Polycarbonate (PC) and phenoxy resin (PKFE) have similar structures derived from bisphenol A. PKFE resin possesses pendant hydroxyl groups along its backbone; instead of the carbonate carbonyl groups found in polycarbonate, PKFE contains 2-hydroxypropyl groups instead. This difference in structure significantly influences thermomechanical properties when these materials are blended with phenyltrisilanol polyhedral oligomeric silsesquioxanes (POSS). While POSS exhibits some level of solubility in the each of the polymer matrixes tested, the glass transition temperatures of phenoxy composites increase with incorporation of POSS, while the glass transition temperatures of polycarbonate composites decrease significantly. Addition of POSS to PC also results in embrittlement of the composites; POSS thus serves as an antiplasticizer in the PC/POSS system. In the case of PKFE/POSS composites, significant interactions are evidenced by the change in the shape of the infrared spectra for the C−H phenyl stretch. While nuclear magnetic resonance spectroscopy shows definite reactions occurring between polycarbonate and POSS, no reactions were detected with the phenoxy resins. The POSS nanoscale filler can act as a plasticizer or as a reinforcing agent, depending upon the availability of filler−polymer interactions within the system.
Poly(ethylene terephthalate) (PET)-based composite fibers were prepared by melt spinning three types of PET/polyhedral oligomeric silsesquioxane (POSS) composites. These composites were made by either melt blending POSS with PET at 5 wt% loading level (non-reactive POSS and silanol POSS) or by in-situ polymerization with 2.5 wt% reactive POSS. Significant increases in tensile modulus and tensile strengths were achieved in PET fibers with non-reactive POSS at room temperature. The hightemperature modulus retention was found to be much better for PET/silanol POSS fiber when compared to that of control PET. Although other PET/POSS nancomposite fibers tested did not show this high retention of modulus at elevated temperatures, PET/isooctylPOSS nanocomposite fibers did show increased modulus at elevated temperature compared to that of PET. Higher compressive strengths, compared to PET fibers, were observed for all three nanocomposite fibers. Gel permeation chromatography measurement suggested that there is no significant change in molecular weight during preparation of PET/POSS nanocomposites. SEM observations suggest that there is no obvious phase separation in any of the three PET/POSS systems. Crystallization behavior and thermal stability of the composite were also studied. The fiber spinning and mechanical performance with 10 and 20 wt% of trisilanolisooctyl POSS2 were also investigated1 the composites with higher concentrations of this nanofiller can be spun without any difficulty. At room temperature, the fiber tensile modulus increased steadily with the POSS concentration while fiber tensile strength showed no significant change. The elongation at break decreased significantly with increasing of POSS concentration. The high-temperature moduli of PET/POSS nanocomposite fibers were found to be rather variable, likely due to the modest compatibility between filler and polymers, which can lead to structural anisotropy within the composite.
ObjectivesPelvic fracture urethral injuries (PFUI) result from traumatic disruption of the urethra. A significant proportion of cases are complex rendering their management challenging. We described management strategies for eight different complex PFUI scenarios.MethodsOur centre is a tertiary referral centre for complex PFUI cases. We maintain a prospective database (1995–2016), which we retrospectively analysed. All patients with PFUI managed at our institute were included.ResultsOver two decades 1062 cases of PFUI were managed at our institute (521 primary and 541 redo cases). Most redo cases were referred to us from other centres. Redo cases had up to five prior attempts at urethroplasty. We managed complex cases, which included bulbar ischemia, young boys and girls with PFUI, PFUI with double block, concomitant PFUI and iatrogenic anterior urethral strictures. Bulbar ischemia merits substitution urethroplasty, most commonly, using pedicled preputial tube. PFUI in young girls is usually associated with urethrovaginal fistula. Young boys with PFUI commonly have a long gap necessitating trans-abdominal approach. Our success rate with individualised management is 85.60% in primary cases, 79.13% in redo cases and 82.40% in cases of bulbar ischemia.ConclusionThe definition of complex PFUI is ever expanding. The best chance of success is at the first attempt. Anastomotic urethroplasty for PFUI should be performed in experienced hands at high volume centres.
Water absorption and other properties of polyamides can potentially be modified by blending with polyesters. The compatibility of a polyester ionomer meltblended with nylon-6 is studied in this article, examining the effect of blending upon crystallization behaviors, morphology, thermal/mechanical properties, and water absorption. Comparisons of the crystallization behaviors of the ionomer/nylon-6 blends with poly(ethylene terephthalate)/nylon-6 blends suggest increased compatibility due to greater interactions between the two phases. The results indicate that the presence of a significant amount of the ionomeric groups is required to improve polyester compatibility with polyamides.
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