In proposed study the effect of the composition and structure of polyurethane/ground rubber (PUR/GR) composites on the mechanical behavior was evaluated. The structure-properties relationship was studied for PUR matrices with different polarity, porosity and mechanical properties. The morphology of PUR/GR composites was expressed by two structural parameters-interspace filling and interspace volume. Experimental data of mechanical testing were fitted by powerlaw functions containing mentioned structural parameters whereas exponents of these parameters reflect differences in mechanical properties and chemical composition of PUR matrices. Obtained equations describe the mechanical behavior with respect to the structure and morphology of porous PUR/GR composites consisting of one filler and different PUR matrices. Proposed study suggests new approach to the description of the relationship between mechanical behavior and structure of porous composite materials.

The current limitations of calcium phosphate cements (CPCs) used in the field of bone regeneration consist of their brittleness, low injectability, disintegration in body fluids and low biodegradability. Moreover, no method is currently available to measure the setting time of CPCs in correlation with the evolution of the setting reaction. The study proposes that it is possible to improve and tune the properties of CPCs via the addition of a thermosensitive, biodegradable, thixotropic copolymer based on poly(lactic acid), poly(glycolic acid) and poly(ethylene glycol) (PLGA–PEG–PLGA) which undergoes gelation under physiological conditions. The setting times of alpha-tricalcium phosphate (α-TCP) mixed with aqueous solutions of PLGA–PEG–PLGA determined by means of time-sweep curves revealed a lag phase during the dissolution of the α-TCP particles. The magnitude of the storage modulus at lag phase depends on the liquid to powder ratio, the copolymer concentration and temperature. A sharp increase in the storage modulus was observed at the time of the precipitation of calcium deficient hydroxyapatite (CDHA) crystals, representing the loss of paste workability. The PLGA–PEG–PLGA copolymer demonstrates the desired pseudoplastic rheological behaviour with a small decrease in shear stress and the rapid recovery of the viscous state once the shear is removed, thus preventing CPC phase separation and providing good cohesion. Preliminary cytocompatibility tests performed on human mesenchymal stem cells proved the suitability of the novel copolymer/α-TCP for the purposes of mini-invasive surgery.

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