On the volume organisation of thermoplastic vulcanisates (TPVs) as revealed by scanning transmission electron microscopy (STEM) tomography

• Published in: Polymer (Guilford) Vol. 53; no. 19; pp. 4171 - 4177
• Main Authors: Lu, Kangbo, van Duin, Martin, Loos, Joachim, de With, Gijsbertus
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 31.08.2012; Elsevier
• Subjects: additives; Applied sciences; crosslinking; Exact sciences and technology; Morphology; Organic polymers; Physicochemistry of polymers; polypropylenes; Properties and characterization; rheological properties; rubber; STEM tomography; Structure, morphology and analysis; talc; Thermoplastic vulcanisate; thermoplastics; tomography; transmission electron microscopy; zinc oxide; STEM tomography; Morphology; Thermoplastic vulcanisate; Polymer blends; Dispersion degree; Propylene polymer; Composition effect; Dispersion reinforced material; Experimental study; Heterogeneous mixture; EPDM rubber; Vulcanizate; Isotactic polymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2012.06.041

The phase organisation of thermoplastic vulcanisates (TPVs) has been analysed in detail by applying scanning transmission electron microscopy (STEM) tomography. High contrast between the crosslinked rubber (EPDM) and the isotactic polypropylene (iPP) phases has been achieved without staining the samples. STEM tomography at low-converge-angle conditions allows for the investigation of micrometre thick samples enabling analysis of dispersion and (possible) connectivity of the phases in the TPVs for ultra-large (>50 μm3) volumes. EPDM is dispersed in the iPP phase in a TPV with low EPDM content, whereas it forms a co-continuous phase in a TPV with high EPDM content. The latter could up to now not been demonstrated unambiguously and has impact on the rheological behaviour of the TPV. Moreover, it is demonstrated that zinc oxide and talc particles used as additives in the TPV formulation are located exclusively in the iPP phase of the TPV blend, which suggests that wetting of the solid particles by the relatively low viscous iPP phase during dynamic vulcanisation determines the location of these inorganic additives. [Display omitted]