Materials Science Forum Vol. 714

Abstract: Aim of the work was production of nanocomposite polymer fibres containing ceramic particles using the electrospinning method and characterisation of morphology and bioactivity of the produced materials. The first stage of investigations consisted in preparation of a series of poly-L-lactide (PLA) solutions in various solvents mixtures in order to reach viscosity which would allow formation of fibres by the electrospinning method. Ceramic nanoparticles such as tricalcium phosphate (TCP) and silica (SiO₂) were used as nanofillers of the polymer matrix. Their particle size distribution in the solvent solution as well as in the polymer suspension was determined by dynamic light scattering method (DLS). Morphology of the nanoparticles was observed using transmission electron microscopy (TEM). Distribution of the nanofillers in the nanocomposite fibres as well as diameter and morphology of the fibres was assessed using scanning electron microscopy with energy dispersive spectroscopy method (SEM/EDS). Effect of the nanofillers addition and the shaping method on the structure of the PLA matrix was investigated on the basis of the thermal analysis methods (TG/DSC) on the nanocomposite foils prepared by casting. It was revealed that the nanocomposite fibres showed apatite nucleation in in vitro conditions i.e. after incubation in SBF (37°C/ 3 days).

Abstract: Processing of the poultry feather biomass into useful products presents interesting opportunities of recycling agricultural waste material. According to a chemical process developed in our laboratory, poultry feathers were converted into wool, fibers or powder so as to meet several applications in many fields. Due to of their unique structure and to their physical properties, a suitable molding technique was performed in order to produce composite samples highly filled. The concentration range was varied from 10 to 50% by weight with an increase of 10, because of practical reasons. The morphological, thermophysical and mechanical investigations of polyester matrix filled with several concentrations of the keratin fibers show interesting results.

Abstract: Among the many applications of polylactide (PLA) in medicine, one of the most famous is porous scaffold for bone and cartilage regeneration. A new direction in the development of biodegradable polymer scaffolds is their modification using different types of nanoadditives. One type of these nanomaterials could be carbon nanotubes (CNT), which could influence the mechanical, electrical, physicochemical and biological properties of polymer matrices. Porous nanocomposite scaffolds were prepared using different techniques, such as salt leaching and a combination of salt leaching and gas foaming techniques. The bioactivity of MWCNTs was determined through their incubation in simulated body fluid (SBF) and verified using scanning electron microscopy (SEM). The best concentration of nanoadditives in the polymer matrices was evaluated on the basis of mechanical and in vitro tests of nanocomposite films using a universal testing machine (Zwick) and osteoblast-like human cells (MG63). The morphology, porosity and mechanical properties of the porous scaffold before and after modification with MWCNTs were evaluated using SEM, hydrostatic weighing and a universal test machine.

Abstract: Recycled T800S carbon fibre from a polymer composite using a pyrolysis process was compared with virgin T800S fibre and the contact angle and interfacial shear strength with epoxy and vinyl ester resins were measured. The contact angles were measured using drop length-height method, and the interfacial shear strengths were measured using micro-bond method. For the same type of resin, the recycled T800S carbon fibre had a greater contact angle and lower interfacial shear strength than those of the virgin fibre.

Abstract: In this research, the core-shell structured fiber was fabricated by coaxial electrospinning technique. A set of biodegradable polymers namely polylactic acid (PLA) and cellulose acetate (CA) were used as the shell material. Gentamicin sulfate (GS) as antimicrobial drug with polyethylene glycol (PEG) was used as the core structure. PEG formed the core section of the coreshell fibers for GS encapsulation. In-vitro drug release activity of the core-shell fibers was determined by total immersion method in pH 7.4 phosphate buffer solutions (PBS). It was found that core-shell fibers sPLA-cPEG/GS exhibit higher initial release compared to that of core-shell fibers sPLA/CA-cPEG/GS.

Abstract: This paper deals with blends of ethylene-octene rubber (POE) with nanostructured metal oxides: magnesium oxide (MgO), calcium oxide (CaO), zinc oxide (ZnO) and unsaturated acids: itaconic acid (IA), sorbic acid (SA) and crotonic acid (CA), as co-agents. Dicumyl peroxide (DCP) was used as a vulcanizing agent. Elastomer composites were prepared in Brabender measuring mixer N50. Rheometric properties of rubber mixes and crosslink density of vulcanizates were measured. Mechanical properties of the samples were also investigated. Dispersion degree of coagents in elastomer matrix was studied by SEM images. Cross-link density analysis revealed that POE vulcanizates contained both ionic bonds and covalent bonds. The results showed that the nanostructured metal oxides and unsaturated acids used as co-agents can greatly improve the modulus at 100% of elongation and tensile strength of the vulcanizates.

Abstract: New multiblock polymer-matrix nanocomposites were prepared by the in situ polycondensation. Polymers containing 30% hard segments of poly (butylene terephthalate) (PBT) and 70% soft segments built up from dimerized fatty acid (DLA), were modified with silica nanopowder. The nanocomposite materials were prepared by polycondensation in situ with the use of two different catalysts. Two types of nanosilica (Evonic Aerosil R 972 hydrophobic, and Aerosil 130 - hydrophilic) in amount of 0.1, 0.2 and 0.3 wt. % were used. Physical and mechanical properties were examined. The results indicate a strong influence of transesterification stoichiometry and type of catalyst on physical and mechanical properties. The amount of nanofiller and its character (hydrophilic or hydrophobic) showed also an influence on mechanical properties of synthesized nanocomposites indicating the best mechanical properties for nanocomposite containing 0.1wt% hydrophobic silica nanopowder (over 70% increase in elongation and 30% increase in tensile strength).

Abstract: Poly (L-lactic acid) (PLLA) and composite of PLLA with osteoconductiveβ-tricalcium phosphate fine powder (PLLA/TCP) compression moulded specimens were subjected to in vitro biodegradation up one year. Samples were investigated in terms of physical-chemical evaluation after several periods of incubationin simulated body fluid solution. Reduction in PLLA molecular weights occurred during thermal processing of compounding of the polymer with TCP. 3-point bending measurements revealed some decay in the flexural strength and increase in stiffness after incorporation of the inorganic particles into the polymer. Those parameters remained nearly stable during the biodegradation period despite constant drop of polymer molecular weight. Thermal properties of both kinds of samples did not changed significantly, however degree of crystallinity of PLLA matrix was increasing slowly in pure PLLA samples. Despite no mass loss,extent of surface deteriorationincreased steady during the incubation. Current study is intended to develop material for implants, mainly fusion cages targeted for spinal applications.

Abstract: The synthesis of polymer brushes containing poly (methyl methacrylate) (PMMA) chains grafted from hydroxyapatite (HAP) particles was disscussed. Surface of commercially available hydroxyapatite was first modified with atom transfer radical polymerization (ATRP) initiator and hydrophobized with isobutyric acid, and then surface-initiated ATRP was conducted. Properties of obtained hybrids were studied by dynamic light scattering (DLS) and gel permeation chromatography (GPC). Polymers with various molecular weight up to M_n=96,100 g/mol were obtained with good control;M_w/M_n<1.2. Copolymer brushes of poly (methyl methacrylate-stat-benzophenone methacrylate) (P(MMA-stat-BPMA) were also synthesized and cross-linking ability of such materials under UV radiation was confirmed.