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The unique properties and sustainability advantages of sulfur polymer cement have led to efforts to use them as alternatives to traditional Portland cement. The current study explores the impact of environmental stresses on the strength development of polymer composite SunBG90, a material composed of animal and plant fats/oils vulcanized with 90 wt. % sulfur. The environmental stresses investigated include low temperature (−25 °C), high temperature (40 °C), and submersion in water, hexanes, or aqueous solutions containing strong electrolyte, strong acid, or strong base. Samples were analyzed for the extent to which exposure to these stresses influenced the thermo-morphological properties and the compressional strength of the materials compared to identical materials allowed to develop strength at room temperature. Differential scanning calorimetry (DSC) analysis revealed distinct thermos-morphological transitions in stressed samples and the notable formation of metastable γ-sulfur in hexane-exposed specimens. Powder X-ray diffraction confirmed that the crystalline domains identified by DSC were primarily γ-sulfur, with ~5% contribution of γ-sulfur in hexane-exposed samples. Compressive strength testing revealed high strength retention other than aging at elevated temperatures, which led to ~50% loss of strength. These findings reveal influences on the strength development of SunBG90, lending important insight into possible use as an alternative to OPC.

 

Herein we report the preparation of high sulfur-content materials (HSMs) using food waste and elemental sulfur.

 

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.

 

High sulfur-content materials (HSMs) formed via inverse vulcanization of elemental sulfur with animal fats and/or plant oils can exhibit remarkable mechanical strength and chemical resistance, sometimes superior to commercial building products. Adding pozzolan fine materials—fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBFS), or metakaolin (MK)—can further improve HSM mechanical properties and stability. Herein, we detail nine materials comprised of rancidified chicken fat, elemental sulfur, and canola or sunflower oil (to yield CFS or GFS, respectively) and, with or without FA, SF, GGBFS, or MK. The base HSMs, CFS90 or GFS90, contained 90 wt% sulfur, 5 wt% chicken fat, and 5 wt% canola or sunflower oil, respectively. For each HSM/fine combination, the resulting material was prepared using a 95:5 mass input ratio of HSM/fine. No material exhibited water uptake >0.2 wt% after immersion in water for 24 h, significantly lower than the 28 wt% observed with ordinary Portland cement (OPC). Impressively, CFS90, GFS90, and all HSM/fine combinations exhibited compressive strength values 15% to 55% greater than OPC. After immersion in 0.5 M H2SO4, CFS90, GFS90, and its derivatives retained 90% to 171% of the initial strength of OPC, whereas OPC disintegrated under these conditions. CFS90, GFS90, and its derivatives collectively show promise as sustainable materials and materials with superior performance versus concrete.

 

Herein we report a method for the chemical recycling of poly(ethylene terephthalate) (PET) by a three-stage process employing sustainably-sourced organic materials and industrial byproduct sulfur. In this protocol, PET was subject to glycolysis with diethylene glycol to yield low molecular weight oligomers with hydroxyl end groups. The glycolyzed PET (GPET) was then reacted with oleoyl chloride to yield esterified PET (EPET) containing vulcanizable olefin units. The oligomers constituting GPET and EPET were elucidated by MALDI-TOF spectrometry. EPET underwent inverse vulcanization with elemental sulfur (90 wt%) for 35 min or 24 h to yield xPES or mPES, respectively. The composition, thermal, morphological, thermal and mechanical properties were characterized. The composites exhibited good to excellent mechanical properties that were improved significantly by extending the reaction time from 35 min used to prepare xPES (compressive strength = 10.5 MPa, flexural strength = 2.7 MPa) to 24 h used to prepare mPES (compressive strength = 26.9 MPa, flexural strength = 7.7 MPa). Notably, the compressive and flexural strengths of mPES represent 158% and 208% of the values required for residential building foundations made from traditional materials such as ordinary Portland cement. The three-stage approach delineated herein thus represents a way to mediate chemical recycling of waste plastic with green coreagents to yield composites having mechanical properties competitive with existing commercial structural materials. 

