Polymers

Research

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14 pages, 2080 KiB

Open AccessArticle

Synthesis and Application Studies of DOPO-Based Organophosphorous Derivatives to Modify the Thermal Behavior of Polybenzoxazine

by Thorben Sören Haubold, Andreas Hartwig and Katharina Koschek

Polymers 2022, 14(3), 606; https://doi.org/10.3390/polym14030606 - 3 Feb 2022

Cited by 7 | Viewed by 2049

Abstract

The DOPO-based flame-retardant additives DOPO-HQ, DOPO-AP and DOPO-Van were synthesized in varying numbers of phenolic hydroxyl groups and amine groups. Moreover, their influence on the polymerization of a bisphenol F-based benzoxazine, as well as the thermal properties of the resulting materials, were studied. [...] Read more.

The DOPO-based flame-retardant additives DOPO-HQ, DOPO-AP and DOPO-Van were synthesized in varying numbers of phenolic hydroxyl groups and amine groups. Moreover, their influence on the polymerization of a bisphenol F-based benzoxazine, as well as the thermal properties of the resulting materials, were studied. All DOPO-based derivatives influenced the polymerization temperature onset with a reduction of up to 20 °C, while thermo-mechanical properties remained high. Surprisingly, phosphorous content below 0.4 wt% significantly improved the reaction against small flames yielding an increase in the limited oxygen index by 2% and a V-0 rating in the UL-94 test. DOPO-HQ proved to be the most effective additive regarding the reaction against small flames at an astonishingly low phosphorous concentration of below 0.1 wt%, whereas DOPO-AP and DOPO-Van simultaneously lowered the polymerization temperature. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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15 pages, 3586 KiB

Open AccessArticle

Bio-Based Bisbenzoxazines with Flame Retardant Linker

by Thorben Sören Haubold, Laura Puchot, Antoine Adjaoud, Pierre Verge and Katharina Koschek

Polymers 2021, 13(24), 4330; https://doi.org/10.3390/polym13244330 - 10 Dec 2021

Cited by 5 | Viewed by 2323

Abstract

This work explores the strategy of incorporating a highly substituted reactive flame retardant into a benzoxazine moiety. For this purpose, a DOPO-based flame retardant received a chain extension via reaction with ethylene carbonate. It was then reacted with phloretic acid to obtain a [...] Read more.

This work explores the strategy of incorporating a highly substituted reactive flame retardant into a benzoxazine moiety. For this purpose, a DOPO-based flame retardant received a chain extension via reaction with ethylene carbonate. It was then reacted with phloretic acid to obtain a diphenol end-capped molecule, and further reacted with furfurylamine and paraformaldehyde to obtain a benzoxazine monomer via a Mannich-like ring closure reaction. This four-step synthesis yielded a partly bio-based halogen-free flame retardant benzoxazine monomer (DOPO-PA-fa). The successful synthesis was proven via NMR, IR and MS analysis. The polymerization behavior was monitored by DSC and rheological analysis both showing the polymerization starts at 200 °C to yield pDOPO-PA-fa. pDOPO-PA-fa has a significant thermal stability with a residual mass of 30% at 800 °C under ambient atmosphere. Furthermore, it reached a V-0 rating against small flames and an OI of 35%. Blended with other benzoxazines, it significantly improves their thermal stability and fire resistance. It emphasizes its potential as flame retardant agent. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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14 pages, 1518 KiB

Open AccessArticle

Multipurpose Processing Additives for Silica/Rubber Composites: Synthesis, Characterization, and Application

by Arpan Datta Sarma, Carlos Eloy Federico, Frida Nzulu, Marc Weydert, Pierre Verge and Daniel Frederick Schmidt

Polymers 2021, 13(21), 3608; https://doi.org/10.3390/polym13213608 - 20 Oct 2021

Cited by 3 | Viewed by 2519

Abstract

Processing additives are a special group of chemicals included in rubber formulations to facilitate the flowability of the resultant compounds. Their addition generally affects the cured properties of the subsequent rubber composites, and fine-tuning of the compound formulation is therefore required. In this [...] Read more.

Processing additives are a special group of chemicals included in rubber formulations to facilitate the flowability of the resultant compounds. Their addition generally affects the cured properties of the subsequent rubber composites, and fine-tuning of the compound formulation is therefore required. In this work, an attempt has been made to address this issue through the preparation of new bio-based processing additives capable of promoting the mixing of the rubber compound while at the same time enhancing mechanical properties following curing. A significant decrease in the mixing energy at the first stage of mixing (~10%) has been observed by substituting only a small percentage of the conventional petroleum-derived process oil with aminated epoxidized soybean oil. Concomitantly, it is found that this aminated epoxidized soybean oil promotes rubber curing and increases the tensile strength of the final composite by ~20% compared to the control. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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19 pages, 4625 KiB

Open AccessArticle

Sustainable Esterification of a Soda Lignin with Phloretic Acid

by Antoine Adjaoud, Reiner Dieden and Pierre Verge

Polymers 2021, 13(4), 637; https://doi.org/10.3390/polym13040637 - 21 Feb 2021

Cited by 25 | Viewed by 3253

Abstract

In this work, a sustainable chemical process was developed through the Fischer esterification of Protobind^® lignin, a wheat straw soda lignin, and phloretic acid, a naturally occurring phenolic acid. It aimed at increasing the reactivity of lignin by enhancing the number of [...] Read more.

