Microstructure hull

In quantifying the different possible microstmctures, it is important not only to consider the orientations of the constituent crystallites, but also their compositions, as well as other parameters. The complete set of feasible statistical distributions that describe the relevant details of the microstructure are termed the microstructure hull (each point in... 

The interest in multicomponent materials, in the past, has led to many attempts to relate their mechanical behaviour to that of the constituent phases (Hull, 1981). Several theoretical developments have concentrated on the study of the elastic moduli of two-component systems (Arridge, 1975 Peterlin, 1973). Specifically, the application of composite theories to relationships between elastic modulus and microstructure applies for semicrystalline polymers exhibiting distinct crystalline and amorphous phases (Andrews, 1974). Furthermore, as discussed in Chapter 4, the elastic modulus has been shown to be correlated to microhardness for lamellar PE. In addition, H has been shown to be a property that describes a semicrystalline polymer as a composite material consisting of stiff (crystals) and soft, compliant elements. Application of this concept to lamellar PE involves, however, certain difficulties. This material has a microstructure that requires specific methods of analysis involving the calculation of the volume fraction of crystallized material, crystal shape and dimensions, etc. (Balta Calleja et al, 1981). 

Enolates are powerful carbon nucleophiles and addition of enolates to carbonyl groups (aldol reactions) serve as a useful method for C-C bond formation. The Mukaiyama aldol reactions involving fluoride ion-promoted addition of silyl enolates to aldehydes are very popular and are frequently employed in the construction of carbon skeletons in organic synthesis [ 1 ]. The Mukaiyama aldol reaction with the silyl enol ether of cyclohexanone and 4-bromobenzaldehyde can be performed based on the electroosmotic flow (EOF) technique with a four-chaimel microstructured flow reactor (charmel dimensions 100 x 50pm). The reactor was prepared using a standard fabrication procedure developed at the University of Hull [2, 3]. Based on GC-MS analysis, quantitative conversion of the starting material was achieved in 20 min, whereas in the case with a traditional batch system a quantitative yield was obtained only when an extended reaction time of 24 h was employed (Figure 5.1). 

Microstructure of crazes in thin films by transmission electron microscope. In thin PS films e (craze initiation) =1% Fibrils of 25-50 nm are a common feature of the microstructure of crazes in cast and bulky films. Major fibrils diameter = 20-30 nm. Minor fibrils connecting major fibrils have a diameter >10 nm and they tend to orient normally to major fibrils. At large total deformation at low e, there is a gradual transition from coarse to fine micro structure of crazes. Beahan, Bevis Hull (1151 PS... 

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