by changing the amount of magnetic nanoparticles in the material. Key words: Couroupita guianensis, Biopolymer, Sorbent, Magnetic composites, Synthesis References S. Gnanasekar et al., J. Appl. Biomed., 2017, 146, 7 V. Marinho et al, Macromolecular Symp., 2018, 380, 1800116 E. G. Grance et al., J. Appl. Biomed., 2012, xxx H. Bigdoli et al., J. Env. Che. Eng., 2019, 7, 103340 A. Varela et al., Pol. Eng. Sci, 2012, xxx S. Songsaeng et al., J. Adv. Res., 2019, 70, 79-89

Egyptian crude oil sorbent based on coated polyurethane foam waste

In this study, free radical polymerization of hydrophobic monomer namely lauryl methacrylate & hexadecene is coated on the flexible polyurethane foam waste as an modifier of the non-polar moiety. Also various contents of magnetic nanoparticle are incorporated to the synthesized coated polyurethane foam waste. The coated sorbers are confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The coated polyurethane waste is used to absorb Egyptian crude oil to alleviate petroleum oil spill pollution. Moreover, Swelling and network parameters including maximum oil absorption (Qmax), swelling kinetics rates, polymer solvent interaction (χ), effective crosslink density (νe), equilibrium modulus of elasticity (GT), and average molecular weight among crosslinks (Mc) were decided and correlated to the efficiency of the synthesized coated waste.

Growth plate cartilage shows different strain patterns in response to static versus dynamic mechanical modulation.

Longitudinal growth of long bones and vertebrae occurs in growth plate cartilage. This process is partly regulated by mechanical forces, which are one of the underlying reasons for progression of growth deformities such as idiopathic adolescent scoliosis and early-onset scoliosis. This concept of mechanical modulation of bone growth is also exploited in the development of fusionless treatments of these deformities. However, the optimal loading condition for the mechanical modulation of growth plate remains to be identified. The objective of this study was to evaluate the effects of in vitro static versus dynamic modulation and of dynamic loading parameters, such as frequency and amplitude, on the mechanical responses and histomorphology of growth plate explants. Growth plate explants from distal ulnae of 4-week-old swines were extracted and randomly distributed among six experimental groups: baseline ([Formula: see text]), control ([Formula: see text]), static ([Formula: see text]) and dynamic ([Formula: see text]). For static and dynamic groups, mechanical modulation was performed in vitro using an Indexed CartiGen bioreactor. A stress relaxation test combined with confocal microscopy and digital image correlation was used to characterize the mechanical responses of each explant in terms of peak stress, equilibrium stress, equilibrium modulus of elasticity and strain pattern. Histomorphometrical measurements were performed on toluidine blue tissue sections using a semi-automatic custom-developed MATLAB toolbox. Results suggest that compared to dynamic modulation, static modulation changes the strain pattern of the tissue and thus is more detrimental for tissue biomechanics, while the histomorphological parameters are not affected by mechanical modulation. Also, under dynamic modulation, changing the frequency or amplitude does not affect the biomechanical response of the tissue. Results of this study will be useful in finding optimal and non-damaging parameters for the mechanical modulation of growth plate in fusionless treatments.

EFFECT OF HEAT TREATMENT ON THE RHEOLOGICAL PROPERTIES AND COLOR OF PUMPKINS (Cucurbita moschate)

B.CEPPA, Curitiba, v. 33, n. 1, p. 87-97, jan./jun. 2015EFFECT OF HEAT TREATMENT ON THE RHEOLOGICALPROPERTIES AND COLOR OF PUMPKINS (Cucurbitamoschate)Keila de Souza Silva*Carolina Castilho Garcia**Javier Telis Romero***Maria Aparecida Mauro****The aim is to investigate the eff ects of stepwise blanching and itscombination with drying on rheological properties and change ofcolor in pumpkins (Cucurbita moschata). 1 cm thick samples wereimmersed in water at 55 °C for diff erent times, followed by diff erentholding times prior to inactivation of the enzyme (97 °C/5minutes).Controled samples were obtained after blanching at 97 °C for 5minutes. The texture and color of the samples were measured and therheological parameters calculated according to the Maxwell model.The results showed that stepwise blanching for 40 minutes with 30minutes of holding time provided samples with equilibrium modulusof elasticity greater than the control samples. These parameterswere used as blanching pre-treatment to convective drying with airat 60 °C and a velocity of 1.5 m/s for diff erent drying times. Stepwiseblanched samples showed fi rmer tissues than control samples afterdrying. There were no signifi cant diff erences in the lightness andredness of stepwise blanched samples and control samples duringdrying.

