More Like this

1. Polybutadiene Modification of Brown Grease‐Sulfur Materials

   https://doi.org/10.1002/pol.20250491  

   Guinati, Bárbara_G S; Tennyson, Andrew G; Smith, Ashlyn D; Smith, Rhett C (November 2025, Journal of Polymer Science)

   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. 

   more » « less
2. Chemical Recycling of Bakelite Thermoset Resin by Thiocracking To Yield a High-Strength, Recyclable Composite

   https://doi.org/10.1007/s10924-025-03750-x  

   Shivers, Carson B; Tennyson, Andrew G; Smith, Rhett C (January 2026, Journal of Polymers and the Environment)

   Abstract Bakelite is a phenol–formaldehyde thermoset with exceptional thermal stability and is an environmentally persistent material for which viable recycling methods are lacking. Elemental sulfur, an overproduced petroleum refining byproduct, similarly accumulates in large stockpiles. We report a one-pot, 100% atom economical thiocracking strategy to upcycle intractable Bakelite waste into a thermally processable composites (BLS₉₀) via reaction of Bakelite with molten sulfur at 230 °C. Model compound studies reveal the effective breakdown of the Bakelite structure via C–C and C–O s-bond scission with concomitant benzylic S–C bond formation, leading the crosslinking via oligo/polysulfur catenates. The resulting composite exhibits a glass transition at − 36 °C, a melting transition at 118 °C, and decomposition onset at 235 °C.BLS₉₀demonstrates a compressional strength of 27 ± 2 MPa, exceeding that required for ordinary Portland cement building foundations (17 MPa), and flexural strength of 4.9 ± 0.6 MPa. These findings demonstrate that thiocracking enables effective partial replacement of the thermally intractable C–C crosslink network with thermally reversible sulfur catenate crosslinks. This process yields a mechanically robust and thermally reprocessable material from the otherwise non-recyclable thermoset. This approach offers a dual waste-mitigation pathway for Bakelite and surplus elemental sulfur, producing composites suitable for structural applications while advancing the sustainable management of polymer and industrial sulfur waste streams. Graphical Abstract 

   more » « less
3. Upcycling waste PMMA to durable composites via a transesterification‐inverse vulcanization process

   https://doi.org/10.1002/pol.20230609  

   Wijeyatunga, Shalini K; Derr, Katelyn M; Maladeniya, Charini P; Sauceda‐Oloño, Perla Y; Tennyson, Andrew G; Smith, Rhett C (February 2024, Journal of Polymer Science)

   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. 

   more » « less
4. Thermal Conductivity Determination of Ga-In Alloys for Thermal Interface Materials Design

   https://doi.org/10.3390/thermo2010001  

   Maivald, Parker; Sridar, Soumya; Xiong, Wei (March 2022, Thermo)

   Thermal interface material (TIM) that exists in a liquid state at the service temperature enables efficient heat transfer across two adjacent surfaces in electronic applications. In this work, the thermal conductivities of different phase regions in the Ga-In system at various compositions and temperatures are measured for the first time. A modified comparative cut bar technique is used for the measurement of the thermal conductivities of GaxIn1−x (x = 0, 0.1, 0.214, 0.3, and 0.9) alloys at 40, 60, 80, and 100 °C, the temperatures commonly encountered in consumer electronics. The thermal conductivity of liquid and semi-liquid (liquid + β) Ga-In alloys are higher than most of the TIM’s currently used in consumer electronics. These measured quantities, along with the available experimental data from literature, served as input for the thermal conductivity parameter optimization using the CALPHAD (calculation of phase diagrams) method for pure elements, solution phase, and two-phase region. A set of self-consistent parameters for the description of the thermal conductivity of the Ga-In system is obtained. There is good agreement between the measured and calculated thermal conductivities for all of the phases. Due to their ease of manufacturing and high thermal conductivity, liquid/semi-liquid Ga-In alloys have significant potential for TIM in consumer electronics. 

   more » « less
5. High Strength Composites from Wastewater Sludge, Plant Oils, and Fossil Fuel By-Product Elemental Sulfur

   https://doi.org/10.1007/s10924-025-03507-6  

   Tisdale, Katelyn A; Wijeyatunga, Shalini K; Graham, Matthew J; Sauceda-Oloño, Perla Y; Tennyson, Andrew G; Smith, Ashlyn D; Smith, Rhett C (April 2025, Journal of Polymers and the Environment)

   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. 

   more » « less