scholarly journals Polydopamine-Coated Paraffin Microcapsules as a Multifunctional Filler Enhancing Thermal and Mechanical Performance of a Flexible Epoxy Resin

2020 ◽  
Vol 4 (4) ◽  
pp. 174
Author(s):  
Giulia Fredi ◽  
Cordelia Zimmerer ◽  
Christina Scheffler ◽  
Alessandro Pegoretti
Keyword(s):  
Phase Change ◽  
Storage Modulus ◽  
Mechanical Performance ◽  
Value Added ◽  
Mechanical Analysis ◽  
Scanning Calorimetry ◽  
Management Capability ◽  
Deposition Parameters ◽  
Potential Applications ◽  
Ep Matrix

This work focuses on flexible epoxy (EP) composites containing various amounts of neat and polydopamine (PDA)-coated paraffin microcapsules as a phase change material (PCM), which have potential applications as adhesives or flexible interfaces with thermal management capability for electronics or other high-value-added fields. After PDA modification, the surface of PDA-coated capsules (MC-PDA) becomes rough with a globular appearance, and the PDA layer enhances the adhesion with the surrounding epoxy matrix, as shown by scanning electron microscopy. PDA deposition parameters have been successfully tuned to obtain a PDA layer with a thickness of 53 ± 8 nm, and the total PDA mass in MC-PDA is only 2.2 wt %, considerably lower than previous results. This accounts for the fact that the phase change enthalpy of MC-PDA is only marginally lower than that of neat microcapsules (MC), being 221.1 J/g and 227.7 J/g, respectively. Differential scanning calorimetry shows that the phase change enthalpy of the prepared composites increases with the capsule content (up to 87.8 J/g) and that the enthalpy of the composites containing MC-PDA is comparable to that of the composites with MC. Dynamic mechanical analysis evidences a decreasing step in the storage modulus of all composites at the glass transition of the EP phase, but no additional signals are detected at the PCM melting. PCM addition positively contributes to the storage modulus both at room temperature and above Tg of the EP phase, and this effect is more evident for composites containing MC-PDA. As the capsule content increases, the mechanical properties of the host EP matrix also increase in terms of elastic modulus (up to +195%), tensile strength (up to +42%), Shore D hardness (up to +36%), and creep compliance (down to −54% at 60 min). These effects are more evident for composites containing MC-PDA due to the enhanced interfacial adhesion.

scholarly journals Biocomposites from Rice Straw Nanofibers: Morphology, Thermal and Mechanical Properties

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2138 ◽  
Author(s):  
José Carlos Alcántara ◽  
Israel González ◽  
M. Mercè Pareta ◽  
Fabiola Vilaseca
Keyword(s):  
Rice Straw ◽  
Mechanical Performance ◽  
Cellulose Nanofibers ◽  
Nucleating Agent ◽  
Mechanical Analysis ◽  
Nanocomposite Films ◽  
Chemical Extraction ◽  
Poly Vinyl Alcohol ◽  
Scanning Calorimetry ◽  
The Matrix

Agricultural residues are major potential resources for biomass and for material production. In this work, rice straw residues were used to isolate cellulose nanofibers of different degree of oxidation. Firstly, bleached rice fibers were produced from the rice straw residues following chemical extraction and bleaching processes. Oxidation of rice fibers mediated by radical 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) at pH 10 was then applied to extract rice cellulose nanofibers, with diameters of 3–11 nm from morphological analysis. The strengthening capacity of rice nanofibers was tested by casting nanocomposite films with poly(vinyl alcohol) polymer. The same formulations with eucalyptus nanofibers were produced as comparison. Their thermal and mechanical performance was evaluated using thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. The glass transition of nanocomposites was shifted to higher temperatures with respect to the pure polymer by the addition of rice cellulose nanofibers. Rice nanofibers also acted as a nucleating agent for the polymer matrix. More flexible eucalyptus nanofibers did not show these two phenomena on the matrix. Instead, both types of nanofibers gave similar stiffening (as Young’s modulus) to the matrix reinforced up to 5 wt.%. The ultimate tensile strength of nanocomposite films revealed significant enhancing capacity for rice nanofibers, although this effect was somehow higher for eucalyptus nanofibers.

