Detection of incipient rubber particle cavitation in toughened PMMA using dynamic mechanical tests

• Published in: Polymer (Guilford) Vol. 41; no. 11; pp. 4149 - 4156
• Main Authors: Bucknall, C.B, Rizzieri, R, Moore, D.R
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-05-2000; Elsevier
• Subjects: Applied sciences; Cavitation; Dynamic mechanical properties; Exact sciences and technology; Mechanical properties; Organic polymers; Physicochemistry of polymers; Properties and characterization; Rubber toughening; Dynamic mechanical properties; Rubber toughening; Cavitation; Compressive stress; Tensile stress; Polymer blends; Investigation method; Acrylic elastomer; Methyl methacrylate polymer; Dispersion reinforced material; Experimental study; Heterogeneous mixture
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(99)00639-4

Dynamic mechanical measurements were carried out on rubber-toughened poly(methyl methacrylate) (RT-PMMA) under superimposed static tensile and compressive stresses, in the temperature range −40 to 10°C, which includes the glass transition of the rubber phase. Under compression, where the dynamic loss curves were very reproducible, the tan
δ peak due to the rubber particles shifted to higher temperatures with increasing superimposed stress. Under tension, by contrast, the loss curves were much more variable, in some cases splitting into two peaks, and the peak temperature was no longer a function of the superimposed stress. This behaviour is consistent with incipient cavitation in a proportion of rubber particles under tensile stress. It is concluded that the transition from reproducible to variable dynamic mechanical behaviour marks the onset of cavitation in the rubber phase. The specimen-to-specimen variations observed under superimposed tension appear to be due to differences in strain distributions within and between rubber particles. The procedure provides a method for measuring the resistance of rubber particles to cavitation in response to mechanically and thermally generated stresses, and for distinguishing the cavitation event from subsequent dilatational yielding.