Filler interaction, binder

Binder-Filler Interaction. A strong bond between binder and filler is important for obtaining high tensile strength. In Figure 9 the tensile properties obtained from two different filler materials are compared. The... 

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. 

Volume swelling measurements have produced erratic results even under the most carefully controlled conditions. One important contribution in this regard is the work of Bills and Salcedo (8). These investigations showed that the binder-filler bond could be completely released with certain solvent systems and that the volume swelling ratio is independent of the filler content when complete release is achieved. Some thermodynamic problems exist, however, when such techniques are used to measure crosslink density quantitatively. First, equilibrium swelling is difficult to achieve since the fragile swollen gel tends to deteriorate with time even under the best conditions. Second, the solubility of the filler (ammonium perchlorate) and other additives tends to alter the solution thermodynamics of the system in an uncontrollable manner. Nonreproducible polymer-solvent interaction results, and replicate value of crosslink density are not obtained. 

The mechanical parameter of a highly filled syntactic foam must in general be analyzed taking into account the interactions at the binder—filler interface and the system s stresses since both of these factors are important for highly filled systems 8 W0). 

Still, it is important that fillers interact with the polymer (binder) for various reasons. One is the rheological characteristic of paints. Figure 19.5 shows that many processes may affect how a filler behaves in the system. The simple drying of aluminum hydroxide prior to use contributes to an increased paint viscosity. It should be noted that aluminum hydroxide loses water at 220°C, therefore drying at 80 C may only remove the water adsorbed on the surface of particles. But this is apparently sufficient to increase the interaction with the binder since, when the partially dried filler is added, viscosity almost doubles. Similarly, treatment with 1% triethoxymethacryloylpropylsilane, MPS, contributes to an increased viscosity. This data shows that the same filler can be readily modified to give a variety of different results. 

Attachment of molecules to the surface of a solid filler in polymeric biocomposites affects a variety of innate properties, particularly those related to the surface of (he filler material. An overview of the surface modification techniques and how they alter specific filler properties is outlined in Table 3.3. The attachment of molecules affects the immediate physical and chemical composition of a surface, which can alter secondary surface properties related to surface interactions, such as wetting, zeta potential, suiface solution reactions including dissolution/degradation, as well as cellular interactions. These primary and secondary properties do not necessarily alter how the filler interacts with polymer binders in a biocomposite setting, but these properties can change the inherent overall properties of the resultant filler. 

Incompatibilities have also been observed in solid dosage forms. A typical tablet contain binders, disin-tegrants, lubricants and fillers. Compatibility screening for a new drug should consider two or more excipients from each class. Serajuddin et al. have developed a drug-excipient compatibility screening model to predict interactions of drug substances with excipients [49],... 

Irrespective of the filler-binder used, in tablets prepared with crospovidone as a disintegrant, all three adjustable factors influenced the SIR of crushing strength. Also the interaction between the concentration and the relative humidity was significant (y0i3,siR(s) 0)-... 

The dimensional stability of the propellant grain is the result of the chemically crosslinked polymeric binder. Many of the mechanical properties of the final cured propellant will be dictated by binder characteristics. Another important consideration is the effect of filler, owing to its presence as well as its degree of interaction with the binder. 

Back (10) has indicated that superior board performance is achieved with covalent bonding of the adhesive to the wood. A binder, then, must have at least the minimum number of reactive sites per molecule. If there is one or fewer such sites, then the lignin should behave as a filler, which may or may not be chemically bound to the resin. In the case of two reactive sites, a linear macromolecule is possible, or the lignin may be considered to behave as an extender for a resin. When three or more sites are available, crosslinking can occur and the lignin could then become a full partner in the crosslinked binder. One may project how the lignin could behave, once the reactive sites on the lignin molecule have been mapped. For this chapter, the interactive sites will be alcohols and benzyl alcohols, to simulate the reaction of PF resins with the carbohydrates in the wood. 

For a two-level factorial design, only two excipients can be selected for each factor. However, for the filler-binder, a combination of brittle and plastic materials is preferred for optimum compaction properties. Therefore, different combinations such as lactose with MCC or mannitol with starch can count as a single factor. Experimental responses can be powder blend flowability, compactibility, blend uniformity, uniformity of dose unit, dissolution, disintegration, and stability under stressed storage conditions. The major advantage of using a DOE to screen prototype formulations is that it allows evaluation of all potential factors simultaneously, systematically, and efficiently. It helps the scientist understand the effect of each formulation factor on each response, as well as potential interaction between factors. It also helps the scientist identify the critical factors based on statistical analysis. DOE results can define a prototype formulation that will meet the predefined requirements for product performance stability and manufacturing. 

It should be noted that a similar approach can be used for an optimum composition of a composite based on a polyfractional filler with a maximum possible packing fraction. One should remember, however, in that case that for a correct choice of the composite composition it is necessary to take into account the interactions existing at the mineral filler — liquid binder interface and leading to formation on the filler surface of the so-called boundary layers [105]. A comparatively simple method for a rough estimation of these interactions for highly-loaded composites is to be found in [106]. 

A study of paint technology reveals other interactions. The layer of paint in immediate contact with the surface of the substrate is depleted of filler. The next layer is enriched with filler. Between the last layer and the bulk of paint there is still polymer-rich layer. This effect is attributed to the affinity of the polymer with the substrate. This affinity leads to polymer migration. It also causes binder orientation... 

Figure 19.6 shows that interaction involves not only a chemical interaction but can also be physical in nature. Here, different acid/base interactions of different grades of titanium dioxide are involved. The choice of the type of titanium dioxide results in a different thickness in the layer of adsorbed binder. This layer increases the sizes of particles and changes the amount of fillers contributing to the maximum packing density. The calculation of maximum packing density is complicated by... 

Ludipress is a speciality derived from lactose, Kollidon 30, and Kollidon CL. It thus combines the properties of a filler, binder, disintegrant, and flowability agent and also often acts as a release accelerator. By virtue of its versatility formulations containing it are usually very simple. It can also be combined with almost all active substances with the exception of those that enter into a chemical interaction with lactose (Maillard reaction). 

The action of an aggressive environment on polymer concretes depends on their permeability and subsequent dissolution and elution of the binder components by hydrolysis of molecular bonds and the weakening of the interaction between the polymer and filler. 

The ultimate compressive strength of drying epoxy polymer concrete samples is about 92% of the control sample strength, which testifies to a high degree of reversibility of the process associated with the adhesive nature of the interaction between binder and filler. 

The effect of technological additives on permeability of pol3Tuers is connected with variations in their sorption capacity, formation of defects and interactions of the electrolyte and additives. Impregnation of fillers improves, as a rule, permeability of polymers and intensifies clusterization of water and the penetrant. When polyethylene is filled by talc, HCl and H2O clusters formed in the polymer can be observed in microscope. Water and HCl sorption increases proportionally to the volume content of talc up to 17% concentration. Further increase in talc concentration does not result in sorption growth because of filler particle aggregation in the polymer binder. 

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