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Special Issue "New Trends in Polymeric Foams"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 15 December 2018

Special Issue Editors

Guest Editor
Prof. Miguel Angel Rodríguez-Pérez

Cellular Materials Laboratory (CellMat Laboratory), Condensed Matter Physics Department, University of Valladolid, 47011 Valladolid, Spain
Website | E-Mail
Interests: cellular polymers; nanocellular polymers; cellular nanocomposites; biocellular polymers; polyurethane foams
Guest Editor
Dr. Ester Laguna-Gutierrez

Cellular Materials Laboratory (CellMat Laboratory), Condensed Matter Physics Department, University of Valladolid, Valladolid, Spain
Website | E-Mail
Interests: rheology; nanocellular polymers; nanocomposite foams; foaming mechanisms

Special Issue Information

Dear Colleagues,

The journal “Materials” is preparing a Special Issue titled “New Trends in Polymeric Foams”. In this Special Issue, recent research on advanced polymeric foams is considered.

Polymeric foams—also known as cellular polymers—are materials of great interest that can be found everywhere in our present world. Their particular structure gives them unique properties that allow a broadening of the range of properties of their solid counterparts. The applications of these foamed materials are thus very extensive. They are of special interest in sectors like construction, automotive, aeronautics, packaging and protection, biotechnology, energy management, etc. Currently, more than 10% of the polymers produced around the world are used to produce polymeric foams.

The needs of today’s society, in which both reducing the energy consumption and the amount of raw materials and using environmentally-friendly technologies are a must, make necessary the development of advanced foaming technologies and cellular materials with improved properties. In this way, current polymer foams could be substituted by materials with improved performance, the applications of traditional foamed polymers could be extended, and finally, solid plastics could be replaced by foamed ones.

In the last few years, special importance has been given to reducing the cell size up to the nanometre range, giving rise to nanocellular polymers, to understand the complex mechanisms underlying the formation of cellular materials, to develop improved foaming technologies, and to obtain improved properties by tuning the formulations used to produce these materials.

Research on nanocellular polymers has increased significantly due to their potential properties. These novel materials could have better mechanical properties than conventional foams, thermal conductivities well below those presented by current insulation materials, they can be transparent, and they have enhanced dielectric properties. As a consequence, the door is opened to a significant number of new applications, such as super thermal insulation, filtering, sensing, catalysis, etc.

On the other hand, understanding the mechanisms taking place during the foaming process is a factor of major importance in establishing a relationship between cellular structure, properties, and applications. The use of conventional and non-conventional experimental techniques to analyse the foamability of different complex polymeric formulations can be helpful to design new materials with advanced properties. Thermal and rheological techniques, visualization techniques to evaluate nucleation and growth during injection moulding, in-situ rheological measurements during extrusion, X-ray radioscopy and tomography, among others, are examples of these non-conventional techniques.

In addition, the development and/or the improvement of the technologies to produce cellular polymers and the development of improved formulations are hot topics in the field, being in many cases the results of this research of direct application in the industry.

This Special Issue considers recent research on advanced polymeric foams. Of special interest are the research topics focused on developing new formulations and technologies to produce improved cellular materials, as well as those related to the analysis of the foaming mechanisms by using different conventional and non-conventional experimental techniques.

Research in these particular fields is required which considers the needs of today’s society, including the reduction of energy consumption and the amount of raw materials as well as the development of environmentally-friendly technologies.

It is our pleasure to invite you to submit a manuscript for this Special Issue.

Prof. Miguel Angel Rodríguez-Pérez
Dr. Ester Laguna-Gutierrez
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 papers will be 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 monthly 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 1600 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

  • Nanocellular foams
  • Foaming mechanisms
  • Structure–properties relationship
  • Advanced polymeric foams

Published Papers (5 papers)

