Sinopec Yanshan Petrochemical Co., Ltd.

Sinopec Yanshan Petrochemical Co., Ltd. EPDM grades are processed in dense profile extrusion for automotive weatherseal systems, where the compound must retain collapse resistance during heat ageing and maintain low compression set after long-term door closure. The selection is typically a medium-ethylidene norbornene grade containing 4.0–5.5 wt% ENB and exhibiting Mooney viscosity ML 1+4 at 125 °C of 40–55 measured by ISO 289-1:2018; higher ENB shortens scorch time without proportional improvement in low-temperature set. The mixing formula uses 100 phr polymer, N550 carbon black 70–90 phr, N774 carbon black 30–40 phr, paraffinic oil 40–60 phr, zinc oxide 5.0 phr, stearic acid 1.0 phr, sulfur 1.5–2.2 phr, mercaptobenzothiazole 0.8 phr, zinc dibutyldithiocarbamate 0.8 phr, and tetramethylthiuram monosulfide 0.4–0.6 phr. Compounds are mixed in an intermeshing rotor internal mixer with dump temperatures of 130–140 °C, then sheeted on a two-roll mill at 50–60 °C to disperse curatives before cooling. Cold-feed extrusion uses an L/D ratio of 16:1, barrel zones at 65–80 °C, screw temperature near 75 °C, and die head at 105–115 °C; die swell is controlled by a drawdown of 5–8% before the profile enters microwave/hot-air continuous vulcanization at 220–240 °C. A production-scale failure mode is surface porosity caused by pellet moisture above 0.10 wt%; pre-drying at 70 °C for 2 h is mandatory when storage relative humidity exceeds 60%. Finished profiles are tested under ISO 37:2017 for tensile stress-strain properties, ISO 815-1:2019 for compression set, and ISO 188:2011 for heat ageing at 70 h at 100 °C. The compound is incompatible with high-diene rubber residues in shared mixing equipment because residual dithiocarbamate accelerators migrate into the EPDM phase and reduce scorch safety.

What Limits Service Life of Single-Ply EPDM Roofing Membranes at Reduced Thickness?

Service life prediction for black EPDM single-ply membranes is controlled by filler selection, crosslink density, and residual plasticizer volatility rather than polymer content alone. A roofing formulation combines 100 phr EPDM, N660 carbon black 50–70 phr, calcined clay 40–60 phr, paraffinic oil 20–35 phr, zinc oxide 5.0 phr, stearic acid 1.0 phr, and a sulfur-donor package of thiuram disulfide 1.0–1.5 phr with elemental sulfur kept below 0.5 phr. Calendering on a four-roll inverted-L calender produces sheet thickness of 1.14 mm or 1.52 mm with width tolerance of ±1.5%; the sheet is cured in a hot-air tunnel or autoclave at 160–180 °C for 45–60 min. Field seaming is performed with uncured EPDM tape and butyl-based adhesive; seam peel adhesion is evaluated according to ASTM D4637/D4637M. Heat ageing is assessed under ASTM D4637/D4637M at 116 °C for 670 h, while EN 13956 requires low-temperature bend testing at −45 °C and dimensional stability after ageing. Shrinkage greater than 2% after heat ageing is a known field complaint and is controlled by post-cure annealing and by limiting paraffinic oil to 25 phr or below in the production recipe. Published data for Yanshan EPDM grades specifically optimized for thin-gauge membrane below 0.5 mm is limited; reducing thickness below the standard 1.14 mm requires factorial revalidation of tensile retention and puncture resistance.

Low-Voltage Flexible Cable Insulation and Sheath Compound Requirements

For low-voltage flexible cable insulation, peroxide-cure EPDM compounds require low moisture absorption, high volume resistivity, and stable performance after water immersion. The insulation formulation contains 100 phr EPDM, calcined clay 80–100 phr, zinc oxide 5.0 phr, stearic acid 1.0 phr, paraffinic oil 5–15 phr, dicumyl peroxide 2.5–3.0 phr, and trimethylolpropane trimethacrylate 1.0–1.5 phr. Fillers are pre-dried at 80 °C for 2 h to maintain residual moisture below 0.2 wt%; steam continuous vulcanization at 180–200 °C converts trapped moisture into microvoids that lower insulation resistance. Extrusion is carried out on a cold-feed vented extruder with L/D 20:1, screw temperature 90–105 °C, and die temperature 115–125 °C; the uncured insulation enters a steam CV tube at 1.0–1.5 MPa. Finished cables are evaluated against IEC 60502-1 for 0.6/1 kV power cable construction and UL 44 where North American listing is required. Volume resistivity after 16 h water immersion at 85 °C typically remains above 10¹⁴ Ω·cm. The compound excludes lead-based stabilizers to comply with 2011/65/EU Annex II; amine-based antioxidants are also excluded because they scavenge peroxide decomposition radicals. Table 2 lists the production-scale test matrix.

Cellular EPDM sponge profiles for low-closure-force door seals and trunk gaskets are produced with a chemical blowing agent system rather than a dense-compound cure. The cellular formulation uses 100 phr EPDM, N550 carbon black 40–70 phr, calcium carbonate 20–40 phr, paraffinic oil 40–60 phr, zinc oxide 5.0 phr, stearic acid 1.0 phr, sulfur 1.5–2.0 phr, and azodicarbonamide 3–5 phr as the blowing agent. Mixing is performed as a two-pass procedure: the first pass disperses fillers and oil without curatives, and the second pass adds sulfur and the blowing agent below 90 °C to prevent premature gas release. Extrusion uses a cold-feed extruder with L/D 16:1, screw temperature 70–80 °C, and die temperature 85–95 °C; the profile then passes through a microwave/hot-air tunnel at 220–240 °C where the blowing agent decomposes and the sulfur system crosslinks the expanding cell walls. Final sponge density is controlled between 0.5 g/cm³ and 0.7 g/cm³ by adjusting blowing agent dose and extrusion head pressure. The cellular structure is tested under ASTM D1056-20, with compression set and water absorption limits specified by the end-use line call-out. A known production failure is irregular cell formation caused by moisture pickup in the blowing agent; azodicarbonamide must be stored below 50% RH and added only after polymer and filler are below 0.15 wt% moisture.

