09/28/2021
By Sokny Long

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Ph.D. proposal defense by Michael Shone on “Powder Injection Molding (PIM) – Metal Stearates and Their Effects on Rheological Properties, Feedstock Stability, and Process-Ability."

Ph.D. Candidate Name: Michael R. Shone
Defense Date: Thursday, Oct. 7, 2021
Time: 2 to 3:30 p.m.
Location: This will be an in-person defense held in Saab ETIC 445. There will also be a virtual Zoom log-in for anyone who is interested in attending the defense and unable to attend in person. Those interested in attending should contact the student, Michael_Shone@student.uml.edu, and committee advisor Stephen_Johnston@uml.edu at least 24 hours prior to the defense to request access to the meeting.

Committee Chair (Advisor): Stephen Johnston, Professor, Plastics Engineering, UMass Lowell

Committee Members:

  • Carol Barry, Professor and Chair, Plastics Engineering, UMass Lowell
  • Margaret Sobkowicz-Kline, Associate Professor, Plastics Engineering, UMass Lowell

Brief Abstract:

Powder injection molding (PIM) is a growing industry that uses multiphase systems, known as feedstocks, with conventional thermoplastic technology to form complex net shapes, with high volumes and tight tolerances, that subsequently are post processed to remove the undesired phases to be left with a final product of the desired powder in its desired net shape. The powders that are used can consist of ceramics or metals but to facilitate flow, in the injection molding process, the powder must be suspended in a binder system that consists of wax, polymer, or a combination of the two. The post processing is used to remove the binder system and densify the powder into a ceramic or metal part which results in loading levels of the feedstock to be high, meaning greater than 40% by volume.

These heavily filled feedstocks use several types of processing aids such as dispersants, plasticizers, stabilizers, and lubricants to keep the powder suspended in the binder system and ease the injection molding process. Forms of these ingredients exist in categorical families such as, stearates, oils, waxes, and acids. In most recipes stearic acid is used and while research has focused on making a ‘good’ feedstock and how to characterize such a unique material, the longevity of a feedstock has not been explored. Likewise, the focus on how different dispersants other than stearic acid might be better suited for a feedstock is not fully understood.

Through this dissertation with the use of capillary rheometry, parallel plate rheometry, cone and plate rheometry, contact angle measurements, and injection molding equipment, a conventional recipe with stearic acid and modified recipes with metal stearates, as the dispersant, will be explored for their rheological properties as a suitability test and molding for a practical application of the rheological properties as predictors for suitability. The rheological properties will be assessed by looking at viscosity curves, characteristic yield stress, zero shear viscosity, and non-linear testing of the powder stability in the binder. Contact angle measurements will be conducted to looking at the interactions between binder and powder as well as binder and mold surface. The molding of the feedstock will consist of spiral flow testing at a range of volumetric flow rates and pressures.

All interested students and faculty members are invited to attend the online defense via remote access.