Editorial

3 pages, 171 KiB

Open AccessEditorial

Special Issue “Renewable Polymers: Processing and Chemical Modifications”

by Tizazu Mekonnen and Marc A. Dubé

Processes 2019, 7(7), 398; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7070398 - 26 Jun 2019

Cited by 5 | Viewed by 2216

The use of renewable resources for polymer production is receiving substantial and ever-growing interest [...] Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

Research

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21 pages, 6536 KiB

Open AccessFeature PaperArticle

Hydroxymethylation-Modified Lignin and Its Effectiveness as a Filler in Rubber Composites

by Nor Anizah Mohamad Aini, Nadras Othman, M. Hazwan Hussin, Kannika Sahakaro and Nabil Hayeemasae

Processes 2019, 7(5), 315; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7050315 - 25 May 2019

Cited by 37 | Viewed by 4853

Abstract

Kraft lignin was modified by using hydroxymethylation to enhance the compatibility between rubber based on a blend of natural rubber/polybutadiene rubber (NR/BR) and lignin. To confirm this modification, the resultant hydroxymethylated kraft lignin (HMKL) was characterized using Fourier transform infrared (FTIR) and nuclear [...] Read more.

Kraft lignin was modified by using hydroxymethylation to enhance the compatibility between rubber based on a blend of natural rubber/polybutadiene rubber (NR/BR) and lignin. To confirm this modification, the resultant hydroxymethylated kraft lignin (HMKL) was characterized using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. It was then incorporated into rubber composites and compared with unmodified rubber. All rubber composites were investigated in terms of rheology, mechanical properties, aging, thermal properties, and morphology. The results show that the HMKL influenced the mechanical properties (tensile properties, hardness, and compression set) of NR/BR composites compared to unmodified lignin. Further evidence also revealed better dispersion and good interaction between the HMKL and the rubber matrix. Based on its performance in NR/BR composites, hydroxymethylated lignin can be used as a filler in the rubber industry. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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17 pages, 5009 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Nitroxide-Mediated Copolymerization of Itaconate Esters with Styrene

by Sepehr Kardan, Omar Garcia Valdez, Adrien Métafiot and Milan Maric

Processes 2019, 7(5), 254; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7050254 - 01 May 2019

Cited by 5 | Viewed by 4427

Abstract

Replacing petro-based materials with renewably sourced ones has clearly been applied to polymers, such as those derived from itaconic acid (IA) and its derivatives. Di-n-butyl itaconate (DBI) was (co)polymerized via nitroxide mediated polymerization (NMP) to impart elastomeric (rubber) properties. Homopolymerization of DBI by [...] Read more.

Replacing petro-based materials with renewably sourced ones has clearly been applied to polymers, such as those derived from itaconic acid (IA) and its derivatives. Di-n-butyl itaconate (DBI) was (co)polymerized via nitroxide mediated polymerization (NMP) to impart elastomeric (rubber) properties. Homopolymerization of DBI by NMP was not possible, due to a stable adduct being formed. However, DBI/styrene (S) copolymerization by NMP at various initial molar feed compositions f_DBI,0 was polymerizable at different reaction temperatures (70–110 °C) in 1,4 dioxane solution. DBI/S copolymerizations largely obeyed first order kinetics for initial DBI compositions of 10% to 80%. Number-average molecular weight (M_n) versus conversion for various DBI/S copolymerizations however showed significant deviations from the theoretical M_n as a result of chain transfer reactions (that are more likely to occur at high temperatures) and/or the poor reactivity of DBI via an NMP mechanism. In order to suppress possible intramolecular chain transfer reactions, the copolymerization was performed at 70 °C and for a longer time (72 h) with f_DBI,0 = 50%–80%, and some slight improvements regarding the dispersity (Ð = 1.3–1.5), chain activity and conversion (~50%) were observed for the less DBI-rich compositions. The statistical copolymers produced showed a depression in T_g relative to poly(styrene) homopolymer, indicating the effect of DBI incorporation. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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12 pages, 1090 KiB

