ABSTRACT
Polymer modification using silicone rubber represents a promising avenue for enhancing physico-mechanical properties. However, achieving optimal performance through direct blending is hindered by the poor interface compatibility between silicone rubber and the matrix. In this study, we prepared super-tough thermoplastic vulcanizates (TPVs) of polylactic acid/silicone rubber through dynamic vulcanization with PLA, methyl vinyl silicone rubber (MVQ), glycidyl methacrylate grafted MVQ (MVQ-g-GMA), and fumed silica nanoparticles (SiO2). The impact of the SiO2 addition in MVQ on the morphology, mechanical properties, crystallization, and thermal properties of the TPVs was investigated. The results showed that MVQ-g-GMA and SiO2 exhibited a synergistic compatibilization effect significantly improving the interfacial adhesion between PLA and MVQ. Therefore, the impact and tensile strength of the TPVs increased from 8.0 kJ/m2 and 22.2 MPa to 62.6 kJ/m2 and 36.7 MPa, respectively. Moreover, the TPVs also presented good low-temperature toughness with a maximum impact strength of 40.4 kJ/m2 at -20 °C. Additionally, improvements in thermal stability and crystallization rate were also observed. Overall, combining organic and inorganic synergistic compatibilization is a feasible and effective method to fabricate outstanding low-temperature toughness to PLA.
Subject(s)
Silicon Dioxide , Silicone Elastomers , Polyesters , PolymersABSTRACT
BACKGROUND: It is controversial whether prophylactic endotracheal intubation (PEI) protects the airway before endoscopy in critically ill patients with upper gastrointestinal bleeding (UGIB). The study aimed to explore the predictive value of PEI for cardiopulmonary outcomes and identify high-risk patients with UGIB undergoing endoscopy. METHODS: Patients undergoing endoscopy for UGIB were retrospectively enrolled in the eICU Collaborative Research Database (eICU-CRD). The composite cardiopulmonary outcomes included aspiration, pneumonia, pulmonary edema, shock or hypotension, cardiac arrest, myocardial infarction, and arrhythmia. The incidence of cardiopulmonary outcomes within 48 h after endoscopy was compared between the PEI and non-PEI groups. Logistic regression analyses and propensity score matching analyses were performed to estimate effects of PEI on cardiopulmonary outcomes. Moreover, restricted cubic spline plots were used to assess for any threshold effects in the association between baseline variables and risk of cardiopulmonary outcomes (yes/no) in the PEI group. RESULTS: A total of 946 patients were divided into the PEI group (108/946, 11.4%) and the non-PEI group (838/946, 88.6%). After propensity score matching, the PEI group (n=50) had a higher incidence of cardiopulmonary outcomes (58.0% vs. 30.3%, P=0.001). PEI was a risk factor for cardiopulmonary outcomes after adjusting for confounders (odds ratio [OR] 3.176, 95% confidence interval [95% CI] 1.567-6.438, P=0.001). The subgroup analysis indicated the similar results. A shock index >0.77 was a predictor for cardiopulmonary outcomes in patients undergoing PEI (P=0.015). The probability of cardiopulmonary outcomes in the PEI group depended on the Charlson Comorbidity Index (OR 1.465, 95% CI 1.079-1.989, P=0.014) and shock index >0.77 (compared with shock index ≤0.77 [OR 2.981, 95% CI 1.186-7.492, P=0.020, AUC=0.764]). CONCLUSION: PEI may be associated with cardiopulmonary outcomes in elderly and critically ill patients with UGIB undergoing endoscopy. Furthermore, a shock index greater than 0.77 could be used as a predictor of a worse prognosis in patients undergoing PEI.
ABSTRACT
Preparing a super-tough polylactic acid (PLA) material while maintaining its biodegradability is a significant challenge. This study synthesized a biodegradable unsaturated poly(butylene succinate-co-fumarate)-poly(ethylene glycol) multiblock copolymer (PBSFG) and dynamically vulcanized it with PLA to obtain super-tough blends. The PBSFG self-vulcanized and formed a crosslinked "hard-soft" core-shell rubber phase in the blending process, where the PBSF segment acted as the core and PEG as the shell. As a result, the elongation at break and notched Izod impact strength of PLA increased significantly from 3 % to 66 % and from 3.2 to 58.0 kJ/m2, respectively. Furthermore, adding a small amount of dicumyl peroxide (DCP) promoted dynamic vulcanization and improved the compatibility between PLA and PBSFG. With the addition of 0.03 % DCP, the elongation at break and notched Izod impact strength of PLA/PBSFG were further increased to 218 % and 88.9 kJ/m2, respectively. Meanwhile, the crystallization rate of PLA was enhanced by the addition of PBSFG and DCP. The PLA/PBSFG blends also degraded in a proteinase K Tris-HCl buffered buffer solution. Finally, fully biodegradable and super-tough PLA blends were achieved.
