Elastomer matrix

As shown in Fig. IIB, dispersion morphology for the nylon 6/Vectra B/SA-g-EPDM blend was totally different from that of the PBT-Vectra A-SA-g-EPDM blend. TLCP phases were very uniformly and finely dispersed in the nylon 6-Vectra B-SA-g-EPDM blend and a large fibril shape observed in the PBT-Vectra A-SA-g-EPDM blend could not be seen under polarized microscope. It should be noted that the size of the dispersed TLCP phase is very small (submicron size). This small size of the TLCP phase in the nylon 6/elastomer matrix was not observed by any others [4,54,55,58]. A closer look by SEM more clearly revealed the dispersion of Vectra B in the matrix (Fig. 12B). TLCP phases are very... 

The study of the mechanical properties of filled elastomer systems is a chaUenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward mle of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fiUers hke sihca and carbon black on the reinforcement of elastomers.In general, the strucmre-property relationships developed for filled elastomers have evolved into the foUowing major areas FiUer structure, hydrodynamic reinforcement, and interactions between fiUers and elastomers. 

In order to produce high-performance elastomeric materials, the incorporations of different types of nanoparticles such as layered silicates, layered double hydroxides, carbon nanotubes, and nanosilica into the elastomer matrix are now growing areas of rubber research. However, the reflection of the nano effect on the properties and performance can be realized only through a uniform and homogeneous good dispersion of filler particles in the rubber matrix. 

Orug/Silicone Fluid Suspension e Drug/Sllicone Elastomer Matrix... 

V. Collin and E. Peuvrel-Disdier, Disperion Mechanisms of Carbon Black in an Elastomer Matrix, Elastomery, Vol. 9 (2005) Special Edition JSSN PL 1427-3519 see also V. Collin and E. Peuvrel-Disdier, presentation at the Conference of European Rubber Research Practical Improvements of Mixing Processer, Paterbom, Germany, January 25-26 (2005), pp. 219-241. 

Based on the IR data of samples before extraction, it is concluded that the allyl groups react rapidly to completion within about 2 minutes, whereas the ester absorption remains constant. More allyl groups per unit of time react than peroxide radical fragments are initiated, it can be concluded that the allyl groups react predominantly via radical addition reactions, probably accompanied by radical transfer reactions. FT-IR analysis after vulcanisate extraction indicates that the co-agent is covalently bound to the elastomer matrix, as shown by the 100% recovery of the ester absorption after 2 minutes of curing. 

Nonoxynol-9 is an approved spermicide with strong antiviral activity. A vaginal device which facilitates the controlled release of nonoxynol-9 has been developed for contraceptive and anti-STD purposes. The device, available as a diaphragm or a disk pessary, is fabricated from silicone elastomer matrix system. The drag release profile demonstrates square root time kinetics (M co tV2) (see Section 4.4.2). 

Even dynamic measurements have been made on mixtures of carbon black with decane and liquid paraffin [22], carbon black suspensions in ethylene vinylacetate copolymers [23], or on clay/water systems [24,25]. The corresponding results show that the storage modulus decreases with dynamic amplitude in a manner similar to that of conventional rubber (e.g., NR/carbon blacks). This demonstrates the existence and properties of physical carbon black structures in the absence of rubber. Further, these results indicate that structure effects of the filler determine the Payne-effect primarily. The elastomer seems to act merely as a dispersing medium that influences the magnitude of agglomeration and distribution of filler, but does not have visible influence on the overall characteristics of three-dimensional filler networks or filler clusters, respectively. The elastomer matrix allows the filler structure to reform after breakdown with increasing strain amplitude. 

The mean average molecular mass of the network chains is determined for the elastomer matrix outside the adsorption layer. Contributions to the network structure fi om different types of junctions (chemical junctions, adsorption junctions, and topological hindrances due to confining of chains in the restricted geometry (entropy constraints or elastomer-filler entanglements) are estimated. The major contributions to the total network density are provided by the topological hindrances near the filler surface and by the adsorption junctions. The apparent number of the elementary chain units between the topological hindrances is estimated to be approximately 40-80 elementary chain units. 

Stress-strain properties for unfilled and filled silicon rubbers are studied in the temperature range 150-473 K. In this range, the increase of the modulus with temperature is significantly lower than predicted by the simple statistical theory of rubber elasticity. A moderate increase of the modulus with increasing temperature can be explained by the decrease of the number of adsorption junctions in the elastomer matrix as well as by the decrease of the ability of filler particles to share deformation caused by a weakening of PDMS-Aerosil interactions at higher temperatures. 

The presence of active fillers causes significant changes in the elastomer matrix adjacent to the filler surface due to ... 

An increase of the intrinsic chain deformation in the elastomer matrix compared with that of... 

The elastic properties of rubbers are primarily governed by the density of netw ork junctions and their ability to fluctuate [35]. Therefore, knowledge of the network structure composed of chemical, adsorption and topological junctions in filled elastomers as well as their relative weight is of a great interest. The H T2 NMR relaxation experiment is a well established method for the quantitative determination of the network structure in the elastomer matrix outside the adsorption layer [14, 36]. The method is especially attractive for the analysis of the network structure in filled elastomers since filler particles are "invisible" in this experiment due to the low fraction of protons at the Aerosil surface as compared with those in the host matrix. 

