In the EVA (Ethylene-Vinyl Acetate) injection molding process, encountering sticky mold issues despite using odorless crosslinking agents may be attributed to several factors:
Incorrect Crosslinker Dosage: Even with an odorless crosslinker like HJ-30, if the amount added is not appropriate, such as not following the recommended 1.8 times of the normal dosage for odorless crosslinkers, it can lead to insufficient crosslinking and incomplete material curing, causing adherence to the mold.
Process Parameters: Incorrect settings of injection parameters including injection pressure, material volume, mold temperature, and cooling time can all contribute to sticky molds. Overly high pressure or excessive material can saturate the mold cavity, while inadequate cooling prevents full solidification.
Mold Design & Maintenance: The draft angle, surface finish, and venting system design of the mold play crucial roles. Insufficient draft angles, mold damage, or lack of proper polishing can increase the likelihood of sticking. Additionally, poor venting can trap gases, exacerbating the issue.
Release Agent Application: Even when a release agent is used, incorrect selection, uneven application, or degradation due to high temperatures can reduce its effectiveness, leading to mold adhesion.
Crosslinker Characteristics: The decomposition temperature, efficiency, and crosslinking capability of the odorless crosslinker itself are vital. If the crosslinker's decomposition conditions do not align well with the actual molding conditions, it may fail to adequately promote crosslinking within the material, affecting demolding properties.
Addressing these issues typically involves a multifaceted approach, including optimizing the crosslinker dosage, fine-tuning the molding parameters, enhancing mold design and maintenance, and ensuring the effective use of release agents. Moreover, adopting specialized solutions designed for EVA materials, such as the AT-2323 mold release aid, can effectively tackle sticky mold problems.
