Adhesion polymer-filler

The authors of [99] proposed a calorimetric method for determining the degree of the polymer-filler interaction the exothermal effect manifests itself in the high energy of the polymer-filler adhesion, the endothermal effect is indicative of a poor, if any, adhesion. The method was used to assess the strength of the PVC-Aerosil interaction with Aerosil surface subjected to different pre-treatments... 

It is quite a long time ago, now that Tshoegl [258] showed that the strength of filled systems could be greatly improved if the system were subjected to a hydrostatic pressure, whereby matrix separation is prevented even in systems with zero polymer-filler adhesion. 

The results of mechanical properties (presented later in this section) showed that up to 20 phr, the biofillers showed superior strength and elongation behavior than CB, cellulose being the best. After 30 phr the mechanical properties of biocomposites deteriorated because of the poor compatibility of hydrophilic biopolymers with hydrophobic natural rubber(results not shown). While increasing quantity of CB in composites leads to constant increase in the mechanical properties. Scanning electron micrographs revealed presence of polymer-filler adhesion in case of biocomposites at 20 phr. 

Fillers were initially introduced to reduce costs they have significantly lower cost than low cost commodity polymers. However, fillers are now added to polymers to enhance performance in many applications. Many of these benefits have emerged because of the greater adhesion between the polymer-filler interface. This arises from the use of coupling agents, which provide a bond, both physical and chemical, between the filler and the polymer matrix. 

In order to calculate polymer/filler interaction, or more exactly the reversible work of adhesion characterizing it, the surface tension of the polymer must also be known. This quantity is usually determined by contact angle measurements or occasionally the pendant drop method is used. The former method is based on the Young, Dupre and Eowkes equations (Eqs. 21,8, and 10), but the result is influenced by the surface quality of the substrate. Moreover, the surface (structure, orientation, density) of polymers usually differs from the bulk, which might bias the results. Accuracy of the technique maybe increased by using two or more liquids for the measurements. The use of the pendant drop method is limited due to technical problems (long time to reach equilibrium, stability of the polymer, evaluation problems etc.). Occasionally IGC is also used for the characterization of polymers [30]. 

The filler-elastomer chemical interactions take place through its surface functional groups and hydrogen atoms. Coupling agents improve polymer-filler adhesion. From the point of view of dynamic-mechanical properties for low strains, the filler-elastomer bonds have a positive effect in the reinforcement process. 

Hydrosilylation is also a very useful chemical modification which leads to silane modified polymers with special properties [60-62]. Silane modified polymers have improved adhesion to fillers and better heat resistance. It also acts as a reactive substrate for grafting or moisture catalysed room temperature vulcanisation. Guo and co-workers [61] carried out catalytic hydrosilylation of BR using RhCl(PPh3)3 as the catalyst. Hydrosilylation reactions followed anti-Markovnikov rule as shown in the Scheme 4.4. 

It is usually not possible to match the adhesive s coefficient of thermal expansion to the substrate, because of the high filler loadings that would be required. High loading volumes increase viscosity to the point where the adhesive could not be easily applied or wet a substrate. For some base polymers, filler loading values up to 200 parts per hundred (pph) may be employed, but optimum cohesive strength values are usually obtained with lesser amounts. 

In addition to the modulus prediction, the ultimate properties including elongation and ultimate tensile strength, assuming good adhesion between filler and polymer, can be modeled by the following equations ... 

In any preparation of polymer-filler composites, there is concern about the quality of adhesion at the filler/matrix interface, and consequently over the interaction between filler and molten polymer at the compounding stage. Various technologies have been proposed to enhance adhesion in our laboratories, we have developed surface treatment (encapsulation) techniques in which mica is exposed to a "cold" microwave plasma (l.e. Tgiectron Tgas "Large Volume Microwave Plasma Generator"(LMP)... 

The dispersive component is associated with polymer-filler interaction and the specific component is associated with filler networking and agglomeration. The dispersive component of different fillers is more conveniently measured by inverse gas chromatography although it can also be measured by contact angle methods. The work of adhesion is given by the following equation, which has been modified to account for Fowkes theoiy. 

In PET films containing CaCOs, the adhesion of the film was less than that of unfilled film. This is due to the replacement of the adhesion promoting surface by filler which has no adhesive properties.In UV cured adhesives, quartz filler contributed to a faster development of adhesion due to its transparency to the UV radiation used for curing.In polymer blends filler was accumulated at the interphase between polymers. Adhesion depended on the interaction of filler with both polymers and on the particle size of filler. ... 

