Research

Polymer Manufacturing Processes of Interest

  1. Additive Manufacturing                            
  2. Injection Molding (Cold Runner)
  3. Injection Molding (Hot Runner)
  4. Micro and Nano Injection Molding
  5. Extrusion

 

Research Projects

Rheo-Printing (Additive Manufacturing)

 

In this project, a technique that is called “Rheo-Printing” was developed to optimize 3D printing in many ways:

  1. Induce tunable molecular orientation and crystallinity into 3-D printed parts, thus enabling  additive manufacturing to  build  parts with tunable mechanical, thermal and biodegredation properties.
  2. Enable multi material printing with single extrusion head.
  3. Control helical fiber alignment to enhance mechanical properties of 3-D printed parts.
  4. Prevent nozzle clogging by reducing the viscosity at the nozzle for extrusion.
  5. Mix two different materials to impart desired properties into final printed parts.

 

How does it work?

The main idea behind the Rheo-Printing technique is to precisely control melt rheology of 3-D printing in order to control the morphology of the final printed parts. Shear rate is tuned precisely in both the circumferential direction through a spinning nozzle and the axial direction through controlling the area of the flow as shown in the pictures above. The melting temperature and the stage temperature are also controlled precisely based on the material and desired outcome. Parts with tunable molecular structure were developed and tested.

 

The following link shows a video of the Rheo-Printing technology.

Rheo-Printing

Melt Manipulation of Injection Molding (Injection Molding-Cold Runner)

Vibration assisted injection molding (VAIM) is the process of applying oscillatory pressure during filling and packing. Several studies were carried out fabricating different polymers using VAIM in the past years. Most recent research in our group found that VAIM can enhance fabrication of polymers in the following ways:

  1. VAIM can reduce the cycle time of molding semi crystalline polymers by enhancing the crystallization kinetics and allowing crystals to develop faster.
  2. VAIM can can enhance the mechanical performance of molded parts.
  3. VAIM can mold parts with tunable biodegredation properties by tuning the molecular orientation and crystallization that are imparted into molded products.

How does it work?

In this project, we control the molding processing parameters such as melt temperature, mold temperature and screw vibration oscillation. By controlling and optimizing these parameters, we were able to enhance the crystallization kinetics of semi crystalline PLA and reduce cycle time by up to 40%. The parts that were molded using the VAIM developed higher crystallinity compared to the one molded using conventional injection molding.

 

Hybrid Rheo-Drop Technology for Hot Runner Systems (Injection Molding-Hot Runner)

In this research, we developed an innovative technology called “Rheo-drop” to advance the process of injection molding utilizing hot runner systems. The new technology controls the rheology of molten polymers at the hot drops. The concept is to precisely control the viscosity of the molten polymer through controlling shear rate. Shear is applied by incorporating rotating valve pins at the hot drops. The valve pins are rotated at different rotational speeds based on the desired shear rate and viscosity. This technology was developed to solve several issues such as incomplete filling when manufacturing thin walled parts due to the higher viscosity of the melt. Also, this technology has shown to advance injection molding of hot runners in many ways:

  1. Increase the production rate.
  2. Minimize the required pressure.
  3. Resolve thermal degradation issue when dealing with thermally sensitive polymers.
  4. Increase the efficiency.

 

 

 

 

Melt Modulation and Manipulation (Injection Molding-Cold Runner)

The melt manipulation and modulation technology incorporates vibration assisted injection molding in addition to rotary valves to manipulate the flow during the injection molding process. The vibration assisted injection molding applies oscillatory motion to the polymer melt during the process using the screw, while the melt modulation adds rotary valves in the runners to control the flow. The parameters that can be controlled include the oscillatory motion of the screw and the valve angles, thus, locally molecular orientation, mechanical properties, and weld lines positions can be controlled to meet specific needs of the product. This technology can ensure maximum and uniform packing and it also can move the weld line to any desired position.

 

The technology enhances the properties of recycled materials, where the parts developed from recycled materials molded using this technology can achieve similar properties to the  non-recycled material’s parts molded with conventional Injection Molding machines. This can produce significant environmental impact since it will encourage industries to use more recycled materials as their properties will be comparable to non recycled materials.

 

Micro and Nano Injection Molding

In this project, we developed a strategy for manufacturing biomedical substrates that can mimic human tissue topography with high quality and biocompatibility, which intends to enhance cell culture process. Micro injection molding is a low-cost process that can fulfill the requirements of micro fluidic devices and biological testing applications. Despite all the advancements that have been done to overcome certain limitations of micro injection molding, it still has its limitations especially when it comes to fabricating features with high aspect ratio and demolding. Also, in order to satisfy the market needs, this technology needs more investigations on pattern filling accuracy and improved replication rate.

Numerical simulation Moldflow® was used to gain a better understanding of the melt rheology inside a closed mold under high clamping pressure and optimize the processing with this newly acquired insight. Preliminary processing parameters as done during this study is a better alternative to trial and error type experiments.

 

 

Smart Extrusion Device Project (Extrusion)

What is Smart Extrusion?

It is a novel adaptive die technology that can be incorporated to current polymer extruders to enable more efficient extrusion process:

  1. Extrude multiple profiles simultaneously using a single extruder.
  2. Extrude related profiles, different thicknesses, sequentially using one single extruder with one extrusion die.  

This project is mainly focused on Polyvinyl Chloride (PVC)

Essential steps before smart extrusion

  1. Development of optimal PVC composite extrusion formulations.
  2. Scientifically understand & optimize conventional non-adaptive extrusion processes.

How does it work?

The smart extrusion device has an adjustable inner part that could change extrusion profile thickness by changing its dimension. By changing the dimension of inner part, the smart extrusion device can make similar parts with different thickness to meet different customer needs. Thus, eliminating the need to replace the die to make different parts with different shapes, which will increase the efficiency of extrusion and reduce cost per part.