Novel shape-memory polyurethane fibers for textile applications

2018 ◽  
Vol 89 (6) ◽  
pp. 1027-1037 ◽  
Author(s):  
Míriam Sáenz-Pérez ◽  
Tariq Bashir ◽  
José Manuel Laza ◽  
Jorge García-Barrasa ◽  
José Luis Vilas ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Shape Memory ◽  
Tensile Testing ◽  
Melt Spinning ◽  
Mechanical Analysis ◽  
Knitted Fabric ◽  
Scanning Calorimetry ◽  
Moisture Management ◽  
Potential Applications ◽  
Shape Memory Polyurethane

In this work, thermoresponsive shape-memory polyurethane (SMPU) fibers were produced by melt spinning from different SMPU pellets. Afterwards, the knitted fabric samples were prepared by the obtained fibers. Some of the SMPUs used were synthesized previously in our laboratory whereas a commercial one, named DIAPLEX MM4520, was also evaluated in order to carry out comparative studies. All the SMPUs were characterized by different techniques, such as thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. Moreover, the shape-memory capabilities of the fabrics were measured by thermo-mechanical analysis. The obtained results show that the synthesized SMPUs could be attractive candidates for potential applications such as breathable fabrics or moisture-management textiles.

scholarly journals The Influence of Sub-Zero Conditions on the Mechanical Properties of Polylactide-Based Composites

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5789
Author(s):  
Olga Mysiukiewicz ◽  
Mateusz Barczewski ◽  
Arkadiusz Kloziński
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Mechanical Performance ◽  
Mechanical Analysis ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Linseed Cake ◽  
Static Mechanical

Polylactide-based composites filled with waste fillers due to their sustainability are a subject of many current papers, in which their structural, mechanical, and thermal properties are evaluated. However, few studies focus on their behavior in low temperatures. In this paper, dynamic and quasi-static mechanical properties of polylactide-based composites filled with 10 wt% of linseed cake (a by-product of mechanical oil extraction from linseed) were evaluated at room temperature and at −40 °C by means of dynamic mechanical analysis (DMA), Charpy’s impact strength test and uniaxial tensile test. It was found that the effect of plasticization provided by the oil contained in the filler at room temperature is significantly reduced in sub-zero conditions due to solidification of the oil around −18 °C, as it was shown by differential scanning calorimetry (DSC) and DMA, but the overall mechanical performance of the polylactide-based composites was sufficient to enable their use in low-temperature applications.

Study on Thermal and Mechanical Properties of Natural Rubber Latex Modified by Trichlorobromomethane

2011 ◽  
Vol 295-297 ◽  
pp. 36-40
Author(s):  
Xiao Xue Liao ◽  
Shuang Quan Liao ◽  
Bing Tang ◽  
Ming Chao Luo ◽  
Yan Fang Zhao ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Natural Rubber Latex ◽  
Mechanical Analysis ◽  
Thermal And Mechanical Properties ◽  
Rubber Latex ◽  
Scanning Calorimetry ◽  
And Storage ◽  
Thermal Stability Of

Natural rubber latex (NRL) modified by holgonated addition with trichlorobromomethane was prepared. The thermal properties of modified NRL were analyzed by thermogravimetric analysis (TG/DTG),differential scanning calorimetry (DSC) and dynamic mechanical analysis(DMA). The results showed that the thermal stability of modified NRL was lower than NRL and the thermal degradation of modified NRL was two-stage decomposition. With increasing of stress frequency, loss modulus and storage modulus of latex increased,while loss modulus and storage modulus of modified latex decreased,compared with NRL.

scholarly journals EFFECT OF POLYMER CHAIN MODIFICATIONS ON ELASTOMER PROPERTIES

2019 ◽  
Vol 92 (1) ◽  
pp. 69-89 ◽  
Author(s):  
Katarzyna S. Bandzierz ◽  
Louis A. E. M. Reuvekamp ◽  
Jerzy Dryzek ◽  
Wilma K. Dierkes ◽  
Anke Blume ◽  
...  
Keyword(s):  
Polymer Chain ◽  
Crosslink Density ◽  
Mechanical Performance ◽  
Transition Process ◽  
Mechanical Analysis ◽  
Polymer Chains ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Scanning Calorimetry ◽  
Tetramethylthiuram Disulfide

ABSTRACT Considerable attention is paid to the influence of crosslink density and crosslink structures on the behavior of polymer chains and properties of elastomers. However, a very important parameter seems to be underestimated: the modifications to the polymer chains by curatives, formed by sulfur and fragments of accelerators. We draw attention to this important contribution to performance of spatial networks. The emulsion styrene–butadiene rubber samples, cured with tetramethylthiuram disulfide and sulfur (TMTD/S8) and zinc dialkyl dithiophosphate with sulfur (ZDT/S8), were studied. They were characterized in detail in terms of crosslink density and crosslink structures. Microscale techniques were used to obtain information about the behavior of the polymer chains: positron annihilation lifetime spectroscopy (PALS) to study the free volume structure and differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to monitor the glass transition process. Properties such as static mechanical performance and thermo-oxidative stability were also evaluated. All of the investigated characteristics were influenced by a combination of crosslink density, crosslink structures, and, to a large extent, by the modifications of the polymer chains. The effect of the modifications is dependent on the amount and the structure of the curatives' molecules. On the basis of the obtained results, the usefulness of the “phr” unit used for calculation of the curatives' amount has been queried. Furthermore, it has been demonstrated that DSC, DMA, and PALS techniques can provide evidence for the presence of the modifications on the polymer chain by curatives.

