Interphase distribution of fillers

Investigations of polymer blends has developed an increased understanding of interphase organization. In blends two interfaces exists the interface between two matrix types and distribution of filler and its interfaces with this matrices. The interphase of carbon black in blends of natural rubber and EPDM depends on the character of carbon black (surface groups available for interaction), the viscosity,... 

Although a number of filler characteristics influence composite properties, particle size, specific surface area, and surface energetics must again be mentioned here. All three also influence interfacial interactions. In the case of large particles and weak adhesion, the separation of the matrix/ filler interface is easy, debonding takes place under the effect of a small external load. Small particles form aggregates which cause a deterioration in the mechanical properties of the composites. Specific surface area, which depends on the particle size distribution of the filler, determines the size of the contact surface between the polymer and the filler. The size of this surface plays a crucial role in interfacial interactions and the formation of the interphase. 

The properties of filled materials are eritieally dependent on the interphase between the filler and the matrix polymer. The type of interphase depends on the character of the interaction which may be either a physical force or a chemical reaction. Both types of interaction contribute to the reinforcement of polymeric materials. Formation of chemical bonds in filled materials generates much of their physical properties. An interfacial bond improves interlaminar adhesion, delamination resistance, fatigue resistance, and corrosion resistance. These properties must be considered in the design of filled materials, composites, and in tailoring the properties of the final product. Other consequences of filler reactivity can be explained based on the properties of monodisperse inorganic materials having small particle sizes. The controlled shape, size and functional group distribution of these materials develop a controlled, ordered structure in the material. The filler surface acts as a template for interface formation which allows the reactivity of the filler surface to come into play. Here are examples ... 

Shaterzadeh et al. (1998) notes the importance of filler distribution as well as interphase in the generalized self-consistent three-phase model used to predict the dynamic moduli of an epoxy/A-glass-bead system. 

At ambient and processing temperatures, elastomers are viscous fluids with persistent transport phenomenon. In immiscible blends, these lead to change in the size and shape of the elastomer phases and migration of the fillers, plasticizers, and curatives from one phase to another. These changes are accelerated by processing and plasticization but retarded by the ultimate vulcanization. Retention of the favorable properties of a metastable blend, which is often attained only at a select interphase morphology and filler/plasticizer distribution, thus requires careful control of both the processing and the vulcanization procedures. 

Polymer alloys may be considered as independent composite materials because they have many common features similar to filled systems such as two-phase structure and interphase layer. Considering the reinforcement of pol5Tner alloys, one should have in mind a very complicated structure of the matrix, consisting conventionally of three phases. The distribution of particulate filler in such a system will be dependent both on the structure of various regions and on their composition, determining the affinity of the matrix to the filler surface. In its turn, as shown below, the filler may influence the formation of the alloy structure, which is especially important when reinforcing with fibrous fillers. 

Abstract Multicomponent materials based on synthetic polymers were designed and used in a wide variety of common and hi-tech applications, including the outdoor applications as well. Therefore, their response to the UV radiation and complex weathering conditions (temperature, seasonal or freeze—thaw cycles, humidity, pH, pollutants, ozone, microorganisms) is a matter of utmost importance in terms of operational reliability and lifetime, protection of the environment and health safety. This chapter offers an overview of this subject and a critical assessment of more particular topics related to this issue. Thus, various types of multicomponent systems based on thermoplastic and thermosetting polymer matrices were subjected to natural and/or simulated UV radiation and/or weathering conditions. Their behavior was evaluated in correlation with their complex formulation and taking into consideration that the overall effect is a sum of the individual responses and interactions between components. The nature and type of the matrix, the nature, type and size distribution of the filler, the formation of the interphase and its characteristics, the interfacial adhesion and specific interfacial interactions, they all were considered as factors that influenced the materials behavior, and, at the same time, were used as classification criteria for this review. 

New concepts combining micromechanical models with the macromechanics of composite bodies were able to explain experimental data and predict limits of mechanical properties. Proposed models were used as the link between micro-and macromechanics of the composite body. In the calculations, in addition to properties of the matrix and the filler, properties and spatial arrangement of the interphase have been included (5). This model allows for a prediction of the structure-property relationships in PP filled wifh randomly distributed core-shell inclusions with EIL shell. This is of a pivotal importance in an attempt to develop and manufacture materials tailored to a particular end-use application. 

An important aspect defining the mechanical behaviour of NR based polar synthetic rubber blend vulcanizates is the mechanical response of the individual components and the interphase involved, influenced by the curative (and filler) distribution. The synergetic action of the blend phases escalates the ability of... 

Significant improvement of mechanical properties of the polymer composite is related to the filler particle size as well as its distribution in the matrix. The reduction in aggregates size formed by the primary particles results in an better contact between the filler and elastomer chains. Moreover it determines the size of the interphase between the surface and an elastomeric matrix what strongly influences on the mechanical properties. The aggregates can be the weak centre in which breaking of the material start. 

In the case of fiber-reinforced composites, even where the filler consists of wood fibers and other ligno-cellulosic or proteic fibers, the main issue is the interfacial adhesion between matrix and fibers, as a sine qua non requirement for the load transfer, as the fibers carry the load, while the matrix distributes and transfers it from fiber to fiber. Hence, the relevance of the interphase that may be formed spontaneously, no matter the fibers are raw or modified by a surface treatment, and which strongly affects the properties of the composite through its thickness, structure and properties [3]. 

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