Mechanical Properties Of Polymer Blends Research Articles

Miscibility and mechanical properties of polymer blends

AbstractThe tensile properties of 16 blends prepared from 12 different polymers were investigated in the whole composition range. The composition dependence of Young's modulus has shown less, while that of the yield and ultimate properties exhibited more significant variations with miscibility. The quantitative evaluation of the yield stress and tensile strength data resulted in a parameter, which could be related to the interfacial tension and miscibility.

Investigations of the influence on the phase morphology of PP-EPDM-blends on their mechanical properties

This work covers the dependence of the mechanical properties of polymer blends on their composition and their phase morphology. Blends of EPDM-elastomers and polypropylene were prepared covering the whole concentration range. The phase morphology was varied strongly by employing different mixing techniques and its morphology was characterized by means of electron microscopy and light microscopy, as well as by x-ray scattering and calorimetry.

Evidence for cleavage of polymer chains by crack propagation

CRACK propagation in polymers is a topic of considerable importance to the technological application of these materials. In high-molecular-weight glassy polymers, crack propagation is normally assumed to require the breaking of covalent bonds in polymer chains that span the crack path, as opposed to chain slip and disentanglement. The fraction of such broken chains in a bulk sample would be very small, however, so that there is little direct evidence for this chain breakage1. Interfaces between immiscible polymers are often very weak, but can be strengthened by the presence of a diblock copolymer (a polymer in which each molecule consists of a block of one polymer bonded to a block of a different polymer) for which each of the two blocks is miscible with one of the homopolymers2. The diblock copolymer is thought to organize at the interface and so 'stitch' the homopolymers together. Here we show that crack propagation along the interface between the homopolymers involves breaking all the copolymer chains at a point in the region of the junction between the two blocks. Thus we demonstrate both that the block copolymer does indeed organize at the interface and that fracture involves the breaking of polymer chains. This information may suggest means by which the mechanical properties of polymer blends could be systematically improved.

Influence of the Mechanical Properties of Polymer Blends with Complete Miscibility on Wood Adhesion

Influence of the Mechanical Properties of Polymer Blends with Complete Miscibility on Wood Adhesion

Effects of dispersion on flow and mechanical properties of polymer blends

AbstractBlends of linear polyethylene and ethylene‐propylenediene elastomer, representing the entire composition range, were prepared under various conditions of shear intensity. It was found that both viscoelastic flow parameters and mechanical properties at large deformation respond strongly to variations in shear history of material preparation. Mechanical degradation of the polymers not being detected, it is postulated that property variations are due to morphological effects related to domain sizes of the two components and to the ease of molecular diffusion across domain boundaries. Thus, mechanical properties develop over finite times of mixing, consistent with the attainment of steady states in domain sizes. Maximum sensitivity of mechanical properties to mixing variables is found for 50/50 blends of the polymers, which have maximum interdomain contact areas. It appears feasible to develop desired balances of flow and mechanical properties in such polyblends through the close control of component dispersion processes.

Two-Dimensional Model of Mechanical Properties of Polymer Blends: Application to Polypropylene and Polyethylene Blends

Two new mechanical models for the description of mechanical properties of two-component polymer blends are proposed. On the basis of these models the dependence of the dynamic complex moduli on the blend content is theoretically calculated. Results obtained theoretically are compared with experimental data for polyethylene and polypropylene blends.

A Theory of Polymer Blend, as Extension of the Theory of Filler Reinforcement and of a Theoretical View of Stress-Strain Behavior of Model Polymer Blend System

The molecular theory of filler reinforcement which was previously proposed by one of the authors (Y.S.) has been applied by extension to the analysis of the mechanical properties of polymer blends. Almost the same model has been used in the present experiment of the theory of filler reinforcement as those which were used in the previous experiment of the theory of the same, and almost the same assumptions are made for the present theory as was made for the previous theory, except that the dispersed spherical particles are rigid, because the spherical particles dispersed in polymers as demonstrated in the present theory are no longer to be necessarily designated rigid, but only deformable bearing the rigidity G0.Of the blend of two kinds of polymers with rigidity G and G0, the stress-strain relation of simple extension is obtained as follows where σ denotes the tension at extension ratio α, Y and (1-ζ) denote the volume fraction of the dispersed polymer and the degree of adhesion, respectively, and K is the ratio of the surface modulus to the volume modulus and is a parameter expressing the surface effects, φ is the ratio of the volume of the sample before and after deformations, γ1 and γ represent the deformation of the inner surface of the medium facing the dispersed particles in the direction of extension in a perfect adhesion state and an actual adhesion state, respectively, γ1' and γ' represent the deformation perpendicular in the direction of extension in perfect adhesion state and an actual adhesion state, respectively. Upon this relation, it has been examined theoretically how Y or X (Volume ratio of two polymers), (1-ζ) and K will affect the stress-strain behavior of polymer blends. The two cases of blend system have been considered; the system composed of two kind of polymers in which a polymer medium with rigidity of 2.5 includes softer polymer particles with rigidity of 1.25, and harder polymer particles with rigidity of 5.0. The results show that in the case of a perfect adhesion state, the calculated tension σ for both the systems increased with increasing α and X, while in the case of a perfect non-adhesion state, σ increased with α but the rate of increase changed at an extension ratio of about 1.5 or 2.0 and decreased with increasing X. It was also found that σ was fairly sensitive to the change in the value of K.

A Generalized Model Representation Relating the Degree of Mixing to the Mechanical Properties of Physically Blended System of Two Polymer Components

The mechanical properties of polymer blends depend on the degree of mixing of the blended components. If the blended polymers are poorly compatible or incompatible, which is oftener met in actual and is more significant in modifying the mechanical properties of a single polymer component in a practical point of view, it presents a sort of physically blending rather than a sort of solvation. This common type of blending usually shows the existence of two glass-transition temperatures which correlate, more or less, to the original glass-transition temperatures of each component and suggest that the physically blending leaves homogeneous regions of each polymer component.In this paper, it is intended to relate the viscoelastic properties of this type of physically blended system of two polymer components to the degree of mixing by using a generalized model representation, as shown in Fig. 2, consisted of n elements coupled in parallel by the volume fraction λ, in which the ith element consists of two polymer components coupled in series by the volume fraction φi.Considering λi as a function of φi and n as infinite, then the following mathematical relations will be obtained:E(T)=∫10E(T, φA)λ(φA)dφA (2')1=∫10λ(φA)dφA (3')VA=∫10λ(φA)φAdφA (4')and1/E(T, φA)=φA/EA(T)+(1-φA)/EB(T) (1')where E(T) is temperature dependence of Young's modulus of the whole blended system; E(T, φA) is that of the element having the volume fraction of A component φA; and VA, EA and EB are volume fraction of A component in the whole system, temperature dependence of Young's modulus of A component and that of B component, respectively.The degree of mixing, λ(φA) is obtained by solving the integral equation (2') under the additional conditions of Eqs. (3') and (4'), since E(T), EA(T) and EB(T) are measurable functions and thereby E(T, φA) is a known function. It is, however, difficult to solve Eq. (2') analytically, and the equation must be solved numerically.The degree of mixing λ(φA) of the blended systems of 30/70 butadiene-styrene copolymer and polystyrene varying VA from 0 to 100% is determined from the temperature dependence of E(T) of the blended systems given by Tobolsky. λi(φAi) determined by the numerical method shows maxima at the extremes of φAi, i.e., near φA=0 and 1, and reveals gradual increase of λi(φAi≅1) or decrease of λi(φAi≅0) with increase of VA.