PSI - Issue 53

João Soeiro et al. / Procedia Structural Integrity 53 (2024) 367–375 Soeiro et al. / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 8. SEM micrographs of parts molded with preheated inserts: optimal contact achieved at a pre-heating temperature of 50 ◦ C (a), 85 ◦ C (c) and 120 ◦ C (d); observed adhesion failures at a pre-heating temperature of 50 ◦ C(b), 85 ◦ C (d) and 120 ◦ C(f).

4. Conclusions

The selection, application, and testing of adhesion enhancement strategies were carried out for both polymer polymer and polymer-metal parts manufactured through overmolding and insert molding, respectively. The following conclusions were drawn: • Pull-out test results showed a 16 % increase in the maximum force values for parts manufactured with 5 wt% of the compatibilizer additive, HDPE-g-MAH, relatively to the parts without. Hence, indicating that the adhesion strength was improved. • Surface treatments of sanding and flame treatment applied to the insert were found to enhance the adhesion quality. The SEM images showed improved contact between the polymer and metal, with only adhesion failure of the first polymer layer occurring. This suggests that surface treatments can e ff ectively eliminate voided adhesion failures and significantly reduce the separation of the initial polymer layer. • The pre-heating of the metal inserts also improved adhesion quality. SEM images showed no meaningful consequence on the parts with pre-heated inserts at 50 ◦ C. However, close contact between the polymer and metal was achieved by increasing the pre-heating temperature, with only minimized adhesion failures observed with 85 °C and lesser with 120 °C pre-heating temperature. This suggests that the adhesion quality had a tendency to improve with the increasing of the pre-heating temperature. The adhesion can be enhanced by maintaining the polymer in its crystallization temperature range for a longer duration, promoting stronger intermolecular bonds.

Acknowledgements

Authors gratefully acknowledge the funding of Project Hi-rEV – Recuperac¸a˜o do Setor de Componentes Automo´veis (C644864375-00000002) cofinanced by Plano de Recuperac¸a˜o e Resilieˆncia (PRR), Repu´blica Portuguesa through NextGeneration EU.