  Citation: Wr˛ eczycki, J.; Demchuk, Y.; Bieli ´ nski, D.M.; Bratychak, M.; Gunka, V.; Anyszka, R.; Gozdek, T. Bitumen Binders Modified with Sulfur/Organic Copolymers. Materials 2022, 15, 1774. https:// doi.org/10.3390/ma15051774 Academic Editor: Marek Iwa ´ nski Received: 5 January 2022 Accepted: 23 February 2022 Published: 26 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Bitumen Binders Modified with Sulfur/Organic Copolymers Jakub Wr˛ eczycki 1, * , Yuriy Demchuk 2, * , Dariusz M. Bieli ´ nski 1 , Michael Bratychak 2 , Volodymyr Gunka 2 , Rafal Anyszka 1 and Tomasz Gozdek 1 1 Instituteof Polymerand Dye Technology, Faculty of Chemistry, Lodz University of Technology, 16 Stefanowskiego Street, 90-537 Lodz, Poland; dariusz.bielinski@p.lodz.pl (D.M.B.); rafal.anyszka@p.lodz.pl (R.A.); tomasz.gozdek@p.lodz.pl (T.G.) 2 Department of Chemical Technology of Oil and Gas Processing, Institute of Chemistry and Chemical Technologies, Lviv Polytechnic National University, 12 Bandery Street, 79013 Lviv, Ukraine; mbratychak@gmail.com (M.B.); vgunka@gmail.com (V.G.) * Correspondence: jakub.wreczycki@dokt.p.lodz.pl (J.W.); yuriy_demchuk@ukr.net (Y.D.) Abstract: With the continuing growth of waste sulfur production from the petroleum industry processes, its utilization for the production of useful, low-cost, and environmentally beneficial materials is of primary interest. Elemental sulfur has a significant and established history in the modification of bitumen binders, while the sulfur-containing high-molecular compounds are limited in this field. Herein, we report a novel possibility to utilize the sulfur/organic copolymers obtained via the inverse vulcanization process as modifiers for bitumen binders. Synthesis and thermal characterization (TGA-DSC) of polysulfides derived from elemental sulfur (S 8 ) and unsaturated organic species (dicyclopentadiene, styrene, and limonene) have been carried out. The performance of modified bitumen binders has been studied by several mechanical measurements (softening point, ductility, penetration at 25 ◦ C, frass breaking point, adhesion to glass and gravel) and compared to the unmodified bitumen from the perspective of normalized requirements concerning polymer-modified bitumen. The interaction of bitumen binder with sulfur/organic modifier has been studied by means of FTIR spectroscopy and DSC measurements. The impact of the modification on the performance properties of bitumen has been demonstrated. The bitumen binders modified with sulfur/organic copolymers are in general less sensitive to higher temperatures (higher softening point up to 7 ◦ C), more resistant to permanent deformations (lower penetration depth), and more resistant to aging processes without intrusive deterioration of parameters at lower temperatures. What is more, the modification resulted in significantly higher adhesion of bitumen binders to both glass (from 25% up to 87%) and gravel surfaces in combination with a lower tendency to form permanent deformations (more elastic behavior of the modified materials). Keywords: polysulfides; sulfur polymers; inverse vulcanization; polymer-modified bitumen 1. Introduction The utilization of sulfur excess, mainly manufactured as a side product of the petroleum industry processes, constitutes an important and challenging problem for the chemical industry and related branches [1,2]. Exploration of low-cost, high-sulfur content organic or polymeric materials fabricated from elemental sulfur (S 8 ) and its further utilization pathways should be therefore of primary interest to sustain the proper cycle of sulfur con- version [2,3]. Recently, remarkable progress and renewed interest have been observed in elemental sulfur-based polymer chemistry. The scope of possibilities, accurate comparisons of the polysulfides synthesis methods as well as the green aspects of inclusion of elemental sulfur to polymer chemistry was summarized in exemplary comprehensive reviews [4–6]. The addition of high-molecular materials to a raw bitumen binder constitutes a very promising trend in the modification of its properties nowadays. The modification makes fatigue resistance of bitumen extended, its stiffness at higher temperatures increased, Materials 2022, 15, 1774. https://doi.org/10.3390/ma15051774 https://www.mdpi.com/journal/materials