C5 Industry Chain Market Morning Briefing (September 18, 2026)

I. Key Points

1. The United States has signaled that the US-Iran conflict is nearing its end, with multiple parties continuing to push for de-escalation in the Middle East, leading to a decline in international oil prices. NYMEX WTI crude oil futures (October contract) closed at $101.91/barrel, down $0.52/barrel (-0.51% WoW); ICE Brent crude oil futures (November contract) closed at $104.82/barrel, down $1.01/barrel (-0.95% WoW). China INE crude oil futures (contract 2611) fell by 33.4 yuan to 805 yuan/barrel, with the night session dropping by 42.5 yuan to 762.5 yuan/barrel.

2. As of the 17th, Japanese naphtha closed at $920.75/ton, down $20.5/ton from the previous trading day. Singapore naphtha closed at $99.66/barrel, down $2.73/barrel from the previous trading day.

3. Today, prices for pyrolysis C5 from major domestic enterprises remained stable, while private enterprise prices for pyrolysis C5 dropped significantly, gradually converging with those of major enterprises. Shandong mixed C5 prices saw a slight intraday pullback, with the sales-to-production ratio plummeting to 38%, indicating a clear downward trend. Traders in various regions reported minimal transactions for residual liquid. In terms of deep processing, piperylene monomer prices remained temporarily stable, and petroleum resin quotes maintained firmness.

4. Yesterday, the market for pyrolysis C5 residual liquid maintained stability while executing contracts, with sporadic declines in other areas. Gasoline prices in the Shandong market fell, with a sales-to-production ratio of 71%. Prices for similar products, such as mixed C5, declined. The market for pyrolysis C5 residual liquid adopted a wait-and-see approach with stable pricing, alongside sporadic declines.

5. Yesterday, the domestic piperylene market remained temporarily stable. Upstream costs weakened due to falling crude oil and private enterprise pyrolysis C5 prices; however, downstream resin prices rose, improving order activity. Market sentiment leaned cautious, with downstream buyers mostly maintaining rigid demand purchases. Mainstream ex-factory prices ranged from 8,900 to 10,000 yuan/ton.

6. Yesterday, the domestic isoprene market remained temporarily stable. Weakening cost pressures suppressed the market trend, and trader sentiment was cautious. However, supply within the market remained tight, giving sellers strong willingness to maintain prices, keeping quotes firm. Mainstream bid/ask prices in the East China market ranged from 13,600 to 14,200 yuan/ton.

7. Yesterday, the lower bound of dicyclopentadiene (DCPD) prices shifted upward, ranging between 8,900 and 9,300 yuan/ton. Lower-end prices were stable for existing customers, while higher-end spot prices were subject to negotiation. Market supply remained limited, inventories were generally low, and combined with support from raw material prices, the high-price trend is expected to continue in the short term.

8. Yesterday, mainstream prices for C5 petroleum resin used in road marking paints rose by 300/200 yuan to 9,600–10,800 yuan/ton. Due to increased downstream demand, resin plant operating rates rose. However, driven by shortages and higher costs, prices continued to climb.

9. Yesterday, mainstream prices for C5 petroleum resin used in piperylene-based adhesives rose by 500/600 yuan to 11,500–13,600 yuan/ton. Mainstream prices for C5 petroleum resin used in non-cyclic adhesive applications stood at 10,800–11,200 yuan/ton. With spot quantities remaining tight and costs continuing to rise, the market faces short-term supply shortages, pushing negotiated prices higher.

Core Logic: Pyrolysis C5 consolidating; Isoprene stable; Piperylene stable; DCPD rising; C5 petroleum resins steady with slight upward momentum.

II. Price Table

Table 1: Domestic Pyrolysis C5 Industry Chain Summary (Unit: Yuan/Ton)

III. Market Outlook

Domestic pyrolysis C5 prices are expected to remain temporarily stable. Shandong mixed C5 prices may see a slight softening following yesterday's sharp drop in the sales-to-production ratio. Private enterprise pyrolysis C5 prices are under continuous pressure, gradually approaching those of major enterprises. Poor recent shipments of residual liquid have reduced some enterprises' enthusiasm for accepting raw materials. Regarding deep processing, piperylene monomers currently benefit from low inventory levels, and the resin market remains acceptable.

The market for pyrolysis C5 residual liquid is expected to weaken further. Refinery gasoline inventories are low, providing some basis for price maintenance, but mixed C5 trends are declining slightly. Given negative market news, Chempricehub Information predicts that refinery prices for pyrolysis C5 residual liquid will likely decline in the near term.

Overnight crude oil prices fell, though the impact on the market is limited. Refinery gasoline inventories have accumulated consecutively, prompting price reductions for shipments today. Market sentiment is bearish, and trading activity for mixed C5 was poor yesterday. Chempricehub Information expects mixed C5 market prices to slip slightly today.

Isoprene prices are expected to consolidate at high levels. Although crude oil closed lower, the tight supply pattern for isoprene continues, supporting factories' willingness to hold prices and limit sales. Prices are projected to stabilize at current highs.

Piperylene prices are expected to remain stable with a wait-and-see attitude. While crude oil closed lower, support comes from reduced factory output and increased self-consumption inventory. Limited tradable resources in the market suggest piperylene will consolidate stably.

DCPD is expected to continue running at elevated levels. Downstream demand performance is average, but spot tightness is unlikely to ease in the short term. Combined with significant cost support from raw material prices and the pre-holiday stocking period for Mid-Autumn and National Day festivals, supply and cost factors will dominate the market in the short term, maintaining firm high-level trends for individual products.

For C5 petroleum resin used in road marking paints, terminal construction volumes may be delayed due to excessively high raw material prices, and downstream acceptance of current prices is weak. Additionally, resin supply has increased slightly. Consequently, prices are expected to remain firm at high levels in the short term. For C5 petroleum resin used in adhesives, manufacturers face increasing cost pressures, and downstream rigid demand is rising, suggesting prices will continue to edge upward.

IV. Data Calendar

Table 2: Domestic Pyrolysis C5 Industry Chain Data Overview (Unit: 10,000 Tons)