Melt index is one of the key indicators to measure the properties of plastics. For plastic bottle caps with extremely high stability requirements, the melt index of the raw materials is particularly important. The stability here includes not only the stability of the cap performance, but also the production and molding of the cap. Regarding the stability of the process, Mingsanfeng Cap Mold Co., Ltd. will elaborate below on the impact of melt index on bottle caps.
1. Effect of melt index on bottle cap strength
The higher the melt index, the easier it is for the plastic to flow, and the lower the strength of the plastic itself. Everyone should understand that the strength of a melt that is difficult to flow is usually higher, and the strength of a melt that is easy to flow is lower, so the melt It means that the strength of bottle caps made of low-density polyethylene will increase.
2. Effect of melt index on dimensional stability of bottle caps
The higher the melt index, the easier the bottle cap will be to deform. The lower the melt index, the higher the dimensional stability of the bottle cap made of high-density polyethylene will be.
3. Effect of melt index on bottle cap deformation
The higher the melt index, the softer the bottle cap is, and the bottle cap is relatively easier to deform. After long-distance transportation, the proportion of bottle cap deformation will be higher. Deformed bottle caps are easy to get stuck on the filling line, and melt It means that the bottle cap made of low-density polyethylene has less deformation effect.
4. Effect of melt index on mold fitting accuracy
The higher the melt index of high-density polyethylene, the easier it is for flash to appear on the parting surface and moving parts of the mold. Because the fluidity of the melt is good, wear and flash will be more obvious especially when the mold is running for a long time. On the contrary, the melt index is low. The probability of flash appearing in high-density polyethylene will be lower.
5. Effect of melt index on molding process
For high-density polyethylene with a high melt index, because it has relatively good fluidity and is easy to extrude, the bottle cap is not prone to lack of glue, and the screw temperature/forming pressure/injection pressure can be relatively low; for compression molding equipment, the melt index is low The high-density polyethylene relatively increases the molding and mold closing pressure, and also needs to increase the heating temperature of the screw accordingly.
Post time: Nov-23-2023