Eugenol-based non-isocyanate polyurethane and polythiourethane

Synthesis and Characterization of Cardanol-Based Non-Isocyanate Polyurethane

This paper describes the synthesis of NIPU by using cardanol as starting material. A cardanol formaldehyde oligomer was first prepared through the reaction of cardanol and formaldehyde, catalyzed by citric acid. The resulting oligomer was then subjected to epoxidation with m-chloroperbenzoic acid to obtain an epoxide compound, which was subsequently used to fix carbon dioxide (CO2) and form a cyclic carbonate. Using this cyclic carbonate, along with an amine, cardanol-based isocyanate polyurethane (NIPU) was prepared. Different characterization methods, such as Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA), were used to confirm the synthesis of the four intermediate products and NIPU in the reaction process. This study highlights the promise of bio-based NIPU as a sustainable alternative in a number of applications while offering insightful information on the synthesis and characterization of the material.

Eugenol-Based Polymeric Materials-Antibacterial Activity and Applications

Eugenol (4-Allyl-2-methoxy phenol) (EUG) is a plant-derived allyl chain-substituted guaiacol, widely known for its antimicrobial and anesthetic properties, as well as the ability to scavenge reactive oxygen species. It is typically used as a mixture with zinc oxide (ZOE) for the preparation of restorative tooth fillings and treatment of root canal infections. However, the high volatility of this insoluble-in-water component of natural essential oils can be an obstacle to its wider application. Moreover, molecular eugenol can be allergenic and even toxic if taken orally in high doses for long periods of time. Therefore, a growing interest in eugenol loading in polymeric materials (including the encapsulation of molecular eugenol and polymerization of EUG-derived monomers) has been noted recently. Such active macromolecular systems enhance the stability of eugenol action and potentially provide prolonged contact with pathogens without the undesired side effects of free EUG. In this review, we present an overview of methods leading to the formation of macromolecular derivatives of eugenol as well as the latest developments and further perspectives in their pharmacological and antimicrobial applications.

High-Performance Nonisocyanate Thermoplastic Polythiourethane with High Hydrogen Bond Content

Nonisocyanate polyurethane (NIPU) has been extensively studied because of its sustainability potential. However, the low reactivity of five-membered cyclocarbonates with amines and the side reactions at higher temperatures always sacrifice the performance of NIPUs. In this work, a bisphenol-S cyclic thiocarbonate and different amino-terminated dimer-acid polyamides (DAPAs) were used to prepare nonisocyanate polythiourethanes (SPTU-DAs). Wherein bisphenol-S acts as a hard segment due to a π-π package, plentiful hydrogen bonds introduced by DAPA units induce crystallization and nanophase separation. They both endow the NIPUs with high mechanical performance. Meanwhile, active cyclic thiocarbonate, instead of cyclic carbonate, ensures rapid synthesis under mild conditions without side reactions. The experimental results of DSC, WAXD, and DMA confirmed the existence of crystallization of SPTU-DAs. The as-prepared thermoplastic polythiourethane has a maximum strength of more than 10 MPa, which is stronger than those of the cross-linked nonisocyanate polythiourethanes reported. It is of key significance to obtain the high performance of nonisocyanate polythiourethanes.

Eugenol, a Promising Building Block for Biobased Polymers with Cutting-Edge Properties

Biobased materials, derived from biomass building blocks, are essential in the pursuit of sustainable materials. Eugenol, a natural phenol obtained from clove oil, but also from lignin depolymerization, possesses a chemical structure that allows its easy modification to obtain a broad and versatile platform of biobased monomers. In this Perspective, an overview of the variety of reactions that have been executed on the allylic double bond, phenol hydroxyl group, aromatic ring, and methoxy group is given, focusing our attention on those to obtain monomers suitable for different polymerization reactions. Furthermore, possible applications and perspectives on the eugenol-derived materials are provided.

Improving Oxygen Permeability and Thermostability of Polycarbonate via Copolymerization Modification with Bio-Phenol Polysiloxane

As a new kind of functionalized polysiloxane with chemical reactivity, bio-phenol polysiloxane was synthesized through facile heterogeneous catalytic route. Bio-phenol polysiloxane/polycarbonate (Si/PC) block copolymer was synthesized via a three-step approach, and the effect of the amount of bio-phenol polysiloxane on the properties of Si/PC copolymer was then studied. The structure and morphology of Si/PC copolymer were characterized, showing that, when the amount of bio-phenol polysiloxane reached 20%, the pyrolysis temperature of Si/PC copolymer at 5% weight loss was 450.8 °C which was 76.1 °C higher than pure PC. The oxygen permeability of 20%Si/PC copolymer membrane was 502.65 cm³/m²·24h·0.1MPa, which was increased by 128.4% compared with pure PC membrane. The mechanical property and hydrophobicity of Si/PC copolymer had been improved.

