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At the Freiburger Materialforschungszentrum we have developed a new process (3DBioplotting TM) that permits most kind of polymers and biopolymers to be used in 3D scaffold design, including hydrogels (e.g. collagen, agar), polymer melts (e.g. PLLA, PGA, PCl) and twocomponent systems (e.g. chitosan, fibrin). Cells can be incorporated within the construction process, making this an ideal Rapid Prototyping technique for Organ Printing. Tailor-made biodegradable soft or hard scaffolds can so be fabricated in a short time using individual computer-tomography data from the patient. In-vitro tests showed promising results and in-vivo experiments are now under observation.

A novel phase-separating liquid rubber based on oligo(alkylmethacrylate) in combination with microglass beads was used to toughen an anhydride-cured epoxy resin. The resulting hybrid composites containing 5 or 10 wt% of oligomeric liquid rubber and between 10 wt% and 60 wt% glass beads as well as composites containing corresponding amounts of glass beads but no liquid rubber were characterized mechanically. The experimental data show that modification with glass beads results in increased stiffness and toughness compared to the neat resin but reduces tensile strength. Compared to the glass bead filled composites additional modification with methacrylic rubber leads to further increase in toughness and also to an increase in strength but does not alter stiffness and glass transition temperature. This synergistic behavior is explained by the fact that the rubber separat es preferably on the surface of the glass bead forming a core-shell morphology during curing.

Novel liquid rubbers based on bishydroxy-terminated oligo(butylmethacrylate) were used to toughen anhydride cured epoxy resins. Concentration and molecular weight of the toughening agents were varied in order to examine the effects on important mechanical properties such as toughness, strength, stiffness, and glass transition temperature. Experimental data show that telechelic methacrylates are suitable toughening agents for epoxies. The compatibility between resin and toughener can be adjusted by varying the molecular weight of the rubber. Best results are obtained modifying an epoxy resin with 10 wt per cent of bishydroxy-terminated oligo(butylmethacrylate) of a molecular weight of 5000 g/mol. Fracture toughness K(Ic) increases by 150 per cent accompanied by a decrease in modulus of only 1 1 per cent and in strength of 16 per cent as compared to the corresponding properties of the neat resin. Due to an almost complete phase separation of the rubber upon curing glass transition temper ature is scarcely affected.

Mechanical and fracture mechanics properties of transparent multiphase epoxy resins toughened with various amounts of compatibilized silicone liquid rubbers consisting of polycaprolactone-block-poly(dimethylsiloxane)block-polycaprolactone triblock-copolymer have been investigated. At silicone liquid rubber contents < 10 wt% significantly improved toughness has been achieved without adversely affecting thermal and mechanical properties. Fractographic and interferometric methods have been applied to study crack propagation in such siliconemodified resins.