Specific absorption surface resistivity

A common approach to the study of properties, in particular variations of properties under external effects, should include, as one of the basic ideas, the conception of polymeric foams as heterogeneous systems with developed surface (see Chap. 5.4). As became apparent in the early 1970 s, the specific surface of these materials is of the order of dozens and even hundreds of square meters per gram Such high values of the specific surface are quite exceptional among polymeric materials and lead to marked (in relation to expected) changes in several physicochemical properties of plastic foams, for example water absorption and resistance to thermal oxidation. 

Some of the properties documented in the specification sheets of IPC-4101 include Tg, copper peel strengths at different conditions, volume resistivity, surface resistivity, moisture absorption, dielectric breakdown voltage, permittivity, loss tangent, flexural strengths and arc resistance. These properties will be discussed further in Chap. 8. 

Table 3 shows the main physical properties of poly(ether-6-amide)s with different PA/PE ratios and chemical structural units. Hydrophilic PEBA Samples K and L (see Table 3) have higher density and water absorption and lower surface resistivity than hydrophobic grades A, D, G, I from various PA/PE ratios. The hydrophilic K and L grades have inherent static dissipative properties and are used in specific antistatic applications. 

Air content of freshly mixed concrete by the pressure method Air content of freshly mixed concrete by the volumetric method Unit weight, yield, and air content of concrete Specific gravity, absorption, and voids in hardened concrete Resistance of concrete to rapid freezing and thawing Scaling resistance of concrete surfaces exposed to deicing chemicals... 

Where a number of properties are relevant to a product the testing may be carried out with a sequence of tests without superimposing any ageing. Where environmental effects have to be accounted for they are applied separately and the rig tests repeated. An example of this approach is artificial sports surfaces where such characteristics as ball bounce, energy absorption, dynamic stiffness and spike resistance are measured using specifically developed rigs. 

Fig. 4. Schematic of a single-step array fabrication process for in vivo biotinylated proteins. Step a A cmde lysate containing the desired biotinylated recombinant protein is printed onto a streptavidin-coated surface coderivatized with a polymer that resists nonspecific protein absorption. Step b Unbound proteins are washed away to leave the purified recombinant protein, specifically immobilized and oriented on the array surface via the biotin moiety on the BCCP tag.

Whatever the coupling agent is, the control of non-specific protein absorption is important to the use of nanomaterials in specific protein binding. There are plenty of molecules used for protection of various surfaces from proteins with mechanisms as steric repulsion, hydration and solvent structuring. For example, the modification of CNTs with the absorption of biotinylated Tween 20 allowed streptavidin recognition by the specific biotin-streptavidin interaction, but provided resistance towards other protein absorption [133]. 

Much work has been done with polymers to create biocompatible surfaces that resist protein fouling, i.e., non specific adsorption. A membrane composed of modified polyethersulfone (PES) (Omega Membrane) resisted albumin (ALB) absorption 24 times better than unmodified PES, and three times better than regenerated cellulose, a material known to resist biofouling. We compared porous SiC, both n-type and p-type, to the Omega Membrane [14] and found a very similar resistance to ALB absorption (Figure 12.3). 

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