Structure-thermomechanical relationships

Physical characterization of macromolecular systems strives to determine chemical structure/property relationships. This subfield includes study of thermomechanical performance viscoelastic properties surface properties, adhesion science thermal transitions morphological analysis, including semicrystalline, amorphous, liquid-crystalline, and microphase-separated structures. Structural analysis employs electron microscopy, con-focal microscopy, optical microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, and x-ray and neutron scattering of macromolecular compositions. 

Structure-property relationship for poly(lactic acid) (PLA) filaments physical, thermomechanical and shape memory characterization. /. Polym. 

As noted earlier, whether for cryostabilization, encapsulation, thermomechanical stabilization, or facilitation of drying processes, the utility of such SHPs derives from the structure-function relationship defined by the entanglement plateau region in Figure 6. 

This article reviews recent developments in polymer thermomechanics both in theory and experiment. The first section is concerned with theories of thermomechanics of polymers both in rubbery and solid (glassy and crystalline) states with special emphasis on relationships following from the thermomechanical equations of state. In the second section, some of the methods of thermomechanical measurements are briefly described. The third section deals with the thermomechanics of molecular networks and rubberlike materials including such technically important materials as filled rubbers and block and graft copolymers. Some recent data on thermomechanical behaviour of bioelastomers are also described. In the fourth section, thermomechanics of solid polymers both in undrawn and drawn states are discussed with a special focus on the molecular and structural interpretation of thermomechanical experiments. The concluding remarks stress the progress in the understanding of the thermomechanical properties of polymers. 

In the field of high thermomechanical performance polymers, linear and thermosetting systems offer complementary properties. Among the thermosetting materials, BMIs and BNIs have been extensively studied and are now commercially available. In this chapter, firstly the main preparation and characterization methods are reviewed, and then the chemistry of the polymerization processes is discussed for both families. For the BMIs, due to the electrophilic character of their double bond, different polymerization pathways have been published, which is not the case for BNIs. Special attention has been paid to thermal polymerization which has already been used in industrial achievements however, on the other hand, the structure of these materials has been considered for the purpose of establishing relationships between processability, stability and thermomechanical properties. 

The term water dynamics indicates the mobility of the plasticizing diluent and a theoretical approach to understanding how to control the water movement in glassforming food systems. The term glass dynamics deals with the time and temperature dependence of relationships among composition, structure, and thermomechanical properties, as well as the functional behavior of food systems. 

One of the principal characteristics of the continuum description of materials is the frame-invariance of constitutive laws. That is, the form of the relationship relating the response of materials to changes in their thermomechanical environment must be independent of the coordinate system employed to describe the behavior [5,6], This requires that material properties and descriptions of the structure of materials must be expressed in tensorially invariant form. 

The joint use of several thermal techniques enables us to solve more complex problems, e.g. to correlate through the study of TG, DTA and thermomechanical analysis (TMA) dehydration traces of zeolite Linde A and some of its cation-exchanged forms, the single recorded thermal eflFect with the removal of water molecules from a specific structural site [11, 12], or to find, through TG, DTA and thermodilatometry (TD) measurements, the structural relationships between cymrite (BaAl2Si208.H20) and hexagonal barium feldspar [13]. 

A detailed understanding of the underlying mechanisms for the SME requires a systematic characterization, especially quantification of the shape-memory properties. As typical for a material function, numerous physical parameters are in-fiuencing the SME. Therefore the determination of structure/physical parameter function relationships is challenging. Specific methods are required for dual-shape or triple-shape properties as well as for the different stimuli. The knowledge-based development of SMPs can be supported by modeling approaches for simulating the thermomechanical behavior of such polymers. 

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