Find out about.......Plastics, Polymer Engineering and Leadership: Design Properties for Engineers: Weldline Strength of High Performance Polymers

In this post, I present you the weldline strength of selected high performance polymers. Most injection-moulded products have weldlines and these are unavoidable.

There are cases where the weldline is barely seen. However, every weldline represents a source of weakness in the overall product. In general, a weldline is generated when two separate melt streams initiated through a multigated mould join each other, or when the melt flows around an obstacle and joins after the obstacle. Especially in polymers which are reinforced with fibers or platelets, multiphase polymers and liquid crystal polymers, lower weldline strength should be considered. Therefore, obtaining information on the weldline performance, in comparison to the regular tensile strength, is essential for an engineer.

There are different design techniques to overcome weldlines in a part. Among those techniques are overflow tabs and temperature control in critical areas.