Polymer properties INDEX

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

In the past three decades, industrial polymerization research and development aimed at controlling average polymer properties such as molecular weight averages, melt flow index and copolymer composition. These properties were modeled using either first principle models or empirical models represented by differential equations or statistical model equations. However, recent advances in polymerization chemistry, polymerization catalysis, polymer characterization techniques, and computational tools are making the molecular level design and control of polymer microstructure a reality. 

Water absorption can also cause significant changes in the permittivity and must be considered when describing dielectric behavior. Water, with a dielectric constant of 78 at 25°C, can easily impact the dielectric properties at relatively low absorptions owing to the dipolar polarizability contribution. However, the electronic polarizability is actually lower than solid state polymers. The index of refraction at 25°C for pure water is 1.33, which, applying Maxwell s relationship, yields a dielectric constant of 1.76. Therefore, water absorption may actually act to decrease the dielectric constant at optical frequencies. This is an area that will be explored with future experiments involving water absorption and index measurements. 

Many of the optical properties of a polymer are related to the refractive index n, which is a measure of the ability of the polymer to refract or bend light as it passes through the polymer. The index n is equal to the ratio of the sine of the angles of incidence, i, and refraction, r, of light passing through the polymer ... 

FIGURE 2-17. Contribution of molecular weight to polymer properties, (a) Molecular weight distribution profile of a typical polymer. (b) Quality control of an alkyd resin. It was determined that a good paint resulted only when the ratio of the peak heights was between 0.6 and 0.8. Detector refractive index. 

Although many polymer properties are greatly influenced by molecular weight, some other important properties are not. For example, chain length does not affect a polymer s resistance to chemical attack. Physical properties such as color, refractive index, hardness, density, and electrical conductivity are also not greatly influenced by molecular weight. 

The ratio MJM is a measure of the breadth of the molecular weight range in a polymer sample, and is called polydispersity index, PDI, or molecular weight distribution, MWD. Molecular weight distribution is an important characteristic of polymers, and can significantly affect polymer properties. The molecular weight distributions of commercial... 

Table 1 Physicochemical polymer properties [66]. Data according to [62] and Goodfellow Cambridge Ltd, Huntington. Absorption coefficient at 2=308 nm. Refractive index in the visible spectral region... 

The polymer properties in thin films are then compared with the bulk as measured by FTIR attenuated total reflection spectroscopy (ATR). A modest refractive index of the internal reflection element (IRE made of ZnSe, n=2.43 at 2000 cm ) and an incident angle of 65° - still low but well above the critical angle of total reflection - are chosen for the p-polarized light in order to obtain an information depth of several microns. Hence, the ATR spectra provide the bulk properties of the polymer sample. 

CAS 818-61-1 EINECS/ELINCS 212-454-9 Uses Crosslinkable paint resin binder for textiles and paper urethane acrylates reactive thinners for curing by radiation comonomer for refinishing paints adhesion promoter for polymers Properties Pt-Co 50 max. clear liq. ester-like si. yel. odor misc. with water m.w. 116.1 sp.gr. 1.11 vise. 9 mPa s (20 C) vapor pressure 0.1 mbar b.p. 230 C solid, pt. -60 C flash pt. 104 C ref. index 1.450 95% min. purity 0.02% max. water 0.5% max. acid Toxicoiogy LD50 (oral, rat) 650 mg/kg severe skin irritant and sensitizer caustic TSCA listed... 

As mentioned above, van Krevelen (1990) presents semi-empirical, group-contribution methods and data for each group in a polymer repeating unit. Data are provided to estimate a host of polymer properties, including the density, specific heat, glass-transition temperature, water absorption, and refractive index. For a specific property, these are in one of two forms ... 

Previous results were used for computer simulation of optical properties of the fabricated structures. By substitution to the RSoft software of measured polymer refractive index and the structure surface profile the inside and output optical field distribution were calculated using beam propagation method. The calculated output optical field is given in Fig 20C. In addition, calculation proved that the effective refractive index for fundamental mode is approximately 1.6276 at 632.8 ran. The prepared multimode structure supported 30 modes at wavelength 632.8 ran. 

Besides mechanical properties, fillers change the optical and electrical properties, chemical and weathering resistance, flammability and density of polymers. In particular, most fillers destroy optical translucency, unless their refractive index (see Table 4.4) is the same as that of the polymer. Close agreement between the fibre and the polymer refractive index is required for translucency. Feldspar has a refractive index very similar to that of several polymers and so filled, translucent products can be obtained, but it is abrasive to processing equipment. 

This 160 page monograph presents thermodynamic data for materials which are chemical mixtures, polymers, composite materials, solid wastes, and substances not easily identifiable by a single stoichiometric formula. The thermodynamic properties given are heats of reaction and transitions, heat capacities and heat contents, and vapor and sublimation pressures. Included is a material name and property index which covers approximately 600 materials, many of which are of biological Interest, and including data on animals. 

A change in the material can cause a problem in extrusion when it affects one or more polymer properties that determine the extrusion behavior of the material. If a material problem is suspected, one should first examine the quality control (QC) records on incoming material to see if a change in feedstock properties was determined. Unfortunately, often the only QC test on incoming material is a melt index (MI) test. This test is only able to detect a very limited number of material-related extrusion problems. Thus, in many cases, material testing may have to be more extensive than the regular QC testing. 

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