Research on the Resourceful and Efficient Recycling Technology of Waste Thermal Insulation Pipe Material

This study was conducted to explore a new method for degrading and recycling waste chemical pipe insulation and cooling materials. A chemical degradation method was employed, utilizing alkali metal catalysts and a two-component alcoholysis system consisting of specific ratios of diethylene glycol and butylene glycol. The system effectively degraded the polyisocyanurate (PIR) insulation with the aim of reusing the waste material. The experimental results show that the best reaction performance is obtained with 1,4-BG/DEG ratio of 43:57 at 180 and 190 °C 1 h. The resulting regenerated pipe has an apparent density of 0.041 g/cm3 and a compressive strength of 0.413 MPa. With remarkable thermal stability, well-preserved porosity, and strong skeletal structure, the cold loss on the outer surface of the insulated pipe is lower than the design requirement of 23 W/m2, which is qualified for the energy efficiency of the insulated pipe. The proposed strategy for degradation and recycling of waste chemical pipe insulation and cold insulation materials provides a pioneering green treatment method for the task of recycling polyurethane waste with fire-resistant degradability and a high cross-linking degree.

Valorising End-of-Life Mattress Waste into Sustainable Construction Insulation Materials

Shredded mattress waste was valorised into an insulation material via the addition of a cellulose/urea gel. The addition of the cellulose-based gel was found to successfully bond the miscellaneous shred, creating a composite with a unique pore structure. The composites were tested for their thermal conductivity to explore their use as insulation materials in construction applications. From the testing, the thermal conductivity was found to range between 49 and 60 mW/mK depending on the composition and processing steps. While some of the produced composites showed poor thermal resistance not suitable for an insulation product, we report that additional processing resulted in thermal conductivities that were lower than the existing commercial insulation product (45 mW/mK). Numerical simulations revealed that it is possible to further reduce the thermal conductivity of the samples by optimising the porosity and pore sizes. Hence, there is a strong promise of recycling a common waste product into sustainable building insulation products with further optimisations.

Dynamic Mechanical Properties and Energy Absorption Capabilities of Polyureas Through Experiments and Molecular Dynamic Simulation

Polyurea (PUR) has been widely used as a protective coating in recent years. In order to complete the understanding of the relationship between PUR microstructure and its energy absorption capabilities, the mechanical and dynamic performance of PURs containing various macrodiol structural units were compared using material characterization techniques and molecular dynamic simulation. The results showed that the PUR polycarbonate diols formed as energy absorbing materials showed high tensile strength, high toughness, and excellent loss factor distribution based on the comparison of stress-strain tensile curves, glass transition temperatures, phase images, and dynamic storage loss modulus. External energy from simple shear deformation was absorbed to convert non-bond energy, in particular, based on fractional free volume, interaction energy, and total energy and hydrogen bond number change from the molecular dynamic simulation. Hydrogen bonds formed between soft segments and hard segments in the PURs have been proven to play a significant role in determining their mechanical and dynamic performance. The mechanical and dynamic properties of PURs characterized and tested using experimental techniques were quantified effectively using molecular dynamic simulation. This is believed to be an innovative theoretical guidance for the structural design of PURs at the molecular level for the optimization of energy absorption capabilities.

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure-Properties Relationship, and Nanocomposites for Ballistic Protection Applications

This review presents polyurea (PU) synthesis, the structure-properties relationship, and characterization aspects for ballistic protection applications. The synthesis of polyurea entails step-growth polymerization through the reaction of an isocyanate monomer/prepolymer and a polyamine, each component possessing a functionality of at least two. A wide range of excellent properties such as durability and high resistance against atmospheric, chemical, and biological factors has made this polymer an outstanding option for ballistic applications. Polyureas are an extraordinary case because they contain both rigid segments, which are due to the diisocyanates used and the hydrogen points formed, and a flexible zone, which is due to the chemical structure of the polyamines. These characteristics motivate their application in ballistic protection systems. Polyurea-based coatings have also demonstrated their abilities as candidates for impulsive loading applications, affording a better response of the nanocomposite-coated metal sheet at the action of a shock wave or at the impact of a projectile, by suffering lower deformations than neat metallic plates.

Polyurea for Blast and Impact Protection: A Review

Polyurea has attracted extensive attention from researchers and engineers in the field of blast and impact protection due to its excellent quasi-static mechanical properties and dynamic mechanical properties. Its mechanical properties and energy absorption capacity have been tuned by means of formulation optimization, molecular dynamics (MD) simulation and the addition of reinforcing materials. Owing to the special molecular structure of polyurea, the mechanism of polyurea protection against blasts and impacts is the simultaneous effect of multiple properties. For different substrates and structures, polyurea needs to provide different performance characteristics, including adhesion, hardness, breaking elongation, etc., depending on the characteristics of the load to which it is subjected. The current article reviews relevant publications in the field of polyurea blast and impact protection, including material optimization, protection mechanisms and applications in blast and impact protection.