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.

One of the main strategies for sustainable human society progress is the development of efficient strategies to limit waste production and maximize renewable resource utilization. In this context, this review highlights the opportunity to transform vegetable biomass residues into valuable commercial products. Biomass conversion entails the depolymerization of lignocellulosic biomass towards biopolyols and the synthesis and characterization of the valuable products obtained by using them. The influence of the reaction parameters in both acid and basic catalysis is highlighted, respectively the influence of microwaves on the liquefaction reaction versus conventional heating. Following the depolymerization reaction, polyols are employed to produce polyurethane foams. As a special characteristic, the addition of flame-retardant properties was emphasized. Another interesting topic is the biodegradability of these products, considering the negative consequences that waste accumulation has on the environment.

The present work describes the synthesis of new versatile polyurea (PU) and polyurethane (PUR) matrices, including different chain extenders, which facilitate the design of distinct, tunable properties, and high-performance derivatives. These polymers can be used for various defense and security applications, such as coatings for ballistic protection, CBRN protection, binders for energetic formulations, etc. Combining aliphatic and aromatic molecules in PU or PUR structures enables the synthesis of polymers with improved and controllable thermo-mechanical properties. Thus, for polyurea synthesis, we utilized two types of polymeric aliphatic diamines and three types of aromatic chain extenders (1,1’-biphenyl-4,4’-diamine, benzene-1,2-diamine, and 1,2-diphenylhydrazine). An analogous method was used to synthesize polyurethane films by employing one polymeric aliphatic polyol and three types of aromatic chain extenders (benzene-1,3-diol, benzene-1,4-diol, and benzene-1,2,3-triol). Subsequently, various analytic techniques (Fourier transform infrared spectroscopy–attenuated total reflectance (FTIR-ATR), single cantilever dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), frequency-dependent shear modulus survey, tensile tests, water contact angle measurements, and scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX)) have been utilized to characterize the synthesized materials and to evaluate the influence of each chain extender on their final properties.

The aim of this paper was the synthesis of amphiphilic copolymers by employing an atom transfer radical polymerization (ATRP), control polymerization “grafting from” method, initiated both on the surface of an iodinated polyvinyl chloride (PVC–I) membrane and in solution. The iodination of PVC was performed through a Conant-Finkelstein reaction that afforded a 30% molar transformation. Using the contact angle measurements, we highlighted the higher degree of grafting polyacrylic acid (PAA) in the case of solution polymerization, the polar fraction increasing significantly. The micromembrane obtained by surface grafting has pores with a homogenous distribution, which contain –COOH functional groups and with a pore size that decreased about 10 times compared to the initial membrane. The TGA analysis highlighted the thermal resistance changes that the polymers registered.