Green Polymer Materials for Circular Economy and Sustainable Development

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15 pages, 4680 KiB

Open AccessArticle

Recyclable Thermoplastic Elastomer from Furan Functionalized Hairy Nanoparticles with Polystyrene Core and Polydimethylsiloxane Hairs

by Md Hanif Uddin, Sultan Alshali, Esam Alqurashi, Saber Alyoubi, Natalia Walters and Ishrat M. Khan

Polymers 2024, 16(22), 3117; https://doi.org/10.3390/polym16223117 - 7 Nov 2024

Viewed by 533

Abstract

Polymers synthesized with end-of-life consideration allow for recovery and reprocessing. “Living-anionic polymerization (LAP)” and hydrosilylation reaction were utilized to synthesize hair-end furan functionalized hairy nanoparticles (HNPs) with a hard polystyrene (PS) core and soft polydimethylsiloxane (PDMS) hairs via a one-pot approach. The synthesis was carried out by first preparing the living core through crosslinking styrene with divinylbenzene using sec-butyl lithium, followed by the addition of the hexamethylcyclotrisiloxane (D3) monomer to the living core. The living polymer was terminated by dimethylchlorosilane to obtain the HNPs with Si-H functional end groups. The furan functionalization was carried out by the hydrosilylation reaction between the Si-H of the functionalized HNP and 2-vinyl furan. Additionally, furan functionalized polystyrene (PS) and polydimethylsiloxane (PDMS) were also synthesized by LAP. ¹H NMR and ATR-IR spectra confirmed the successful synthesis of the target polymers. Differential scanning calorimetry showed two glass transition temperatures indicative of a polydimethylsiloxane soft phase and a polystyrene hard phase, suggesting that the HNPs are microphase separated. The furan functionalized HNPs form thermo-reversible networks upon crosslinking with bismaleimide (BMI) via a Diels−Alder coupling reaction. The kinetics of the forward Diels–Alder reaction between the functionalized polymer and BMI were studied at three different temperatures: 50 °C, 60 °C, and 70 °C by UV–Vis spectroscopy. The activation energy for the furan functionalized HNPs reaction with the bismaleimide was lower compared to the furan functionalized polystyrene and polydimethylsiloxane linear polymers. The crosslinked polymer network formed from the Diels−Alder forward reaction dissociates at around 140–154 °C, and the HNPs are recovered. The recovered HNPs can be re-crosslinked at 50 °C. The results suggest that furan functionalized HNPs are promising building blocks for preparing thermo-reversible elastomeric networks. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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15 pages, 4729 KiB

Open AccessArticle

Differentiation between Hydrolytic and Thermo-Oxidative Degradation of Poly(lactic acid) and Poly(lactic acid)/Starch Composites in Warm and Humid Environments

by Victoria Goetjes, Jan-Christoph Zarges and Hans-Peter Heim

Materials 2024, 17(15), 3683; https://doi.org/10.3390/ma17153683 - 25 Jul 2024

Viewed by 1285

Abstract

For the application of poly(lactic acid) (PLA) and PLA/starch composites in technical components such as toys, it is essential to know their degradation behavior under relevant application conditions in a hydrothermal environment. For this purpose, composites made from PLA and native potato starch were produced using twin-screw extruders and then processed into test specimens, which were then subjected to various one-week ageing processes with varying temperatures (23, 50, 70, 90 °C) and humidity levels (10, 50, 75, 90%). This was followed by mechanical characterization (tensile test) and identification of degradation using Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance spectroscopy (NMR). With increasing temperature and humidity, there was a clear degradation of the PLA, which could be reduced or slowed down by adding 50 wt.% starch, due to increased crystallinity. Hydrolysis was identified as the main degradation mechanism for PLA and PLA/starch composites, especially above the glass transition temperature, with thermo-oxidative degradation also playing a subordinate role. Both hydrolytic degradation and thermo-oxidative degradation led to a reduction in mechanical properties such as tensile strength. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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33 pages, 7786 KiB

