Effects of Varied Mold Temperature on Polyethylene Injection Molded Parts
Category
Sciences and Technology
Department
Plastics Engineering Technology
Student Status
Undergraduate
Research Advisor
Dr. Jeanne Norton
Document Type
Event
Location
Student Center Ballroom
Start Date
10-4-2025 2:00 PM
End Date
10-4-2025 4:00 PM
Description
The cooling process is the biggest contributor to injection molding cycle time, and it is the most impactful on final part properties. One way to control both cycle time and part properties as a function of cooling is to manipulate mold temperatures. For this study, we molded HDPE from three different sources (control, virgin, and crate) at three different mold temperatures: 15.6 oC (low), 22.2 oC (mid-range) and 49 oC (high). Parts were analyzed for changes in part dimensions, mechanical, and thermal properties. To establish the degree of part shrinkage after injection molding, parts were measured immediately after molding, after one hour, after 24 hours, and after 168 hours. Each material shrank after processing with the greatest shrinkage occurring within one hour of molding. The greatest shrinkage was observed in all materials at the mid-range mold temperature. Parts were also characterized for tensile, flexural, and impact properties. Crate material demonstrated the highest tensile and flexural moduli overall. Mid-range mold temperatures yielded the highest tensile modulus for all materials. Virgin material demonstrated the highest overall elongation while crate material had the lowest elongation. Low-range mold temperature showed the greatest elongation in all materials. No clear trend was observed for impact properties. Differential scanning calorimetry was used to analyze thermal transitions as a function of mold temperature. Crystallization and melting temperatures were not significantly affected. Crate material had the highest percent crystallinity overall. We have demonstrated that mid-range mold temperatures result in optimized part properties for the HDPE materials in this study.
Effects of Varied Mold Temperature on Polyethylene Injection Molded Parts
Student Center Ballroom
The cooling process is the biggest contributor to injection molding cycle time, and it is the most impactful on final part properties. One way to control both cycle time and part properties as a function of cooling is to manipulate mold temperatures. For this study, we molded HDPE from three different sources (control, virgin, and crate) at three different mold temperatures: 15.6 oC (low), 22.2 oC (mid-range) and 49 oC (high). Parts were analyzed for changes in part dimensions, mechanical, and thermal properties. To establish the degree of part shrinkage after injection molding, parts were measured immediately after molding, after one hour, after 24 hours, and after 168 hours. Each material shrank after processing with the greatest shrinkage occurring within one hour of molding. The greatest shrinkage was observed in all materials at the mid-range mold temperature. Parts were also characterized for tensile, flexural, and impact properties. Crate material demonstrated the highest tensile and flexural moduli overall. Mid-range mold temperatures yielded the highest tensile modulus for all materials. Virgin material demonstrated the highest overall elongation while crate material had the lowest elongation. Low-range mold temperature showed the greatest elongation in all materials. No clear trend was observed for impact properties. Differential scanning calorimetry was used to analyze thermal transitions as a function of mold temperature. Crystallization and melting temperatures were not significantly affected. Crate material had the highest percent crystallinity overall. We have demonstrated that mid-range mold temperatures result in optimized part properties for the HDPE materials in this study.
