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1.
Polymers (Basel) ; 14(14)2022 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-35890737

RESUMO

In this study, the mechanical and thermophysical properties of carbon fiber-reinforced polyethersulfone are investigated. To enhance the interfacial interaction between carbon fibers and the polymer matrix, the surface modification of carbon fibers by thermal oxidation is conducted. By means of AFM and X-ray spectroscopy, it is determined that surface modification changes the morphology and chemical composition of carbon fibers. It is shown that surface modification dramatically increases the mechanical properties of the composites. Thus, flexural strength and the E-modulus of the composites reinforced with modified fibers reached approximately 962 MPa and 60 GPa, respectively, compared with approximately 600 MPa and 50 GPa for the composites reinforced with the initial ones. The heat deflection temperatures of the composites reinforced with the initial and modified fibers were measured. It is shown that composites reinforced with modified fibers lose their stability at temperatures of about 211 °C, which correlates with the glass transition temperature of the PES matrix. The thermal conductivity of the composites with different fiber content is investigated in two directions: in-plane and transverse to layers of carbon fibers. The obtained composites had a relatively high realization of the thermal conductive properties of carbon fibers, up to 55-60%.

2.
Polymers (Basel) ; 13(5)2021 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-33806287

RESUMO

Antifriction hybrid fluorinated ethylene propylene-based composites filled with quasicrystalline Al73Cu11Cr16 powder, polytetrafluoroethylene, synthetic graphite and carbon black were elaborated and investigated. Composite samples were formed by high-energy ball milling of initial powders mixture with subsequent consolidation by injection molding. Thermal, mechanical, and tribological properties of the obtained composites were studied. It was found that composite containing 5 wt.% of Al73Cu11Cr16 quasicrystals and 2 wt.% of nanosized polytetrafluoroethylene has 50 times better wear resistance and a 1.5 times lower coefficient of dry friction comparing with unfilled fluorinated ethylene propylene. Addition of 15 wt.% of synthetic graphite to the above mentioned composition allows to achieve an increase in thermal conductivity in 2.5 times comparing with unfilled fluorinated ethylene propylene, at that this composite kept excellent tribological properties.

3.
Knee Surg Sports Traumatol Arthrosc ; 29(12): 4251-4260, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33811490

RESUMO

PURPOSE: To understand if anatomic physeal-sparing ACL reconstruction in the immature host preserves range of motion, permits a return to sports, and avoids limb length discrepancy and accelerated intra-articular degeneration with a cross-sectional radiographic, physical examination and patient-reported outcomes analysis. METHODS: A cross-sectional recall study included 38 patients aged 7-15 who underwent all-epiphyseal ACL reconstruction with hamstring allograft performed by a single surgeon at a large academic medical center. All-epiphyseal reconstructions were performed using a modified Anderson physeal-sparing technique, with the femoral tunnel placed using an "inside-out" technique. Assessments consisted of a physical exam, long leg cassette radiographs, KT-1000 measurements, subjective patient metrics, and magnetic resonance imaging. RESULTS: Thirty-eight (56.7%) of 66 eligible patients returned for in-person clinical and radiographic exams. Patients were 11.4 ± 1.8 years at the time of surgery. Five patients were females (13.2%). Mean follow-up was 5.5 ± 2.4 years. ACL re-injuries occurred in four patients (10.5%), all of whom underwent revision reconstructions. Thirty-three of the remaining 34 (97.1%) patients returned to sports following their reconstruction, and 24 (70.6%) returned to their baseline level of competition. Mean limb length discrepancy (LLD) was 0.2 ± 1.4 cm. Nine patients had an LLD of > 1 cm (26.5%), which occurred at an equivalent age as those with < 1 cm LLD (10.8 ± 2.0 vs. 11.7 ± 1.7, n.s.). Pre-operative Marx scores (13.1 ± 3.5) were not significantly different from post-operative values (12.3 ± 5.1, n.s.). Patients who required ACL revisions had significantly lower Marx scores than those with intact primary grafts (8.3 ± 7.1 vs. 13.4 ± 4.5, p = 0.047). Cohort mean International Knee Documentation Committee (IKDC) score was 89.7 ± 12.7. CONCLUSION: Anatomic all-epiphyseal anatomic ACL reconstruction appears to be useful in patients with significant projected remaining growth, with good return-to-sport outcomes and minimal risk of clinically significant physeal complications. However, given the limited patient recall possible in the present study, further large sample size, high-quality works are necessary to validate our findings. LEVEL OF EVIDENCE: Level IV.