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Research

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Open AccessArticle Hollow Fiber Porous Nanocomposite Membranes Produced via Continuous Extrusion: Morphology and Gas Transport Properties
Materials 2018, 11(11), 2311; https://doi.org/10.3390/ma11112311 (registering DOI)
Received: 25 October 2018 / Revised: 14 November 2018 / Accepted: 15 November 2018 / Published: 17 November 2018
PDF Full-text (2945 KB)
Abstract
In this work, hollow fiber porous nanocomposite membranes were successfully prepared by the incorporation of a porous nanoparticle (zeolite 5A) into a blend of linear low-density polyethylene (LLDPE)/low-density polyethylene (LDPE) combined with azodicarbonamide as a chemical blowing agent (CBA). Processing was performed via
[...] Read more.
In this work, hollow fiber porous nanocomposite membranes were successfully prepared by the incorporation of a porous nanoparticle (zeolite 5A) into a blend of linear low-density polyethylene (LLDPE)/low-density polyethylene (LDPE) combined with azodicarbonamide as a chemical blowing agent (CBA). Processing was performed via continuous extrusion using a twin-screw extruder coupled with a calendaring system. The process was firstly optimized in terms of extrusion and post-extrusion conditions, as well as formulation to obtain a good cellular structure (uniform cell size distribution and high cell density). Scanning electron microscopy (SEM) was used to determine the cellular structure as well as nanoparticle dispersion. Then, the samples were characterized in terms of mechanical and thermal stability via tensile tests and thermogravimetric analysis (TGA), as well as differential scanning calorimetry (DSC). The results showed that the zeolite nanoparticles were able to act as effective nucleating agents during the foaming process. However, the optimum nanoparticle content was strongly related to the foaming conditions. Finally, the membrane separation performances were investigated for different gases (CO2, CH4, N2, O2, and H2) showing that the incorporation of porous zeolite significantly improved the gas transport properties of semi-crystalline polyolefin membranes due to lower cell wall thickness (controlling permeability) and improved separation properties (controlling selectivity). These results show that mixed matrix membranes (MMMs) can be cost-effective, easy to process, and efficient in terms of processing rate, especially for the petroleum industry where H2/CH4 and H2/N2 separation/purification are important for hydrogen recovery. Full article
(This article belongs to the Special Issue New Trends in Polymeric Foams)
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Open AccessArticle Multifunctional, Polyurethane-Based Foam Composites Reinforced by a Fabric Structure: Preparation, Mechanical, Acoustic, and EMI Shielding Properties
Materials 2018, 11(11), 2085; https://doi.org/10.3390/ma11112085
Received: 11 September 2018 / Revised: 20 October 2018 / Accepted: 22 October 2018 / Published: 25 October 2018
PDF Full-text (3972 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes multifunctional, fabric-reinforced composites (MFRCs) based on a bionic design, which are prepared by two-step foaming and a combination of different fabric constructs. MFRCs are evaluated in terms of sound absorption, compression resistance, electromagnetic interference shielding effectiveness (EMI SE), and drop
[...] Read more.
This study proposes multifunctional, fabric-reinforced composites (MFRCs) based on a bionic design, which are prepared by two-step foaming and a combination of different fabric constructs. MFRCs are evaluated in terms of sound absorption, compression resistance, electromagnetic interference shielding effectiveness (EMI SE), and drop impact, thereby examining the effects of fabric structures. The test results indicate that the enhanced composites have superiority functions when combined with carbon fabric in the upper layer and spacer fabric in the lower layer. They have maximum compression resistance, which is 116.9 kPa at a strain of 60%, and their compression strength is increased by 135.9% compared with the control specimen. As a result of the fabric structure on the cell morphology, the maximum resonance peak shifts toward high frequency when using spacer fabric as the intermediate layer. The average sound absorption coefficient is above 0.7 at 1000–4000 Hz. The reinforced composites possessed EMI SE of 50 dB at 2 GHz; an attenuation rate of 99.999% was obtained, suggesting a good practical application value. Furthermore, the cushioning effect of the MFRCs improved significantly, and the maximum dynamic contact force during the impact process was reduced by 57.28% compared with composites without any fabric structure. The resulting MFRCs are expected to be used as sound absorbent security walls, machinery equipment, and packaging for commercial EMI shielding applications in the future. Full article
(This article belongs to the Special Issue New Trends in Polymeric Foams)
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Open AccessArticle Thermal Energy Storage and Mechanical Performance of Crude Glycerol Polyurethane Composite Foams Containing Phase Change Materials and Expandable Graphite
Materials 2018, 11(10), 1896; https://doi.org/10.3390/ma11101896
Received: 1 August 2018 / Revised: 22 September 2018 / Accepted: 27 September 2018 / Published: 4 October 2018