Open AccessFeature PaperArticle

Pelletization of Torrefied Wood Using a Proteinaceous Binder Developed from Hydrolyzed Specified Risk Materials

by Birendra B. Adhikari, Michael Chae, Chengyong Zhu, Ataullah Khan, Don Harfield, Phillip Choi and David C. Bressler

Processes 2019, 7(4), 229; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7040229 - 23 Apr 2019

Cited by 21 | Viewed by 3839

Abstract

Pressing issues such as a growing energy demand and the need for energy diversification, emission reduction, and environmental protection serve as motivation for the utilization of biomass for production of sustainable fuels. However, use of biomass is currently limited due to its high [...] Read more.

Pressing issues such as a growing energy demand and the need for energy diversification, emission reduction, and environmental protection serve as motivation for the utilization of biomass for production of sustainable fuels. However, use of biomass is currently limited due to its high moisture content, relatively low bulk and energy densities, and variability in shape and size, relative to fossil-based fuels such as coal. In recent years, a combination of thermochemical treatment (torrefaction) of biomass and subsequent pelletization has resulted in a renewable fuel that can potentially substitute for coal. However, production of torrefied wood pellets that satisfy fuel quality standards and other logistical requirements typically requires the use of an external binder. Here, we describe the development of a renewable binder from proteinaceous material recovered from specified risk materials (SRM), a negative-value byproduct from the rendering industry. Our binder was developed by co-reacting peptides recovered from hydrolyzed SRM with a polyamidoamine epichlorohydrin (PAE) resin, and then assessed through pelleting trials with a bench-scale continuous operating pelletizer. Torrefied wood pellets generated using peptides-PAE binder at 3% binder level satisfied ISO requirements for durability, higher heating value, and bulk density for TW2a type thermally-treated wood pellets. This proof-of-concept work demonstrates the potential of using an SRM-derived binder to improve the durability of torrefied wood pellets. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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15 pages, 7750 KiB

Open AccessArticle

Preparation and Performance of Different Modified Ramie Fabrics Reinforced Anionic Polyamide-6 Composites

by Ze Kan, Hao Shi, Erying Zhao and Hui Wang

Processes 2019, 7(4), 226; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7040226 - 22 Apr 2019

Cited by 8 | Viewed by 3670

Abstract

Anionic polyamide-6 (APA-6) composites are prepared by the VARIM process using different modified ramie fabrics to study the structure and properties of different composites. This study can not only evaluate the optimal modification method for the ramie fabrics, but also further explore the [...] Read more.

Anionic polyamide-6 (APA-6) composites are prepared by the VARIM process using different modified ramie fabrics to study the structure and properties of different composites. This study can not only evaluate the optimal modification method for the ramie fabrics, but also further explore the interface interaction mechanism between ramie fabrics and APA-6. In this article, the ramie fabrics are modified by a pretreatment, coupling agent and alkali modification. Different modification methods have different effects on the structure, surface properties and mechanical properties of ramie fabrics, which will further affect the impregnation process, interfacial and mechanical properties of the composites. Through the performance analysis of different modified ramie fabrics reinforced APA-6 composites, the conversion, crystallinity and molecular weight of these composites are at a high level, which indicate that the polymerization of these composites is well controlled. The coupling agent modified ramie fabrics composites and the pretreated ramie fabrics composites have higher flexural modulus, tensile strength and dynamic mechanical properties. Alkali-modified ramie fabrics composites have slightly lower mechanical properties, which however have the highest interlaminar shear strength and outperformed interface properties of the composites. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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17 pages, 4857 KiB

Open AccessArticle

Development of Environmental Friendly Dust Suppressant Based on the Modification of Soybean Protein Isolate

by Hu Jin, Wen Nie, Yansong Zhang, Hongkun Wang, Haihan Zhang, Qiu Bao and Jiayi Yan

Processes 2019, 7(3), 165; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7030165 - 20 Mar 2019

Cited by 60 | Viewed by 6310

Abstract

Aiming to further improve the dust suppression performance of the dust suppressant, the present study independently develops a new type of biodegradable environmentally-friendly dust suppressant. Specifically, the naturally occurring biodegradable soybean protein isolate (SPI) is selected as the main material, which is subject [...] Read more.

