Special Issue "Cellular Polymeric Materials"

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (31 May 2020).

Special Issue Editor

Dr. Uģis Cābulis
Website
Guest Editor
Laboratory of Polymers, Latvian State Institute Wood Chemistry, Riga, Latvia
Interests: polyurethane foams from renewable materials; cryogenic insulation
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Cellular materials are used today in a wide variety of everyday situations and industries. They help not only to save weight without losing any mechanical properties, but they also play an irreplaceable role in saving heat. Various polymers can be formed, obtaining completely new materials with different characteristics and uses compared to the original monolith. Today’s traditionally produced synthetic polymers are being increasingly replaced by polymers derived from renewable feedstock, which do not lag behind or even overcome previous generation polymers. The procurement of cellular materials is a complex physico-chemical process, where the hardening of polymers, gas expansion, cell formation, etc., should be balanced. In addition, there is a wide variety of technologies available for the production of foams, which can often complement each other.

The purpose of this Special Issue is to bring together polymer scientists working with cellular materials, to gather up-to-date research and innovations in the field, to reflect the current situation, not only in scientist laboratories, but also to update the requirements and settings of the industry. Authors are welcome to submit their latest results in the form of original full articles, communications, or reviews on this broad topic.

Dr. Uģis Cābulis
Guest Editor

Keywords

  • Cellular materials
  • Lightweight materials
  • Thermal and cryogenic insulation
  • Foaming process
  • Cell structure
  • Renewable resources
  • Life cycle and biodegradability.

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Published Papers (4 papers)