Recently, Vaia et al. [8] reported a new process for direct polymer intercalation based on a predominantly enthalpic mechanism. By maximization of the number of polymer host interactions, the unfavorable loss of conformational entropy associated with intercalation of the polymer can be overcome leading to new intercalated nanostructures. They also reported that this type of intercalated polymer chain adopted a collapsed, two-dimensional conformation and did not reveal the characteristic bulk glass transition. This behavior was qualitatively different from that exhibited by the bulk polymer and was attributed to the confinement of the polymer chains between the host s layers. These types of materials have important implications not only in the synthesis and property areas, where ultrathin polymer films confined between adsorbed surfaces are involved. These include polymer filler interactions in polymer composites, polymer adhesives, lubricants, and interfacial agents between immiscible phases. 

In [16] it was proposed to characterise the degree of polymer-filler interaction (adhesion level) by the following parameter ... 

It is worth noting that at the minimum value of d = 2, value A becomes negative. That means, in accordance with Equation (12.1), that tan < tan 8m- In other words, at small d (smooth surfaces of the filler particles) the packing of the polymer molecules at the interface may be more dense compared with the bulk. This fact leads to the diminishing molecular mobility in the interfacial layer [1, 37, 38] Extrapolation of the dependence of A on d to maximum value of d = 3 gives the limiting value of A 4.5. This value meets the value A = 4.2, that was derived from the extrapolation of the volume of the interfacial layer on d to d = 3 [39]. Thus, this analysis allows an estimation of the structural factors influencing formation of the adhesion joints. The main factors are fractal dimensions of the particle surface, d and of the polymer df, which determine adhesion at the polymer-filler particle interface. 

Disperse oxides unmodified or modified by organics (OC) or OSC are used as fillers, adsorbents, or additives [1-11]. OSCs are used as promoters of adhesion, inhibitors of corrosion, for the stabilization of monodisperse oxides and the formation of the nanoscaled particles. Oxide modification by alcohols or other OC is of interest for synthesis of polymer fillers, as such modification leads to plasticization and reinforcement of the filled coating, but in this case a question arises about hydrolyz-ability of the =M—O—C bonds between oxide surface and alkoxy groups, as those are less stable than =M—O— M= formed, for example, upon the silica modification by silanes or siloxanes. The high dispersity, high specific surface area, and high adsorption ability of fumed oxides have an influence on their efficiency as fillers of polymer systems. 

Inverse gas chromatography (IGC) is a method very well used by the adhesion community for obtaining thermodynamic and morphological information on a variety of materials such as fillers, pigments, colloids, fibers, powder, wood, and polymers [17,60,61,85-94]. The term inverse means that the stationary phase is of interest by contrast to conventional gas chromatography in which the mobile phase is of interest. Its success lies in the fact that it is simple, versatile, usable over a very wide range of temperature, and very low cost. IGC has a well established background for the assessment of yg acid-base parameters for polymers and fillers. Such thermodynamic parameters can be further used to estimate the reversible work of adhesion at polymer-fiber and polymer-filler interfaces [95,96],... 

The importance of acid-base interactions in adhesion continues to attract several researchers, however, still there seems to be a lack of consistency in the approaches as stated by K. L. Mittal in the Preface of [19]. It is hoped that Round Tables will be organized in order to define common strategies for polymers, fillers, fibers, etc. which will permit inter-laboratory comparison. 

For lower filler volume fractions the first effect is stronger raising the sample modulus, while with the increase of filler content the second one becomes dominating and the modulus drops. Let us notice that the alternate explanation of the modulus increase for lower - and its decrease for higher filler concentrations seems to be invalid as it would require strong polymer filler adhesion in the initial stages of deformation decreasing with the increase of filler content. The shape of ef/ EP YF EP curves can be explained... 

Chem. Descrip. Bis-(3-[triethoxisily0 propyl)-tetrasulfane CAS 40372-72-3 EINECS/ELINCS 254-896-5 Uses Coupling agent for polysulfide and styrene-butadiene polymers, butyl polymers, for adhesives, coatings, filler treatment, foundry, inks, rubber, sealants, and textile applies. 

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