Aiming to further improve the dust suppression performance of the dust suppressant, the present study independently develops a new type of biodegradable environmentally-friendly dust suppressant. Specifically, the naturally occurring biodegradable soybean protein isolate (SPI) is selected as the main material, which is subject to an anionic surfactant, i.e., sodium dodecyl sulfonate (SDS) for modification with the presence of additives including carboxymethylcellulose sodium and methanesiliconic acid sodium. As a result, the SDS-SPI cementing dust suppressant is produced. The present study experimentally tests solutions with eight different dust suppressant concentrations under the same experimental condition, so as to evaluate their dust suppression performances. Key metrics considered include water retention capability, cementing power and dust suppression efficiency. The optimal concentration of dust suppressant solution is determined by collectively comparing these metrics. The experiments indicate that the optimal dust suppressant concentration is 3%, at which level the newly developed environmentally-friendly dust suppressant solution exhibits a decent dust suppression characteristic, with the water retention power reaching its peak level, and the corresponding viscosity being 12.96 mPa·s. This performance can generally meet the requirements imposed by coal mines. The peak efficiency of dust suppression can reach 92.13%. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to analyze the dust suppression mechanism of the developed dust suppressant. It was observed that a dense hardened shell formed on the surface of the pulverized coal particles sprayed with the dust suppressant. There is strong cementation between coal dust particles, and the cementation effect is better. This can effectively inhibit the re-entrainment of coal dust and reduce environmental pollution. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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18 pages, 2104 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Viscoelastic Properties of Crosslinked Chitosan Films

by Joseph Khouri, Alexander Penlidis and Christine Moresoli

Processes 2019, 7(3), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7030157 - 14 Mar 2019

Cited by 41 | Viewed by 6330

Abstract

Chitosan films containing citric acid were prepared using a multi-step process called heterogeneous crosslinking. These films were neutralized first, followed by citric acid addition, and then heat treated at 150 °C/0.5 h in order to potentially induce covalent crosslinking. The viscoelastic storage modulus, [...] Read more.

Chitosan films containing citric acid were prepared using a multi-step process called heterogeneous crosslinking. These films were neutralized first, followed by citric acid addition, and then heat treated at 150 °C/0.5 h in order to potentially induce covalent crosslinking. The viscoelastic storage modulus, E′, and tanδ were studied using dynamic mechanical analysis, and compared with neat and neutralized films to elucidate possible crosslinking with citric acid. Films were also prepared with various concentrations of a model crosslinker, glutaraldehyde, both homogeneously and heterogeneously. Based on comparisons of neutralized films with films containing citric acid, and between citric acid films either heat treated or not heat treated, it appeared that the interaction between chitosan and citric acid remained ionic without covalent bond formation. No strong evidence of a glass transition from the tanδ plots was observable, with the possible exception of heterogeneously crosslinked glutaraldehyde films at temperatures above 200 °C. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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19 pages, 5895 KiB

Open AccessArticle

Chemical Recycling of Used Printed Circuit Board Scraps: Recovery and Utilization of Organic Products

by Se-Ra Shin, Van Dung Mai and Dai-Soo Lee

Processes 2019, 7(1), 22; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7010022 - 04 Jan 2019

Cited by 17 | Viewed by 6524

Abstract

The disposal of end-of-life printed circuit boards (PCBs) comprising cross-linked brominated epoxy resins, glass fiber, and metals has attracted considerable attention from the environmental aspect. In this study, valuable resources, especially organic material, were recovered by the effective chemical recycling of PCBs. Pulverized [...] Read more.

