The benefits of resin testing under realistic conditions
The Melt Flow Rate (MFR) is known as the result of a traditional lab scale test method to compare different grades of a similar material group. It's a sufficient tool for quality controlling.
But if it comes to optimize our advanced materials for our customers' compact and gas-assisted injection molding process, we prefer the Spiral Flow test. Unlike the MFR, it replicates the true conditions seen in injection molding equipment.
The disadvantage of MFR
The MFR describes the viscosity of a material in grams per 10 minutes. The measurements of common MFR tests are determined at shear rates between 1 and 50 s-1. These rates are low, if we take into account that the actual shear rates in an injection molding machine vary from 100 to 10,000 s-1 and beyond.
We consider the MFR not to be a fundamental polymer property. It does not deliver accurate and sufficient information about the practical flow of a material.
The advantages of Spiral Flow
Spiral Flow measures the ultimate flow path of a resin when a specific injection pressure is exerted on the resin. The behavior of a tested polymer can be evaluated based on process output data such as flow length, part weight, and pressure at transfer. If we mold a Spiral Flow specimen, our shear rates vary from 100 to 10,000 s-1 and beyond, as they do in an injection machine. The further the resin flows, the greater its practical, overall flow.
A higher practical flow can significantly reduce injection pressure when used with the same wall thickness. As a result there are many advantages both in existing tools as in the design of new tools, where even thinner walls and more complex designs become possible.
The benefits of a high practical flow
- reduced reject rate as a result of better appearance
- reduced painting costs combined with the correct design
- improved practical toughness due to reduced resin stress levels
- faster machining, faster cooling
- longer tool lifetimes, reduced tooling costs
For more details and information on Spiral Flow, reach out to Norwin van Riel, our Development Leader, via email@example.com.