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Applications brief: Analysis of nanodomain composition in high-impact polypropylene by atomic force microscopy-infrared

Key points


  • Breakthrough AFM-IR technique provides quantification of chemical concentrations of polymer nanodomains

  • Quantitative technique demonstrated on complex high impact polypropylene structure (HIPPS) with high correlation to bulk FTIR

  • Measurements showed clear contrast between the continuous and discrete domains for these phase-separated systems

Key words

AFM-IR | NanoTA | LCR | high impact polypropylene | nanoFTIR | nanoscale IR spectroscopy

Authors

Fuguang Tang, Peite Bao, and Zhaohui Su

Abstract

In this paper, compositions of nanodomains in a commercial high-impact polypropylene (HIPP) were investigated by an atomic force microscopy-infrared (AFM-IR) technique. An AFM-IR quantitative analysis method was established for the first time, which was then employed to analyze the polyethylene content in the nanoscopic domains of the rubber particles dispersed in the polypropylene matrix.

It was found that the polyethylene content in the matrix was close to zero and was high in the rubbery intermediate layers, both as expected. However, the major component of the rigid cores of the rubber particles was found to be polypropylene rather than polyethylene, contrary to what was previously believed.

The finding provides new insight into the complicated structure of HIPPs, and the AFM-IR quantitative method reported here offers a useful tool for assessing compositions of nanoscopic domains in complex polymeric system

domain
replicates analyzed
average PE
content (wt %)
StdDev
(wt %)
matrix
19
2.0
6.0
intermediate layer
21
38.8
10.1
core
37
17.2
6.9

Quantitative analysis of composition of different domains in HIPP sample. DOI:10.1021/acs.analchem.6b00798
(a) AFM height image and (b) AFM-IR map of the methyl symmetric C−H bending at 1378 cm−1. (c) AFM-IR spectra taken at the locations marked in (a) and (b), normalized to the 1378cm−1 band, indicative of different ethylene contents as shown by the intensity of the 1456cm−1 band.
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