Elastomeric domain

It is somewhat difficult conceptually to explain the recoverable high elasticity of these materials in terms of flexible polymer chains cross-linked into an open network structure as commonly envisaged for conventionally vulcanised rubbers. It is probably better to consider the deformation behaviour on a macro, rather than molecular, scale. One such model would envisage a three-dimensional mesh of polypropylene with elastomeric domains embedded within. On application of a stress both the open network of the hard phase and the elastomeric domains will be capable of deformation. On release of the stress, the cross-linked rubbery domains will try to recover their original shape and hence result in recovery from deformation of the blended object. 

Fig. 18 CG15920 gene sequence and primary structure. The consensus repeat sequences are also represented. The highlighted regions correspond to the signal sequence, R R chitin-binding domain, and the elastomeric domains containing repeat motifs A and B. Reproduced from [182, 188] with permission from Elsevier, copyright Elsevier 2001, 2010...

Tables Sequences of repeat motifs of elastomeric domains...

The wear of the pins on the glass disk was observed with an optical microscope. The worn end of the pin was covered with material from the elastomeric domains. As the tests proceeded, the elastomer appeared to be rolled into thin cylinders oriented perpendicular to the sliding direction. 

The tenet of classical rubber theory has been that the chains are in random networks and the networks comprise a Gaussian distribution of end-to-end chain lengths. However, the mechanisms and molecular bases for the elasticity of proteins are more complex than that of natural rubber. In biological systems elastomeric proteins consist of domains with blocks of repeated sequences that imply the formation of regular stmctures and domains where covalent or noncovalent cross-linking occurs. Although characterised elastomeric proteins differ considerably in their precise amino acid sequences they all contain elastomeric domains comprised of repeated sequences. It has also been suggested that several of these proteins contain p-tums as a structural motif (Tatham and Shewry 2000). 

Frequently, on the basis of T measurements, blends of engineering resins with such copolymers as SBS or ABS-type e.g., PPE/SBS, PC/ABS, or PPE/MBS) are identified as miscible. Obviously, the method focuses on the interactions between the viscoelastic components of the blend, neglecting the elastomeric domains. These remain immiscible and may show (or not, depending on their content) another T at lower temperatures. 

Compositions of these adhesives are suggested in a number of recent patents (5- )- All of these reactive adhesive patents indicate essentially the same concept an elastomer is colloidally dispersed in a monomer, or a monomer/oligomer/polymer solution. The system is then polymerized using a free radical mechanism. What occurs is a rapid, "in situ" polymerization of a (typically) methyl methacrylate system, toughened by elastomeric domains which have beer, incorporated into the structure by grafting. 

Aerobic adhesives are composed of proprietary catalysts, elastomeric domain fillers, and low-vapor-pressure monomers. Formulations derived from this technology do not exhibit the severe sensitivity toward air inhibition shown by other acrylic adhesives. The result is that aerobic adhesives are usable on more porous surfaces and in wider gaps than was previously considered practical. 

Sequence-based stmctural prediction algorithms suggest that the elastomeric domains of tropoelastin and other elastomeric... 

Despite the foregoing evidence, the type-II p-tum has not been unequivocally established as the determinative element for the development of elastomeric behavior within the elastomeric domains of elastin and other native polypeptide materials. Spectroscopic analyses of native elastin and elastin-mimetic polypeptides have provided strong evidence for the presence of alternative conformations, particularly above the inverse transition temperature, which may contribute to the elastomeric behavior of the material in its coacervate state. In addition, the elastomeric domains of native tropoelastin display quite substantial sequence diversity, although it appears that Pro-Gly sequences are conserved... 

Compositions are suggested in the patent literature (4-8). The concept is essentiallyr that an elastomer is colloidally dispersed in a monomer or in a monomer/-oligomer/polymer solution. The resultant polymer is toughened by "elastomeric domains" resulting from the dispersed elastomer. 

Since the homopolymer is fairly brittle, PMMA can be toughened via copolymerization with another monomer (such as polybutadiene) or blended with an elastomer in the same way that high-impact polystyrene is, to enable better stress distribution via the elastomeric domain. 

Incorporation of nanopartides into a polymeric phase enhances its medianical performance. Thus, it is desirable to place nanopartides in the stiffer polymer, preserving the toughening effects of the dispersed elastomeric domains. 

Thermoplastic polyolefin (TPO) n. Any of a group of elastomers produced by either of two processes. In one, polypropylene is melt-blended with from 15 to 85% of ter-polymer elastomer, ethylenepropylene rubber, or styrene-butadiene rubber. In the other, propylene is co-polymerized with ethylene-propylene elastomer in a series of reactions. The smaller elastomeric domains obtained in the latter process are claimed to provide improved properties over the blended materials. 

---