Advances in Eco-Friendly Polyurethane Foams and Adhesives

Dear Colleagues,

Polyurethanes result from the condensation reaction between polyols and isocyanates. By varying the proportions of these compounds and incorporating different additives, a range of products such as foams, films, or adhesives can be manufactured. Historically, both polyols and isocyanates have been derived from petroleum sources. However, recent efforts have been directed towards the utilization of lignocellulosic materials for polyol production, employing techniques like the use of vegetable oils or liquefied lignocellulosic materials. At the same time, non-isocyanate polyurethane (NIPU) represents a promising advancement in polymeric materials, offering an environmentally friendly alternative to traditional polyurethane foams or adhesives that rely on isocyanate chemistry. NIPU is synthesized using chemical routes that do not involve the use of isocyanates, addressing concerns related to toxicity, handling hazards, and environmental impact associated with conventional polyurethane production. 

Both foams and adhesives are highly versatile materials with different applications. Polyurethane foams, in particular, offer numerous advantages such as low density, low thermal conductivity, and excellent mechanical properties. One of their key benefits is the ability to adjust their density and rigidity to meet market demands. Flexible polyurethane foams are extensively used in furniture manufacturing for cushions, mattresses, and sofas, as well as in automotive applications for bumpers, seats, and upholstery. Rigid polyurethane foams find utility in construction for acoustic and thermal insulation, among other uses. On the other hand, polyurethane adhesives are considered ideal for bonding wood to wood or wood to other materials and are commonly used in furniture assembly, cabinet making, and woodworking applications. Additionally, they are employed in automotive, construction, electronics, footwear, marine, and aerospace applications due to their ability to adhere to diverse materials. While polyurethane adhesives offer numerous advantages, it is crucial to assess each application's specific requirements to select the most appropriate adhesive for optimal performance.

The aim of this Special Issue is to present the advances in the production of eco-friendly polyurethanes in the form of foams, films, or adhesives for various applications, particularly within the following topics: 

• Effect of formulation in shaping polyurethane foam, films, or adhesives properties;
• New process technologies for polyurethane production;
• Use of novel bio-based materials to substitute the polyol in polyurethane foams, films, or adhesives;
• Recycling of polyurethane wastes;
• Use of polyurethane foams in 3D printing;
• Non-isocyanate polyurethane (NIPU) synthesis methods, process optimization, and environmental impact;
• Enhancement of polyurethane foam, films, or adhesives properties.

Prof. Dr. Bruno Esteves
Prof. Dr. Luisa Paula Cruz Lopes
Guest Editors

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• adhesives
• foams
• lignocellulosic materials
• NIPU
• polyurethane