Flexible polyurethane foams (FPUFs) are versatile materials used in various applications due to their unique properties. Understanding the phase separation behavior in FPUFs is crucial for tailoring their properties to specific applications. In this study, we investigated FPUFs with varying levels of urea phase connectivity using small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray scattering (WAXS). We explored the effect of water, lithium chloride, and isocyanate structures on the phase separation behavior by employing these methods. An increase in water content in the FPUF formulation resulted in a higher amount of formed urea and larger globular size of urea aggregates. Incorporating LiCl into FPUF formulations demonstrated its ability to prevent hydrogen bond formation, leading to alterations in the urea phase. Moreover, we found that foams prepared with asymmetric diisocyanates showed difficulty in forming the urea phase, while foams prepared with symmetric and aliphatic diisocyanates readily formed the urea phase. Our study sheds light on the morphology of the urea phase, the packaging nature of the hard segment, and the hydrogen bonding behavior of the FPUFs. These findings contribute to a better understanding of phase separation in FPUFs and offer insights into tailoring their properties for specific applications.

Drought and water shortage are serious problems in many arid and semi-arid regions. This problem is getting worse and even continues in temperate climatic regions due to climate change. To address this problem, the use of biodegradable hydrogels is increasingly important for the application as water-retaining additives in soil. Furthermore, efficient (micro-)nutrient supply can be provided by the use of tailored hydrogels. Biodegradable polyaspartic acid (PASP) hydrogels with different available (1,6-hexamethylene diamine (HMD) and L-lysine (LYS)) and newly developed crosslinkers based on diesters of glycine (GLY) and (di-)ethylene glycol (DEG and EG, respectively) were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) and regarding their swelling properties (kinetic, absorbency under load (AUL)) as well as biodegradability of PASP hydrogel. Copper (II) and zinc (II), respectively, were loaded as micronutrients in two different approaches: in situ with crosslinking and subsequent loading of prepared hydrogels. The results showed successful syntheses of di-glycine-ester-based crosslinkers. Hydrogels with good water-absorbing properties were formed. Moreover, the developed crosslinking agents in combination with the specific reaction conditions resulted in higher water absorbency with increased crosslinker content used in synthesis (10% vs. 20%). The prepared hydrogels are candidates for water-storing soil additives due to the biodegradability of PASP, which is shown in an exemple. The incorporation of Cu(II) and Zn(II) ions can provide these micronutrients for plant growth.

This work introduces a promising biodegradable copolymer synthesized through the fusion of D,L-aspartic acid (ASP) and L-glutamic acid (GA) utilizing melt polymerization. Employing infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR), and X-ray diffraction (XRD), the copolymer’s structural characterization highlights its distinctive physicochemical attributes. The synthesis, conducted with a facile and controllable melt polymerization method, yielded a remarkable product yield of up to 81%. The optimization of water absorption properties involved a meticulous exploration of various diamine cross-linking agents—hexamethylene diamine (HMD), lysine (LYS), and a synthesized tartaric acid dihydrazide (TD) derivative. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), and scanning electron microscopy (SEM) were employed to confirm the copolymer’s structure, morphology, and cross-linking efficiency. The findings underscore exceptional water retention capabilities, with a peak swelling ratio of 11.874% achieved at a 10% concentration of hexamethylene diamine. Beyond advancing superabsorbent materials, this study contributes to mitigating environmental concerns associated with non-biodegradable alternatives.

This study investigated the potential of bis(2-hydroxyethyl) terephthalate (BHET), derived from the glycolysis of polyethylene terephthalate (PET) waste, as an additive in the synthesis of flexible polyurethane foam (FPUF), addressing the escalating environmental concerns associated with PET waste accumulation and the demand for sustainable material solutions. The influence of varying BHET content on the synthesis process, cellular architecture, and the intricate interplay between compositional variations and the resultant physical, mechanical, and thermal properties of FPUFs has been investigated. Our examination approach included analyses of foam density and cell morphology, comprehensive Fourier transform infrared (FTIR) spectroscopy for chemical structure elucidation, thermogravimetric analysis (TGA) to assess thermal stability, and differential scanning calorimetry (DSC) alongside mechanical property evaluations to discern the impact of BHET on foam performance metrics. Results emphasized the pivotal role of BHET in refining foam characteristics, where its inclusion facilitated the formation of foams with improvement in cell uniformity, subsequently affecting the foam’s apparent density. FTIR spectra analysis provided insight into the hydrogen bonding dynamics within polyurethane segments, revealing how BHET integration influenced microphase separation and the structural coherence of the material. The thermal and mechanical property assessments through TGA and mechanical testing demonstrated that the addition of BHET substantially augmented the thermal stability and mechanical performance of FPUFs.