Linear and nonlinear viscoelasticity of oleogels based on vegetable oil and ethylene vinyl acetate copolymer/isotactic polypropylene blends

ABSTRACTThis work deals with a rheological study of oleogels based on high‐oleic sunflower oil (HOSO) and ethylene vinyl acetate copolymer (EVA) / isotactic polypropylene (iPP) blends. EVA copolymers with different vinyl acetate content were used. With this aim, linear small amplitude oscillatory shear (SAOS) and nonlinear (relaxation) measurements combined with polarized optical microscopy were carried out. Oleogels were prepared by using the mixing rheometry technique in a batch mixer. Oscillatory strain amplitude sweep tests showed that the end from the viscoelastic linear region for oleogels was accompanied by opposite trends for viscoelastic moduli. SAOS tests showed that all the oleogels present similar behavior characteristic of polymeric systems with physical entanglements. It was found that the elastic equilibrium modulus and loss tangent increases with iPP content. On the other hand, nonlinear relaxation tests presented a strong dependence on the strain applied and the Soskey–Winter model was found to provide an accurate description of the damping function of these oleogels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42477.

Comb-like crosslinked alkyl acrylates-vinyl acetate terpolymers for oil sorption

A series of comb-like crosslinked dodecyl acrylate-co-octadecyl acrylate-co-vinyl acetate terpolymers (DOVs) were synthesized with four different feed ratios of vinyl acetate while keeping other monomer ratios constant. Crosslinking was carried out using trimethylol propane triacrylate (hexafunctional) or divinyl benzene (tetrafunctional). Terpolymers were characterized by FTIR spectroscopic analysis and their swelling properties, such as oil sorbency, were evaluated. Structure-performance relationship was discussed, especially in regards to crystallinity, crosslinker type, and feed ratio. Moreover, network parameters including polymer solvent interaction (χ), effective crosslink density (ν e ), equilibrium modulus of elasticity (G T ), and average molecular weight between crosslinks (M c ), were determined and correlated to the efficiency of the synthesized terpolymers. The highest oil absorbency of crosslinked DOVs is 43.22 gg−1 attained after 20 min of immersion.

Swelling and network parameters of crosslinked porous octadecyl acrylate copolymers as oil spill sorbers

AbstractIn previous work crosslinked copolymers were prepared from cinnamoyloxy ethyl methacrylate (CEMA) and several monomers feed ratios of octadecyl acrylate (ODA). Networks so produced are both flexible and porous; we now report their swelling efficacies as a function of temperature in toluene and in crude petroleum. Network characteristics is presented including the polymer + solvent interaction parameter χ, effective crosslink density υe, equilibrium modulus of elasticity E, average molecular weight between crosslinks Mc and the theoretical crosslink density υt. These parameters are correlated with structures of the synthesized sorbers.

Synthesis and characterization of oil sorbers based on docosanyl acrylate and methacrylates copolymers

AbstractDocosanyl acrylate (DCA) monomer was copolymerized with different monomer feed ratios of cinnamoyloxy ethyl methacrylate (CEMA) or methyl methacrylate (MMA) monomer to produce different compositions for DCA/CEMA or DCA/MMA copolymer with low conversions.1H NMR spectroscopy was used to confirm the copolymer structure. DCA was crosslinked with different mol % of CEMA or MMA using dibenzoyl peroxide as initiator and various weight percentages of either 1,1,1‐trimethylolpropane triacrylates or 1,1,1‐trimethylolpropane trimethacrylates crosslinkers. The effects of monomer feed composition, crosslinker concentration, and the hydrophobicity of the copolymer units on swelling properties of the crosslinked polymers were studied through the oil absorbency tests. The network parameters, such as polymer solvent interaction (χ), effective crosslink density (υe), equilibrium modulus of elasticity (GT), and average molecular weight between crosslinks (Mc), were determined and correlated with the structure of the synthesized copolymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Repair of osteochondral defects with biphasic cartilage-calcium polyphosphate constructs in a Sheep model

