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Mechanical and Rheological Behaviour of Polymer-Based Systems

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (30 January 2020) | Viewed by 27515

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Prof. Dr. Marco Morreale

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Department of Engineering and Architecture, Kore University of Enna, 94100 Enna, Italy
Interests: green composites and biocomposites; biodegradable polymers; nanocomposites; polymer blends; polymer processing; mechanical behaviour of polymer-based systems; rheological behaviour of polymer-based systems; aging of polymer-based systems
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Prof. Dr. Francesco Paolo La Mantia

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Department of Engineering, University of Palermo, RU INSTM, Viale delle Scienze, 90128 Palermo, Italy
Interests: polymer processing; mechanical behaviour of polymer-based systems; rheological behaviour of polymer-based systems; green composites; biocomposites; nanocomposites; biodegradable polymers; polymer blends; degradation and recycling of polymer-based systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymer-based systems have been expanding their role and increasing in importance in current materials engineering, thanks to their outstanding versatility, which allows one to prepare new materials with tailored properties for the most varied applications. However, the first problems, which need to be overcome when designing new polymer-based products, regard processability. This particularly applies to thermoplastic polymers and can be further complicated by the presence of multiple phases, such as in the case of polymer blends, polymer composites containing fillers in the form of particles or short fibers, etc. Therefore, rheology plays a fundamental role in investigating the processability of new polymer-based systems, and rheological characterization requires more and more advanced techniques and interpretations of the results. This is not limited to thermoplastic systems but can apply also to thermoset resins and related composites (even containing, for instance, long fibers). At the same time, predicting and optimizing the processability of polymer-based systems is one of the fundamental aspects, another one being related to the mechanical properties of the obtained products. Depending on the final application, adequate mechanical properties (Young’s modulus, tensile strength, elongation at break, flexural modulus, impact strength, etc.) may be required. It may be often fundamental to find an optimal balance between several mechanical properties.

This Special Issue intends to assess the state-of-the-art and the recent advances in the field of the mechanical and rheological behaviour of polymer-based systems, focusing on effects related to new formulations, the presence of fillers, etc., as well as on the optimization of characterization techniques and the interpretation of results.

It is our pleasure to invite you to submit a manuscript to this Special Issue on the Mechanical and Rheological Behaviour of Polymer-Based Systems. Full papers, communications, and reviews are all welcome.

Dr. Marco Morreale
Prof. Dr. Francesco Paolo La Mantia
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

rheology
mechanical properties
processing
polymer-based systems

Published Papers (9 papers)

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Research

14 pages, 6741 KiB

Open AccessCommunication

Gas Barrier, Rheological and Mechanical Properties of Immiscible Natural Rubber/Acrylonitrile Butadiene Rubber/Organoclay (NR/NBR/Organoclay) Blend Nanocomposites

by Hanna J. Maria, Martin George Thomas, Marco Morreale, Francesco Paolo La Mantia, Ange Nzihou, Kuruvilla Joseph, Didier Rouxel, Susana C. M. Fernandes, Nandakumar Kalarikkal and Sabu Thomas

Materials 2020, 13(11), 2654; https://doi.org/10.3390/ma13112654 - 10 Jun 2020

Cited by 11 | Viewed by 3004

Abstract

In this paper, gas permeability studies were performed on materials based on natural rubber/acrylonitrile butadiene rubber blends and nanoclay incorporated blend systems. The properties of natural rubber (NR)/nitrile rubber (NBR)/nanoclay nanocomposites, with a particular focus on gas permeability, are presented. The measurements of the barrier properties were assessed using two different gases—O₂ and CO₂—by taking in account the blend composition, the filler loading and the nature of the gas molecules. The obtained data showed that the permeability of gas transport was strongly affected by: (i) the blend composition—it was observed that the increase in acrylonitrile butadiene rubber component considerably decreased the permeability; (ii) the nature of the gas—the permeation of CO₂ was higher than O₂; (iii) the nanoclay loading—it was found that the permeability decreased with the incorporation of nanoclay. The localization of nanoclay in the blend system also played a major role in determining the gas permeability. The permeability of the systems was correlated with blend morphology and dispersion of the nanoclay platelets in the polymer blend. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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17 pages, 3921 KiB

