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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 injection molding. Build your Circle of Knowledge lesson by lesson. 

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

  • Learning 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: 
Part and mold designers need to understand not only design principles but also the fundamentals of plastics. The choice of plastic or polymer strongly impacts 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.

This section covers explanations, simulations, cause-and-effect analyses, and the introduction of various polymer material properties. It evaluates and analyzes the relationship between various polymers and how they behave during the molding process. Selecting the optimal polymer material for each design is key to a successful molding project.

Recommendation: Entry-Level Operators, Technicians, & Designers

Length: Lessons are approximately 15-20 minutes long each

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