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Lesson 2: Viscosity

Viscosity is the index of the resistance of a fluid to flow. The viscosity of simple fluids, like water or oil, is usually a constant value at a constant temperature. The viscosity of plastic, however, is more complicated and depends on its chemical structure, composition, and processing conditions. Furthermore, within a chemical structure and formulation, viscosity is dependent on temperature, shear rate, and pressure.

This lesson covers the difference in viscosity of plastic materials between Newtonian and non-Newtonian fluids, how to compare viscosity of different materials within a group using single point MFR (melt flow rate) values, interpreting material viscosity curves, and how pressure, fill speed, and shear rate affect viscosity and temperature inside a molded part.

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Learn the fundamentals of polymer material behavior and how different plastics behave during the injection molding process. Build your own Circle of Knowledge lesson by lesson. 

Goals of Polymer Materials: Material Behavior (Level 1): 

  • Learn the fundamentals of polymer material characteristics and basic polymer categorizations
  • Get a basic understanding of how different material behaviors will impact the molding process and the final molded part
  • Analyze real-life molded parts and learn the cause and effect behaviors of design and process

Section Description: 
It is important for part and mold designers not only to understand design principles, but also to understand the fundamentals of plastics. The choice of a plastic, or polymer, has a strong impact on the outcome of a molded part. Having a general understanding of the basic properties and structures of polymers will help part and mold designers, as well as processors, make choices and decisions that will optimize the final part.

Explanations, simulations, cause and effect analyses, and the introduction of various polymer material properties are covered in this section. The relationship between various polymers and how they behave during the molding process are evaluated and analyzed. Selecting the optimal polymer material for each design is key to a successful molding project.

Recommended For: Entry Level Personnel, All Personnel

Length: Lessons are approximately 15-20 minutes long each

The Kruse Training platform delivers knowledge and expertise developed over two decades in the plastic injection molding industry. Now companies and individuals can access a state-of-the-art online training program, suited for all levels of knowledge.