Open AccessArticle

Effect of the Pyro-Gasification Temperature of Wood on the Physical and Mechanical Properties of Biochar-Polymer Biocomposites

by Ramzi Ayadi, Ahmed Koubaa, Flavia Braghiroli, Sébastien Migneault, He Wang and Chedly Bradai

Materials 2020, 13(6), 1327; https://doi.org/10.3390/ma13061327 - 14 Mar 2020

Cited by 20 | Viewed by 2910

Abstract

The physical and mechanical properties of wood (WPC) and biochar polymer composites (BPC) obtained at different pyro-gasification temperatures and different fiber proportions were investigated. Composite pellets made from wood chips or biochar and thermoplastic polymers (polypropylene or high-density polyethylene) were obtained by twin-screw extrusion, and test specimens were prepared by injection molding. Results showed that BPCs were more dimensionally stable compared to WPCs, but their mechanical properties decreased with increasing pyro-gasification temperatures due to the poor adhesion between the polymer and biochar. Indeed, FTIR investigations revealed the decrease or absence of hydroxyl groups on biochar, which prevents the coupling agent from reacting with the biochar surface. The change in the biochar chemical structure led to an improvement in the dimensional stability and hydrophobicity of the biocomposites. Despite the increased dimensional stability of BPCs compared to WPCs, BPCs still adsorb water. This was explained by the surface roughness and by the biochar agglomerations present in the composite. In conclusion, the thermochemical conversion of black spruce wood chips into biochar makes it brittle but more hydrophobic, thereby reducing the wettability of the BPCs. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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14 pages, 2130 KiB

Open AccessArticle

The Effects of Nanoclay on the Mechanical Properties, Carvacrol Release and Degradation of a PLA/PBAT Blend

by Roberto Scaffaro, Andrea Maio, Emmanuel Fortunato Gulino, Marco Morreale and Francesco Paolo La Mantia

Materials 2020, 13(4), 983; https://doi.org/10.3390/ma13040983 - 22 Feb 2020

Cited by 33 | Viewed by 3566

Abstract

The formulation of polymeric films endowed with the abilities of controlled release of antimicrobials and biodegradability is the latest trend of food packaging. Biodegradable polymer (Bio-Flex^®)-based nanocomposites containing carvacrol as an antimicrobial agent, and a nanoclay as a filler, were processed into blown films. The presence of such hybrid loading, while not affecting the overall filmability of the neat matrix, led to enhanced mechanical properties, with relative increments up to +70% and +200% in terms of elastic modulus and elongation at break. FTIR/ATR analysis and release tests pointed out that the presence of nanoclay allowed higher carvacrol loading efficiency, reasonably hindering its volatilization during processing. Furthermore, it also mitigated the burst delivery, thereby enabling a more controlled release of the antimicrobial agent. The results of mass loss tests indicated that all the formulations showed a rather fast degradation with mass losses ranging from 37.5% to 57.5% after 876 h. The presence of clay and carvacrol accelerated the mass loss rate of Bio-Flex^®, especially when added simultaneously, thus indicating an increased biodegradability. Such ternary systems could be, therefore, particularly suitable as green materials for food packaging applications, and for antimicrobial wrapping applications. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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11 pages, 1487 KiB

Open AccessFeature PaperArticle

Structure Evolution of Epoxidized Natural Rubber (ENR) in the Melt State by Time-Resolved Mechanical Spectroscopy