Open AccessReview

Recent Advances in Environment-Friendly Polyurethanes from Polyols Recovered from the Recycling and Renewable Resources: A Review

by Mengyuan Pu, Changqing Fang, Xing Zhou, Dong Wang, Yangyang Lin, Wanqing Lei and Lu Li

Polymers 2024, 16(13), 1889; https://doi.org/10.3390/polym16131889 - 2 Jul 2024

Cited by 1 | Viewed by 3464

Abstract

Polyurethane (PU) is among the most universal polymers and has been extensively applied in many fields, such as construction, machinery, furniture, clothing, textile, packaging and biomedicine. Traditionally, as the main starting materials for PU, polyols deeply depend on petroleum stock. From the perspective of recycling and environmental friendliness, advanced PU synthesis, using diversified resources as feedstocks, aims to develop versatile products with excellent properties to achieve the transformation from a fossil fuel-driven energy economy to renewable and sustainable ones. This review focuses on the recent development in the synthesis and modification of PU by extracting value-added monomers for polyols from waste polymers and natural bio-based polymers, such as the recycled waste polymers: polyethylene terephthalate (PET), PU and polycarbonate (PC); the biomaterials: vegetable oil, lignin, cashew nut shell liquid and plant straw; and biomacromolecules: polysaccharides and protein. To design these advanced polyurethane formulations, it is essential to understand the structure–property relationships of PU from recycling polyols. In a word, this bottom-up path provides a material recycling approach to PU design for printing and packaging, as well as biomedical, building and wearable electronics applications. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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17 pages, 4608 KiB

Open AccessArticle

Comparative Analysis of the Effects of Incorporating Post-Industrial Recycled LLDPE and Post-Consumer PE in Films: Macrostructural and Microstructural Perspectives in the Packaging Industry

by Ricardo Ballestar de las Heras, Xavier Colom and Javier Cañavate

Polymers 2024, 16(7), 916; https://doi.org/10.3390/polym16070916 - 27 Mar 2024

Cited by 1 | Viewed by 1529

Abstract

In accordance with the Circular Economy Package of the European directive, the Spanish government compels manufacturers of plastic bags to include into their products a minimum of 70% of polyethylene (PE) waste. Following this mandate can be challenging and requires a deep knowledge of the alterations produced by the recycling in the main components of a plastic bag film: lineal low-density polyethylene (LLDPE), the LLDPE recycled post-industry, generated as waste from an industrial process (rLLDPE) and the PE recycled from post-consumer use (rPE), that has been picked up, cleaned, and reprocessed. This study provides insight in the macro and microstructural changes produced by several cycles of recycling in these materials. Specimens in the form of film for supermarket bags formed with these polymers have been subjected to several recycling sequences. The process closely mimics industrial processes. Four cycles have been applied to the samples. The evolution of mechanical properties, including tensile strength, elongation at break, and tear and impact tests, shows an obvious decrease due to degradation that is not an impediment for practical use after the four cycles of recycling according to the main specifications defined by the producer. Colorimetric measurements reveal no significant variations in the color of the films. The results of the FTIR and TGA analysis show degradation phenomena and changes in crystallinity in branching and the apparition of crosslinking that are in consonance with the mechanical data. There is also a difference between both types of recycled PE. In general, rLLDPE is more affected by the recycling than rPE. According to our findings, the limiting property would be the tearing. By comparing these values with bags available in the market, manufactured from 70–80% recycled material, we can infer that while two reprocessing cycles can lead to good results, a maximum of four cycles of recycling is advisable. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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20 pages, 3724 KiB

Open AccessArticle

Ductile Copolyesters Prepared Using Succinic Acid, 1,4-Butanediol, and Bis(2-hydroxyethyl) Terephthalate with Minimizing Generation of Tetrahydrofuran

by Sang Uk Park, Hyeon Jeong Seo, Yeong Hyun Seo, Ju Yong Park, Hyunjin Kim, Woo Yeon Cho, Pyung Cheon Lee and Bun Yeoul Lee

