This study show influence of alkaline treatment on sisal fiber (SF) in different composites of starch matrices (SM) and cellulose acetate matrices (CAM). SF were modified with an aqueous 0.5M NaOH solution. Composites were prepared in proportion of 3% fiber/matrix (m/m) using casting method. The samples were characterized by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy by Attenuated Total Reflection (FTIR-ATR), Thermogravimetric Analysis (TGA) and Dynamic-mechanical thermal analysis (DMA). Through results obtained in FTIR and TGA, it was possible to verify that alkaline treatment partially removed hemicellulose and SF lignin. With SEM, best fiber/matrix adhesion in composites prepared with modified fiber (TSF) has been proven to change fibre morphology. Through DMA analysis it was possible to observe that after addition of SF and TSF, SM composites showed improvements in mechanical properties, while TGA showed an increase in initial temperature of thermal degradation in CAM composites with addition of fiber.

The objective of this study was to characterize the physicochemical-mechanical properties of corn and cassava starch films reinforced with CNF via Tape-Casting. There were differences in size and shape of the starch granules. Corn starch nanocomposites (NCO) showed a significant increase in tensile strength (5.14 to 25.58 MPa) and significant decrease in strain (24.81 to 2.76%) as the CNF concentration increased. Among the cassava starch nanocomposites (NCA), only the cassava starch sample with 1% CNF (NCA-1) showed significant difference both in the maximum stress (4.94 MPa) and strain (15.17%). The corn starch sample with 2% of CNF (NCO-2) presented a lower roughness and NCA-1 a smooth surface. There was no difference in chemical composition between the samples. The CNF-free starch films showed more transparency than other films. The NCA showed more transparency than NCO. Tape-casting technique unveils enhanced mechanical properties of cellulose nanofiber-reinforced starch films. Starch nanocomposites exhibit improved tensile strength and surface characteristics.

This study investigates the incorporation of hafnium (Hf) into polyurethane foams (PUs), an underexplored area in polymer materials research. The synthesis of Hf-containing PU foams was conducted, and their characterization was performed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), optical microscopy (OM), and dynamic mechanical analysis (DMA). The results revealed a significant increase in the stiffness of PU foams due to the potential formation of hafnium isocyanate. Quantitative values obtained through DMA tests demonstrated an approximate increase of 95.97% for PU Hf 0.5% and 342.72% for PU Hf 3%, compared to the sample without Hf. These data highlight the influence of hafnium on enhancing the mechanical properties of polyurethane foams.

This study investigated the kinetics and thermodynamics of starch acetylation and examined the influence of the degree of substitution (DS) on the properties of acetylated starches. Starch acetylation kinetics followed a pseudo-first-order model, reaching a degree of substitution of 2.62 after 50 minutes. Negative enthalpy and entropy values revealed a non-spontaneous reaction requiring catalysis. Fourier Transform Infrared Spectroscopy confirmed acetylation through the appearance of a carbonyl band and the reduction of the glycosidic bond peak. Increasing degree of substitution caused granule breakage, agglutination, and reduced crystallinity, as evidenced by Scanning Electron Microscopy and X-Ray Diffraction. Dynamic Mechanical Analysis demonstrated that these structural changes reduced the glass transition in high degrees of substitution (DS 2.62) and enhanced thermal stability and viscoelastic properties due to the loss of crystallinity. Understanding these processes facilitates the industrial optimization of starch acetylation, resulting in modified starches with improved properties for diverse applications.

Starch acetylation plays a crucial role in the starch industry, offering enhanced versatility and functionality. The study aimed to analyze the kinetics and thermodynamics of starch acetylation. Corn starch was acetylated in different degrees of substitution by esterification reaction with acetic anhydride, acetic acid and sulfuric acid as a catalyst. Order of the reaction was determined by integral analysis method, defined as a pseudo-first order because it presents correlation factor R² closest to 1. From thermodynamic models used, it was possible to determine enthalpy of acetylation (-1.33x10^-2 J.mol^-1), critical temperature (0.0223 K), heat capacity (1.53x10^-3J.mol^-1.K^-1) and entropy change (-2.31x10^-4 J.mol^-1.K^-1). Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) characterized starch and starch acetates. In analysis, acetylation was confirmed with the appearance of band at 1740 cm^-1, corresponding to carbonyl of acetyl group, presence of pores and breakdown of starch granules after acetylation reaction. Starch acetylation increased with reaction time, reaching a maximum degree of substitution of approximately 2.62 after 50 minutes.