Concept

　　Melt index, also known as MI, is a physical parameter that measures the flowability of a material (usually a rubber or plastic material) under certain temperature and pressure conditions, usually in g/10min.

　　Meaning

　　Melt index, since it is a physical term to characterize the material flowability, it determines the molding and processing performance of the material in a certain sense, so it is an important physical parameter to be considered when molding the material. A suitable melt index grade of TPE|TPR material should be selected based on the product mold and runner design, product structure, equipment processing plasticizing ability, and product performance requirements.

　　Question: What is the melt index of TPE|TPR?

　　Answer: General TPE melt index between 0-100, each TPE manufacturer's material melt index is different, depending on what test conditions.

　　Usually there are two conditions: weight and melt temperature. Temperature conditions (150℃, 190℃, 210℃), weight (1.2kg, 2.16kg, 5kg).

　　Generally, the melt index is between 0 and 150 when tested at 2.16kg and 190℃. Usually, if the fluidity is lower than 0, we will change the test condition, such as 5kg, 190℃ or 2.16kg, 210℃, if it is higher than 100, we will use 1.2kg, 190℃ or 2.16kg, 150℃.

　　TPE|TPR melt index influencing factors

　　a Molecular weight of the base material

　　Molecular weight is inversely proportional to melt index. Generally, the higher the molecular weight of the base material (such as SBS, SEBS), the lower the melt index of TPE|TPR.

　　b Molecular chain structure of the base material

　　Generally speaking, the higher the molecular chain branching of the base material, the lower the melt index of TPE blending system; in addition, the melt index of TPE|TPR with star structure as the base material is lower than that with linear structure as the base material.

　　c Reinforced plastics

　　Reinforced plastics such as PP, PS, PPO, PE, etc., the higher the fluidity, the higher the melt index of TPE blends.

　　d Other additives

　　The addition of certain additives, such as flame retardants, etc., will lead to TPE|TPR blend system fluidity (melt index) decline, and with the addition of increased melt index of the blend system to show a certain degree of reduction.

　　In general, the injection molding process than extrusion processing of TPE|TPR material melt index to be higher.