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Abstract The valorization of waste‐derived feedstocks for polymer synthesis represents a sustainable alternative to petroleum‐based materials. In this study, brown grease, a low‐value waste lipid source, is utilized as a precursor for polyol monomer synthesis via a two‐step functionalization process. Transesterification of brown grease with allyl alcohol generates allyl esters, which are subsequently modified via thiol‐ene click chemistry with 2‐mercaptoethanol to yield hydroxyl‐functionalized polyols (BG‐diol). The thiol‐ene reaction proceeds under mild UV‐initiated conditions, achieving high conversion efficiency (>90%) while preserving the structural integrity of the derived polyol.BG‐diolis further polymerized with 4,4′‐methylene diphenyl diisocyanate (MDI) through step‐growth polymerization to form brown grease‐derived polyurethane (BG‐PU). Comparative analysis ofBG‐PUwith polyurethane (PU) synthesized from purified oleic acid (OLA‐PU) demonstrates comparable molecular weight distributions (M_n = 14.4 kDa,M_w = 20.4 kDa forBG‐PU) and thermal properties (T_g = 24 °C,T_d,5%= 270 °C forBG‐PU). These results underscore the feasibility of brown grease as a cost‐effective and renewable alternative to plant oil‐based polyols, offering a pathway toward sustainable PU production while mitigating food security concerns. This approach exemplifies the potential of waste lipids in circular economy strategies for high‐performance polymer synthesis. 

ABSTRACT High sulfur‐content materials (HSMs) prepared via inverse vulcanization are attractive for a range of sustainable material applications, particularly when synthesized from waste‐derived feedstocks such as brown grease (BG). Two BG‐based composites,SunBG₉₀andaBG₉₀, were prepared using elemental sulfur and either native or allylated brown grease, respectively. This study explores the effect of reinforcing these sulfur‐rich networks with low loadings (0.5–2 wt. %) of highcis‐1,4‐content liquid polybutadiene (PBD). Incorporation of PBD resulted in significant increases in storage modulus, with a near‐linear relationship between PBD content and stiffness enhancement for both material types. At −60°C, storage modulus increased more than fivefold foraBG₉₀and more than tripled forSunBG₉₀. In contrast, flexural strength and flexural modulus exhibited non‐linear responses, with diminishing or reversed gains at higher PBD loadings, suggesting limits to rubber domain compatibility and dispersion. Thermal analysis confirmed high decomposition temperatures (212°C–226°C) and stable glass transitions, indicating thermal robustness of the reinforced networks. Compared with previous studies requiring higher PBD loadings, these results demonstrate that BG‐based HSMs can be effectively reinforced at low additive levels, offering mechanically robust, low‐cost, and renewable alternatives for structural applications. 

ABSTRACT Brown grease (BG) is a high‐free fatty acid (FFA) waste coproduct from the food industry that remains largely unexploited. Herein, we describe a design strategy to upcycle BG into high sulfur‐content materials (HSMs) via inverse vulcanization, circumventing the need for costly transition metals or food‐grade compatibilizers. First, BG was esterified with methyl or allyl groups, yielding MeBG and aBG, respectively. This modification masked the polar carboxylic acids and enhanced miscibility with molten sulfur. Subsequent inverse vulcanization produced remeltable HSMs at 80 or 90 wt% sulfur with uniform elemental distributions by SEM–EDX. FT‐IR spectroscopy revealed the consumption of C=C moieties and the formation of C–S bonds, signifying robust cross‐linking. Thermal analysis (TGA, DSC) indicated good thermal stability (T_d,5%up to 223°C) and glass transitions characteristic of polysulfide networks. Mechanical evaluations demonstrated compressive strengths up to 19.2 MPa, exceeding the minimum requirement for residential foundation‐grade cement (17 MPa) and rivaling previously reported HSMs containing similarly high sulfur content. Notably, MeBG and aBG incorporate organics comprising up to 97 wt% BG, significantly improving the upcycled mass efficiency relative to earlier BG‐based composites. This esterification‐driven approach thus offers a practical, scalable pathway to convert low‐value BG into advanced materials with tunable thermomechanical properties. 