In this work, a sustainable chemical process was developed through the Fischer esterification of Protobind^® lignin, a wheat straw soda lignin, and phloretic acid, a naturally occurring phenolic acid. It aimed at increasing the reactivity of lignin by enhancing the number of unsubstituted phenolic groups via a green and solvent-free chemical pathway. The structural features of the technical and esterified lignins were characterized by complementary spectroscopic techniques, including ¹H, ¹³C, ³¹P, and two-dimensional analysis. A substantial increase in p-hydroxyphenyl units was measured (+64%, corresponding to an increase of +1.3 mmol g⁻¹). A full factorial design of the experiment was employed to quantify the impact of critical variables on the conversion yield. The subsequent statistical analysis suggested that the initial molar ratio between the two precursors was the factor predominating the yield of the reaction. Hansen solubility parameters of both the technical and esterified lignins were determined by solubility assays in multiple solvents, evidencing their high solubility in common organic solvents. The esterified lignin demonstrated a better thermal stability as the onset of thermal degradation shifted from 157 to 220 °C, concomitantly to the shift of the glass transition from 92 to 112 °C. In conclusion, the esterified lignin showed potential for being used as sustainable building blocks for composite and thermoset applications. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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12 pages, 3200 KiB

Open AccessArticle

Effects of Alkyl-Substituted Polybenzoxazines on Tribological Properties of Non-Asbestos Composite Friction Materials

by Anun Wongpayakyotin, Chanchira Jubsilp, Sunan Tiptipakorn, Phattarin Mora, Christopher W. Bielawski and Sarawut Rimdusit

Polymers 2021, 13(4), 567; https://doi.org/10.3390/polym13040567 - 14 Feb 2021

Cited by 11 | Viewed by 2510

Abstract

A series of substituted polybenzoxazines was synthesized and studied as binders in non-asbestos friction composite materials. The structures of the polybenzoxazines were varied in a systemic fashion by increasing the number and position of pendant alkyl (methyl) groups and was accomplished using the [...] Read more.

A series of substituted polybenzoxazines was synthesized and studied as binders in non-asbestos friction composite materials. The structures of the polybenzoxazines were varied in a systemic fashion by increasing the number and position of pendant alkyl (methyl) groups and was accomplished using the respective aromatic amines during the polymer synthesis step. By investigating the key thermomechanical and tribological characteristics displayed by the composite materials, the underlying structure-properties relationships were deconvoluted. Composite friction materials with higher thermomechanical and wear resistance properties were obtained from polybenzoxazines with relatively high crosslink densities. In contrast, polybenzoxazines with relatively low crosslink densities afforded composite friction materials with an improved coefficient of friction values and specific wear rates. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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10 pages, 2394 KiB

Open AccessArticle

Design of High-Performance Polybenzoxazines with Tunable Extended Networks Based on Resveratrol and Allyl Functional Benzoxazine

by Yunliang Xing, Xianru He, Rui Yang, Kan Zhang and Shengfu Yang

Polymers 2020, 12(12), 2794; https://doi.org/10.3390/polym12122794 - 26 Nov 2020

Cited by 16 | Viewed by 2195

Abstract

A novel resveratrol-based bio-benzoxazine monomer (RES-al) containing an allyl group has been synthesized using resveratrol, allylamine, and paraformaldehyde via Mannich condensation reaction, and its chemical structures have been characterized by FT-IR spectroscopy and NMR techniques. The polymerization behavior of this benzoxazine resin has [...] Read more.

A novel resveratrol-based bio-benzoxazine monomer (RES-al) containing an allyl group has been synthesized using resveratrol, allylamine, and paraformaldehyde via Mannich condensation reaction, and its chemical structures have been characterized by FT-IR spectroscopy and NMR techniques. The polymerization behavior of this benzoxazine resin has been investigated using in situ FT-IR and differential scanning calorimeter (DSC) measurements, and the thermal-mechanical properties of its corresponding polybenzoxazines are evaluated by DMA and TGA. We show that by controlling the curing process of the oxazine ring, the C=C bond in resveratrol, and the allyl group in RES-al, the cross-linking network of the polybenzoxazine can be manipulated, giving rise to tunable performance of thermosets. As all curable functionalities in RES-al are polymerized, the resulted polybenzoxazine exhibits a good thermal stability with a Tg temperature of 313 °C, a T_d5 value of 352 °C, and char yield of 53% at 800 °C under N₂. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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25 pages, 6655 KiB

Open AccessArticle

Nacre-Mimetic Green Flame Retardant: Ultra-High Nanofiller Content, Thin Nanocomposite as an Effective Flame Retardant

by Irlaine Machado, Isabel Hsieh, Veronica Calado, Thomas Chapin and Hatsuo Ishida

Polymers 2020, 12(10), 2351; https://doi.org/10.3390/polym12102351 - 14 Oct 2020

Cited by 10 | Viewed by 2540

Abstract

A nacre-mimetic brick-and-mortar structure was used to develop a new flame-retardant technology. A second biomimetic approach was utilized to develop a non-flammable elastomeric benzoxazine for use as a polymer matrix that effectively adheres to the hydrophilic laponite nanofiller. A combination of laponite and [...] Read more.