There has been interest in developing novel biological treatments to repair focal cartilage defects. We have developed a method of forming biphasic constructs (“osteochondral”-type plug) in vitro consisting of cartilaginous tissue, formed on and anchored to the intended articulation surface of a porous ceramic substrate. The purpose of this study was to evaluate the biochemical and biomechanical properties and morphology of in vitro-formed biphasic constructs 3 and 9 months after implantation into 4 mm diameter full thickness osteochondral defects in the trochlear groove of sheep stifles. The implants withstood loading in vivo up to 9 months with evidence of fusion to adjacent native cartilage and fixation by bone ingrowth into the ceramic substrate. The cartilage layer was eroded from those implants that were proud to the joint surface. Control implants (ceramic only) had fibrous tissue on the articulating surface after implantation for 3–4 months. Neither the cellularity nor proteoglycan content of the implanted cartilage, when it remained, changed significantly between 3 and 9 months and the collagen content increased slightly. The elastic equilibrium modulus of the cartilage improved with time with the greatest improvement (10-fold) occurring early during the first 3–4 months after implantation. This study suggests that biphasic constructs may be suitable to repair joint defects as the implants were maintained up to 9 months in sheep. Importantly the mechanical properties of the implanted cartilage improved significantly after implantation suggesting that cartilage can mature in vivo after implantation. The results indicate that further study of this treatment approach is warranted to attempt to overcome the technical surgical difficulties identified in this study.

Swelling and Network Parameters of Oil Sorbers Based on Alkyl Acrylates and Cinnamoyloxy Ethyl Methacrylate Copolymers

Cinnamoyloxy ethyl methacrylate (CEMA) monomer was copolymerized with different monomer feed ratios of alkyl acrylate, such as dodecyl and octadecyl acrylate DDA and ODA, respectively. The monomers were copolymerized with different mole% to produce different compositions for each CEMA/alkylacrylate copolymer with low conversion. 1HNMR was used to determine the copolymer compositions. The monomer reactivity ratios of each CEMA/alkylacrylate copolymer were determined using Fineman-Ross and Kelen-Tudos methods. CEMA was copolymerized with DDA or ODA and crosslinked using azobis isobutyronitrile (AIBN) as the initiator and 1% weight content of either 1,1,1-trimethylolpropane triacrylate (TPT) or 1,1,1-trimethylolpropane trimethacrylate (TPTm) crosslinkers. The swelling parameters, such as the maximum oil absorbency (Qmax), characteristic oil sorbency (Q), characteristic swelling time (T), and swelling rate constant (k), were evaluated for the synthesized sorbers. The network parameters, such as the polymer solvent interaction (χ), effective crosslink density (υe), equilibrium modulus of elasticity (GT), average molecular weight between crosslinks (Mc), and the theoretical crosslink density (υt), were determined and correlated with the structure of the synthesized sorbers.

Texture Changes During the Ripening of Port Salut Argentino Cheese in 2 Sampling Zones

ABSTRACT: Texture changes during ripening of Port Salut Argentino cheese for different sampling zones were studied. Compression relaxation tests were performed and results were analyzed using both Maxwellian and Peleg's models. Elastic equilibrium modulus obtained from the Maxwellian model decreased from 1.22 to 0.11 104Pa during ripening. The constants derived from Peleg's model, k1 and k2, diminished with ripening time from 1.18 to 0.71 min and from 1.27 to 1.12, respectively. Asymptotic equilibrium modulus from Peleg's model decreased from 0.95 to 0.07 104Pa during ripening. Rate parameters derived from a 1st order kinetics applied to both equilibrium moduli showed that the decrease was faster in the external zone (0.0846 d−1) than in the central zone (0.0368 d−1). The correlation between equilibrium moduli, salt concentration, moisture content, and maturation indexes was obtained with a determination coefficient of 0.76.

