A new approach to the structure–properties relationship evaluation for porous polymer composites

Influence of the Inclusion of Propylene Carbonate Electrolyte Solvent on the Microstructure and Thermal and Mechanical Stability of Poly(l-lactic acid) and Poly(vinylidene fluoride-co-hexafluoropropylene) Battery Separator Membranes

The influence of the inclusion of the organic solvent propylene carbonate (PC) in microporous membranes based on poly(l-lactic acid) (PLLA) and poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) has been studied based on its relevance for the application of those separator membranes in lithium-ion batteries. The membranes have been produced through solvent casting and characterized with respect to the swelling ratio originated by the uptake of the organic solvent. The organic solvent uptake affects the porous microstructure and crystalline phase of both membrane types. The organic solvent uptake amount affects the crystal size of the membranes as a consequence of the interaction between the solvent and the polymer, since the presence of the solvent modifies the melting process of the polymer crystals due to a freezing temperature depression effect. It is also shown that the organic solvent partially penetrates into the amorphous phase of the polymer, leading to a mechanical plasticizing effect. Thus, the interaction between the organic solvent and the porous membrane is essential to properly tailor membrane properties, which in turn will affect lithium-ion battery performance.

The Influence of Porosity on Mechanical Properties of PUR-Based Composites: Experimentally Derived Mathematical Approach

The work is focused on the mechanical behavior description of porous filled composites that is not based on simulations or exact physical models, including different assumptions and simplifications with further comparison with real behavior of materials with different extents of accordance. The proposed process begins by measurement and further fitting of data by spatial exponential function z_c = z_m · p₁^b · p₂^c, where z_c/z_m is mechanical property value for composite/nonporous matrix, p₁/p₂ are suitable dimensionless structural parameters (equal to 1 for nonporous matrix) and b/c are exponents ensuring the best fitting. The fitting is followed by interpolation of b and c, which are logarithmic variables based on the observed mechanical property value of nonporous matrix with additions of further properties of matrix in some cases. The work is dedicated to the utilization of further suitable pairs of structural parameters to one pair published earlier. The proposed mathematical approach was demonstrated for PUR/rubber composites with a wide range of rubber filling, various porosity, and different polyurethane matrices. The mechanical properties derived from tensile testing included elastic modulus, ultimate strength and strain, and energy need for ultimate strain achievement. The proposed relationships between structure/composition and mechanical behavior seem to be suitable for materials containing randomly shaped filler particles and voids and, therefore, could be universal (and also hold materials with less complicated microstructure) after potential following and more exact research.

A New Approach to the Structure-Properties Relationships Determination for Porous Filled Reinforced Materials

This study describes a new mathematical approach to the relationship between mechanical properties (tensile modulus, ultimate strength, and strain), composition as well as structure of porous-filled reinforced composites. The composite system consisted of a polyurethane matrix, a rubber filler, and a small amount of polyethylene terephthalate as a reinforcement. The newly proposed equations are based on a special mixing rule with the same basic form for all studied properties. The mixing rule contains a correction parameter η, which differs in different filler content in the filled part of the composite. Here, a cubic exponential function including the product of suitable structural parameters and exponents ensuring the best fitting and describable by matrix properties were successfully defined to fit the different values of correction parameter. The proposed equations should be a suitable step to obtain a relationship for describing the mechanical behavior of porous-filled and reinforced composites in the case of a small amount of reinforcement.