Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals

Abstract

Freeze‐dried cellulose nanocrystals (CNCs) were dispersed in the thermoplastic polyurethane [Pellethane 2363‐55D (P55D)] by a solvent casting method to fabricate CNC‐reinforced nanocomposites. This study demonstrated that the addition of small amounts (1–5 wt %) of CNCs to P55D increased the thermal degradation temperature while maintaining a similar stiffness, strength, and elongation of the neat P55D. CNC additions to P55D did not alter the glass‐transition temperature, but the onset decomposition temperature was shifted from 286 to 327°C when 1 wt % CNCs was dispersed in the matrix. The higher onset decomposition temperature was attributed to the formation of hydrogen bonds between the hydroxyl groups on the CNC surface and urethane groups in the hard block of P55D. The ultimate tensile strength and strain to failure (εf) of the nanocomposites were minimally affected by additions up to 5 wt % CNCs, whereas the elastic modulus was increased by about 70%. The observation that εf was unchanged with the addition of up to 5 wt % CNCs suggested that the flow/sliding of the hard blocks and chains were not hindered by the presence of the CNCs during plastic deformation. The ramifications of this study was that CNC additions resulted in wider processing temperatures of P55D for various biomedical devices while maintaining a similar stiffness, strength, and elongation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41970.

Reinforcement effect of cellulose nanocrystals in thermoplastic polyurethane matrices characterized by different soft/hard segment ratio

“…The presence of double crystallization peaks disappeared in the case of TPU_C74D50 based nanocomposites and the presence of CNC induce a shift to higher crystallization temperature. This shift to higher crystallization temperatures were registered for all the produced nanocomposites (TPU_1185A10 had the most soft chemical composition, TPU_C85A10 had a medium composition and finally TPU_C74D50 had the hardest composition) as a function of CNC presence and content, as previously observed in literature by Liu et al . In particular, the addition of 1%wt of CNC in TPU_1185A10 matrix was able to shift the T c about 20°C with respect to the neat polymer, while a shift of 25°C to higher temperature was observed in the case of TPU_ C85A10_1CNC nanocomposite with respect to the pure TPU_ C85A10 film.…”

“…, while crystallization temperatures and enthalpies values ( T c and Δ H c ), obtained from the curves, were summarized in Table . It is reported only the analysis of cooling scan with the idea to analyze the effect of cellulose nanocrystals as nucleating agent into TPU matrices, as previously observed in the literature using different thermoplastic matrices .…”

Cellulose nanocrystals reinforced thermoplastic polyurethane nanocomposites

“…19 The CNC variants obtained via the HEBM process all show a higher thermal stability when compared to the thermal stability of the CNC obtained via typical sulphuric acid hydrolysis, which typically start to decompose at 150°C. 19,40 It is to be noted that the processing temperature of many thermoplastic polymers falls within the range of thermal stability exhibited by CNC obtained via HEBM process. obtained from MCC, retainment of thermal stability.…”

“…However, the soft segments are still able to rotate and deform under tensile stress. 40 Only at higher stoichiometric ratio (1.02 for 0.5 wt. % and 1.03 for 0.8 wt.…”

“…This also indicates the nanoparticle has moderate dispersibility in water. 39,40 No element of P and S has been traced due to their low levels and their inability to be detected by the instrument (minimum sensitivity is 1%). Table 4.5 Characterisation of CNC on elemental analysis, zeta potential and amount of charges.…”