PDF Full-text (4137 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The aim of this study was to enhance the thermal comfort properties of crude glycerol (CG) derived polyurethane foams (PUFs) using phase change materials (PCMs) (2.5–10.0% (wt/wt)) to contribute to the reduction of the use of non-renewable resources and increase energy
[...] Read more.
The aim of this study was to enhance the thermal comfort properties of crude glycerol (CG) derived polyurethane foams (PUFs) using phase change materials (PCMs) (2.5–10.0% (wt/wt)) to contribute to the reduction of the use of non-renewable resources and increase energy savings. The main challenge when adding PCM to PUFs is to combine the low conductivity of PUFs whilst taking advantage of the heat released/absorbed by PCMs to achieve efficient thermal regulation. The solution considered to overcome this limitation was to use expandable graphite (EG) (0.50–1.50% (wt/wt)). The results obtained show that the use of PCMs increased the heterogeneity of the foams cellular structure and that the incorporation of PCMs and EG increased the stiffness of the ensuing composite PUFs acting as filler-reinforcing materials. However, these fillers also caused a substantial increase of the thermal conductivity and density of the ensuing foams which limited their thermal energy storage. Therefore, numerical simulations were carried using a single layer panel and the thermal and physical properties measured to evaluate the behavior of a composite PUF panel with different compositions, and guide future formulations to attain more effective results in respect to temperature buffering and temperature peak delay. Full article
(This article belongs to the Special Issue New Trends in Polymeric Foams)
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Open AccessArticle Thermoelectric Nanocomposite Foams Using Non-Conducting Polymers with Hybrid 1D and 2D Nanofillers
Materials 2018, 11(9), 1757; https://doi.org/10.3390/ma11091757
Received: 23 August 2018 / Revised: 7 September 2018 / Accepted: 11 September 2018 / Published: 18 September 2018
PDF Full-text (2525 KB) | HTML Full-text | XML Full-text
Abstract
A facile processing strategy to fabricate thermoelectric (TE) polymer nanocomposite foams with non-conducting polymers is reported in this study. Multilayered networks of graphene nanoplatelets (GnPs) and multi-walled carbon nanotubes (MWCNTs) are deposited on macroporous polyvinylidene fluoride (PVDF) foam templates using a layer-by-layer (LBL)
[...] Read more.
A facile processing strategy to fabricate thermoelectric (TE) polymer nanocomposite foams with non-conducting polymers is reported in this study. Multilayered networks of graphene nanoplatelets (GnPs) and multi-walled carbon nanotubes (MWCNTs) are deposited on macroporous polyvinylidene fluoride (PVDF) foam templates using a layer-by-layer (LBL) assembly technique. The open cellular structures of foam templates provide a platform to form segregated 3D networks consisting of one-dimensional (1D) and/or two-dimensional (2D) carbon nanoparticles. Hybrid nanostructures of GnP and MWCNT networks synergistically enhance the material system’s electrical conductivity. Furthermore, the polymer foam substrates possess high porosity to provide ultra-low thermal conductivity without compromising the electrical conductivity of the TE nanocomposites. With an extremely low GnP loading (i.e., ~1.5 vol.%), the macroporous PVDF nanocomposites exhibit a thermoelectric figure-of-merit of ~10−3. To the best of our knowledge, this ZT value is the highest value reported for organic TE materials using non-conducting polymers and MWCNT/GnP nanofillers. The proposed technique represents an industrially viable approach to fabricate organic TE materials with enhanced energy conversion efficiencies. The current study demonstrates the potential to develop light-weight, low-cost, and flexible TE materials for green energy generation. Full article
(This article belongs to the Special Issue New Trends in Polymeric Foams)
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Review

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Open AccessReview Polyurethane Foams: Past, Present, and Future
Materials 2018, 11(10), 1841; https://doi.org/10.3390/ma11101841
Received: 12 August 2018 / Revised: 19 September 2018 / Accepted: 23 September 2018 / Published: 27 September 2018
Cited by 1 | PDF Full-text (2215 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and thermal conductivity combined with their interesting mechanical properties make them
[...] Read more.
Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and thermal conductivity combined with their interesting mechanical properties make them excellent thermal and sound insulators, as well as structural and comfort materials. Despite the broad range of applications, the production of PUFs is still highly petroleum-dependent, so this industry must adapt to ever more strict regulations and rigorous consumers. In that sense, the well-established raw materials and process technologies can face a turning point in the near future, due to the need of using renewable raw materials and new process technologies, such as three-dimensional (3D) printing. In this work, the fundamental aspects of the production of PUFs are reviewed, the new challenges that the PUFs industry are expected to confront regarding process methodologies in the near future are outlined, and some alternatives are also presented. Then, the strategies for the improvement of PUFs sustainability, including recycling, and the enhancement of their properties are discussed. Full article
(This article belongs to the Special Issue New Trends in Polymeric Foams)
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