Sulfur copolymers (SDIB) from inverse vulcanization of elemental sulfur (S₈) for polymer blend

Abstract

Elemental sulfur (S8) is largely available resource as by-product from petroleum refining process which is causing “excess sulfur problem’ due to its limited usage. The utilization of sulfur as valuable material will not only address environmental concerns but provide cost-effective ways of consuming this huge amount of waste to develop new high-value, high-volume products. One facile synthetic method of utilizing sulfur directly as feedstock to produce polymeric material is inverse vulcanization. In this study, sulfur copolymers (SDIB) was synthesized via inverse vulcanization from S8 and processed into polymer blend with component polymers, polybenzoxazine (PBz) and poly(methyl methacrylate) (PMMA) to show its potential processability into polymer blend. Initially, synthesis of SDIB with varying feed ratios of sulfur to comonomer 1, 3-diisopropenylbenzene (DIB) was evaluated for its resulting properties. Spectroscopy showed copolymerization reactions occurred based on the change in characteristic absorption peaks (C=C-H, C=C, C-H) present in the spectra. Thermogravimetric analysis (TGA) indicated that SDIB is more thermally stable with the increase in onset temperature of degradation. Differential scanning calorimetry (DSC) profile exhibited new single glass transition temperature (Tg) that slightly increased with higher DIB ratio indicating evolution of microstructures of copolymers produced. The processability of SDIB into polymer blend was investigated by using SDIB (50 wt% S) with PBz and PMMA. Blending process using simple mixing technique with solvents was carried out for SDIB/PBz (10/10 wt%) and SDIB/PMMA (7.65/7.65 wt%) blend compositions. The results of this study demonstrated that polymercopolymers interactions influenced the phase structure and behaviour with polymer blend of SDIB/PBz showing higher degree of miscibility with more homogeneous and transparent blend as compared to SDIB/PMMA blend. The suitability of polymer blend in electrospinning of nanofibers could provide variety of new applications for SDIB.

Enhancement of thermomechanical properties of sulfur-rich polymers by post-thermal treatment

“…The chemical structure of sulfur-rich polymer with 70 wt% sulfur is expected to be a hyperbranched polymer according to previously reported results. 29…”

“…The chemical structure of sulfur-rich polymer with 70 wt% sulfur is expected to be a hyperbranched polymer according to previously reported results. 29 The composition of neat poly(S 70 -r-DVB 30 ) powder was measured by TGA and EDX. As the elemental sulfur degrades completely above 300 °C, we can determine the DVB contents in neat poly(S 70 -r-DVB 30 ) powder by measuring weight percent of the residue at 350 °C.…”

Effect on thermal stability of microstructure and morphology of thermally-modified electrospun fibers of polybenzoxazines (PBz) blended with sulfur copolymers (SDIB)

“…Sulfur (S 8 ) (powder, sublimed, Alfa Aesar 99.5%) and 1,3-diisopropenylbenzene (DIB) (TCI Chemicals, >97.0%) were used as received without any purification. Sulfur copolymers (SDIB) were synthesized in the lab based on the procedure described in the works of Chung et al 22 S 8 and DIB mass ratio used in the synthesis was 50/50 wt/wt% as previously studied in the works of Parreño et al 23 Polybenzoxazines (PBz) was prepared in the lab as described in the works of Lin et al 24 Dimethyl sulfoxide (DMSO) (ACS grade, Echo, 99.9%), and tetrahydrofuran (THF) (inhibitor free high purity, Tedia, 99.8%) were used as received.…”