ABSTRACT Lignin, comprising 20%–35% of lignocellulosic biomass, is the second most abundant biopolymer after cellulose. As the bioethanol industry expands, the accumulation of lignin by‐products necessitates innovative valorization strategies. This study explores the synthesis and characterization of lignin‐derived composites. Specifically, the reaction of 20 wt. % lignin‐derived guaiacol or syringol with 80 wt. % elemental sulfur gives composites GS₈₀and SS₈₀, respectively. The chemical structures of composites were elucidated using GC–MS,¹H NMR, and UV–Vis spectroscopy, revealing the formation of both SC_aryland SC_alkylbonds. Thermal and morphological analysis (via TGA, DSC, PXRD, and SEM‐EDS) indicated SS₈₀has higher crystallinity and thermal stability than GS₈₀, attributed to a higher degree of crosslinking and a greater content of dark sulfur. Mechanical testing showed SS₈₀exhibits superior compressional and flexural strengths, and enhanced Young's modulus and Shore hardness, compared to GS₈₀. Notably, the mechanical strength parameters for SS₈₀are comparable to those of C62 class bricks used in construction applications. These findings suggest that lignin‐derived composites, particularly those incorporating syringol, can provide viable alternatives to traditional materials in various applications, contributing to both waste valorization and sustainable materials science. 

Abstract Herein high-strength composites are prepared from elemental sulfur, sunflower oil, and wastewater sludge. Fats extracted from dissolved air flotation (DAF) solids were reacted with elemental sulfur to yield compositeDAFS(10 wt% DAF fats and 90 wt% sulfur). Additional composites were prepared from DAF fat, sunflower oil and sulfur to giveSunDAF_x(x = wt% sulfur, varied from 85–90%). The composites were characterized by spectroscopic, thermal, and mechanical methods. FT-IR spectra revealed a notable peak at 798 cm^–1indicating a C–S stretch inDAFS,SunDAF₉₀, andSunDAF₈₅indicating successful crosslinking of polymeric sulfur with olefin units. SEM/EDX analysis revealed homogenous distribution of carbon, oxygen, and sulfur inSunDAF₉₀andSunDAF₈₅. The percent crystallinity exhibited byDAFS(37%),SunDAF₉₀(39%), andSunDAF₈₅(45%) was observed to be slightly lower than that of previous composites prepared from elemental sulfur and fats and oils.DAFSandSunDAF_xdisplayed compressive strengths (26.4–38.7 MPa) of up to 227% above that required (17 MPa) of ordinary Portland cement for residential building foundations. The composite decomposition temperatures ranged from 211 to 219 °C, with glass transition temperatures of − 37 °C to − 39 °C. These composites thus provide a potential route to reclaim wastewater organics for use in value-added structural materials having mechanical properties competitive with those of commercial products. 

Abstract Lignin is the most abundant natural source of aromatics but remains underutilized. Elemental sulfur is a plentiful by-product of fossil fuel refining. Herein we report a strategy for preparing a durable composite by the one-pot reaction of elemental sulfur and lignin oil comprising lower molecular weight lignin derivatives. A lignin oil-sulfur composite (LOS₉₀) was prepared by reacting 10 wt. % lignin oil with 90 wt. % elemental sulfur. The composite could be remelted and reshaped over several cycles without loss of properties. Results from the study showed thatLOS₉₀has properties competitive with or exceeding values for commercial ordinary Portland cement and brick formulations. For example,LOS₉₀displayed impressive compressive strength (22.1 MPa) and flexural strength (5.7 MPa).LOS₉₀is prepared entirely from waste materials with 98.5% atom economy of composite synthesis, a lowEfactor of 0.057, and lignin char as the only waste product of the process for its preparation. These results suggest the potential applications of lignin and waste sulfur in the continuous efforts to develop more recyclable and sustainable materials. 

Abstract Lignocellulosic biomass remains underutilized despite its annual production in gigaton quantities. Sulfur is another vastly underutilized waste product of fossil fuel refining. New mechanistic insight into the reactions of sulfur unveiled since 2020 suggest a rich and hitherto unexplored chemistry between biomass‐derived olefins and elemental sulfur. In this study, four biomass‐derived olefins (eugenol (1), 4‐allyl‐2,6‐dimethoxyphenol (2),o‐eugenol (3), and 2‐allyl‐6‐methylphenol(4)) were reacted with elemental sulfur to elucidate the S−C bond‐forming and other reactivity of these compounds. Each of the compounds was reacted with elemental sulfur in three sulfur : organic reactant ratios (2 : 1, 4 : 1 and 9 : 1) and at two temperatures (180 °C or 230 °C). Product mixtures were characterized using¹H NMR spectrometry and GC‐MS analysis. Products resulting from a range of mechanisms were unveiled, including inverse vulcanization, S−C_{allylic/benzylic}bond formation, S−C_arylbond formation, intramolecular cyclization, C−C σ‐bond scission, and C−O σ‐bond scission. It is anticipated that the insights from this study will support further synergy between the critical sustainability goals of biomass and sulfur utilization. 