Polymers 2024, 16(4), 519; https://doi.org/10.3390/polym16040519 - 14 Feb 2024

Viewed by 1558

Abstract

Poly(1,4-butylene succinate) (PBS) is a promising sustainable and biodegradable synthetic polyester. In this study, we synthesized PBS-based copolyesters by incorporating 5–20 mol% of –O₂CC₆H₄CO₂– and –OCH₂CH₂O– units through the polycondensation of succinic acid (SA) with 1,4-butanediol (BD) and bis(2-hydroxyethyl) terephthalate (BHET). Two different catalysts, H₃PO₄ and the conventional catalyst (nBuO)₄Ti, were used comparatively in the synthesis process. The copolyesters produced using the former were treated with M(2-ethylhexanoate)₂ (M = Mg, Zn, Mn) to connect the chains through ionic interactions between M²⁺ ions and either –CH₂OP(O)(OH)O⁻ or (–CH₂O)₂P(O)O⁻ groups. By incorporating BHET units (i.e., –O₂CC₆H₄CO₂– and –OCH₂CH₂O–), the resulting copolyesters exhibited improved ductile properties with enhanced elongation at break, albeit with reduced tensile strength. The copolyesters prepared with H₃PO₄/M(2-ethylhexanoate)₂ displayed a less random distribution of –O₂CC₆H₄CO₂– and –OCH₂CH₂O– units, leading to a faster crystallization rate, higher T_m value, and higher yield strength compared to those prepared with (nBuO)₄Ti using the same amount of BHET. Furthermore, they displayed substantial shear-thinning behavior in their rheological properties due to the presence of long-chain branches of (–CH₂O)₃P=O units. Unfortunately, the copolyesters prepared with H₃PO₄/M(2-ethylhexanoate)₂, and hence containing M²⁺, –CH₂OP(O)(OH)O⁻, (–CH₂O)₂P(O)O⁻ groups, did not exhibit enhanced biodegradability under ambient soil conditions. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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16 pages, 4910 KiB

Open AccessArticle

Comparative Study of Different Pretreatment and Combustion Methods on the Grindability of Rice-Husk-Based SiO₂

by Yunhai Ma, Shengwang Yuan, Zichao Ma, Yihao Hou, Shichao Niu, Li Lekai, Guoqin Liu and Feipeng Cao

Nanomaterials 2023, 13(22), 2951; https://doi.org/10.3390/nano13222951 - 15 Nov 2023

Cited by 1 | Viewed by 1233

Abstract

The rice husk (RH) combustion pretreatment method plays a crucial role in the extraction of nanoscale SiO₂ from RH as a silicon source. This study examined the effects of diverse pretreatment methods and combustion temperatures on the particle size distribution of nanoscale high-purity amorphous SiO₂ extracted from rice husk ash (RHA) post RH combustion. The experiment was structured using the Taguchi method, employing an L9 (2¹ × 3³) orthogonal mixing table. The median diameter (D50) served as the output response parameter, with the drying method (A), combustion temperature (B), torrefaction temperature (C), and pretreatment method (D) as the input parameters. The results showed the torrefaction temperature (C) as being the predominant factor affecting the D50, which decreased with an increasing torrefaction temperature (C). The optimal parameter combination was identified as A2B2C3D2. The verification test revealed that roasting could improve the abrasiveness of Rh-based silica and reduce the average particle size. Torrefaction at medium temperatures might narrow the size distribution range of RHA-SiO₂. We discovered that the purity of silica increased with an increasing roasting temperature by evaluating the concentration of silica in the sample. The production of RHA with silica concentrations up to 92.3% was investigated. X-ray diffraction analysis affirmed that SiO₂’s crystal structure remained unaltered across different treatment methods, consistently presenting as amorphous. These results provide a reference for extracting high-value products through RH combustion. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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18 pages, 3510 KiB