by Rossella Arrigo, Leno Mascia, Jane Clarke and Giulio Malucelli

Materials 2020, 13(4), 946; https://doi.org/10.3390/ma13040946 - 20 Feb 2020

Cited by 6 | Viewed by 2172

Abstract

In this work, time-resolved mechanical spectroscopy (TRMS) was used to accurately characterize the rheological behavior of an epoxidized natural rubber (ENR) containing 25 mol% of epoxy groups. Conventional rheological tests are not suitable to characterize with accuracy the frequency-dependent linear viscoelastic behavior of materials, such as ENR, in a transient configurational state. For this reason, TRMS was used to determine the true rheological behavior of ENR, as well as to gain some insights into the changes of its macromolecular architecture under the dynamic conditions experienced during the measurements. The constructed master curves for the moduli revealed a gradual transition of the ENR rheological state from liquid-like to solid-like through the formation of an “elastic gel” throughout the bulk of the polymer. Furthermore, the evolution of the stress relaxation modulus revealed a slow relaxation mechanism, resulting from thermally activated reactions in the molten state attributed to the formation of crosslinks. Finally, the crosslink density evolution was estimated from the TRMS data and compared with results derived from equilibrium solvent-swelling measurements. These demonstrated the accuracy of the TRMS data in the prediction of the structural changes that can take place in polymers during processing. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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17 pages, 4183 KiB

Open AccessArticle

Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

by Andrea Dorigato, Daniele Rigotti and Alessandro Pegoretti

Materials 2020, 13(4), 819; https://doi.org/10.3390/ma13040819 - 11 Feb 2020

Cited by 12 | Viewed by 2504

Abstract

The aim of this work was the development of a thermoplastic/thermosetting combined system with a novel production technique. A poly(caprolactone) (PCL) structure has been designed and produced by fused filament fabrication, and impregnated with an epoxy matrix. The mechanical properties, fracture toughness, and thermal healing capacities of this blend (EP-PCL(3D)) were compared with those of a conventional melt mixed poly(caprolactone)/epoxy blend (EP-PCL). The fine dispersion of the PCL domains within the epoxy in the EP-PCL samples was responsible of a noticeable toughening effect, while in the EP-PCL(3D) structure the two phases showed an independent behavior, and fracture propagation in the epoxy was followed by the progressive yielding of the PCL domains. This peculiar behavior of EP-PCL(3D) system allowed the PCL phase to express its full potential as energy absorber under impact conditions. Optical microscope images on the fracture surfaces of the EP-PCL(3D) samples revealed that during fracture toughness tests the crack mainly propagated within the epoxy phase, while PCL contributed to energy absorption through plastic deformation. Due to the selected PCL concentration in the blends (35 vol %) and to the discrepancy between the mechanical properties of the constituents, the healing efficiency values of the two systems were rather limited. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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15 pages, 2507 KiB

Open AccessArticle

Evaluation of the Mechanical, Thermal and Rheological Properties of Recycled Polyolefins Rice-hull Composites

by Berlinda O. Orji and Armando G. McDonald

Materials 2020, 13(3), 667; https://doi.org/10.3390/ma13030667 - 03 Feb 2020

Cited by 15 | Viewed by 3130

Abstract

Understanding the properties and flow characteristics of recycled polyolefins in rice hull composite blends is of importance to facilitate process optimization whilst promoting sustainability. The influence of milled rice hull particle size (<0.5 mm and <1 mm) on properties of recycled polyolefins composites was studied with major focus on recycled high-density polyethylene (rHDPE) and polypropylene (rPP) together with added maleated polymer coupling agents. Composites were compounded/extruded using a twin-screw extruder and the thermal, mechanical, and physical properties were analyzed as well as their melt flow, dynamic. and capillary rheology tests. The incorporation of the <0.5 mm rice-hulls particles enhanced the composite properties of viscosity, flexural strength, moduli, water absorption, and thermal stability for both polyolefins with rHDPE composites showing more reliable properties as compared to rPP. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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15 pages, 2717 KiB

Open AccessArticle

A Study of the Synergistic Interaction of Konjac Glucomannan/Curdlan Blend Systems under Alkaline Conditions

by Weijian Ye, Bowen Yan, Jie Pang, Daming Fan, Jianlian Huang, Wenguo Zhou, Xueqian Cheng, Hui Chen and Hao Zhang

