Additives mechanical property modifiers

Stevens, M. P. Polymer Additives Mechanical Property Modifiers. /. Chem. Educ. 1993, 70,444. 

Stevens, M. P. 1993. Polymer additives. I. Mechanical property modifiers. Journal of Chemical Education 70 (6) 444-8. 

In developing reinforcing fillers, the aims of process or material modifications are to increase the aspect ratio of the particles and to improve their compatibility and interfacial adhesion with the chemically dissimilar polymer matrix. Such modifications may not only enhance and optimize the primary function of the filler (in this case, its use as a mechanical property modifier) but also introduce or enhance additional functions. New functions attained by substitution or modification of existing fillers, thus broadening their range of applications, are illustrated in the examples below. 

In addition to their primary function as mechanical property modifier, the high electrical conductivity of carbon fibers provides carbon-based composites with static dissipation and radio frequency shielding characteristics. This opens up a whole range of applications and with carbon nanotubes this can be achieved at enormously low loading levels. One application with future potential is the use of carbon... 

Similarly, virtually all polymers in commercial use contain additives. Their purpose is two-fold to alter the polymer properties and to enhance ease of processing. Plasticizers are used to modify mechanical properties. Modifiers can be lubricants, cross-linking agents, emulsifiers, and thickening agents, just to name a few. Pigments and odorants are common additives used for aesthetic reasons. 

Powdered and pelletized concentrates of ultrahigh molecular weight silicones are finding numerous apphcations, because of their convenient form (concentrates contain up to 50% silicone) and properties (mechanical property modifiers, release, shp, and lubricating additives). These additives are thermally stable non-migrating and non-volatile, that determines their permanence. 

The shallow penetration of ion implantation would in itself make it appear useless as a technique for engineering appHcations however, there are several situations involving both physical and chemical properties in which the effect of the implanted ion persists to depths fat greater than the initial implantation range. The thickness of the modified zone can also be extended by combining ion implantation with a deposition technique or if deposition occurs spontaneously during the ion implantation process. In addition, ion implantation at elevated temperatures, but below temperatures at which degradation of mechanical properties could occur, has been shown to increase the penetration depths substantially (5). 

Nylon. Nylons comprise a large family of polyamides with a variety of chemical compositions (234,286,287). They have excellent mechanical properties, as well as abrasion and chemical resistance. However, because of the need for improved performance, many commercial nylon resins are modified by additives so as to improve toughness, heat fabrication, stabiUty, flame retardancy, and other properties. 

The term filler is usually applied to solid additives incorporated into the polymer to modify its physical (usually mechanical) properties. Air and other gases which could be considered as fillers in cellular polymers are dealt with separately. A number of types of filler are generally recognised in polymer technology and these are summarised in Figure 7.1. 

Strained set of lattice parameters and calculating the stress from the peak shifts, taking into account the angle of the detected sets of planes relative to the surface (see discussion above). If the assumed unstrained lattice parameters are incorrect not all peaks will give the same values. It should be borne in mind that, because of stoichiometry or impurity effects, modified surface films often have unstrained lattice parameters that are different from the same materials in the bulk form. In addition, thin film mechanical properties (Young s modulus and Poisson ratio) can differ from those of bulk materials. Where pronounced texture and stress are present simultaneously analysis can be particularly difficult. 

To introduce some interfacial physico-chemical linkage between EVA and PRP, blends were made by adding different quantities of M AH-PP. Some results are demonstrated in Table 12, The physico-mechanical properties of the PRP-EVA compositions modified with MAH-PP showed that properties are influenced by MAH-PP concentration. Compositions with better impact strength and improved brittleness can be prepared by varying the modifier concentration. Tensile strength and elongation are not significantly influenced by the addition of a modifier. An increase in the modifier con-... 

The mechanical properties of these blends are also increased with an increase in compatibilizer concentration. The improvement in tensile strength and tear strength on the addition of modified polyolefins are shown in Fig. 15. The mechanical properties also show a leveling off after the optimum concentration. The im-... 

The polymer is based on a simple head-to-tail arrangement of monomer units and is amorphous, since the specific position of the benzene ring is somewhat variable and hence inhibits crystallisation. Despite its generally desirable properties, for many applications it is considered too brittle. Because of this, a number of approaches have been made to modify the mechanical properties of poly (styrene). The most successful of these have been (i) copolymerisation and (ii) the addition of rubbery fillers. 

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