As discussed in the section on C5 Aliphatic Hydrocarbon Resins, the feedstocks for hydrocarbon resins are produced via cracking of naphtha. Basic C9 aromatic hydrocarbon resins are produced from C9 hydrocarbon resin oil that contains various monomers as illustrated in Figure 1.

Figure 1: C9 Hydrocarbon Resin Oil Composition


A cationic polymerization reaction converts the liquid feed to a hard resin as seen in Figure 2.

Figure 2: C9 Hydrocarbon Resin Oil Polymerization

The aromatic characteristics of the feedstocks are preserved in the final resin polymer so the molecular weight and solubility properties of C9 hydrocarbon  resins are considerably different from those of C5 aliphatic tackifiers. Since C9 hydrocarbon resin oil is a relatively unrefined material, its polymerization leads to much darker resins than other petroleum resins. Due to their aromatic structure, C9 resins are more compatible with polar elastomers than C5 hydrocarbon resins. They are most commonly used in systems based on styrene butadiene rubber, styrene-butadiene-styrene block copolymers, polychloroprene rubber, ethylene vinyl acetate copolymers with high levels of vinyl acetate (>28%), chlorinated paraffins, paints, and concrete curing compounds.
Table 1: Property Ranges of C9 Aromatic Hydrocarbon Resins

Properties	Range
Ring and ball softening point, °C	100–142
Gardner color (50% in toluene)	5–12
Glass transition temperature, °C	40–85
MMAP cloud point, °C	2–45
DACP cloud point, °C	35–100

C9 aromatic hydrocarbon resins produced by LESCO CHEMICAL LIMITED are:
LESTAC-CP Series Cold Polymerization Light Color C9 Aromatic Petroleum Resin
LESTAC-TP Series Thermal Polymerization Yellow Color C9 Aromatic Hydrocarbon Resin
LESTAC-DP Sereis Dark Color C9 Aromatic Petroleum Resin