Multicomponent surface, etching

Effect of different components in multicomponent blends based on polyamide 6 (PA 6) and styrenic polymers. Addition of a reactive compatibilizer maleic anhydride grafted styrene acrylonitrile (SANMA) changed the matrix-dispersed particle structure of PA6/styrene acrylonitrile (SAN) to a cocontinuous one. Replacement of part of SAN by polybutadiene particles led to a coarse cocontinuous structure (PA6/acrylobutadiene styrene [ABS]), which was refined after compatibUizer addition. SEM of cut surfaces etched in different solvents. (A) PA6/SAN = 50/50 wt%, SAN etched in tetrahydrofurane (B) PA6/ABS = 50/50 wt%, PA6 etched in formic add (C) PA6/ABS = 50/50 wt%, SAN etched in tetrahydrofurane (D) PA6/SAN+SANMA, PA6 etched in formic add (E) PA6/ABS+ SANMA, PA6 etched in formic add and (F) PA6/ABS = 50/50 wt%, PA6 etched in formic add. (From S. H. Jafari, P. Potschke, M. Stephan, G. Pompe, H. Warth, and H. Alberts, Polymer 43,6985-6922,2002. With permission.)... 

Figure 13.6a shows the SEM of cryofractured and etched (with THF and xylene to remove the ABS and PP phases respectively) surfaces of ternary blends with OTPB modified MWNTs. Figure 13.6b shows the SEM of cryofractured and etched (with THF and hot xylene to remove ABS, PP and HDPE phases respectively) surfaces of quaternary blends. In both these SEM images one can clearly observe the remaining continuous PA6 phase. Further, the strands were observed to be intact even after extracting ABS and PP (in case of ternary blends) and ABS, PP and HDPE (in case of quaternary blends). This clearly manifests the co-continuous nature of the blends. The morphologies of the multicomponent blends with OTPB modified MWNTs and the solution experiments are discussed in detail in ref. 18. Both the ternary and the quaternary... 

Another potential difficulty with dynamic SIMS is that, in multicomponent systems, various elements may sputter at different rates. This will lead to segregation of the more slowly sputtering component at the surface. At steady state this surface segregation must exactly compensate for the lower sputtering rate, so that the ratio of sputtered ions will accurately reflect the composition of the material, but transient effects will occur before this steady state is reached. This is a problem if one is interested in the composition profile immediately beneath the surface. What can be done is to coat the sample with a thin, sacrificial layer of polymer (typically about 50 nm thick) steady state is then reached by the time etching has reached the sample... 

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