Blown Films of High Melt Strength Polypropylene hmsPP

AFM Imaging of Processed Polymers (1) Blown Films of High Melt Strength Polypropylene (hmsPP) 

To reveal the morphology normal to the film surface (ND), films are etched with a 0.7 wt% solution of potassium permanganate in a 2 1 (v/v) mixture of concentrated sulfuric acid and 85% orthophosphoric acid [153]. Specimens are etched for 2-4-h until the thickness is reduced by 40-60%. Etching preferentially removes the amorphous phase thereby revealing the lamellar morphology. Finally, the etched and microtomed specimens are rinsed with methanol and blown dry with compressed air or nitrogen. 

We use a standard tapping/intermittent contact mode set-up, which is assembled as described in Sect. 3.2.1. After inserting the TM cantilever into the cantilever holder, the optical head is mounted, the laser is aligned and the resonance peak is analyzed. The operation frequency and amplitude are adjusted to v at 0.85 Ac and 100 nm, respectively. Prior to engaging, the phase signal is zeroed. The crude and fine engagement procedures are carried out as described in Chap. 2 and Sect. 3.2. After the successful engagement the operation point must be carefully adjusted to maximize the contrast between the EPR and PP phases present (compare 

The use of hard tapping conditions with an amplitude setpoint A/A0 ratio of 0.5 is suggested. 

In the intermittent contact mode phase images shown in Fig. 3.74 a clear contrast between the constituent phases can be observed both for the compression-molded hmsPP (panel a), as well as for the blown film (in the machine and transverse direction in panels band c, respectively). The soft EPR phase appears with dark phase contrast indicating that a substantial amount of energy is dissipated in this phase compared to the PP phase. The EPR particles measure 1 pm or smaller in diameter dispersed in the polypropylene matrix. The horizontal lines and the occasional vertical streaks in the images are artifacts of microtoming. 

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