scholarly journals Relationships between the Decomposition Behaviour of Renewable Fibres and Their Reinforcing Effect in Composites Processed at High Temperatures

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4448
Author(s):  
Janez Slapnik ◽  
Thomas Lucyshyn ◽  
Gerald Pinter
Keyword(s):  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Mechanical Analysis ◽  
Fibre Reinforcement ◽  
Reinforcement Effect ◽  
Scanning Calorimetry ◽  
Melt Flow Rate ◽  
Decomposition Behaviour

Engineering polymers reinforced with renewable fibres (RF) are an attractive class of materials, due to their excellent mechanical performance and low environmental impact. However, the successful preparation of such composites has proven to be challenging due to the low thermal stability of RF. The aim of the present study was to investigate how different RF behaves under increased processing temperatures and correlate the thermal properties of the fibres to the mechanical properties of composites. For this purpose, hemp, flax and Lyocell fibres were compounded into polypropylene (PP) using a co-rotating twin screw extruder and test specimens were injection moulded at temperatures ranging from 180 °C to 260 °C, with 20 K steps. The decomposition behaviour of fibres was characterised using non-isothermal and isothermal simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC). The prepared composites were investigated using optical microscopy (OM), colorimetry, tensile test, Charpy impact test, dynamic mechanical analysis (DMA) and melt flow rate (MFR). Composites exhibited a decrease in mechanical performance at processing temperatures above 200 °C, with a steep decrease observed at 240 °C. Lyocell fibres exhibited the best reinforcement effect, especially at elevated processing temperatures, followed by flax and hemp fibres. It was found that the retention of the fibre reinforcement effect at elevated temperatures can be well predicted using isothermal TGA measurements.

Calorimetric and Thermomechanical Properties of Titanium-Based Orthodontic Wires: DSC–DMA Relationship to Predict the Elastic Modulus

2011 ◽  
Vol 26 (7) ◽  
pp. 829-844 ◽  
Author(s):  
Giuliana Laino ◽  
Roberto De Santis ◽  
Antonio Gloria ◽  
Teresa Russo ◽  
David Suárez Quintanilla ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Young’S Modulus ◽  
Mechanical Performance ◽  
Young's Modulus ◽  
Experimental Tests ◽  
Mechanical Analysis ◽  
Thermomechanical Properties ◽  
Scanning Calorimetry ◽  
Orthodontic Wires ◽  
Gum Metal

Orthodontic treatment is strongly dependent on the loads developed by metal wires, and the choice of an orthodontic archwire should be based on its mechanical performance. The desire of both orthodontists and engineers would be to predict the mechanical behavior of archwires. To this aim, Gum Metal (Toyota Central R&L Labs., Inc.), TMA (ORMCO), 35°C Copper NiTi (SDS ORMCO), Thermalloy Plus (Rocky Mountain), Nitinol SE (3M Unitek), and NiTi (SDS ORMCO) were tested according to dynamic mechanical analysis and differential scanning calorimetry. A model was also developed to predict the elastic modulus of superelastic wires. Results from experimental tests have highlighted that superelastic wires are very sensitive to temperature variations occurring in the oral environment, while the proposed model seems to be reliable to predict the Young’s modulus allowing to correlate calorimetric and mechanical data. Furthermore, Gum Metal wire behaves as an elastic material with a very low Young’s modulus, and it can be particularly useful for the initial stage of orthodontic treatments.

scholarly journals Mechanical Properties of Membranes of Poly(L-co-DL-lactic acid) with Poly(caprolactone triol) and StudyIn Vivo

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Marcia Adriana Tomaz Duarte ◽  
Adriana Cristina Motta ◽  
Eliana Aparecida de Rezende Duek
Keyword(s):  
Lactic Acid ◽  
Subcutaneous Tissue ◽  
Mechanical Analysis ◽  
Initial Time ◽  
Scanning Calorimetry ◽  
Time Intervals ◽  
Aliphatic Polyesters ◽  
Potential Applications ◽  
Poly Caprolactone

