additives feature | Nucleation and reinforcement
FIGURE 6. DIFFERENTIAL SHRINKAGE (%) IN EXTRUDED 2MFR HPP SHEET
FIGURE 7. CUP SHRINKAGE AND OVALITY
only increased crystallization temperature and % crystallinity, but a balanced orientation in the MD/TD plane. Talcum also directs a similar orientation to HPN- 20E, but the weak nucleating power of this mineral requires higher loadings that are detrimental to impact resistance. As a result, there is growing interest out in the field to replace and upgrade PP grades that utilize talcum today due to the much greater efficacy of HPN-20E at lower use levels, and the similar orientation effect overall.
Orientation effect of HPN-600ei Hyperform HPN-600ei directs the same orientation as that of HPN-20E. The major difference is the additional benefit of enhanced optical effects seen in thermofor- med PP articles – especially medium-and deep-draw parts. Figure 5 shows the excellent haze perfromance compared to a phosphate ester salt.
The balanced orientation of HPN-600ei is evident
when comparing the differential shrinkage in the sheet (Figure 6) and the resulting ovality of the thermoformed cups (Figure 7). The overall effect of the balanced orientation induced by 600ei was the reduction in warpage in the final parts, resulting in reduced cycle times and the ability to stack parts without nesting issues.
Orientation effect of HPN-68L Hyperform HPN-68L particles also orient very strongly in molten PP during processing, but induce a shrinkage profile opposite to that of HPN-20E (Figure 8). While HPN-20E directs orientation into the normal
direction of fabricated PP articles, HPN-68L orients nucleated domains equally around MD and TD. As a result, HPN-68L induces high and balanced shrinkage
High and Isotropic Shrinkage
Minimal Shrinkage
FIGURE 8. ISOTROPIC SHRINKAGE PROPERTIES OF HYPERFORM HPN-68L
36 COMPOUNDING WORLD | April 2012
FIGURE 9. B-AXIS ORIENTATION OF PP CRYSTAL INTO THE MD AND TD DIRECTION BY HPN-68L
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