Characterization of powders needed

For the process designers assigned to the new plant, the objective is to design equipment that can process powder continuously and efficiently according to the requirements of the design brief.In contrast, engineers on one production team are rarely able to replace equipment, so efforts must be made to use existing plant equipment for acceptable operational performance.Although these goals vary, the two groups need to understand the process in detail, understand the interrelationship between the characteristics of the powder and the process equipment, and how to combine to produce a product that meets performance and quality standards.This could be a formidable challenge for the particle industry.In order to successfully design and implement the powder processing process, engineers need to determine the specific requirements of specific unit operations on the powder and then measure the response of the powder to these environmental conditions.

If it is a mixture from the hopper into the press feed boot example.Whenever the powder plane is below a certain height, a new batch of powder refills the hopper.It is worth noting that after some mixtures are injected again, the discharge flow becomes unstable within a short time, which may lead to factory shutdown.When the powder in the hopper returns to flow, the blockage will be transferred to the feed shoe position, resulting in poor flow into the mold, resulting in uneven powder filling.However, not all mixtures exhibit this behavior.

Figure 1 - compression principle

Through the analysis of these simple process steps, the conditions of powder processing can be obtained.In the process of feeding, the powder at the outlet of the hopper is compressed by the weight of the powder above, while gravity is closely related to the height of the powder.When the powder in the feed shoe stops flowing, the surrounding mechanical vibration may cause consolidation problems.Therefore, the response of powders to consolidation caused by direct compression or vibration is highly correlated.More problems may occur if the consolidation of powders results in significant changes in flow characteristics.

The universal powder tester integrates integral, shear and dynamic measurement functions in one instrument, thus providing engineers with intuitive and sensitive methods to measure moving powders and analyze samples in the state of consolidation, pretreatment, inflation and even fluidization.Consolidation index (CI) can be obtained by comparing flow energy after sample pretreatment with flow energy through compression or consolidation.In this way, the response of the powder is quantified, thus providing the necessary insight to rationalize the above processing behavior.

By comparing and studying the filling performance of two different powders A and B in the mold, the above argument can be proved well.The CI value of sample A (after vibration) is 1.11, while that of sample B is 2.32.This indicates that sample B is A more viscous material with very fine (4 micron) angular particles, which is significantly more affected by vibration than sample A.The mold filling test confirmed that the performance of sample B would decline significantly after consolidation, and it could also be verified from the test results.Sample A may show better performance.

Figure 2 - medium module filling

In this case, the data designer of the powder tester has the following options - choose a hopper with a steeper wall and easier to adjust;Follow the principle of reducing equipment vibration;Or install components that can quickly unclog the hopper.With the above information, the production team can adopt a better method in the hopper filling process and actively deal with the blockage problem.Using less powder and feeding more frequently may be one of the best ways to reduce interference with the process.The two groups of powder materials use detailed performance indicators and more relevant tests. Therefore, the information obtained from the test results can effectively control the design parameters or get the actual method, so as to achieve the production goal.

Since the late 1990 s, Tim Freeman as powder characterization, general manager of company in FT4 powder rheometer ® and the design of general-purpose powder tester and played an important role in sustainable development.Tim has cooperated with various professional institutions and participated in industrial activities, which has made outstanding contributions to the development of powder processing field.

Tim has a degree in mechatronics from the university of Sussex in the UK.He is the mentor of many project teams in the Engineering Research Center for Structured Organic Particulate Systems in the United States, and often organizes industry conferences in the field of powder characterization and processing.A former chairman of the American association of pharmaceutical scientists (AAPS) focus group on "process analysis techniques," Tim is a member of the advisory committee of pharmaceutical technology editors and a member of the industry expert group at the European journal of pharmaceutical review.Tim is also a member of the special interest group for pellet technology of the society of chemical engineers, vice-chairman of the ASTM subcommittee D18.24, which is responsible for the properties and treatment of powder and bulk solids, and a member of the USP general theory - physical analysis expert committee (gc-pa EC).