Critical interparticle distance

Figure 14.12 shows that the impact strength increases sharply as the interparticle distance is reduced. The toughness increases as the interparticle distance decreases to a critical size, but becomes lower again as the distance becomes too small. It can be seen that the critical interparticle distance for PET is 50 nm. 

Previous explanations of the impact modification effect and its phase transition like the brittle-to-tough transition have assumed a basically statistical distribution of the dispersed rubber phase in the continuous polymer matrix [139], From there the critical interparticle distance model originated [139b], which is essentially a percolation-type theoretical interpretation. Experimental results like those reported by Bucknall [139a], but also many crack surfaces published in the literature, show that more rubber phase is present in the visible area of the crack surface than would be expected from a statistical distribution, SEM evaluations are consistent with our findings of a non-statistical distribution, but a phase separation of the dispersed material into some kind of layer. 

Gonzalez, L, Eguiazabal, J. L, and Nazabal, J. 2008. Effects of the processing sequence and critical interparticle distance in PA6-clay/mSEBS nanocomposites. Eurovean Polymer Journal 44 287-299. 

Poly(lactic acid)/ethylene-octene copolymer-g-GMA (>10 wt%) Mechanical properties/FTIR/ Molau test/morphology/critical interparticle distance of dispersed domains Feng et al. 2013a... 

PET/EP/EP-g-GMA Morphology/critical interparticle distance/mechanical properties Loyens and Groeninckx 2002... 

IDcrit Critical interparticle distance K Bulk modulus Kj Stress intensity factor... 

The effect of matrix strand yielding occurs only below a critical interparticle distance which is dependent on the matrix polymer and the temperature and is similar to the concepts of critical interparticle distance and critical thickness seen in rubber-toughened semicrystalline polymers see Chapter 5. Small interparticle distances below the critical size and, therefore, optimum conditions for good toughness are easier to realize with small particles, in particular with nanoparticles [6]. 

PP SEBS Toughness increases strongly with PP M. increase sharp brittle-ductile transition observed below a critical interparticle distance 45... 

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