Assuntos
Lesões do Ligamento Cruzado Anterior , Reconstrução do Ligamento Cruzado Anterior , Lesões do Ligamento Cruzado Anterior/cirurgia , Estudos Transversais , Feminino , Seguimentos , Humanos , Estudos Retrospectivos , Volta ao Esporte , Resultado do Tratamento
4.
Polymers (Basel) ; 13(9)2021 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-33925323

RESUMO

The structure of self-reinforced composites (SRCs) based on ultra-high molecular weight polyethylene (UHMWPE) was studied by means of Wide-Angle X-ray Scattering (WAXS), X-ray tomography, Raman spectroscopy, Scanning Electron Microscopy (SEM) and in situ tensile testing in combination with advanced processing tools to determine the correlation between the processing conditions, on one hand, and the molecular structure and mechanical properties, on the other. SRCs were fabricated by hot compaction of UHMWPE fibers at different pressure and temperature combinations without addition of polymer matrix or softener. It was found by WAXS that higher compaction temperatures led to more extensive melting of fibers with the corresponding reduction of the Herman's factor reflecting the degree of molecular orientation, while the increase of hot compaction pressure suppressed the melting of fibers within SRCs at a given temperature. X-ray tomography proved the absence of porosity while polarized light Raman spectroscopy measurements for both longitudinal and perpendicular fiber orientations showed qualitatively the anisotropy of SRC samples. SEM revealed that the matrix was formed by interlayers of molten polymer entrapped between fibers in SRCs. Moreover, in situ tensile tests demonstrated the increase of Young's modulus and tensile strength with increasing temperature.

5.
Polymers (Basel) ; 12(4)2020 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-32294997

RESUMO

The effect of thermal treatment of glass fibers (GF) on the mechanical and thermo-mechanical properties of polysulfone (PSU) based composites reinforced with GF was investigated. Flexural and shear tests were used to study the composites' mechanical properties. A dynamic mechanical analysis (DMA) and a heat deflection temperature (HDT) test were used to study the thermo-mechanical properties of composites. The chemical structure of the composites was studied using IR-spectroscopy, and scanning electron microscopy (SEM) was used to illustrate the microstructure of the fracture surface. Three fiber to polymer ratios of initial and preheated GF composites (50/50, 60/40, 70/30 (wt.%)) were studied. The results showed that the mechanical and thermo-mechanical properties improved with an increase in the fiber to polymer ratio. The interfacial adhesion in the preheated composites enhanced as a result of removing the sizing coating during the thermal treatment of GF, which improved the properties of the preheated composites compared with the composites reinforced with initial untreated fibers. The SEM images showed a good distribution of the polymer on the GF surface in the preheated GF composites.

6.
Polymers (Basel) ; 11(8)2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31430860

RESUMO

Interfacial interaction is one of the most important factors that affect the mechanical properties of the fiber reinforced composites. The effect of fabrics' sizing removal from glass fibers' surface by thermal treatment on the mechanical characteristics of polyethersulfone based composites at different fiber to polymer weight ratios was investigated. Three fiber to polymer weight ratios of 50/50, 60/40, and 70/30 were studied. Flexural and shear tests were carried out to illustrate the mechanical properties of the composites; the structure was studied using Fourier-transform infrared spectroscopy and scanning electron microscopy. It was shown that solution impregnation of glass fabrics with polyethersulfone before compression molding allows to achieve good mechanical properties of composites. The thermal treatment of glass fabrics before impregnation results in an increase in flexural and shear strength for all the composites due to the improvement of fiber-matrix interaction.

