New ecological composites based on natural renewable resources (original) (raw)
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Polymers, 2023
Using Kraft lignin, bio-based adhesives have been increasingly studied to replace those petrochemical-based solutions, due to low cost, easy availability and the potential for biodegradability of this biomaterial. In this study, lignin-based phenol-formaldehyde (LPF) resins were synthesized using commercial Eucalypt Kraft Lignin (EKL), purified at 95%, as a phenol substitute in different proportions of 10%, 20%, 30% and 50%. The properties of bio-based phenol formaldehyde (BPF) synthesized resin were compared with phenol-formaldehyde resin (PF) used for control sampling. The results indicated that viscosity, gel time and solid contents increased with the addition of pure EKL. The shear strength test of glue line was studied according to American Society for Testing and Materials (ASTM), and BPF-based results were superior to samples bonded with the PF as a control sample, being suitable for structural purposes. Changes in the curing behavior of different resins were analyzed by Differential Scanning Calorimetry (DSC), and sample comparison indicated that the curing of the LPF resin occurred at lower temperatures than the PF. The addition of EKL in PF reduced its thermal stability compared to traditional resin formulation, resulting in a lower decomposition temperature and a smaller amount of carbonaceous residues.
Resole phenol formaldehyde resins have been used in various applications due to their outstanding physical and chemical properties, flame retardancy, solvent resistance, and thermal stability. However, there are major disadvantages associated with synthesis of resole phenol formaldehyde resins including health risks. One such disadvantage involves the toxic effects of phenol and formaldehyde chemical precursors on the humans. Many studies have been done using renewable resources such as lignin, as partial replacement with the phenolic synthesis starting precursors to produce less hazardous materials. Lignin is a three-dimensional, highly cross-linked macromolecule composed of three types of substituted phenols; coniferyl, sinapyl, and p-coumaryl alcohols by enzymatic polymerization, yielding a vast number of functional groups and linkage. As a natural and renewable raw material, obtainable at an affordable cost, and great chemical and physical properties, lignin's substitution potential extends to many products currently sourced from petrochemical substances. In order to produce less hazardous materials, the goal of the current research is geared towards the synthesis of novel resole phenolic type systems based on the most thermally stable lignin extracted from different biomass resources. Lignin was extracted from wheat straw, pine straw, alfalfa fiber, and flax fiber by formic/acetic acid treatment followed by peroxyformic/acetic acid treatment. Obtained lignin from each source was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for structural, thermal and chemical composition comparison. In addition, void-free, homogenous, solid novel resole phenolic type resin systems have been synthesized using various ratios of the extracted lignin for the phenol precursor. Resulting novel resole phenolic-type systems were characterized using TGA.
Synthesis and Characterization of Composite Material Based on Modified Phenolic Resin
American Journal of Applied Chemistry, 2016
Acid and base catalyzed polycondensationreaction of phenol and bisphenol A with crotonaldehyde and cardanol results in novolac and resol type phenolic resins. Phenolic oligomers are characterized by their viscosity, average molecular weight and FT-IR spectral studies. Glass reinforced composites of all phenolic oligomers were prepared. Composites are characterized by their synergetic thermal stability by Thermo gravimetric analysis (TGA), Differential scanning calorimery (DSC), Scanning electron microscopy (SEM), and mechanical properties such as flexural strength, impact strength and hardness, chemical resistance, fibre content over a broad range of compositions. The thermal and curing behavior of the resins are found to vary markedly with the mole ratio and the purity of crotonaldehyde or cardanol. Composites prepared from these resin having very good mechanical properties.
Application of lignin in production wood-polymer composites
E3S Web of Conferences, 2020
The rational use of wood cannot be imagined without the use of synthetic resins and adhesives, on the basis of which all the main types of wood composite materials are made. The use of synthetic resins provides: production of high-quality glued products with an increased service life due to strength properties; reducing the material consumption of manufactured products and more complete use of low-grade raw materials; improve the fire, bio - and chemical resistance of manufactured materials. Due to the lower consumption of raw materials for the manufacture of glued parts, their cost is usually lower than that of solid wood parts. The international market of adhesives is represented by a wide range, in which 63% are synthetic adhesives. When wood is processed at pulp and paper enterprises, 40-50 million tons of alkaline lignin, 5 million tons of lignosulfonate, 3.5 million tons of technical hydrolytic lignin are produced annually in the world. In the future, the volume of industrial ...