Large-aspect-ratio sample

Figure 8 Response of a large-aspect-ratio sample to an impact [5]. (a,b) Oscillations after the impact at St = 300 and St = 480, respectively, (c) Oscillations after the impact was lifted at 8toFF = 214. White arrows...

As mentioned previously, the barrier properties of PLA nanocomposites depend both on the particle size and on the dispersion. If the dispersion in two samples is of the same order, the barrier properties depend on the size of the particles and vice versa [118]. Gas and vapor barrier properties of polymer nanocomposite films are increased because of the large aspect ratios of the clays that result in strong interfacial interactions between the polymeric matrix and the nanoclays [123]. Depending on the strength of the polymer/clay interfacial interactions, three broad classes of nanocomposites are thermodynamically achievable (Figure 12.9) [118] ... 

The mini-column should be as small as possible to minimise dispersion and increase sample throughout, yet large enough to ensure efficient mass transfer. The aspect ratio (length intemal diameter) is therefore an important parameter to optimise. In general, a mini-column is assembled... 

There are several other contributions to this term. A fairly common one is associated with the distribution of the sample over the cross section of the column and the collection of the band at the column outlet. This may especially play a role with large-diameter columns or more specifically with columns of low aspect ratio (ratio of column length to column diameter). In this case, distributors are needed to distribute the flow and the sample evenly over the entire cross section. We will discuss column design in Chapter 3. 

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