Salami morphology

Figure 10.3 Typical salami morphology in a HIPS sample. AmpUflcation x 10,000. The sample was treated with OSO4. Dark areas correspond to PB segments and clear areas to PSt. Picture kindly provided by Dr. R. Diaz de Ledn, CIQA.

HIPS and ABS are heterogeneous materials containing dispersed rubber particles in continuous vitreous matrixes. Figure 4.4(a) and (b) exhibit the typical salami morphologies of HIPS and ABS when produced in bulk processes with PBD rubber. These products are nontransparent, due to their relatively large particle sizes. Figure 4.5 compares the stress-strain curves of PS, poly(styrene-co-acrylonitrile) (SAN), HIPS and ABS. The area under... 

The structure of ABS is similar to that of HIPS but with a SAN matrix instead of the PSt matrix in HIPS. PB grafted with SAN acts as a compatibilizer between the rubber particles and the SAN matrix. The rubber particle morphology in ABS can be similar to that in HIPS, with salami-type particles, but ABS particles can also be of the core-shell type, with a core of solid PB and a shell of graft copolymer, especially if the ABS is produced by the emulsion process [34]. In addition to craze formation, an important fracture mechanism in ABS polymers is shear yielding, which leads to tougher materials [46]. 

Figure 19 Transmission electron micrographs of thin sections cut from ABS materials. The rubbery domains appear darker, (a) An ABS material prepared by bulk polymerization showing the characteristic salami-like morphology of the toughening particl which contain several SAN domains within the rubber, (b) ABS materials prepared by emulsion polymerization showing cote-shell partides (i) widi and (ii) widiout subinclusions. (Reproduced with permission from ref. 29.)...

This morphology was appropriately nicknamed the salami structure by M. Matsuo (private communication). 

In addition to co-continuous morphology, droplet-within-droplet (composite droplets, subinclusion, salami-like) morphologies are sometimes formed in blends with a higher content of minor component (see Fig. 6) (70,82). In some systems, ribbon like or stratified morphology was detected instead of classic co-continuous one (75). Rules for formation of individual types of morphology have not been formulated so far. 

Morphology of a ternary system of PP-Ox/PS-Ox (2/1 by wt.) plus hyperbranched polymer (HBP, 5 wt%) obtained by simultaneous mixing for 5 min (A) or 30 min (B). The HBP enriches in the (bright) PS phase resulting in a salami-like phase in phase morphology. (DACA Micro Compounder SEM, cryocut, HBP etched out with NaOH solution.) (From J. Pionteck, P. Potschke, N. Proske, H. Zhao, H. Malz, D. Beyerlein, U. Schulze, and B. Voit, Macromol. Symp. 198,209-220,2003. With permission.)... 

There are some interesting types of structure or morphology, which are named after culinary products, like shish kebab structures (from schaschlik) in PE and PP or salami particles in HIPS. They are listed in Part III in Table 4. 

Guo et al. synthesized a series of block-type amphiphilic copolymers via copolymerization of methacrylate end-capped oligo-urethane and MPS via the sol-gel process [167]. After hydrolysis and condensation of the copolymer precursors (self-assembled in the form of spherical micelles), polyurethane-silica hybrid materials with excellent thermal stability and mechanical properties were obtained. Etmimi et al. synthesized PS-GO nanocomposites via surface RAFT-mediated miniemulsion polymerization [155]. The molar mass and dispersity of PS in the nanocomposites were dependent on the amount of RAFT-grafted GO in the system. The PS-GO nanocomposites were of exfoliated morphology, and their thermal stability and mechanical properties were dependent on the modified GO content and better than those of neat PS polymer. Salami-Kalajahi et al. studied the effect of pristine nanoparticle loading on the properties of PMMA-silica nanocomposites prepared... 

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