Thermoreversible gels in oil/EVA systems

In this work we investigate the gel formation of EVA/recycled motor oil systems as a route to obtain synthetic binders which could be used instead of natural bitumen, as well as mixed with natural bitumen to modify adequately its viscoelastic response. The EVA copolymer studied in this work has a vinyl acetate content of 18 wt% and solutions of EVA/motor oil have been prepared up to a concentration of 50 wt%. Dynamic viscoelastic frequency sweeps between 10−2 Hz and 102 Hz have shown that above 3 wt%, at 25 °C, EVA/motor oil systems form gels. It has been possible to define an elastic equilibrium modulus, Ge, for each gel. The dependence of Ge on concentration has been compared with that of PVC/DOP and SBS/oil gels on the basis of the De Gennes model. Thermal stability of EVA/motor oil gels has also been analyzed, indicating that for the highest polymer concentrations gel point is above 80 °C.

Effect of galactomannans on the viscoelastic behaviour of pectin/calcium networks

Abstract An investigation was carried out on the effect of the addition of galactomannans to pectin/calcium networks with different structural and rheological characteristics. For those pectin/calcium gels characterized by an elastic equilibrium modulus, the addition of the galactomannan increased both the storage and loss moduli, especially at short time scales. This increase was greater than that which could be expected by simple additivity of the viscoelastic properties of each isolated system. The pectin/calcium network remained the continuous gel matrix controlling the viscoelastic behaviour of these systems at low frequency. For pectin/calcium systems close to the sol-gel transition or at low pH, the mixed systems evolved towards the behaviour of viscoelastic liquids in the presence of increasing concentration of the non-gelling polymer. These overall results suggest that there is no specific interaction and that the changes in the rheological properties of the pectin gels are due to galactomannan microphase separation limited by the entrapment of these macromolecules in the pectin-calcium network.

Proteolytic and Rheological Evaluation of Maturation of Tybo Argentino Cheese

Changes in the rheological behavior and viscoelastic properties were analyzed during ripening of a semi-hard cheese (Tybo Argentino) packaged in a plastic film. Casein breakdown was measured by electrophoresis. Degradation of αs1- casein was rapid compared with that of β-casein. Some rheological parameters obtained from uniaxial compression tests changed during ripening. Hardness decreased, and adhesiveness increased; however, cohesiveness did not change significantly.An exponential decay equation with two Maxwellian elements and one elastic element in parallel was fitted to characterize stress relaxation curves. Viscoelastic parameters (elastic moduli and relaxation times) were obtained using non-linear regression analysis. The elastic equilibrium modulus and the viscosity of the element with the highest relaxation time decreased during the ripening period.The rheological parameters were correlated to the formation of water-soluble and TCA-soluble nitrogen and to the concentration of αs1-casein by linear regression equations. Hardness and viscosity had the highest correlation coefficients.

Changes in rheological and viscoelastic properties and protein breakdown during the ripening of ‘Port Salut Argentino’ cheese

SummaryChanges in the rheological behaviour and viscoelastic properties during ripening at 10°C of a soft cheese (Port Salut Argentino) packaged in a plastic film (EVA‐EVA) were analysed. Casein degradation was measured by electrophoresis slab gels; αs1 casein degradation was rapid and striking compared with that of β casein. Rheological parameters obtained from uniaxial compression tests changed during ripening: hardness decreased, adhesiveness and cohesiveness increased.An exponential decay equation with two maxwellian elements and one elastic in parallel was fitted to characterize stress relaxation curves. Viscoelastic parameters (elastic moduli and relaxation times) were obtained using non‐linear regression analysis. The elastic equilibrium modulus decreased 80% during the ripening period and the viscosity of the element with the highest relaxation time decreased 20%. These parameters represented the changes observed in cheese hardness and elasticity during ageing time and were related to the extent of casein breakdown.

