The thesis discusses the mold design for highly filled polymer melts, with
a special emphasis on powder injection molding (PIM) compounds, which
substantially differs from mold design requirements applied to conventional
thermoplastic injection molding.
First part of the Thesis is devoted to a phase separation during injection
molding. The mold design to quantify separation recently proposed by the PIM
research group at TBU is treated with flow simulation approach (Moldflow). The
data obtained from a capillary rheometry (viscosity) and differential scanning
calorimetry (specific heat capacity) and modified transient plane source technique
(thermal conductivity) is implemented to Cross model, where temperatureinduced
physical changes are predicted with the help of Williams-Landel-Ferry
equation (WLF). Both models are used for simulations, and according to the
results obtained, the new mold design is proposed. Simultaneously, the phase
separation is detected with computed tomography on the real samples of stainless
steel feedstock used in PIM.
As it is found that the separation is closely related to shear rate gradients
accompanied with temperature changes, infra-red sensors are installed into the
new testing mold to intercept the areas prone to this issue. Real observations made
on PIM compounds are compared with simulated ones, and statistically analysed.
Second part of the Thesis is focused on a common problem during
injection molding – weld line formation, which is most severe for highly filled
polymers due to a lack of polymer entanglement across the approaching of the
flow fronts. To increase time for an entanglement, the mold inserts from various
materials (copper, aluminum, bronze, epoxy resin, and epoxy resin with
hexagonal boron nitride, acrylic 3D printing material) with different thermal
conductivity are used. It is shown (with the support of carefully selected statistical
methods) that in case of conventional highly filled compounds as wooden plastic
composites, weld lines have a considerable effect on the tensile strength, while
for PIM feedstocks have not, but the presence of a weld line in a PIM part may be
beneficial as it results in the shortening of the filling trajectory, and subsequently,
leads to the time saving during molding.
| ISBN: | 978-80-7454-852-9 |
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| EAN: | 9788074548529 |
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| Počet stran |
70 stran |
| Datum vydání |
06. 09. 2019 |
| Pořadí vydání |
První |
| Jazyk |
anglický |
| Vazba |
e-kniha - pdf |
| Autor: |
Jakub Huba |
| Nakladatelství |
Univerzita Tomáše Bati ve Zlíně |
| Tématická skupina |
5 - Technické vědy |
| Neprodejná publikace. Publikaci je možné poptávat zde: Volně dostupné na http://hdl.handle.net/10563/45787 |
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