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.

 

Environmental contamination with bisphenol A (BPA), produced via degradation of plastic waste, constitutes a major hazard for human health due to the ability of BPA to bind to estrogen receptors and thereby induce hormonal imbalances. Unfortunately, BPA cannot be degraded to a “safe” material without breaking C–C σ-bonds, and existing methods required to break these bonds employ petroleum-derived chemicals and environmentally-harmful metal ions. Therefore, there is an urgent need to develop new “green” methods to break BPA into monoaryl compounds without the use of such reagents and, ideally, convert those monoaryls into valuable materials that can be productively utilized instead of being discarded as chemical waste. Herein we report a new mechanism by which O , O ′-dimethyl bisphenol A (DMBPA), obtained from BPA-containing plastic via low-temperature recycling, undergoes C–C σ-bond cleavage via thiocracking, a reaction with elemental sulfur at temperatures lower than those used in many thermal plastic recycling techniques ( e.g. , <325 °C). Mechanistic analyses and microstructural characterization of the DMBPA-derived materials produced by thiocracking elucidated multiple subunits comprising monoaryl species. Impressively, analyses of recoverable organics revealed that >95% of DMBPA had been broken down into monoaryl components. Furthermore, the DMBPA–sulfur composite produced by thiocracking (BC90) exhibited compressive strength (∼20 MPa) greater than those of typical Portland cements. Consequently, this new thiocracking method creates the ability to destroy the estrogen receptor-binding components of BPA wastes using greener techniques and, simultaneously, to produce a mechanically-robust composite material that represents a sustainable alternative to Portland cements. 

Ordinary Portland Cement (OPC) production consumes tremendous amounts of fresh water and energy and releases vast quantities of CO2 into the atmosphere. Not only would an alternative to OPC whose production requires no water, releases little CO2, and consumes less energy represent a transformative advance in the pursuit of industrial decarbonization, but the greater availability of safe drinking water would lead to significantly improved public health, particularly among vulnerable populations most at risk from contaminated water supply. For any OPC alternative to be adopted on any meaningful scale, however, its structural capabilities must meet or exceed those of OPC. An inverse vulcanization of brown grease, sunflower oil, and elemental sulfur (5:5:90 weight ratio) was successfully modified to afford the high-sulfur-content material SunBG90 in quantities > 1 kg, as was necessary for standardized ASTM and ISO testing. Water absorption (ASTM C140) and thermal conductivity (ISO 8302) values for SunBG90 (<1 wt% and 0.126 W·m−1·K−1, respectively) were 84% and 94% lower than those for OPC, respectively, suggesting that SunBG90 would be more resistant against freeze-thaw and thermal stress damage than OPC. Consequently, not only does SunBG90 represent a more environmentally friendly material than OPC, but its superior thermomechanical properties suggest that it could be a more environmentally robust material on its own merits, particularly for outdoor structural applications involving significant exposure to water and seasonal or day/night temperature swings. 

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.

 

Rancid animal fats unsuitable for human or animal food production represent low‐value and abundant, yet underexploited organic chemical precursors. The current work describes a strategy to synthesize high sulfur‐content materials (HSMs) that directly utilizes a blend of partially hydrolyzed chicken fat and plant oils as the organic comonomers, following up on analogous reactions using brown grease in place of chicken fat. The reaction of sulfur and chicken fat with either canola or sunflower oil yielded crosslinked polymer composites CFS_xor GFS_x, respectively (x = wt% sulfur, varied from 85%–90%). The composites exhibited compressive strengths of 24.7–31.7 MPa, and flexural strengths of 4.1–5.7 MPa, exceeding the value of established construction materials like ordinary Portland cement (compressive strength ≥17 MPa required for residential building, flexural strength 2–5 MPa). The composites also exhibited thermal stability up to 215–224 °C. The simple single‐step protocol described herein represents a way to upcycle an affordable and previously unexploited animal fat resource to form structural composites via the atom economical inverse vulcanization mechanism.