摘要:

Today the production and utilization of natural enzymes in processing foods, beverages, textiles, paper, pharmaceuticals, etc., has become a multimillion-dollar industry [1,2]. With the rapidly increasing knowledge of the structures and mode of action of natural enzymes, it should be possible to synthesize relatively simple molecules which would incorporate all the functional features of the natural enzyme, which would possess a catalytic efficiency equivalent to or greater than the natural enzyme, and which would remain stable over a wide range of working conditions. By linking such simple “enzyme units” into an insoluble polymeric framework, additional advantages could be realized, such as activation of the catalysis, avoidance of contamination of the substrate solution by the synthetic enzyme system, and ready filtration of the polymeric system from the solution on completion of reaction.

ISSN:1532-1797    

DOI:10.1080/15583726908545895

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Polycarbonate possesses a number of attractive mechanical properties [1,3] e.g., high impact strength, high elastic modulus, and creep resistance. These features, coupled with the fact that the polymer is almost unaffected by water and many inorganic and organic solvents, permit its use in a variety of applications. In such applications the mechanical properties may alter with time because of the viscoelastic nature of the material.

ISSN:1532-1797    

DOI:10.1080/15583726908545896

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Many of the polymers used in composite systems and in other applications are cross-linked or thermoset polymers. How do such cross-linked polymers differ in properties from the better-understood linear or thermoplastic polymers? This review paper attempts to answer this question. The paper is written from the practical viewpoint of the experimental scientist who is using cross-linked polymers but who is not an expert on the theory of cross-linking. In spite of their intractable nature once they have been formed, and the difficulty of fabricating highly cross-linked polymers, such materials have some outstanding properties that make them ideal for many applications. The properties include (1) excellent dimensional stability and low creep rates, (2) resistance to solvents, and (3) in many cases, high heat-distortion or softening temperatures.

ISSN:1532-1797    

DOI:10.1080/15583726908545897

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The relationship of the thermal stability of a polymer to its chemical structure has been discussed in several papers [2,40,63,105]. Maximum thermal stability in polymers is usually obtained when: 1. Thermally unreactive ring structures constitute a major portion of the polymer composition. 2. Maximum use is made of resonance stabilization. 3. High bond energy exists between the atoms in the chain. 4. Cohesive energy density is high from (a) chain length, (b) crystallinity, (c) Van der Waals' forces. High-resonance-energy structures can be obtained by use of appropriate aromatic or heterocyclic groups; their thermal unreactivity can be estimated from the thermal reactivity data of Lewis [73]. Most of the available bond-energy values have been determined from studies of small molecules in the gaseous or liquid state.

ISSN:1532-1797    

DOI:10.1080/15583726908545898

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor