Toughening Polylactic Acid by a Biobased Poly(Butylene 2,5-Furandicarboxylate)-b-Poly(Ethylene Glycol) Copolymer: Balanced Mechanical Properties and Potential Biodegradability.

Polylactic acid (PLA) is a biodegradable thermoplastic polyester produced from natural resources. Because of its brittleness, many tougheners have been developed. However, traditional toughening methods cause either the loss of modulus and strength or the lack of degradability. In this work, we synthesized a biobased and potentially biodegradable poly(butylene 2,5-furandicarboxylate)-b-poly(ethylene glycol) (PBFEG50) copolymer to toughen PLA, with the purpose of both keeping mechanical strength and enhancing the toughness. The blend containing 5 wt % PBFEG50 exhibited about 28.5 times increase in elongation at break (5.5% vs 156.5%). At the same time, the tensile modulus even strikingly increased by 21.6% while the tensile strength was seldom deteriorated. Such a phenomenon could be explained by the stretch-induced crystallization of the BF segment and the interconnected morphology of PBFEG50 domains in PLA5. The Raman spectrum was used to identify the phase dispersion of PLA and PBFEG50 phases. As the PBFEG50 content increased, the interconnected PBFEG50 domains start to separate, but their size increases. Interestingly, tensile-induced cavitation could be clearly identified in scanning electron microscopy images, which meant that the miscibility between PLA and PBFEG50 was limited. The crystallization of PLA/PBFEG50 blends was examined by differential scanning calorimetry, and the plasticizer effect of the EG segment on the PLA matrix could be confirmed. The rheological experiment revealed decreased viscosity of PLA/PBFEG50 blends, implying the possible greener processing. Finally, potential biodegradability of these blends was proved.

Hemiarthroplasty for the treatment of complex proximal humeral fractures: does a trabecular metal prosthesis make a difference? A prospective, comparative study with a minimum 3-year follow-up.

BACKGROUND: Proper positioning and healing of the greater tuberosity are key for functional shoulder recovery after hemiarthroplasty for complex proximal humeral fractures. The purpose of this study was to compare the outcomes after hemiarthroplasty between a trabecular metal prosthesis and a conventional prosthesis in the treatment of complex proximal humeral fractures. METHODS: A prospective, comparative study was performed. We compared a trabecular metal shoulder prosthesis for the treatment of complex proximal humeral fractures in a cohort of 35 consecutive patients (TM group) with a conventional prosthesis in a cohort of 38 consecutive patients (conventional group). All the patients, with a mean age of 63.9 years, were prospectively followed-up for a mean time of 4.6 years (range, 3-6 years) after surgery. RESULTS: At the last follow-up, radiographic complication rates related to the greater tuberosity were lower in the TM group (6.1%) than in the conventional group (25.7%) (P = .028). The mean functional shoulder scores, as well as mean active forward elevation and external rotation, were better in the TM group than in the conventional group. CONCLUSIONS: Radiographic complication rates related to the greater tuberosity were significantly lower in the TM group than in the conventional group. The functional shoulder scores and active forward elevation and external rotation were all better in the TM group than in the conventional group. These findings could imply better healing potential of the greater tuberosity after hemiarthroplasty with a trabecular metal prosthesis to treat complex proximal humeral fractures.

Acid-triggered, degradable and high strength-toughness copolyesters: Comprehensive experimental and theoretical study.

The popularization and widespread use of degradable polymers is hindered by their poor mechanical properties. It is of great importance to find a balance between degradation and mechanical properties. Herein, poly(butylene terephthalate) (PBT) modified by SPG diol from 10% to 40 mol% were synthesized through a two-step polycondensation reaction. Chemical structures, thermal properties, mechanical properties, viscoelastic behavior and degradation of poly(butylene terephthalate-co-spirocyclic terephthalate) (PBST) were investigated. The SPG could toughen the copolyesters and the elongation at break of PBST20 was up to 260%. Moreover, the introduction of SPG enables to provide an acid-triggered degradable unit in the main chain. PBSTs copolymers maintain stable structures in a neutral environment, and the degradation under acid conditions will be unlocked. As tailoring the content of SPG, the degradation rate of the chain scission in response to acid stimuli will be adjusted. The acid degradation was proved to be occurred at the SPG units in the amorphous phase by DSC, XRD, GPC and 1H NMR tests. After the acid degradation, the hydrolysis rate will also be accelerated, adapting to the requirements of different degradation schedules. The plausible hydrolytic pathways and mechanisms were proposed based on Fukui function analysis and density functional theory (DFT) calculation.