Monday, 12 October 2020

How to Approximately Access the Weld Line Strength - Rule of Thumb for Plastic Part Design

In this blog post, I present to you another helpful rule of thumb for plastics part design and material selection. 

Plastic part designs may have a weld line due to polymer melt fronts merging together to form one melt front. At the weld lines, glass fibers do not function as reinforcements and as a result reduced mechanical strength occurs in this area. 

Accessing the approximately weld line strength of a polymer compound can be done by checking the tensile strength of the associated base polymer.

In the example below, glass fiber reinforced polyamide (PA 66 GF 50) has a tensile strength of 237 MPa and a weld line strength of 92 MPa. The associated base polyamide has a tensile strength of 85 MPa which is in a similar range as the weld line strength of the PA 66 GF 50 compound. 

Thank you for reading & #findoutaboutplastics


Herwig Juster

Other Rule of Thumb posts: 

How to Reduce Environmental Stress Cracking - Rule of Thumb for Plastic Part Design & Material Selection

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[1] Gunter Erhard: Designing with Plastics, Hanser, 2006

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