Physical modification method

When the physical modification method is used, PS is modified by mechanical stirring with various synthetic rubbers such as polybutadiene, polybutadiene styrene, polyisopropene, polychloropropene, polybutadiene styrene-acrylonitrile copolymers. In the chemical modification, PS is modified with polyfunctional modificators in the presence of cationic catalysis. 

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. 

The mechanical properties of composites are mainly influenced by the adhesion between matrix and fibers of the composite. As it is known from glass fibers, the adhesion properties could be changed by pretreatments of fibers. So special process, chemical and physical modification methods were developed. Moisture repel-lency, resistance to environmental effects, and, not at least, the mechanical properties are improved by these treatments. Various applications for natural fibers as reinforcement in plastics are encouraged. 

Physical Modification Methods Chemical Modification Methods Radiation Modification Methods... 

Which kind of physical modification methods have gained importance for phenolics ... 

The physical modification method is simple, convenient, fast, economic, and easy to operate, and is the most widely used method for modification. 

Lipids also influence the properties of starch. Like free amino acids, monoglycerides or fatty acid esters of hydroxy acids, lipids form inclusion compounds with amylose (cf. 4.4.4.14.3). Like di- and triglycerides, they also reduce the swelling capacity and solubility by inhibiting water diffusion. Therefore, both degreasing as well as lipid addition are of importance as physical modification methods of starches. 

Although, the heat resistance of NBR is directly related to the increase in acrylonitrile content (ACN) of the elastomer, the presence of double bond in the polymer backbone makes it susceptible to heat, ozone, and light. Therefore, several strategies have been adopted to modify the nitrile rubber by physical and chemical methods in order to improve its properties and degradation behavior. The physical modification involves the mechanical blending of NBR with other polymers or chemical ingredients to achieve the desired set of properties. The chemical modifications, on the other hand, include chemical reactions, which impart structural changes in the polymer chain. 

The quality of the fiber matrix interface is significant for the application of natural fibers as reinforcement fibers for plastics. Physical and chemical methods can be used to optimize this interface. These modification methods are of different efficiency for the adhesion between matrix and fiber. 

The resultant tailored interface is often vastly superior for biomedical applications over the native silicone interface. Furthermore, surface modification maintains the low materials cost and favorable bulk properties of the original silicone elastomer. The modification methods can be divided into physical and chemical techniques. 

OPT is a new method of physical modification, in which potato starch is suspended in solution saturated with a salt such as sodium sulfate and heated (autoclaved) at temperatures above 100° C for different times. This treatment has been reported to have the same effects on the starch properties as HMT but the starch modified using OPT exhibits better homogeneity (Pukkahuta et al., 2007). 

Pukkahuta, C., Shobsngob, S., Varavinit, S. (2007). Effect of osmotic pressure on starch New method of physical modification of starch. Starch, 58, 78-90. 

Native starches are used as disintegrants, diluents, and wet binders. However, their poor flow and high lubricant sensitivity make them less favorable in direct compression. Different chemical, mechanical, and physical modifications of native starches have been used to improve both their direct compression and controlled-release properties (Sanghvi, 1993 van Aerde and Remon, 1988). Schinzinger and Schmidt (2005) used potato starch as an excipient and compared its granulating behavior with a-lactose-monohydrate and di-calcium phosphate anhydrous in a laboratory fluidized bed granulator using statistical methods. 

Physical immobilization methods there is no chemical modification of the enzyme. 

The principle advantage of the physical labeling method is the possibility of receiving direct information about the structure, mobility and local micropolarity of certain parts of a molecular object of any molecular mass. Developments in synthetic chemistry, biochemistry and site-directed mutagenesis have provided researchers with a wide assortment of labels and probes, and have paved the way for the specific modification of protein function groups, including enzyme active sites. 

The development of physical methods for texturizing proteins has significantly amplified their use in several conventional and simulated foods. The principal techniques of physical modification which have been thoroughly reviewed are thermoplastic extrusion, fiber spinning and steam texturization (3,4,5). 

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]. 

The behavior of immobilized enzymes differs from that of dissolved enzymes because of the effects of the support material, or matrix, as well as conformational changes in the enzyme that result from interactions with the support and covalent modification of amino acid residues. Properties observed to change significantly upon immobilization include specific activity, pH optimum, Km, selectivity, and stability.23 Physical immobilization methods, especially entrapment and encapsulation, yield less dramatic changes in an enzyme s catalytic behavior than chemical immobilization methods or adsorption. The reason is that entrapment and encapsulation result in the enzyme remaining essentially in its native conformation, in a hydrophilic environment, with no covalent modification. 

In order to achieve better hole or electron injection for enhancement of device performance, introduction of appropriate hole-transport and electron-injection materials into the interfaces of anode/PFs and PFs/cathode, respectively, is another useful approach in addition to the chemical and physical modifications of PF chain structure. Besides, choosing a cathode material with a work function close to LUMO levels of PFs has been proven to be a practical method for performance improvement. 

It is reasonable to expect that, if methods for quantitative measurement of the transport of ions in surface phases of semiconductors are developed, the way will open to the exploration of chemical and physical modification of these surface phases. The goal is to make these less conductive solid electrolytes—i.e., surface phases in which ion transport is reduced. Such modification is likely to reduce the cost of encapsulation and packaging and increase the reliability of microcircuits. 

All known modifications of solid SiO are X-ray amorphous. The structure of solid SiO must therefore be deduced by combinations of physical-chemical methods. Several structural models, some of them at variance, were proposed and controversially debated over several decades. An overview is given in ref. 

---