Open AccessArticle

Alternative Solid Activators from Waste Glass for One-Part Alkali-Activated Fly Ash/Red Mud Cements

by Nicolaie Marin, Cristina Orbeci, Liliana Bobiricǎ, Ileana Rău, Calin Deleanu, Elena Iuliana Bîru, Paul Octavian Stănescu, Andrei Constantin Berbecaru, Ecaterina Matei and Constantin Bobiricǎ

Materials 2023, 16(20), 6707; https://doi.org/10.3390/ma16206707 - 16 Oct 2023

Cited by 2 | Viewed by 1413

Abstract

Solid activators based on waste glass for the manufacture of one-part alkali-activated fly ash/red mud materials were synthesized, characterized, and tested in this work. The synthesis was carried out via alkaline fusion with sodium hydroxide at different reaction temperatures and at different sodium hydroxide/waste glass mass ratios. The results showed that the reaction temperature decisively influences the properties of the obtained solid activators. Thus, the best results regarding the water solubility of solid activators were obtained for the synthesis temperature of 600 °C, regardless of the sodium hydroxide/waste glass mass ratio. Also, the use of these assortments of solid activators led to obtaining the best compressive strength of one-part alkali-activated fly ash/red mud materials. The best results were obtained for the solid activator synthesized at a temperature of 600 °C and a sodium hydroxide/glass waste mass ratio of two. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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16 pages, 18189 KiB

Open AccessArticle

Influence of Pyrolytic Carbon Black Derived from Waste Tires at Varied Temperatures within an Industrial Continuous Rotating Moving Bed System

by Haibin Fang, Zhanfeng Hou, Lingdi Shan, Xiaohui Cai and Zhenxiang Xin

Polymers 2023, 15(16), 3460; https://doi.org/10.3390/polym15163460 - 18 Aug 2023

Cited by 5 | Viewed by 1822

Abstract

Nowadays, waste tires have emerged as one of the most significant sources of environmental pollution. To address this issue, pyrolysis has become a widely adopted method. The continuous rotary kiln reactor has particularly gained popularity in industrial production for pyrolysis due to its suitability. In order to guide the development of new industrial continuous rotary kiln reactors and achieve high-performance pyrolytic carbon black (CBp), this study was conducted to investigate the relationship between the physical and chemical characteristics of CBp and pyrolysis temperature. The elevated-temperature procedure led to a reduction in DBP values from 90 to 70 mL/100 mg, accompanied by a rise in the specific surface area from 63 to 77 m²/g. The augmentation of pyrolysis temperature was noted to induce the agglomeration of CBp particles, thereby negatively impacting their dispersion within polymer matrices. CBp particles at 550 °C exhibited greater structural order, as determined by Raman spectroscopy, which can be attributed to the elevated temperature proximate to the cylinder wall surface. Furthermore, the potential of CBp for reinforcement in natural rubber (NR) was taken into consideration. The pronounced propensity of high-temperature CBps to agglomerate led to uneven dispersion within the polymer, consequently causing heightened heat accumulation and the emergence of the Payne effect. Based on a thorough analysis of the outcomes, the optimal pyrolysis temperature for CBp synthesis within the continuous reactor was ascertained. Full article

(This article belongs to the Topic Green Polymer Materials for Circular Economy and Sustainable Development)

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Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Biomolecules biomolecules	4.8	9.4	2011	16.3 Days	CHF 2700
International Journal of Molecular Sciences ijms	4.9	8.1	2000	18.1 Days	CHF 2900
Materials materials	3.1	5.8	2008	15.5 Days	CHF 2600
Nanomaterials nanomaterials	4.4	8.5	2010	13.8 Days	CHF 2900
Pharmaceutics pharmaceutics	4.9	7.9	2009	14.9 Days	CHF 2900
Polymers polymers	4.7	8.0	2009	14.5 Days	CHF 2700

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