Effect of the Binder

The burning rates of AP composite propellants are not only dependent on the AP particles, but also on the binder used as a fuel component. There are many types of binders, with varying physicochemical properties, as described in Section 4.2. The 

Various types of binders are used to formulate AP composite propellants. Binders such as HTPB and HTPE decompose endothermically or exothermically at the burning surface. The burning rates of AP composite propellants thus appear to be dependent on the thermochemical properties of the binders used. Figs. 7.17 and 7.18 show In r versus In p plots for AP composite propellants made with five differ- 

Propellant Binder HTPB AP particle size (pm) 400 200 20 3 Catalyst BEFP 

The relationship between temperature sensitivity and burning rate is shown in Fig. 7.21 as a function of AP particle size and burning rate catalyst (BEFP).li31 The temperature sensitivity decreases when the burning rate is increased, either by the addition of fine AP particles or by the addition of BEFP. The results of the temperature sensitivity analysis shown in Fig. 7.22 indicate that the temperature sensitivity of the condensed phase, W, defined in Eq. (3.80), is higher than that of the gas phase, 5), defined in Eq. (3.79). In addition, 4 becomes very small when the propel- 

The burning rate of propellants is one of the important parameters for rocket mo-tordesign. As described in Section 7.1.2, the burning rate of AP composite propellants is altered by changing the particle size of the AP used. The diffusional mixing process between the gaseous decomposition products of the AP particles and of the polymeric binder used as a fuel component determines the heat flux feedback from the gas phase to the condensed phase at the burning surface.C - ] This process is a 

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Fig. 41 Effect of the binder on the lightfastness. Pigment content in the printing ink 15% Pigment Yellow 3.

A further group of pellets tested were 2.0mm thick, 28mm diameter llmol% scandia, and the preferred mixed dopant zirconia. Fig. 5 shows the results of many slow tests to determine the dependence of elastic modulus with temperature. This is similar to the behaviour of yttria zirconia under temperature, where a significant drop is evidenced irom approximately 300°C upwards. For mechanical integrity the decrease in elastic modulus is good news because it means there is more flexibility to relieve any loads on the electrolyte material by strain. Note that the effect of the binder is to decrease the elastic modulus. There is a 7% reduction at room temperature -and this is very similar to that which would be expected by the increase of 5% porosity indicated by the difference in density. ... 

Binder action models are schematically shown in Figure 13.8 and are valid for all rechargeable batteries. In the case of the negative electrode of lithium-ion batteries, there is a volume expansion during lithium intercalation or insertion. The effect of the binder is that it can buffer this volume change, which may not be negligible. 

An important consideration is the effect of filler and its degree of interaction with the polymer matrix. Under strain, a weak bond at the binder-filler interface often leads to dewetting of the binder from the solid particles to formation of voids and deterioration of mechanical properties. The primary objective is, therefore, to enhance the particle-matrix interaction or increase debond fracture energy. A most desirable property is a narrow gap between the maximum (e ) and ultimate elongation ch) on the stress-strain curve. The ratio, e , eh, may be considered as the interface efficiency, a ratio of unity implying perfect efficiency at the interfacial Junction. 

Lipatov et al. [116,124-127] who simulated the polymeric composite behavior with a view to estimate the effect of the interphase characteristics on composite properties preferred to break the problem up into two parts. First they considered a polymer-polymer composition. The viscoelastic properties of different polymers are different. One of the polymers was represented by a cube with side a, the second polymer (the binder) coated the cube as a homogeneous film of thickness d. The concentration of d-thick layers is proportional to the specific surface area of cubes with side a, that is, the thickness d remains constant while the length of the side may vary. The calculation is based on the Takayanagi model [128]. From geometric considerations the parameters of the Takayanagi model are related with the cube side and film thickness by the formulas ... 

Since the literature cited did not reveal a significant effect of the differing pore systems of the various types of layer the aluminium oxide and silica gel types (60, 80, 100, etc.) are not specified. The same applies to binders, fluorescence indicators and trace impurities in the sorbents. 

Considering this chain of electrical resistors, we should take into account the influence of the binder (dielectric) effecting on all the above contact resistances in the circuit and increasing their value (Rb). Evidently, the main influence on the ESR of electrode is this circuit because of a big number of contact resistances distributed in the bulk of the electrode. 

When evaluating the effect of binder concentration on a number of tablet properties, surface area measurements were used to investigate the bond strength of the binder with the other particles [18]. A steady reduction in the surface area of the granules with increasing binder concentration indicated that the binder had covered or penetrated the particles, with the formation of particle-binder bonds. This was related to friability, and the increased bond strength was related to the decreased surface areas. 

The other important function of the binder is its effect upon the rheological properties of the coating mix. Starch, which is widely used, is unsuitable for use in its unmodified form because its solution viscosity is generally too high and also because of the problem of retrogradation. It is usually modified by reducing its molecular weight by either oxidative or hydrolytic (sometimes enzymatic) procedures. 

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