Materials 2019, 12(21), 3543; https://doi.org/10.3390/ma12213543 - 29 Oct 2019

Cited by 12 | Viewed by 3086

Abstract

To improve the gelation performance of konjac glucomannan (KGM) thermo-irreversible gel in the condition of alkaline, this study investigated the interactions between KGM and curdlan (CUD) in terms of the sol state and gelation process. The apparent viscosity, rheological properties during heating and cooling, thermodynamic properties, gelation properties and water holding capacity of KGM/CUD blend systems in an alkaline environment were studied using physical property testing instruments and methods. The results showed that the viscosity of the KGM/CUD blended solution was greater than the value calculated from the ideal mixing rules in the condition of alkaline (pH = 10.58). As the proportion of CUD in the system increased, the intersection of storage modulus (G’) and loss modulus (G”) shifted to low frequencies, the relaxation time gradually increased, and the degree of entanglement of molecular chains between these two components gradually increased. The addition of CUD helped decrease the gelation temperature of KGM, increased the gelation rate and inhibited the thinning phenomenon of KGM gels at low temperatures (2–20 °C). The addition of CUD increased the hardness and gel strength of KGM but did not significantly improve the water holding capacity of the KGM/CUD blend gel. The process of mixing KGM and CUD improved the thermal stability of the gel. In summary, KGM/CUD exhibited excellent compatibility under alkaline conditions, and the blend systems produced a “viscosifying effect”. KC8 and KC5 show better thermal stability, low temperature resistance and gel strength compared to KGM. This blended gel can be used as a structural support material to provide reference for the development of konjac bionic vegetarian products. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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16 pages, 5538 KiB

Open AccessArticle

Evaluate the Fatigue Life of CFRC Subjected to Coupled Thermo–Mechanical Loading

by Junjie Ye, Wangpeng He, Yang Shi, Yiwei Wang, Gaigai Cai, Zhi Zhai and Xuefeng Chen

Materials 2019, 12(18), 2886; https://doi.org/10.3390/ma12182886 - 06 Sep 2019

Cited by 2 | Viewed by 2259

Abstract

Mechanical properties of composites manufactured by high-temperature polymer polyether ether ketone (PEEK) with continuous reinforced fibers are closely dependent on ambient temperature variations. In order to effectively study fatigue failure behaviors of composites under the coupled thermo–mechanical loading, a well-established microscopic model based on a representative volume element (RVE) is proposed in this paper. Stiffness degradation behaviors of the composite laminates at room and elevated temperatures are firstly investigated, and their failure strengths are compared with experimental data. To describe the fatigue behaviors of composites with respect to complex external loading and ambient temperature variations, a new fatigue equation is proposed. A good consistency between theoretical results and experimental data was found in the cases. On this basis, the temperature cycling effects on the service life of composites are also discussed. Microscopic stress distributions of the RVE are also discussed to reveal their fatigue failure mechanisms. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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22 pages, 6662 KiB

Open AccessArticle

A Study on Exfoliation of Expanded Graphite Stacks in Candelilla Wax

by Francesca Lionetto, Roberto López-Muñoz, Carlos Espinoza-González, Ricardo Mis-Fernández, Oliverio Rodríguez-Fernández and Alfonso Maffezzoli

Materials 2019, 12(16), 2530; https://doi.org/10.3390/ma12162530 - 08 Aug 2019

Cited by 18 | Viewed by 3895

Abstract

A novel, green route for pre-exfoliation of graphite based on a biodegradable polymer and high-power ultrasound is presented. Candelilla wax (CW), derived from the leaves of the candelilla plant, has been used for the first time as a natural non aqueous medium to induce the pre-exfoliation of expanded graphite (EG) under ultrasonic irradiation in an economical way. The proposed method uses also D-limonene as a natural organic solvent for reducing viscosity and increasing the affinity between the polar groups of EG and candelilla wax, thus improving the intercalation/exfoliation of EG. The quality of dispersion of the nanofiller in the natural wax matrix has been evaluated using multiple techniques. The addition of EG to wax and use of ultrasonic treatment leads to a reduced crystallinity, probably due to restrictions of the molecular movements, improved thermal stability of wax, and to an increased shear thinning exponent, which are all indicative of a high degree of EG dispersion. The ultrasonic dynamic mechanical results suggest a reduction in the cluster size and a better filler dispersion in the wax matrix promoted by polar or chemical reactions between the CW fractions and the graphite stacks, which was observed by XPS analysis. The results were compared to those obtained with paraffin, a synthetic wax, and confirmed the dispersion improvement obtained by using natural wax as a pre-exfoliating medium. Full article

(This article belongs to the Special Issue Mechanical and Rheological Behaviour of Polymer-Based Systems)

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