A nacre-mimetic brick-and-mortar structure was used to develop a new flame-retardant technology. A second biomimetic approach was utilized to develop a non-flammable elastomeric benzoxazine for use as a polymer matrix that effectively adheres to the hydrophilic laponite nanofiller. A combination of laponite and benzoxazine is used to apply an ultra-high nanofiller content, thin nanocomposite coating on a polyurethane foam. The technology used is made environmentally friendly by eliminating the need to add any undesirable flame retardants, such as phosphorus additives or halogenated compounds. The very-thin coating on the polyurethane foam (PUF) is obtained through a single dip-coating. The structure of the polymer has been confirmed by proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier transform infrared spectroscopy (FTIR). The flammability of the polymer and nanocomposite was evaluated by heat release capacity using microscale combustion calorimetry (MCC). A material with heat release capacity (HRC) lower than 100 J/Kg is considered non-ignitable. The nanocomposite developed exhibits HRC of 22 J/Kg, which is well within the classification of a non-ignitable material. The cone calorimeter test was also used to investigate the flame retardancy of the nanocomposite’s thin film on polyurethane foam. This test confirms that the second peak of the heat release rate (HRR) decreased 62% or completely disappeared for the coated PUF with different loadings. Compression tests show an increase in the modulus of the PUF by 88% for the 4 wt% coating concentration. Upon repeated modulus tests, the rigidity decreases, approaching the modulus of the uncoated PUF. However, the effect of this repeated mechanical loading does not significantly affect the flame retarding performance. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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11 pages, 1834 KiB

Open AccessCommunication

Design and Effects of the Cinnamic Acids Chemical Structures as Organocatalyst on the Polymerization of Benzoxazines

by Rocío B. Rodríguez, Daniela Iguchi, Rosa Erra-Balsells, M. Laura Salum and Pablo Froimowicz

Polymers 2020, 12(7), 1527; https://doi.org/10.3390/polym12071527 - 9 Jul 2020

Cited by 8 | Viewed by 2851

Abstract

This study focuses on the catalytic effect of the two geometric isomers of a cinnamic acid derivative, E and Z-forms of 3-methoxycinnamic acid (3OMeCA), analyzing the influence of their chemical structures. E and Z-3OMeCA isomers show very good catalytic effect in [...] Read more.

This study focuses on the catalytic effect of the two geometric isomers of a cinnamic acid derivative, E and Z-forms of 3-methoxycinnamic acid (3OMeCA), analyzing the influence of their chemical structures. E and Z-3OMeCA isomers show very good catalytic effect in the polymerization of benzoxazines, decreasing by 40 and 55 °C, respectively, the polymerization temperatures, for catalyst contents of up to 10% w/w. Isothermal polymerizations show that polymerizations are easily realized and analyzed at temperatures as low as 130 °C and at much shorter times using Z-3OMeCA instead of E-3OMeCA. Thus, both cinnamic acids are good catalysts, with Z-3OMeCA being better. The molecular reasons for this difference and mechanistic implications in benzoxazine polymerizations are also presented. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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Review

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24 pages, 4041 KiB

Open AccessEditor’s ChoiceReview

Greener, Faster, Stronger: The Benefits of Deep Eutectic Solvents in Polymer and Materials Science

by Yeasmin Nahar and Stuart C. Thickett

Polymers 2021, 13(3), 447; https://doi.org/10.3390/polym13030447 - 30 Jan 2021

Cited by 79 | Viewed by 9430

Abstract

Deep eutectic solvents (DESs) represent an emergent class of green designer solvents that find numerous applications in different aspects of chemical synthesis. A particularly appealing aspect of DES systems is their simplicity of preparation, combined with inexpensive, readily available starting materials to yield [...] Read more.

Deep eutectic solvents (DESs) represent an emergent class of green designer solvents that find numerous applications in different aspects of chemical synthesis. A particularly appealing aspect of DES systems is their simplicity of preparation, combined with inexpensive, readily available starting materials to yield solvents with appealing properties (negligible volatility, non-flammability and high solvation capacity). In the context of polymer science, DES systems not only offer an appealing route towards replacing hazardous volatile organic solvents (VOCs), but can serve multiple roles including those of solvent, monomer and templating agent—so called “polymerizable eutectics.” In this review, we look at DES systems and polymerizable eutectics and their application in polymer materials synthesis, including various mechanisms of polymer formation, hydrogel design, porous monoliths, and molecularly imprinted polymers. We provide a comparative study of these systems alongside traditional synthetic approaches, highlighting not only the benefit of replacing VOCs from the perspective of environmental sustainability, but also the materials advantage with respect to mechanical and thermal properties of the polymers formed. Full article

(This article belongs to the Special Issue Sustainable Monomers, Catalysts, Polymers and Polymer-Based Materials)

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