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Third monomer: Ethylenedicyclopentadiene (ENB), Dicyclopentadiene (DCPD), 1,4-Hexadiene (HD). Key parameters of EPDM raw rubber: • Ethylene/propylene ratio (ethylene content) • Molecular weight (Mannheim viscosity) • Molecular weight distribution (MWd) • Type and content of dienes (third monomers) • Oil content. Key parameters of EPDM raw rubber: 1: Low ethylene content results in excellent low-temperature performance, lower hardness, easier mixing, and lower strength of the raw rubber； High ethylene content: increased strength of the raw rubber, improved tensile strength, higher hardness of the compounded rubber, increased amount of fillers and oils; poor performance at low temperatures; good mixing properties under appropriate storage conditions and with brittle rubber masses ； Main parameters of EPDM raw rubber 2: Low molecular weight (Mannheim viscosity): Good flowability, easy to process; poor strength of the raw rubber ； High molecular weight (Mannheim viscosity): Increased strength of the raw rubber, improved tensile and tear strengths, better fillability, improved resistance to compression deformation; however, poor rollability and poor extrusion properties (higher extrusion temperatures are required). Key parameters of EPDM raw rubber: 3. Narrow molecular weight distribution MWd: Increased extrusion speed, reduced die shrinkage, faster vulcanization rate, higher degree of vulcanization, faster mixing speed, and improved fillability with fillers/plasticizers ； Wide molecular weight distribution MWd: improved raw rubber strength, enhanced kneading properties, improved calendering processability, smoother surface of extruded products, reduced degree of vulcanization, most suitable for injection molding ； Key parameters of EPDM raw rubber 4: Type of third monomer diene: Dicyclopentadiene (DCPD): Slow vulcanization speed, increased branching. Branching Wider molecular weight distribution Lower viscosity under high shear Improved extrusion properties Deep branching tends to lead to gel formation. Ethylenenebutyral (ENB): Fast vulcanization speed, partial branching. Other diene-based third monomers Vinyleneebutyral (VNB) – highly branched 1,4-Hexadiene (HD) – this type of EPDM is no longer produced. Key parameters of EPDM raw rubber 5: Low content of third monomer diene (2%): Slow vulcanization speed, higher safety against scorching, increased tear strength, good heat resistance. High content of third monomer diene (9%): Fast vulcanization speed, improved compression set resistance, increased modulus, decreased tear strength, reduced heat stability after thermal aging, increased cross-link density, higher cost of the raw rubber