The paper investigates the properties of unsaturated polyester resins and microcrystalline cellulose (MCC) composites. The influence of MCC modification on mechanical, thermomechanical, and thermal properties of obtained materials was discussed. In order to reduce the hydrophilic character of the MCC surface, it was subjected to esterification with the methacrylic anhydride. This resulted in hydroxyl groups blocking and, additionally, the introduction of unsaturated bonds into its structure, which could participate in copolymerization with the curing resin. Composites of varying amounts of cellulose as a filler were obtained from modified MCC and unmodified (comparative) MCC. The modification of MCC resulted in obtaining composites characterized by greater flexural strength and strain at break compared with the analogous composites based on the unmodified MCC.

In this paper flammability tests and detailed investigations of lignin-containing polymer composites’ properties are presented. Composites were obtained using bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BPA.GDA), ethylene glycol dimethacrylate (EGDMA), and kraft lignin (lignin alkali, L) during UV curing. In order to evaluate the influence of lignin modification and the addition of flame retardant compounds on the thermal resistance of the obtained biocomposites, flammability tests have been conducted. After the modification with phosphoric acid (V) lignin, as well as diethyl vinylphosphonate, were used as flame retardant additives. The changes in the chemical structures (ATR-FTIR), as well as the influence of the different additives on the hardness, thermal (TG) and mechanical properties were discussed in detail. The samples after the flammability test were also studied to assess their thermal destruction.

The preparation and the thermal and mechanical characteristics of lignin-containing polymer biocomposites were studied. Bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BPA.GDA) was used as the main monomer, and butyl acrylate (BA), 2-ethylhexyl acrylate (EHA) or styrene (St) was used as the reactive diluent. Unmodified lignin (L) or lignin modified with methacryloyl chloride (L-M) was applied as an ecofriendly component. The influences of the lignin, its modification, and of the type of reactive diluent on the properties of the composites were investigated. In the biocomposites with unmodified lignin, the lignin mainly acted as a filler, and it seemed that interactions occurred between the hydroxyl groups of the lignin and the carbonyl groups of the acrylates. When methacrylated lignin was applied, it seemed to take part in the creation of a polymer network. When styrene was added as a reactive diluent, the biocomposites had a more homogeneous structure, and their thermal resistance was higher than those with acrylate monomers. The use of lignin and its methacrylic derivative as a component in polymer composites promotes sustainability in the plastics industry and can have a positive influence on environmental problems related to waste generation.

This study describes the combination of unique properties of lignin with TiO₂ as an innovative and effective preparation method for high-performance flame-retardant additives that may be utilized as polymer coatings. The use of lignin resulted in numerous advantages including an increased number of functional groups, satisfactory biocompatibility, low toxicity, and high carbon content. The major benefit of lignin is associated with the reduced carbon footprint of the manufactured product. Lignin can be classified as a natural flame-retardant agent owing to the high amount of char formed during combustion. In turn, TiO₂ exhibits high chemical stability and low operating costs and is considered a non-toxic and environmentally friendly material. During the experiments, commercial TiO₂ in anatase crystallographic form, TiO₂ synthesized from titanyl sulfate hydrate, and kraft lignin as well as organic–inorganic hybrid materials composed of these materials were evaluated as functional additives in epoxy-resin-based polymer coatings (Epidian 601) and their properties were investigated in detail. The cone colorimetry test confirmed that the obtained hybrids are effective flame-retardant additives for polymer coatings, with a notable fire hazard reduction observed for samples containing a synergistic system of titanium oxide and lignin. The coating with lignin was the most effective in fire suppression processes. The conducted thermal and mechanical investigations confirmed good performance properties of the coatings indicating thermal resistance up to 360 °C and Shore D hardness in a range of 80.36–86.28°Sh, accordingly. Optical profilometry investigations show that the lignin/TiO₂ hybrids exhibit a stable topological surface shape as well as good dispersion and uniformity in the polymer matrix. All the conducted tests allowed confirmation that the presence of functional additives in polymer coatings in the form of lignin and TiO₂ can be a promising alternative to non-biodegradable synthetic materials which improve flame-retardant properties.