Some variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; and second repeat units comprising an organic, non-aromatic thiol molecule. Other variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; and second repeat units comprising an organic, non-aromatic unsaturated molecule, wherein the polysulfide-based copolymer has a total sulfur concentration of about 10 wt % or greater. Other variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; second repeat units comprising an organic, non-aromatic thiol molecule; and third repeat units comprising an organic, non-aromatic unsaturated molecule. Other variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; and second repeat units comprising an organic, non-aromatic thioether molecule. The disclosed polysulfide-based copolymers provide broadband transparency, fracture toughness, fluid resistance, and low cost.

Some variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; and second repeat units comprising an organic, non-aromatic thiol molecule. Other variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; and second repeat units comprising an organic, non-aromatic unsaturated molecule, wherein the polysulfide-based copolymer has a total sulfur concentration of about 10 wt % or greater. Other variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; second repeat units comprising an organic, non-aromatic thiol molecule; and third repeat units comprising an organic, non-aromatic unsaturated molecule. Other variations provide a polysulfide-based copolymer containing first repeat units comprising S.sub.8-derived sulfur atoms bonded via sulfur-sulfur bonds; and second repeat units comprising an organic, non-aromatic thioether molecule. The disclosed polysulfide-based copolymers provide broadband transparency, fracture toughness, fluid resistance, and low cost.

Methods and systems to decarbonize natural gas using sulfur to produce hydrogen and polymers are provided. Sulfur can be introduced in elemental form or as hydrogen sulfide, as may be desired. Decarbonization of natural gas involves introducing natural gas and H.sub.2S to a first reactor to produce first reactor products including CS.sub.2 and H.sub.2. The CS.sub.2 can subsequently be polymerized and the H.sub.2 recovered in a purified form with little or no carbon emissions.

Methods and systems to decarbonize natural gas using sulfur to produce hydrogen and polymers are provided. Sulfur can be introduced in elemental form or as hydrogen sulfide, as may be desired. Decarbonization of natural gas involves introducing natural gas and H.sub.2S to a first reactor to produce first reactor products including CS.sub.2 and H.sub.2. The CS.sub.2 can subsequently be polymerized and the H.sub.2 recovered in a purified form with little or no carbon emissions.

Disclosed are compositions comprising a liquid carrier, a polysulfide rubber curing agent, a metal cation, and an ionic liquid. Also disclosed are methods for curing a surface of an uncured polysulfide rubber. These methods involve applying the disclosed compositions to the surface of the uncured polysulfide rubber.

Disclosed are compositions comprising a liquid carrier, a polysulfide rubber curing agent, a metal cation, and an ionic liquid. Also disclosed are methods for curing a surface of an uncured polysulfide rubber. These methods involve applying the disclosed compositions to the surface of the uncured polysulfide rubber.

A process for preparing a sulfur copolymer, a sulfur copolymer, and a polymer composition containing one or more sulfur copolymers are provided. The process involves copolymerizing a cyclic monothiocarbonate compound of formula

##STR00001##

wherein
R.sup.1 and R.sup.2 are independently of one another hydrogen, C.sub.1-C.sub.18-alkyl, C.sub.1-C.sub.18-alkyl substituted with halogen or interrupted with O or S; C.sub.6-C.sub.18-aryl or C.sub.6-C.sub.12-aryl substituted with C.sub.1-C.sub.4-alkyl, C.sub.1-C.sub.4-alkoxy, C.sub.1-C.sub.4-alkylthio or halogen; with elemental sulfur in the presence of a polymerization initiator.

According to the present invention, there can be provided a photocurable composition comprising a sulfur (a) having a cyclic structure represented by the following formula (1), an episulfide compound (b), and a photopolymerization initiator (c), wherein the content of the sulfur (a) is 1 to 28 parts by mass, with respect to the total mass (100 parts by mass) of the sulfur (a) and the episulfide compound (b):

##STR00001##

Compositions of flame retardants and methods of enhancing char formation in a flame retardant-treated substrate. A base material is combined with a flame retardant to form the flame retardant-treated substrate. The flame retardant contains a sulfur copolymer prepared by the polymerization of sulfur monomers with organic monomers. The flame retardant can be deposited on a surface of the base material, coated on the base material, or mixed into the base material. When the flame resistant substrate is on fire, the flame retardant forms a charring layer on the flame retardant-treated substrate. The charring layer can extinguish and prevent the fire from spreading.

Compositions of flame retardants and methods of enhancing char formation in a flame retardant-treated substrate. A base material is combined with a flame retardant to form the flame retardant-treated substrate. The flame retardant contains a sulfur copolymer prepared by the polymerization of sulfur monomers with organic monomers. The flame retardant can be deposited on a surface of the base material, coated on the base material, or mixed into the base material. When the flame resistant substrate is on fire, the flame retardant forms a charring layer on the flame retardant-treated substrate. The charring layer can extinguish and prevent the fire from spreading.