The effect of molding conditions on mechanical and morphological properties at the interface of film insert injection molded polypropylene‐film/polypropylene matrix

Abstract

An extensive study on the peel strength between a polypropylene (PP) film and PP substrate fabricated using film insert injection molding technique was carried out through a 180°peel test. Injection molding conditions such as barrel temperature, injection speed and holding pressure were varied to gauge their effects on the mechanical and morphological properties. Morphological observations were made at the filmsubstrate interfacial regions by means of transmission electron microscopy (TEM). The injection molded products, with the films still attached, were subjected to bending and impact tests to determine if there is any relationship between film-substrate adhesion and bulk properties. Observation of the load-displacement curves during the peel test revealed three unique and interesting curves, corresponding to different peeling and film fracture mechanisms. Increases in injection speed, barrel temperature and holding pressure lead to increased bonding between the film and substrate surfaces. The enhancement of bonding between these two polymer surfaces could be attributed to polymer-polymer interdiffusion. Substantiating evidence from TEM, which shows the fading of the interface as the bond strengthens, further boosts the accuracy of this assumption. The hope that the films could contribute to enhancing bulk properties has been diminished since the bending properties appeared to be similar with or without the film attached.

Effect of crystallization and interface formation mechanism on mechanical properties of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate

“…The results shown here confirm the observation from a previous work, 19 that the higher crystallinity of the substrate in film-insert specimens has contributed to enhanced brittleness and lower impact properties.…”

“…This correlates well with the peel test results conducted during a previous study. 19 As expected, the altered molecular orientation does not come without compromising the films' strength. Figure 12 shows the relationship between load at break and heat-treatment temperature.…”

Molded geometry and viscoelastic behavior of film insert molded parts

“…Moreover, the injected hot resin may wet and remelt the film partially, which would enhance adhesion between the film and the substrate after the part is cooled. [1][2][3][4] FIM is an effective technique in the aspect of product cost and manufacturing time because the ejected product can be used without additional bonding or decorating processes like screen printing, spray painting, heat-induced labeling, etc. The FIM method has been widely applied lately to various injection molded products such as automotive interior parts, cellular phone cases, logo design of plastic products, etc.…”

Thermoviscoelastic Behavior of Film‐Insert‐Molded Parts Prepared under Various Processing Conditions

“…Compared with conventional injection molding, film-insert molding is an advanced method offering many benefits to designers and manufacturers, because it can improve the surface quality of the molded part without any post-processing, such as screen printing or spray painting. [1][2][3][4] The FIM method has been widely applied lately to various injection molded products, such as automotive interior parts, cellular phone cases, logo designs for plastic products, etc.…”