Physical modification polymer materials

V.N. Kestelman. Physical Methods of Modification Polymer Materials. Moscow, Khimiya, 1980. 

New elastic polymeric materials (resistance to higher stroke or air) can be obtained by using physical modification methods, but using this method, two phases (PS and rubber) in the mixture were formed. Small rubber particles spread as a PS layer and, after awhile, the relationship between the layers decreases and rubber particles gather in the upper layer of the materials. This can be the cause of the loss of resistance of the materials. These material disadvantages have stimulated the polymer synthesis to increase the PS resistance to higher physico-mechanical properties, such as higher temperature and stroke for the chemical modification of PS with various functional modifiers. 

Radiation-induced modification or processing of a polymer is a relatively sophisticated method than conventional thermal and chemical processes. The radiation-induced changes in polymer materials such as plastics or elastomers provide some desirable combinations of physical and chemical properties in the end product. Radiation can be applied to various industrial processes involving polymerization, cross-linking, graft copolymerization, curing of paints and coatings, etc. 

A kinetic model based on the Flory principle is referred to as the ideal model. Up to now this model by virtue of its simplicity, has been widely used to treat experimental data and to carry out engineering calculations when designing advanced polymer materials. However, strong experimental evidence for the violation of the Flory principle is currently available from the study of a number of processes of the synthesis and chemical modification of polymers. Possible reasons for such a violation may be connected with either chemical or physical factors. The first has been scrutinized both theoretically and experimentally, but this is not the case for the second among which are thermodynamic and diffusion factors. In this review we by no means pretend to cover all theoretical works in which these factors have been taken into account at the stage of formulating physicochemical models of the process... 

Several research groups used another interesting column technology as an alternative to the modification of the capillary surface. This method is inherited from the field of electrophoresis of nucleic acids and involves capillaries filled with solutions of linear polymers. In contrast to the monolithic columns that will be discussed later in this review, the preparation of these pseudostationary phases need not be performed within the confines of the capillary. These materials, typically specifically designed copolymers [85-88] and modified den-drimers [89], exist as physically entangled polymer chains that effectively resemble highly swollen, chemically crosslinked gels. 

The modification of polymers is interdisciplinary in nature cutting across traditional boundaries of chemistry, biochemistry, medicine, physics, biology and materials science and engineering. Because of this interdisciplinary nature, persons involved with polymer modification should be broadly trained to permit the best application of revealed information. 

Sensors are usually attached chemically or physically to other materials here referred as the carrier, like polymers, antibodies, and optical fibers in order to facilitate the sensing process. These carriers generally affect the luminescent characteristics of the sensor molecules. The modification of the luminescent characteristics of the sensor is caused by the creation of more than one microphase or microenvironment for the sensor. Each molecule in its particular microenvironment may return to the ground state following a different set of processes or mechanisms. Alternatively, the nonra-diative decay rate of each microphase may be different for each sensor molecule. Depending on the characteristics of the carrier and the sensor, the number of microphases may be one, two, three, or an infinite number. 

Physical or chemical modification methods have been employed to increase the toughness of polymer materials. The chemical modifications include random copolymerization, block copolymerization, grafting, etc. the physical ones include blending, reinforcing, filling, interpenetrating networks etc. [24-26]. 

Hirotsugu Yasuda is Professor Emeritus of Chemical Engineering and Director of the Center for Surface Science and Plasma Technology, University of Missouri-Columbia. He has over. 300 publications in refereed journals and books and was a pioneer in the exploration of low-pressure plasma for surface modification of materials and deposition of nanofilms as barrier and permselective membranes in the late 1960s. He received the Ph.D. degree in physical and polymer chemistry from the State University of New York, College of Environmental Science and Forestry, Syracuse. 

Of the relevant time scales that drive the frequency effects of the polymer pads, many of them have their origin in the physical structure of the polishing pad. The largest scale of these is represented by the groove. But the basic nature of many of the typical polymer pads includes a somewhat random interruption of the polymer material in the form of pores. The pores have three major impacts (a) they modulate the abrasive surface presented to the wafer (b) they break up the homogenous nature of the pad material itself, causing modification of the physical properties of the material and (c) they provide microreservoirs for both slurry distribution and byproduct... 

Vasilets, VN. (2005), Modification of Physical Chemical and Biological Properties of Polymer Materials Using Gas-Discharge Plasma and Vacuum Ultraviolet Radiation, Dr. Sci. Dissertation, Institute of Energy Problems of Chemical Physics, Russian Academy of Sciences, Moscow. 

For a polymer to be useful, it must be able to function properly in a given application. The performance of a polymer is determined primarily by the composition and structure of the polymer molecule. These control the physical, chemical, and other characteristics of the polymer material. Therefore modification of the composition of the structural units represents one of the main approaches to the modification of polymer behavior. In addition to the chemical nature and composition of the structural units that constitute the polymer backbone, molecular architecture also contributes to the ultimate properties of polymeric products. Thus polymer modification can be accomplished by employing one or more of the following techniques ... 

The key difference between medical polymer material and other polymer materials is that the former has both medical functionality and biocompatibility and resorts to chemical or physical means to achieve polymeric modification of polymer materials. Fourier Transform Infrared Spectroscopy (FT-IR) is an effective method to analyze polymer materials and its modification. 

The main aim for FCC gasoline desulfurization is to remove thiophenic sulfur compounds. Membranes made from polar polymers with solubility parameter close to thiophenic sulfur are used for desulfurization of gasolines by PV It is evident that solubility parameter of primary sulfur components of gasolines, that is, thiophenic sulfur components, is 19-21 (J/cm )", while for other hydrocarbons, these values are 14-15 (J/cm )". This difference can be exploited for separation by PV. Solubility parameter values of most of the polymers used as membrane material lie in the range of 21-26 (J/cm )". Thus, membranes made from these polymers afford good selectivity for thiophenic sulfur. Apart from various homopolymers, chemically and physically modified polymers have also been used for per-vaporative desulfurization. Some of these modifications include using different types and amounts of cross-linkers, blending two polymers, and copolymerization. Composite and treated ionic membranes have also been tried for this separation. Polymer membranes tried for this separation include PDMS/PAN, PDMS/PEI, PDMS/PES, PDMS/ ceramic, polyetherimine (PI)/polyester, PEG/PES, and PU/PTEE. ... 

Supercritical modification of polymers was studied by several scientists to improve or change the properties of polymers. Polymers can either be chemically or physically modified. Examples of chemical modifications are the functionalization of polymers (grafting) or a chemical reaction of the functional groups of polymers to obtain new materials [38, 39]. Examples of physical modifications are the preparation of polymer blends, impregnation of polymers with additives [46], or foaming of polymers [59-61]. Another studied topic of polymer modification and impregnation is the supercritical dyeing of polymer fibers [40, 41). 

Blending is the simplest and easiest method anployed to functionalize a polymer. This is a physical approach with the addition of blending ligand molecules into the polymer solution and then electrospinning the polymer solution. No chemical bonding or attachment is involved between the polymer material and the modified species (Figure 8.3). It is a simple mixing of two or more materials that has been proven to be an effective method for polymer nanofiber modification. Nevertheless, blend molecules are susceptible to detachment and the technique is neither reproducible nor controllable. 

Blending with other polymers and mixing with solid isotropic or anisotropic particles are efficient ways to produce new materials with highly modified properties using physical modification principles. This topic falls somewhat outside the scope of this chapter, but enough data can be found in the recent literature [128, 174]. Hence, only a few remarks will be given here. 

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