Influence of crosslinking density on the properties of polymer networks

The density, refractive index, glass-transition temperature, and the equilibrium modulus of elasticity have been calculated for polymer networks differing in their chemical nature and having different amounts of repeat-units in the fragment between crosslinks. The networks studied were based on PE, on the copolymer of styrene with divinylbenzene and sulphur vulcanized polyisoprene. When the number of repeat-units in the fragment is reduced to five or less, a marked change in the above listed physical characteristics was observed for all the systems under review. This change is attributed to a transition from sparse networks to dense ones.

Large computer simulations on elastic networks: Small eigenvalues and eigenvalue spectra of the Kirchhoff matrix

Computer simulations of the formation of trifunctional and tetrafunctional polydimethyl-siloxane networks that are crosslinked by condensation of telechelic chains with multifunctional crosslinking agents have been carried out on systems containing up to 1.05×106 chains. Eigenvalue spectra of Kirchhoff matrices for these networks have been evaluated at two levels of approximation: (1) inclusion of all midchain modes, and (2) suppression of midchain modes. By use of the recursion method of Haydock and Nex, we have been able to effectively diagonalize matrices with 730 498 rows and columns without actually constructing matrices of this size. The small eigenvalues have been computed by use of the Lanczos algorithm. We demonstrate the following results: (1) The smallest eigenvalues (with chain modes suppressed) vary as μ−2/3 for sufficiently large μ, where μ is the number of junctions in the network; (2) the eigenvalue spectra of the Kirchhoff matrices are well described by McKay’s theory for random regular graphs in the range of the larger eigenvalues, but there are significant departures in the region of small eigenvalues where computed spectra have many more small eigenvalues than random regular graphs; (3) the smallest eigenvalues vary as n−1.78 where n is the number of Rouse beads in the chains that comprise the network. Computations are done for both monodisperse and polydisperse chain length distributions. Large eigenvalues associated with localized motion of the junctions are found as predicted by theory. The relationship between the small eigenvalues and the equilibrium modulus of elasticity is discussed, as is the relationship between viscoelasticity and the band edge of the spectrum.

Relaxational phenomena in polybutadiene-polyarylate block copolymers

The molecular mobility in polybutadiene-polyarylate block copolymers with different ratios of components has been studied in conditions of exposure to constant and variable mechanical fields. For the block copolymers studied several relaxation regions exist; their number regularly rises with increase in the content of the polyarylate component leading to rise in structural heterogeneity of the samples. Between the main relaxation regions additional maxima show up associated with molecular mobility at the boundaries of the different blocks. For the highest polyarylate content (90 wt.%) at raised temperatures the nominal equilibrium modulus of elasticity and the longitudinal speed of sound are constant pointing to the presence of a stable spatial network formed by physical nodes of different types.

Small-Strain Modulus of Model Trifunctional Polydimethylsiloxane Networks

Abstract A number of studies to test quantitatively the molecular basis of the theory of rubber elasticity have been performed during the last few years on elastomeric networks of relatively well-known structure. Many of these studies have been done on end-linked networks, for which the number of chains between junctions, their average length, and the functionalities of the junctions could be calculated. Several studies have been with poly(dimethylsiloxane) (PDMS) networks. One of the major controversial points up to now has been the effect of topological interactions between network chains on mechanical properties. Two groups of researchers have come to quite different conclusions about the role of entanglements with respect to their contribution to the elastic modulus. The first group led by Flory considers that the entanglement contribution to the elastic equilibrium modulus is due to the restrictions that topological interactions impose on junction fluctuations among their mean equilibrium position. The second group follows the hypothesis of Langley and Graessley who argue that these interactions are also present along the chain contour. Their support of this thesis is based on the experimental observation of the rubbery plateau modulus GN0 in linear polymers, which is evidence of topological interactions between chains. These interactions would also be present during network formation, and they will be “trapped”, or prevented from relaxing, by the crosslinking process. Thus, these chain-chain interactions can contribute directly to the modulus. Recently, one of us has reviewed most of the results obtained with PDMS networks. This showed that all the experimental data to date are quite consistent and give support to the second approach. In this work, we add to these data some new experiments obtained by crosslinking trifunctional PDMS networks in different states of dilution. The results give additional evidence of the contribution of chain entanglements to the modulus.