High-Speed Nanomechanical Property Mapping of Polyetherimide/Zinc Titanate Nanocomposites

PEI is a high-performance thermoplastic polymer with excellent mechanical and tribological properties even at elevated temperature due to its high glass transition temperature [1]. In this study, PEI pellets with a melt index of 18g/10min (337°C) and density of 1.27 g/mL at 25°C purchased from Sigma-Aldrich was used. Zinc titanate (ZnTiO₃) nano powder with a molecular weight of 161.26 g/mol and a <100 nm particle size (BET), 99% trace metals basis along with N, N-Dimethylacetamide also purchased from Sigma-Aldrich were used.

At first, 15gm of PEI pellets were mixed with 100ml of N, N-Dimethylacetamide (1000rpm at 150°C) for three hours until all the pellets were completely dissolved. The solution was then poured in an aluminum pan and placed on the hot plate for curing at 140°C for 72 hours. Finally, the cured samples were polished using 1.0, 0.3, 0.05 μm alumina suspensions and then mounted on to a metallic puck using a cyanoacrylate glue.

Quantitative mapping of hardness and modulus was determined by Accelerated Property Mapping (XPM) technique using Hysitron TI-980 Tribonanoindenter with a diamond Berkovich tip. XPM is a recently developed technique through which the distribution of mechanical properties along the phases of material at nano level can be determined and mapped. Also, XPM technique can perform 6 indents per second and these higher testing rates enables otherwise impractical studies requiring several thousands of indents and detailed statistical studies [2,3]. To acquire the XPM maps, a constant force of 200μN with an indent spacing of 1000nm was used over a 20x20 μm area. Several tests were carried out with 100 indents in each test for quantitative hardness and modulus maps for different wt. % of ZnTiO₃.

Hardness maps of PEI neat and 15 wt. % samples showed an average value of 0.48GPa (Figure 1a) and 0.58GPa (Figure 1d), respectively. A linearly increasing trend with the addition of ZnTiO₃ was found. In our previous studies, we found similar enhancement at 5 wt. % loading [4]. However, optimum enhancements in these properties was observed at 15 wt.% loading with a significant increase of 20.84% and 15.96 % increase in hardness and modulus over neat counterpart (Figure 1&2).

Our study showed that the hardness and modulus of PEI composites enhanced significantly with the addition of ZnTiO₃ nanoparticles up to 15% loading. However, we could not use beyond 15 wt. % loading of ZnTiO₃ nanoparticle due to processing limitations.

The authors would like to acknowledge the National Science Foundation for funding this work through DMR-MRI # 1725513 & DMR-REU #1659506 grants.

No conflict of interest.

1. Kumar S, Ratha T, Mahalinga RN, Reddy CS, Das CK, et al. (2007) Study on mechanical, morphological and electrical properties of carbon nanofiber/polyetherimide composites. Materials Science and Engineering: B, 141(1-2): 61-70.
2. Hintsala ED, Hangen U, Stauffer DD (2018) High-Throughput Nanoindentation for Statistical and Spatial Property Determination. JOM 70(4): 494-503.
3. Li D (2015) FASTMAP: High Speed Nanoindentation Mapping.
4. Yildiz K, N Karaku, N Toplan, HÖ Toplan (2007) Densification and grain growth of TiO₂-doped ZnO. Materials Science-Poland 25(4).z
5. Syed Farooq, Shaik Zainuddin, Isaiah Wilson, Mohamed Elafandi, Shaik Jeelani (2019) Quantitative Nanomechanical Property Mapping and in situ SPM Imaging of Polyetherimide Nanocomposites. Microscopy and Microanalysis 25(S2): 704-705.