There is increasing interest in aliphatic polyesters from lactones and lactides because of their biodegradability and biocompatibility. Among these compounds, poly(lactide), and poly(glycolide), poly(ε-caprolactone) and their copolymers are especially interesting because of their potential applications as biomedical materials. The aim of this study was to examine the properties of membranes of poly(L-co-D,L lactic acid) (PLDLA) with poly(caprolactone triol) (PCL-T) obtained by solvent evaporation. The blends were characterized by differential scanning calorimetry, dynamic mechanical analysis, Fourier transform infrared spectroscopy, and tensile strength tests. Based on the results ofin vitrostudies, PLDLA/PCL-T blends of 100/0 and 90/10 were implanted in subcutaneous tissue of Wistar rats for 1, 3, 7, 15, and 60 days to evaluate their biocompatibility. Histological analysis indicated that, although PCL-T-containing membranes caused a more prominent inflammatory reaction in the initial time intervals, by 60 days after implantation, the material was surrounded by dense, organized collagen with almost no inflammatory infiltrate.

scholarly journals Foamed Phase Change Materials Based on Recycled Polyethylene/Paraffin Wax Blends

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1987
Author(s):  
Patrik Sobolčiak ◽  
Miroslav Mrlik ◽  
Anton Popelka ◽  
Antonín Minařík ◽  
Marketa Ilcikova ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Mechanical Stability ◽  
Organic Peroxide ◽  
Mechanical Analysis ◽  
Paraffin Wax ◽  
Micro Computed Tomography ◽  
Scanning Calorimetry ◽  
The Real

Foamed phase-change materials (FPCMs) were prepared using recycled linear low-density polyethylene (LLDPE) blended with 30 wt.% of paraffin wax (PW) and foamed by 1,1′-azobiscarbamide. The protection of pores’ collapse during foaming process was insured through chemical cross-linking by organic peroxide prior foaming. This work represents one of very few attempts for a preparation of polymeric phase change foams without a use of micro-encapsulated phase change component leading to the enhancement of the real PCM component (PW) within a final product. The porous structure of fabricated foams was analyzed using micro-computed tomography, and direct observation, and reconstruction of the internal structure was investigated. The porosity of FPCMs was about 85–87 vol.% and resulting thermal conductivity 0.054–0.086 W/m·K. Differential Scanning Calorimetry was used to determine the specific enthalpies of melting (22.4–25.1 J/g) what is the latent heat of materials utilized during a heat absorption. A stability of samples during 10 heating/cooling cycles was demonstrated. The phase change changes were also investigated using the dynamic mechanical analysis from 0° to 65 °C during the 10 cycles, and the mechanical stability of the system and phase-change transition were clearly confirmed, as proved by DSC. Leaching test revealed a long-term release of PW (around 7% of its original content) from samples which were long term stored at temperatures over PW melting point. This is the usual problem concerning polymer/wax blends. The most common, industrially feasible solution is a lamination of products, for instance by aluminum foils. Finally, the measurement of the heat flow simulating the real conditions shows that samples containing PW decrease the energy passing through the sample from 68.56 to 34.88 kJ·m−2. In this respect, FPCMs provide very effective double functionality, firstly common thermal insulators, and second, as the heat absorbers acting through melting of the PW and absorbing the excessive thermal energy during melting. This improves the heat protection of buildings and reduces temperature fluctuations within indoor spaces.

Increase the Mechanical Performance of Polyvinylidene Fluoride (PVDF)

2011 ◽  
Vol 393-395 ◽  
pp. 144-148 ◽  
Author(s):  
Meng Hou ◽  
Xue Gang Tang ◽  
Jin Zou ◽  
Rowan Truss
Keyword(s):  
Polyvinylidene Fluoride ◽  
Phase Inversion ◽  
Mechanical Performance ◽  
Mechanical Analysis ◽  
Layered Silicates ◽  
Nano Composites ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Phase Inversion Technique ◽  
Fine Tune

Polyvinylidene fluoride (PVDF)/Carbon nanotubes (CNTs) and PVDF/Organo-modified layered silicates (OMLSs) nano-composites were prepared by phase inversion technique. Maleic anhydride grafted PVDF (PVDF-MAH), were used to fine tune the interface. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to characterize the nanocomposites. Elastic modulus and creep resistance of the PVDF nanocomposites were evaluated according to ASTM D-638. The results showed that both CNTs and OMLSs were good candidates to reinforce the PVDF and the addition of PVDF-MAH enhanced the interface between nanoparticles and PVDF, leading to further increase of mechanical property.

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