The disposal of end-of-life printed circuit boards (PCBs) comprising cross-linked brominated epoxy resins, glass fiber, and metals has attracted considerable attention from the environmental aspect. In this study, valuable resources, especially organic material, were recovered by the effective chemical recycling of PCBs. Pulverized PCB was depolymerized by glycolysis using polyethylene glycol (PEG 200) with a molecular weight of 200 g/mol under basic conditions. The cross-linked epoxy resins were effectively decomposed into a low-molecular species by glycolysis with PEG 200, followed by the effective separation of the metals and glass fibers from organic materials. The organic material was modified into recycled polyol with an appropriate viscosity and a hydroxyl value for rigid polyurethane foams (RPUFs) by the Mannich reaction and the addition polymerization of propylene oxide. RPUFs prepared using the recycled polyol exhibited superior thermal and mechanical properties as well as thermal insulation properties compared to conventional RPUFs, indicating that the recycled polyol obtained from the used PCBs can be valuable as RPUF raw materials for heat insulation. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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Review

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40 pages, 6234 KiB

Open AccessReview

On the Use of Starch in Emulsion Polymerizations

by Shidan Cummings, Yujie Zhang, Niels Smeets, Michael Cunningham and Marc A. Dubé

Processes 2019, 7(3), 140; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7030140 - 06 Mar 2019

Cited by 24 | Viewed by 9011

Abstract

The substitution of petroleum-based synthetic polymers in latex formulations with sustainable and/or bio-based sources has increasingly been a focus of both academic and industrial research. Emulsion polymerization already provides a more sustainable way to produce polymers for coatings and adhesives, because it is [...] Read more.

The substitution of petroleum-based synthetic polymers in latex formulations with sustainable and/or bio-based sources has increasingly been a focus of both academic and industrial research. Emulsion polymerization already provides a more sustainable way to produce polymers for coatings and adhesives, because it is a water-based process. It can be made even more attractive as a green alternative with the addition of starch, a renewable material that has proven to be extremely useful as a filler, stabilizer, property modifier and macromer. This work provides a critical review of attempts to modify and incorporate various types of starch in emulsion polymerizations. This review focusses on the method of initiation, grafting mechanisms, starch feeding strategies and the characterization methods. It provides a needed guide for those looking to modify starch in an emulsion polymerization to achieve a target grafting performance or to incorporate starch in latex formulations for the replacement of synthetic polymers. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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27 pages, 5554 KiB

Open AccessFeature PaperReview

Trends in Advanced Functional Material Applications of Nanocellulose

by Prachiben Panchal, Emmanuel Ogunsona and Tizazu Mekonnen

Processes 2019, 7(1), 10; https://0-doi-org.brum.beds.ac.uk/10.3390/pr7010010 - 30 Dec 2018

Cited by 111 | Viewed by 10339

Abstract

The need to transition to more sustainable and renewable technology has resulted in a focus on cellulose nanofibrils (CNFs) and nanocrystals (CNCs) as one of the materials of the future with potential for replacing currently used synthetic materials. Its abundance and bio-derived source [...] Read more.

The need to transition to more sustainable and renewable technology has resulted in a focus on cellulose nanofibrils (CNFs) and nanocrystals (CNCs) as one of the materials of the future with potential for replacing currently used synthetic materials. Its abundance and bio-derived source make it attractive and sought after as well. CNFs and CNCs are naturally hydrophilic due to the abundance of -OH group on their surface which makes them an excellent recipient for applications in the medical industry. However, the hydrophilicity is a deterrent to many other industries, subsequently limiting their application scope. In either light, the increased rate of progress using CNCs in advanced materials applications are well underway and is becoming applicable on an industrial scale. Therefore, this review explores the current modification platforms and processes of nanocellulose directly as functional materials and as carriers/substrates of other functional materials for advanced materials applications. Niche functional attributes such as superhydrophobicity, barrier, electrical, and antimicrobial properties are reviewed due to the focus and significance of such attributes in industrial applications. Full article

(This article belongs to the Special Issue Renewable Polymers: Processing and Chemical Modifications)

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