When EPDM Serves as a PP Impact Modifier in TPO Molding

In injection-molded automotive TPO parts, Yanshan EPDM is introduced as an impact modifier in polypropylene homopolymer at addition levels of 15–30 wt%. The compounded pellets are produced on a co-rotating twin-screw extruder with L/D 40:1 and screw speed 400–600 rpm, with melt temperature maintained at 210–230 °C. Notched Izod impact strength at 23 °C under ISO 180:2019 increases as the elastomer forms discrete domains in the 0.5–2.0 µm range; below 0.3 µm the impact contribution decreases because the dispersed phase becomes too fine to cavitate. Flexural modulus measured by ISO 178:2019 commonly falls from above 1,200 MPa for neat PP homopolymer to 700–900 MPa at 30 wt% EPDM. This trade-off drives lower addition levels for dimensionally stable interior components, while higher loadings are reserved for bumper substrates requiring low-temperature impact resistance. Injection molding machines processing high-rubber TPO grades require clamp force settings of 400–800 t depending on projected area and wall thickness. A known processing bottleneck is screw wear caused by viscosity mismatch between the elastomer phase and the PP melt; barrel temperatures above 240 °C initiate local degradation of the EPDM phase and must be avoided. Published data for specific Yanshan EPDM grades in filled TPO systems is limited; the exact addition level should be confirmed by design of experiments for the chosen PP matrix and filler package.

Thermoplastic vulcanizates based on Yanshan EPDM and polypropylene are produced by dynamic vulcanization in a co-rotating twin-screw extruder with L/D 48:1 and screw speed 300–500 rpm. The feed formula typically contains 100 phr EPDM, polypropylene 40–80 phr, paraffinic extender oil 30–60 phr, phenolic cure resin 3–5 phr, and stannous chloride 0.2–0.5 phr. The melt temperature is held at 190–210 °C during phase inversion, where the EPDM crosslinks into finely dispersed particles within a continuous polypropylene matrix. Solvent swell measurements in xylene are used to track gel content and crosslink density; incomplete phase inversion produces low gel and high permanent set. The finished TPV is tested under ISO 37:2017 for tensile stress-strain properties, ISO 815-1:2019 for compression set, and ISO 1183-1 for density. This process is sensitive to residual peroxide in the extruder; compounds that previously ran peroxide-cure EPDM can induce uncontrolled PP chain scission if the barrel is not purged. The practical upper limit for extender oil in the upstream feed is approximately 60 phr because higher oil addition before phase inversion delays crosslink development and increases die-face instability.

Reducing Compression Set in Coolant Hose Compounds Through Peroxide Cure

To reduce compression set in coolant hose compounds, the inner tube is formulated for peroxide cure when the end-use specification requires compression set below 25% after 70 h at 150 °C under ISO 815-1:2019. The compound contains 100 phr EPDM, N550 carbon black 60–90 phr, paraffinic oil 20–40 phr, zinc oxide 5.0 phr, stearic acid 1.0 phr, dicumyl peroxide 2.5–3.5 phr, and triallyl cyanurate 1.0–2.0 phr. Mixing is performed in an internal mixer with dump temperature not exceeding 120 °C to prevent scorch during the first pass; the peroxide and coagent are added on a two-roll mill at 70–80 °C. Extrusion of the inner tube is followed by knitted polyester reinforcement and cover-layer application, then autoclave vulcanization at 160 °C for 45 min. Final hoses are tested under SAE J20 for coolant service and ISO 1402 for hydrostatic integrity. Continuous service is limited to −40 °C to +150 °C; sustained exposure above 170 °C accelerates reversion unless the compound uses a high-ENB grade and additional coagent. The inner tube compound is incompatible with amine-based antidegradants because they quench peroxide decomposition radicals; phenolic antioxidants are used instead. Production failure modes include inner-tube porosity at moisture levels above 0.10 wt%, requiring pre-drying of carbon black and mineral fillers at 90 °C for 2 h.

Food-Contact Gasket Compounds Require Post-Cure Washing to Meet 21 CFR 177.2600

When face-seal gaskets are used in food processing equipment, the EPDM compound must balance cleaning-agent resistance with low extractables. The formulation is limited to ingredients listed under 21 CFR 177.2600 and includes 100 phr EPDM, N550 carbon black 40–70 phr, paraffinic oil 10–20 phr, zinc oxide 5.0 phr, stearic acid 1.0 phr, dicumyl peroxide 2.5–3.0 phr, and an FDA-cleared coagent. Vulcanization is carried out in compression molds at 175 °C for 10–12 min, followed by post-cure in a vented oven at 150 °C for 4 h and washing in demineralized water at 80 °C for 30 min to remove peroxide decomposition volatiles. Hardness measured by ASTM D2240-15 is controlled at 65–75 Shore A, while compression set after 24 h at 100 °C under ISO 815-1:2019 is maintained below 20%. This compound is not suitable for continuous contact with high-fat foods above 50% oil content unless n-hexane extraction testing under 21 CFR 177.2600 is performed for the finished part and the extractive limits are met. Production-scale batch-to-batch variance is controlled by limiting depressurization cycles during internal mixing and by monitoring low-molecular-weight volatiles by gas chromatography before shipment.