Selection of Polymers for Design Applications

To establish a procedure, it is helpful to sort the data, which need to be considered, into four categories  

The design selection procedure suggested here is to list candidate materials in material comparison tables, and list relative size ratios, relative cost ratios, relative weight ratios, and so on, in these tables, and then to select the materials based on these one of the relative ratios, typically cost. 

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Kinkeldei et al. (2012) also compared different polymeric substrates such as PEN, PI, PPS, and PEI (see Table 7.6), and concluded that the selection of polymer for gas sensor platform depends on the working principle of the sensor designed, hi the case of metal oxide-based gas sensors, the substrate has to be heated during operation of the sensors. This requires temperatures above the melting point of PET/PEN and PPS. This means that these materials are unacceptable for application in metal oxide chemiresistors. In the case of capacitive sensors, the substrate material should be inert against... 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

The sorption and transport characteristics of polymers are important issues in selecting the proper polymer for certain applications. This behavior may be tailored to the application by processing technique, chemical modification, or physical design. The following are selected illustrations chosen to suggest the wide range of applications for which such characteristics may be critical or form the basis for a useful product. 

Candidate polymers for biomedical applications must comply with a variety of requirements characteristic of most biomaterials. These requirements arise either from the specific chemical or physical structure of the polymers (chemical, physical, and mechanical criteria) or from the physiological environment where they will be used (biological criteria). Table I summarizes major criteria for the design and selection of polymers as biomaterials. 

In general, the beaker test results are invaluable in the selection of candidates for a given application. However, the results presented above illustrate the necessity of core tests in the design and testing of gelled polymer formulations. 

The development of highly selective chemical sensors for complex matrixes of medical, environmental, and industrial interest has been the object of greate research efforts in the last years. Recently, the use of artificial materials - molecularly imprinted polymers (MIPs) - with high recognition properties has been proposed for designing biomimetic sensors, but only a few sensor applications of MIPs based on electrosynythesized conductive polymers (MIEPs) have been reported [1-3]. 

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