Abstract Poly(methyl methacrylate) (PMMA) is an important commodity polymer having a wide range of applications. Currently, only about 10% of PMMA is recycled. Herein, a simple two‐stage process for the chemical upcycling of PMMA is discussed. In this method PMMA is modified by transesterification with a bio‐derived, olefin‐bearing terpenoid, geraniol. In the second stage, olefin‐derivatized PMMA is reacted with sulfur to form a network composite by an inverse vulcanization mechanism. Inverse vulcanization of PGMA with elemental sulfur (90 wt.%) yielded the durable compositePGMA‐S. This composite was characterized by NMR spectrometry, IR spectroscopy, elemental analysis, thermogravimetric analysis, and differential scanning calorimetry. Composite water uptake, compressional strength analysis, flexural strength analysis, tensile strength analysis, and thermal recyclability are presented with comparison to current commercial structural materials.PGMA‐Sexhibits a similar compressive strength (17.5 MPa) to that of Portland cement.PGMA‐Sdemonstrates an impressive flexural strength of 4.76 MPa which exceeds the flexural strength (>3 MPa) of many commercial ordinary Portland cements. This study provides a way to upcycle waste PMMA through combination with a naturally‐occurring olefin and industrial waste sulfur to yield composites having mechanical properties competitive with ecologically detrimental legacy building materials. 

Abstract Environmental damage caused by waste plastics and downstream chemical breakdown products is a modern crisis. Endocrine‐disrupting bisphenol A (BPA), found in breakdown products of poly(bisphenol A carbonate) (PC), is an especially pernicious example that interferes with the reproduction and development of a wide range of organisms, including humans. Herein we report a single‐stage thiocracking method to chemically upcycle polycarbonate using elemental sulfur, a waste product of fossil fuel refining. Importantly, this method disintegrates bisphenol A units into monoaryls, thus eliminating endocrine‐disrupting BPA from the material and from any potential downstream waste. Thiocracking of PC (10 wt%) with elemental sulfur (90 wt%) at 320 °C yields the highly crosslinked networkSPC₉₀. The composition, thermal, morphological, and mechanical properties ofSPC₉₀were characterized by FT‐IR spectroscopy, TGA, DSC, elemental analysis, SEM/EDX, compressive strength tests, and flexural strength tests. The compositeSPC₉₀(compressive strength = 12.8 MPa, flexural strength = 4.33 MPa) showed mechanical strengths exceeding those of commercial bricks and competitive with those of mineral cements. The approach discussed herein represents a method to chemically upcycle polycarbonate while deconstructing BPA units, and valorizing waste sulfur to yield structurally viable building materials that could replace less‐green legacy materials. 

Abstract A three‐stage route to chemically upcycle post‐consumer poly(ethylene terephthalate) (PET) to produce high compressive strength composites is reported. This procedure involves initial glycolysis with diethylene glycol to produce a mixture (GPET) comprising oligomers of 2–7 terephthalate units followed by trans/esterification of GPET with fatty acid chains supplied by brown grease, an agricultural by‐product of animal fat of relatively low nutritional or fuel value. This process yields PGB comprising a mixture of mono‐terephthalate ester derivatives. The olefin units provided by unsaturated fatty acid chains in brown grease were crosslinked by an inverse vulcanization reaction with elemental sulfur to give composites GBS_x(x = wt% S, varied from 80%–90%). The compressive strengths of GBS₈₀(27.5 ± 2.6 MPa) and GBS₉₀(19.2 ± 0.8 MPa) exceed the compressive strength required of ordinary Portland cement (17 MPa) for its use in residential building foundations. The current route represents a way to repurpose waste plastic, energy sector by‐product sulfur, and agricultural by‐product brown grease to give high strength composites with mechanical properties suggesting their possible use to replace less sustainably sourced legacy structural materials.