Lignin, an abundant and renewable biopolymer, has gained significant attention as a sustainable modifier and building block in polymeric materials. Recent advancements highlight its potential to tailor mechanical, thermal, and barrier properties of polymers while offering a greener alternative to petroleum-based additives. This review provides an updated perspective on the incorporation of lignin into various polymer matrices, focusing on lignin modification techniques, structure–property relationships, and emerging applications. Special emphasis is given to recent innovations in lignin functionalization and its role in developing high-performance, biodegradable, and recyclable materials such as polyurethanes, epoxy resins, phenol-formaldehyde resins, lignin-modified composites, and lignin-based films, coatings, elastomers, and adhesives. These lignin-based materials are gaining attention for potential applications in construction, automated industries, packaging, textiles, wastewater treatment, footwear, supporting goods, automobiles, printing rollers, sealants, and binders.

Over 80 MT of elemental sulfur, a byproduct of fossil fuel desulfurization, are generated annually. This has spurred the development of high sulfur content materials (HSMs) via inverse vulcanization as a productive pathway towards sulfur utilization. In this study, we evaluate the antimicrobial performance of SunBG₉₀, an HSM made from brown grease and sulfur, as tiles or infused into fabric squares. The static antimicrobial activity of SunBG₉₀ tiles was assessed, revealing excellent efficacy against Gram-positive bacteria, with reductions of 96.84% for Staphylococcus aureus and 91.52% for Listeria monocytogenes. The tiles also exhibited strong antifungal activity, reducing Candida auris by 96.20% and mold (fumigatus) by 83.77%. In contrast, efficacy against Gram-negative bacteria was more variable, with moderate reductions for Escherichia coli (61.10%) and Salmonella enteritidis (62.15%), lower activity against Campylobacter jejuni and Salmonella typhi, and no effect on Clostridium perfringens. Under dynamic conditions, SunBG₉₀-infused fabrics achieved a near-complete inhibition of L. monocytogenes (99.91%) and high reduction of E. coli (98.49%), along with a 96.24% inhibition of Candida auris. These results highlight the potential and limitations of SunBG₉₀ for antimicrobial applications, emphasizing the need for further optimization to achieve consistent broad-spectrum activity.

Although lignin is a plentiful biomass resource, it continually exists as an underutilized component of biomass material. Elemental sulfur is another abundant yet underutilized commodity produced as a by-product resulting from the refining of fossil fuels. The current study presents a strategy for preparing five durable composites via a simple one-pot synthesis involving the reaction of lignin oil and elemental sulfur. These lignin oil–sulfur composites LOS_x@T (where x = wt. % sulfur, ranging from 80 to 90, and T represents the reaction temperature in °C) were prepared via the reaction of elemental sulfur and lignin oil (LO) with elemental sulfur. The resulting composites could be remelted and reshaped several times without the loss of mechanical strength. Mechanical, thermal, and morphological studies showed that LOS_x@T possesses properties competitive with some mechanical properties of commercial building materials, exhibiting favorable compressive strengths (22.1–35.9 MPa) and flexural strengths (5.7–6.5 MPa) exceeding the values required for many construction applications of ordinary Portland cement (OPC) and brick formulations. While varying the amount of organic material did not result in a notable difference in mechanical strength, increasing the reaction temperature from 230 to 300 °C resulted in a significant increase in compressive strength. The results reported herein reveal potential applications of both lignin and waste sulfur during the ongoing effort toward developing recyclable and sustainable building materials.

A series of six composites was prepared from the reaction of lignin-derived guaiacol, fatty acids, and sulfur. In this preparation, the organic comonomers undergo C–S bond-forming reactions to establish a highly crosslinked network material in which some non-covalently incorporated sulfur species are also entrapped. Both monounsaturated oleic acid and diunsaturated linoleic acid were used as fatty acid components to assess the influence of their unsaturation levels on composite properties. The ratio of organics and the proportion of sulfur (70 or 80 wt%) was also varied to assess the effect on thermal, morphological, and mechanical properties. Thermogravimetric analysis showed that composites exhibited good thermal stability up to ~220 °C. Differential scanning calorimetry revealed that the materials generally exhibit melting features for entrapped cyclo-S₈, cold crystallization features for some materials, and a composition-dependent glass transition temperature. The flexural and compressive strengths of the composites revealed that some of the composites exhibit strengths significantly higher than those required of Portland cements used in residential housing fabrication and may be more sustainable structural materials. The thermal and mechanical properties could be tailored by changing the degree of unsaturation of the fatty acid comonomer or by altering the percentage of fatty acid in the monomer feed. The highest mechanical strength was achieved with greater amounts of monounsaturated oleic acid comonomer.