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Research

Open AccessArticle
A Sacrificial Route for Soft Porous Polymers Synthesized via Frontal Photo-Polymerization
Polymers 2020, 12(5), 1008; https://doi.org/10.3390/polym12051008 - 27 Apr 2020
Abstract
Within the very large range of porous polymers and a related immense scope of applications, we investigate here a specific route to design soft porous polymers with controlled porosity: we use aqueous-based formulations of oligomers with mineral particles which are solidified into [...] Read more.
Within the very large range of porous polymers and a related immense scope of applications, we investigate here a specific route to design soft porous polymers with controlled porosity: we use aqueous-based formulations of oligomers with mineral particles which are solidified into a hydrogel upon photo-polymerization; the embedded particles are then chemically etched and the hydrogel is dried to end up with a soft porous polymeric scaffold with micron-scale porosity. Morphological and physical features of the porous polymers are measured and we demonstrate that the porosity of the final material is primarily determined by the amount of initially dispersed sacrificial particles. In addition, the liquid formulations we use to start with are convenient for a variety of material forming techniques such as microfluidics, embossing, etc., which lead to many different morphologies (monoliths, spherical particles, patterned substrates) based on the same initial material. Full article
(This article belongs to the Special Issue Cellular Polymeric Materials)
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Open AccessArticle
Rigid Polyurethane Foams with Various Isocyanate Indices Based on Polyols from Rapeseed Oil and Waste PET
Polymers 2020, 12(4), 738; https://doi.org/10.3390/polym12040738 - 26 Mar 2020
Cited by 3
Abstract
Developing polyols derived from natural sources and recycling materials attracts great interest for use in replacing petroleum-based polyols in polyurethane production. In this study, rigid polyurethane (PUR) foams with various isocyanate indices were obtained from polyols based on rapeseed oil and polyethylene terephthalate [...] Read more.
Developing polyols derived from natural sources and recycling materials attracts great interest for use in replacing petroleum-based polyols in polyurethane production. In this study, rigid polyurethane (PUR) foams with various isocyanate indices were obtained from polyols based on rapeseed oil and polyethylene terephthalate (RO/PET). The various properties of the prepared PUR foams were investigated, and the effect of the isocyanate index was evaluated. The closed-cell content and water absorption were not impacted by the change of the isocyanate index. The most significant effect of increasing the isocyanate index was on the dimensional stability of the resulting foams. This is due to the increased crosslink density, as evidenced by the increased formation of isocyanurate and increase of the glass transition temperature. Additionally, the influence on compression strength, modulus, and long-term thermal conductivity were evaluated and compared with reference PUR foams from commercially available polyols. Rigid PUR foams from RO/PET polyol were found to be competitive with reference materials and could be used as thermal insulation material. Full article
(This article belongs to the Special Issue Cellular Polymeric Materials)
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Open AccessArticle
Anisotropy in Polyurethane Pre-Insulated Pipes
Polymers 2019, 11(12), 2074; https://doi.org/10.3390/polym11122074 - 12 Dec 2019
Cited by 1
Abstract
The polyurethane foam in district heating pre-insulated pipes has a critical role to play both as thermal insulation and as load bearing element, as it serves as bond between the medium pipe and the casing. Hence, knowledge on how the foam behaves under [...] Read more.
The polyurethane foam in district heating pre-insulated pipes has a critical role to play both as thermal insulation and as load bearing element, as it serves as bond between the medium pipe and the casing. Hence, knowledge on how the foam behaves under multiaxial stresses is of great importance for the design as well as for aging predictions of the network. It is known that cell shape anisotropy in polymeric foams leads to anisotropy in its mechanical properties. In this study, we evaluate and quantify the microstructural anisotropy of PU foam from pre-insulated pipes as well as its mechanical behaviour under compression in the three orthogonal directions. We cover rigid and flexible PU foam, batch and continuous manufacturing, and different pipe diameters. The results were compared with those predicted by available rectangular and Kelvin cell shape models. We have found that PU from pre-insulated pipes is orthotropic and present stronger anisotropy than that typically found in PU slabs. The traditional bonded pipes under consideration behaved in a similar way. However, when comparing the two flexible pipes in this study, despite no significant differences in cell shape anisotropy were found, a significantly different behaviour for the E modulus ratio was observed. This shows that while the manufacturing process exerts the main influence on cell shape anisotropy, to explain the difference in stiffness behaviour other factors need to be taken into consideration, such as cell size and cell size variability. Full article
(This article belongs to the Special Issue Cellular Polymeric Materials)
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Open AccessArticle
Open-Cell Rigid Polyurethane Foams from Peanut Shell-Derived Polyols Prepared under Different Post-Processing Conditions
Polymers 2019, 11(9), 1392; https://doi.org/10.3390/polym11091392 - 23 Aug 2019
Cited by 6
Abstract
Bio-based polyurethane materials with abundant open-cells have wide applications because of their biodegradability for addressing the issue of environmental conservation. In this work, open-cell rigid polyurethane foams (RPUFs) were prepared with bio-based polyols (BBPs) derived from the liquefaction of peanut shells under different [...] Read more.
Bio-based polyurethane materials with abundant open-cells have wide applications because of their biodegradability for addressing the issue of environmental conservation. In this work, open-cell rigid polyurethane foams (RPUFs) were prepared with bio-based polyols (BBPs) derived from the liquefaction of peanut shells under different post-processing conditions. The influences of the neutralization procedure and filtering operation for BBPs on the foaming behaviors, density, dimensional stability, water absorption, swelling ratio, compressive strength, and microstructure of RPUFs were investigated intensively. The results revealed that a small amount of sulfuric acid in the polyols exhibited a great impact on physical and chemical properties of RPUFs while the filtering operation for those polyols had a slight effect on the above properties. The RPUFs prepared from neutralized BBPs possessed higher water absorption, preferable dimensional stability and compression strength than that fabricated from the non-neutralized BBPs. Moreover, the prepared RPUFs exhibited preferable water absorption of 636–777%, dimensional stability of <0.5%, compressive strength of >200 KPa, lower swelling rate of ca. 1%, as well as uniform cell structure with superior open-cell rate, implying potential applications in floral foam. Full article
(This article belongs to the Special Issue Cellular Polymeric Materials)
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