It is generally believed that the nature of elastomer-filler interactions is of major importance for marked improvement in mechanical properties of the filled elastomers [39-44]. Adsorption of elastomer chains at the filler surface has a double effect on the enhancement of mechanical properties of filled elastomers. Firstly, the ability of filler particles to share deformation increases due to adsorption interactions between the filler particles and the host matrix. Secondly, these interactions provide significant amount of adsorption and topological junctions in the elastomer matrix outside the adsorption layer. It appears that less mobile chain units in the adsorption layer do not contribute directly to the rubber modulus, since the fiaction of PDMS chain units in this layer is only a few percent of the Aerosil content used in conunercial rubbers [7,8,12,21]. 

A large number of macroscopic properties of elastomer networks are closely related to the density of network junctions and the extent of their fluctuations. Qualitatively, any increase of network density causes an increase in stress, whereas fluctuations of network junctions leads to a decreasing stress. It is generally believed that a formation of additional network junctions resulting fi-om the presence of filler particles in the elastomer matrix is one of the reasons for the improvement of mechanical properties of filled elastomers. However, the application of macroscopic techniques does not provide reliable results for the network structure in filled elastomers. Furthermore, a lack of information exists on the dynamic behavior of adsorption junctions. The present study fills the gap of knowledge in this area. 

It appears that the following peculiarities of the network structure in the elastomer matrix outside the adsorption layer are of importance for a molecular understanding of stress-strain behavior for these materials ... 

Considerable effort has been spent to explain the effect of reinforcement of elastomers by active fillers. Apparently, several factors contribute to the property improvements for filled elastomers such as, e.g., elastomer-filler and filler-filler interactions, aggregation of filler particles, network structure composed of different types of junctions, an increase of the intrinsic chain deformation in the elastomer matrix compared with that of macroscopic strain and some others factors [39-44]. The author does not pretend to provide a comprehensive explanation of the effect of reinforcement. One way of looking at the reinforcement phenomenon is given below. An attempt is made to find qualitative relations between some mechanical properties of filled PDMS on the one hand and properties of the host matrix, i.e., chain dynamics in the adsorption layer and network structure in the elastomer phase outside the adsorption layer, on the other hand. The influence of filler-filler interactions is also of importance for the improvement of mechanical properties of silicon rubbers (especially at low deformation), but is not included in the present paper. 

Stress-strain curves for PDMS, containing different types of Aerosil, are compared in Fig. 14. As can be seen, the total interfacial area between Aerosil particles and elastomer matrix and/or the amount of filler and its adsorption ability are of great importance for the improvement of stress-strain characteristics,... 

The presence of filler in the rubber as well as the increase of the surface ability of the Aerosil surface causes an increase in the modulus. The temperature dependence of the modulus is often used to analyze the network density in cured elastomers. According to the simple statistical theory of rubber elasticity, the modulus should increase twice for the double increase of the absolute temperature [35]. This behavior is observed for a cured xmfilled sample as shown in Fig. 15. However, for rubber filled with hydrophilic and hydrophobic Aerosil, the modulus increases by a factor of 1.3 and 1.6, respectively, as a function of temperature in the range of 225-450 K. It appears that less mobile chain units in the adsorption layer do not contribute directly to the rubber modulus, since the fraction of this layer is only a few percent [7, 8, 12, 21]. Since the influence of the secondary structure of fillers and filler-filler interaction is of importance only at moderate strain [43, 47], it is assumed that the change of the modulus with temperature is mainly caused by the properties of the elastomer matrix and the adsorption layer which cause the filler particles to share deformation. Therefore, the moderate decrease of the rubber modulus with increasing temperature, as compared to the value expected from the statistical theory, can be explained by the following reasons a decrease of the density of adsorption junctions as well as their strength, and a decrease of the ability of filler particles to share deformation due to a decrease of elastomer-filler interactions. 

In contrast to the filled samples, the deformation energy for the unfilled ones increases proportionally to the increase in the absolute temperature according to the prediction of the simple statistical theory of rubber elasticity. Thus, it appears that the change of the modulus and the deformation energy with increasing temperature reveals a decrease of the density of adsorption junctions in the elastomer matrix, as well as a decrease of the ability of filler particles to share deformation, resulting from a weakening of elastomer-filler interactions. 

Snorradottir, B.S., Gudnason, P.J., Scheving, R. et al. 2009. Release of anti-inflammatory dmgs from a silicone elastomer matrix system. Pharmazie. 64 19-25. 

The quality of particulate filler dispersion in the elastomer matrix is of primary importance for compound mechanical and use properties (Gotten, 1983 Funt, 1986 Gerspacher and O Farrell, 1993 Bomo andMorawski, 1983 Richmond etal., 1993). 

In unsaturated poly (ester) resins, the addition of LCP improves the adhesion to glass fibers. In addition, the mechanical properties are enhanced. In elastomer matrix polymers, the addition of LCP causes an enhancement of thermal stability ... 

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