## 3 Results and Discussion
### Mechanical Properties
The elongation increases with an increase of the monomer content added to the sulfur copolymer (Figure 13b). At an incorporated monomer content of 30-35 wt %, most polymers become brittle thermosets (post cross-linking at the hot press), which break under mechanical stress, for instance, during the process of making specimens. The stretching area of pS-DIB extends up to 432%. The fracture point increases continuously with an increase of incorporated monomer content until thermosetting conditions are reached. [PERSON] et al. performed tensile tests based on pS-DIB with 20 and 30 wt % monomer content. If their results are compared to the results obtained in this work, the required stress is two orders of magnitude higher and the \(E\)-modulus is one order of magnitude higher than in the tensile experiments of pS-DIB in this work (Figure 13). These values indicate a material with higher stiffness, and, consequently, a harder material. A monomer content of 20 wt % shows a comparable elongation (100%-250%). However, it is worth mentioning that the elongation of pS-DIB in this work is two orders of magnitude higher for a monomer content of 30 wt % [35] in the event that it is not cross-linked to a thermoset by the  
Figure 12: Ductility experiments of the pS-DVB specimens: (**a**) stress–strain diagram; (**b**) ductility parameters (\(E\)-Modulus \(E\), Ultimate Stress \(\sigma_{F}\) and Fracture Point \(\epsilon_{F}\)). Figure 13: Ductility experiments of the pS-DIB specimens: (**a**) stress–strain diagram; (**b**) ductility parameters (\(E\)-Modulus \(E\), Ultimate Stress \(\sigma_{F}\) and Fracture Point \(\epsilon_{F}\)). processing with the hot press. The curve shape of pS-DIB with 20 wt % corresponds to thermoplastics and the copolymer with 30 wt % DIB corresponds to thermosets [35]. In comparison, the pS-DIB is more ductile than the pS-DVB, since DIB-based copolymers require 10 times less ductility stress for the same elongation than DVB-based copolymers. An increase of the DIB content in the poly(S-\(r\)-DVB-\(r\)-DIB) terpolymer (pS-DVB-DIB) results in an increase of the elongation and of the ultimate stress as well as of the \(E\)-modulus (Figure 14b). STY acts as a plasticizer (like DIB) and increases the elongation (Figure 14a) when added to the DVB-based terpolymer. The terpolymers contain a total of 20 wt % of incorporated vinyl comonomers with varying ratios. By the incorporation of a divinylbenzene network, the mechanical strength values are significantly increased and the ductility is decreased. Regarding the mechanical properties, sulfur copolymer materials are softer than conventional polymers. They are characteristic for low toughness and strength and high ductility [31]. The DMA plots of pS-DVB and pS-DIB (Figure 15) hardly differ in a sulfur copolymer. Only the three respective graphs are shifted in the respective direction (lower or higher temperature), depending on the \(T_{\text{g}}\). Moreover, the terminal plateau of G' increases with higher incorporated comonomer content, which implies a higher cross-linking degree in the form of hyper-branching. Figure 14: Ductility experiments of terpolymer specimens: (a) stress–strain diagram; (b) ductility parameters (\(E\)-Modulus \(E\), Ultimate Stress \(\sigma_{F}\) and Fracture Point \(\epsilon_{F}\)). Constant total incorporated monomer content: 20 wt %. Figure 15: DMA diagrams of sulfur copolymers: (a) pS-DIB; (b) pS-DVB. Above a temperature of approximately \(-10\)\({}^{\circ}\)C, the glassy state of the materials ends and the glass transition range begins with a sharp increase of the loss modulus \(G\)\". Here, the copolymer is increasingly losing its elastic properties and instead a greater conversion of mechanical energy into heat energy takes place. This results in a simultaneous decrease in the storage modulus \(G\)'. The loss modulus reaches its maximum in the glass transition range. This maximum results from the required energy to increase the chain mobility (molecular friction processes), which is irreversible.