What is the acceptable value of particle angle of repose

The qualified standards and testing methods for the angle of repose of particles are as follows:

I. Qualified Range of Angle of Repose

‌Pharmaceutical Industry Standards‌
25-30°: Excellent fluidity (suitable for high-efficiency tableting)
31-35°: Good fluidity
36-40°: Moderate fluidity
41-45°: Acceptable but requires process optimization

45°: Poor fluidity (may cause tablet weight variation or pressing issues)

‌General Standards in Powder Engineering‌
<30°: Excellent fluidity (suitable for automated production lines)
30-45°: Requires evaluation of process adaptability

45°: Needs improvement (e.g., adding flow aids)

II. Testing Methods and Standards

‌GB/T 11986-1989 (Powdered Surfactants)‌
Fixed funnel method: Funnel height 100mm, calculation θ=arctan(2h/D)
Rotating cylinder method: Closer to actual working conditions

‌Pharmaceutical Industry Practices‌
Requires simultaneous testing of particle size distribution (40-75% below 80 mesh) and Carr's index

III. Influencing Factors and Optimization Recommendations

‌Key Factors‌
Smaller and more irregular particle shapes result in larger angles of repose
Humidity >5% significantly increases the angle of repose

‌Improvement Measures‌
Adding 0.5-1% fumed silica can reduce the angle of repose by 5-10°
Using vibration sieving to improve particle uniformity

The ‌ST-F13B Powder and Granule Angle of Repose Tester‌ is designed and manufactured in accordance with the specifications of the ‌National Standard GB-T11986-89‌ (Method for Determining the Angle of Repose of Powdered and Granular Surfactants).

‌Scope of Application‌

This product is intended for use in laboratories of production, trading, and user units to measure the angle of repose of powdered and granular surfactants.

‌Applicable Standard Requirements‌

‌GB/T11986-98‌ (Method for Determining the Angle of Repose of Powdered and Granular Surfactants).