Facile Route for Bio-Phenol Siloxane Synthesis via Heterogeneous Catalytic Method and its Autonomic Antibacterial Property

Eugenol, used as bio-phenol, was designed to replace the hydrogen atom of hydrogenterminated siloxane by hydrosilylation reaction under the presence of alumina-supported platinum catalyst (Pt-Al₂O₃), silica-supported platinum catalyst (Pt-SiO₂) and carbon nanotube-supported platinum catalyst (Pt-CNT), respectively. The catalytic activities of these three platinum catalysts were measured by nuclear magnetic resonance hydrogen spectrometer (¹H NMR). The properties of bio-phenol siloxane were characterized by Fourier transform infrared spectrometer (FT–IR), UV-visible spectrophotometer (UV) and thermogravimeter (TGA), and its antibacterial property against Escherichia coli was also studied. The results showed that the catalytic activity of the catalyst Pt-CNT was preferable. When the catalyst concentration was 100 ppm, the reaction temperature was 80 °C and reaction time was 6 h, the reactant conversion rate reached 97%. After modification with bio-phenol, the thermal stability of the obtained bio-phenol siloxane was improved. For bio-phenol siloxane, when the ratio of weight loss reached 98%, the pyrolysis temperature was raised to 663 °C which was 60 °C higher than hydrogenterminated siloxane. Meanwhile, its autonomic antibacterial property against Escherichia coli was improved significantly.

Recycling of polyurethanes from laboratory to industry, a journey towards the sustainability

The recycling of any kind of plastic to convert it in valuable products is one of the main challenges of today's society. Besides, if the recycling process is itself green, then it would be a great achievement. This paper reviews the way covered from the first attempts of reusing the polyurethane (PU) scraps as a filler for cushions to the last chemical routes employing green recycling agents. Polyurethane is the 6th most used polymer all over the world with a production of 18 millions tons per year, which means a daily production of PU specialties greater than 1 million of cubic meters, equivalent to the volume of the Empire State Building. The thermostable nature of the majority of the polyurethanes specialties has made that the preferred solution for their recycling are the chemical recycling processes. Among them, glycolysis is the one that receives a greater attention from an industrial point of view, so this review puts the spotlight on it. However, the existing reviews in literature do not paid a special attention on glycolysis and only give a superficial description of the process. Nevertheless, in the present review, the scientific literature relative to glycolysis is completely reviewed, updated and ordered according the type of PU specialty recycled. Additionally, the other main chemical recycling processes are also revisited in a more extended and deeper way than in the previous approaches to this topic. Moreover, it is crucial to take into account that some of these technologies, which were described in the literature as promising technologies at laboratory scale are now commercial processes running at industrial scale. For that reason, it is essential to remark that the present review comprises not only a detailed state of art of the scientific literature on the subject, also includes a detailed revision of the past and running on pilot plants and industrial facilities, including several patents, which has never been covered in the current literature. Moreover, this review also describes the most recent studies employing crude glycerol (biodiesel subproduct) as an economic, sustainable and environmental friendly cleavage agent, which should lead the way to the industrial implantation of split-phase glycolysis in a near future, providing high quality recovered products, susceptible of replacing raw ones in the synthesis of new PU specialties. What is more, this review intends that any reader could know and understand the reactions involved in the polyurethane chemistry and recycling, the main polyurethanes types and the fundamentals of the recycling strategies in order to comprehend what are the advantages and drawbacks of each recycling process as starting point for looking for new advantageous alternatives from an environmental, technical and economic point of view. Broader context. This paper reviews the main advances in the polyurethane (PU) recycling field, from laboratory and academia processes to pilot plant and industrial scale ones, including the most relevant patents in the subject. Opposite to other common used plastics, PUs are not polymerization but condensation polymers, synthesized from polyols and isocyanates. The wide diversity of polyols and isocyanates allows the synthesis of numerous different compounds covering a huge range of applications. As a direct consequence of their commercial success, an increasing quantity of PU waste is being disposed by landfilling in the last decades. Such waste comprises not only post-consumer products but also scrap from slabstock manufacturing, which can reach the 10% of the total foam production. However, the massive enforcement of the environmental laws is pointing out a new route in the polymer waste removal sector based in the polymer recycling, and this fact has placed the research in waste treatment as one of the most prolific topics nowadays. In fact, polymer recycling processes have experienced a growing attention from the research and industrial worlds as a direct result of the enforcement of the environmental legislations. Hence, it is essential to develop new environmental sustainable recycling processes with the aim of conserving the natural resources, reducing the amount of waste disposed in landfills and enhancing the sustainability for forthcoming generation.