Priprema i karakterizacija mješavina na osnovi termoplastičnog poliuretana i fibroina svile

Fibroin svile (FS) jedinstven je i obećavajući prirodni polimer te zbog svoje biokompatibilnosti, biorazgradivosti i netoksičnosti ima velik potencijal za primjenu kao biomedicinski materijal. Unatoč svojoj čvrstoći, sam FS nije prikladan zbog svoje slabe fleksibilnosti. S druge strane, termoplastični poliuretan (TPU) vrlo je poželjan materijal za medicinsku primjenu upravo zbog njegove fleksibilnosti. Problem slabe fleksibilnosti FS-a mogao bi se riješiti miješanjem fleksibilnog TPU-a s FS-om. Cilj ovoga rada bio je pripremiti mješavine na osnovi TPU-a i prirodnog polimera FS-a. Mješavine TPU-a s FS-om pripremljene su umješavanjem FS-a u TPU u omjerima 5, 10, 15 i 20 mas. % FS-a u laboratorijskoj gnjetilici Brabender. Uzorci su dobiveni prešanjem na hidrauličkoj preši. Određena je struktura te toplinska i viskoelastična svojstva čistog TPU-a, FS-a i mješavina TPU/FS primjenom infracrvene spektroskopije s Fourierovim transformacijama (FTIR), diferencijalne pretražne kalorimetrije (DSC), dinamičko-mehaničke analize (DMA) i termogravimetrijske analize (TGA). Dobiveni rezultati FTIR analize pokazuju da je FS ugrađen u TPU matricu. Rezultati dobiveni mjerenjem DSC i DMA pokazali su da se dodatkom FS-a u TPU temperature staklastog prijelaza (Tg) izražene kao Teig, Tmg i Tefg snižavaju zbog smještanja amorfne faze FS-a (asparaginska kiselina) u amorfnu fazu TPU-a, čime dolazi do veće pokretljivosti polimernih lanaca. Temperature taljenja (Tm) izražene kao Teim, Tpm i Tefm u mješavinama TPU/FS neznatno se snižavaju u odnosu na čisti TPU zbog nastajanja slabije uređene kristalne strukture dodatkom FS-a. Toplinska postojanost neznatno se smanjuje dodatkom FS-a zbog njegove slabije toplinske postojanosti.
Silk fibroin (SF), a unique and promising natural material extracted from silkworm, has gained much attention for its use as biomedical material, because of its biocompatibility, biodegradability, and nontoxicity. Despite its strength, SF alone is not appropriate because of its poor flexibility. Thermoplastic polyurethane (TPU) is a very desirable material for medical applications because of its flexibility. A solution to the problem of SF’s poor flexibility can be achieved by mixing flexible TPU with SF. The aim of this work was to examine the influence of FS content on the physical and thermal properties of TPU/FS blends. Blends of SF and TPU were prepared with melt mixing of TPU with 5, 10, 15, and 20 wt% of SF in a laboratory Brabender kneading chamber. The specimens of the neat components and their blends were moulded in a hydraulic press. The structural characteristics, thermal, and viscoelastic properties of neat TPU, SF and their blends (TPU/SF blends) were examined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The FTIR results showed that the SF was successfully introduced to TPU matrix. Results obtained with DSC and DMA measurements showed that, when the SF content increased in the TPU/SF blends, the Tg, expressed as Teig, Tmg, and Tefg of the TPU, slightly shifted to lower temperature due to the incorporation of the amorphous phase of FS (aspartic acid) in the amorphous phase of TPU, and mobility of polymer chains increased. The melting temperature (Tm), expressed as Teim, Tpm, and Tefm, decreased because of the less organised crystal structure with the addition of SF. Thermal stability was determined by TGA, which showed that, with the addition of SF, the thermal stability decreased because of the lower thermal stability of SF.