1、 Comparison of core principles and testing scope
Capillary rheometer
Principle: High pressure is used to extrude polymer melt or solution from a capillary tube, measure the relationship between pressure and flow rate during the flow process, and calculate shear stress, shear rate, and viscosity.
Test scope:
Shear rate: covering 10 ²~10 ⁵ s ⁻¹, suitable for high shear scenarios such as injection molding and extrusion.
Viscosity range: 10 ²~10 ⁸ Pa · s, suitable for high viscosity materials such as engineering plastics and rubber.
Function extension: It can analyze elastic behaviors such as extrusion swelling and melt fracture, and guide the optimization of processing technology.
Rotational Rheometer
Principle: Apply steady-state or dynamic loads to the sample by rotating fixtures (such as conical plates, parallel plates), measure stress-strain response, and obtain parameters such as viscosity and modulus.
Test scope:
Shear rate: 10 ⁻⁶~10 ³ s ⁻¹, covering low to moderate shear rates.
Viscosity range: 10 ⁻ ³~10 ⁶ Pa · s, suitable for low viscosity fluids (such as coatings and adhesives) and soft solids (such as gel and biomaterials).
Function extension: Support dynamic oscillation testing (frequency scanning, temperature scanning), analyze the viscoelasticity of materials (storage modulus G ′, loss modulus G ″).
2、 Comparison of application scenarios
Capillary rheometer
Core scenario:
Plastic processing: Optimize injection molding temperature, holding time, and extrusion screw design.
Rubber vulcanization: Evaluate the viscosity changes during the vulcanization process and guide the adjustment of process parameters.
Composite materials: Study the flow behavior of fiber-reinforced materials to avoid processing defects.
Advantage: The data is directly related to actual production conditions, with strong guidance.
Rotational Rheometer
Core scenario:
Coating research and development: Analyze thixotropy, yield stress, and optimize construction performance.
Food industry: Evaluate the rheological properties of cream and sauce, control taste and stability.
Biomaterials: study the viscoelasticity of hydrogels and protein solutions to guide the design of drug carriers.
Advantages: Diverse functions, capable of simulating complex stress states such as tension and compression.
3、 Selection suggestion: Match instruments according to needs
Priority selection of capillary rheometer
Requirement: It is necessary to simulate high shear processing conditions (such as injection molding, extrusion), or analyze the elastic behavior of materials such as extrusion swelling and melt fracture.
Typical materials: engineering plastics (PA, PC), rubber, fiber-reinforced composite materials.
Case: A certain automotive parts manufacturer optimized the PA66 injection molding process using a capillary rheometer, reducing the product scrap rate from 8% to 2%.
Priority selection of rotational rheometer
Requirement: It is necessary to analyze the viscoelasticity, thixotropy, or yield stress of materials, or simulate low shear application scenarios (such as coating application, food chewing).
Typical materials: coatings, adhesives, food, biomaterials, thermosetting resins.
Case: A coating company optimized the formula of latex paint using a rotational rheometer, reducing drying time by 30% while improving anti sagging performance.
Comprehensive consideration of factors
Sample size: The rotational rheometer requires a small amount of sample (0.1~1g), which is suitable for the early stage of research and development; Capillary rheometer requires a large amount of samples (10-50g), suitable for batch testing.
Testing efficiency: The capillary rheometer has a short single testing time (<5 minutes), making it suitable for high-throughput screening; The dynamic testing of the rotational rheometer takes a long time (30 minutes to several hours).
Budget: The price of a rotary rheometer is usually higher than that of a capillary rheometer, but it has more comprehensive functions.
4、 Summary: Choose on demand, balance efficiency and accuracy
High shear processing scenarios (such as plastics and rubber) → Capillary rheometer
(Advantages: Data is directly related to production, with strong guidance; Limitations: Single functionality, limited range of cutting rates)
Low shear or viscoelastic analysis scenarios (such as coatings, food) → rotational rheometer
(Advantages: Diverse functions, capable of simulating complex stresses; Limitations: Large sample size requirements, time-consuming testing)
Integration of R&D and quality control: The formula can be screened using a rotational rheometer first, and thenCapillary rheometerVerify processing performance and achieve full process optimization.