Penetration into polymer material

Almost none of the cited papers dealing with water absorption by syntactic foams deals with the mechanism by which water or other small molecules penetrate into these materials. Filyanov et al.148,149) undertook one of the first attempts using the ED-20 epoxy oligomer—glass microsphere system. Water absorption by a filled polymer is known to depend on the sorptive properties of the binder, the stability of... 

Generally, the irradiation effects of polymers under vacuum or in an inert gas atmosphere are not different between gamma rays and accelerated EB irradiation. For PC, it was confirmed that the irradiation effects including hardness and wear resistance by EB were the same with those by gamma ray irradiation even at 150°C. However, the dose profile was different between gamma rays and EB for thick polymer materials, because the EB penetration depth into polymer materials depends on the EB acceleration voltage. 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

As pointed out in Chapter 1, ionizing radiation includes high-energy electrons (electron beam), y-rays, and x-rays. These not only are capable of converting monomeric and oligomeric liquids into solids, but also can produce major changes in properties of solid polymers. Also, in comparison to UV and visible radiation, they can penetrate considerably deeper into the material. 

Sample preparation may require as little as 5 min (e.g., removing the skin from an apple) or up to an hour or more (e.g., preparation of a food polymer solution and pouring into a mold). The time to run a test will depend on the deformation rate and the desired amount of penetration into the food material. Typically, a... 

We can redefine the elements of the Beer-Lambert law, where / is the sample thickness and c is the molar concentration of chromophores. This can be rearranged to determine the penetration depth of light into a polymer material. Here / is defined as the path length, where 90% of the light of a particular wavelength is absorbed so A approaches 1, giving... 

There have been many investigations to determine the best chemical structures to provide for resistance to moisture and hydrolysis. Attempts have been made to synthesize epoxy adhesives with improved water resistance by replacing some hydrogen atoms by fluorine.50 However, the cost of processing of such materials has restricted commercial development. For electronic sealants, it is highly desirable to keep moisture from penetrating into critical areas. Hydrophobic polymers have been developed to accomplish this task. They are siloxyimides, fluorosilicones, fluoroacrylics, phenylated silicone, and silastyrene. 

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