7.
Polymers (Basel) ; 12(1)2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31905905

RESUMO

Carbon fabrics are widely used in polymer based composites. Nowadays, most of the advanced high-performance composites are based on thermosetting polymer matrices such as epoxy resin. Thermoplastics have received high attention as polymer matrices due to their low curing duration, high chemical resistance, high recyclability, and mass production capability in comparison with thermosetting polymers. In this paper, we suggest thermoplastic based composite materials reinforced with carbon fibers. Composites based on polysulfone reinforced with carbon fabrics using polymer solvent impregnation were studied. It is well known that despite the excellent mechanical properties, carbon fibers possess poor wettability and adhesion to polymers because of the fiber surface chemical inertness and smoothness. Therefore, to improve the fiber-matrix interfacial interaction, the surface modification of the carbon fibers by thermal oxidation was used. It was shown that the surface modification resulted in a noticeable change in the functional composition of the carbon fibers' surface and increased the mechanical properties of the polysulfone based composites. Significant increase in composites mechanical properties and thermal stability as a result of carbon fiber surface modification was observed.

8.
Am J Orthod Dentofacial Orthop ; 139(4): e285-90, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21457833

RESUMO

INTRODUCTION: The aim of this article was to present a new method of analysis for the assessment of facial growth and morphology after surgical resection of the mandible in a growing patient. METHODS: This was a 2-year longitudinal study of facial growth in a child who had undergone segmental resection of the mandible with immediate reconstruction as a treatment for juvenile aggressive fibromatosis. Three-dimensional digital stereo-photogrammteric cameras were used for image acquisition at several follow-up intervals: immediate, 6 months, and 2 years postresection. After processing and superimposition, shell-to-shell deviation maps were used for the analysis of the facial growth pattern and its deviation from normal growth. The changes were seen as mean surface changes and color maps. An average constructed female face from a previous study was used as a reference for a normal growth pattern. RESULTS: The patient showed significant growth during this period. Positive changes took place around the nose, lateral brow area, and lower lip and chin, whereas negative changes were evident at the lower lips and cheeks area. An increase in the vertical dimension of the face at the chin region was also seen prominently. CONCLUSIONS: Three-dimensional digital stereo-photogrammetry can be used as an objective, noninvasive method for quantifying and monitoring facial growth and its abnormalities.


Assuntos
Cefalometria/métodos , Mandíbula/cirurgia , Desenvolvimento Maxilofacial/fisiologia , /métodos , Algoritmos , Placas Ósseas , Bochecha/crescimento & desenvolvimento , Criança , Queixo/crescimento & desenvolvimento , Feminino , Fibromatose Agressiva/cirurgia , Seguimentos , Testa/crescimento & desenvolvimento , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Lábio/crescimento & desenvolvimento , Estudos Longitudinais , Mandíbula/crescimento & desenvolvimento , Neoplasias Mandibulares/cirurgia , Prótese Mandibular , Nariz/crescimento & desenvolvimento , Fotogrametria/métodos , Software , Dimensão Vertical
9.
J Craniomaxillofac Surg ; 37(8): 461-8, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19674914

RESUMO

Gardner's syndrome (GS) is a hereditary autosomal dominant disease of the colon that presents with extra-colonic manifestations such as osteomas, skin lesions and dental abnormalities. Osteomas are commonly found in the skull, jaws and the paranasal sinuses. We present a family of four sisters affected with GS with a wide range of anomalies. The role of Cone beam computed tomography (CBCT) in the early detection and evaluation of osteomas and dental anomalies with precise assessment of their relationship to adjacent anatomic structures is described here in detail. The careful interpretation of CBCT may be of a great value in surgical and orthodontic treatment planning in the presence of jaw lesions. Management of dental problems in GS may be challenging due to the presence of odontomas and increased bone density. A multidisciplinary approach in the management of GS can achieve the best treatment results.


Assuntos
Tomografia Computadorizada de Feixe Cônico , Síndrome de Gardner/genética , Osteoma/genética , Planejamento de Assistência ao Paciente , Neoplasias Cranianas/genética , Densidade Óssea/fisiologia , Detecção Precoce de Câncer , Feminino , Síndrome de Gardner/diagnóstico por imagem , Síndrome de Gardner/terapia , Humanos , Má Oclusão/diagnóstico por imagem , Má Oclusão/genética , Neoplasias Mandibulares/diagnóstico por imagem , Neoplasias Mandibulares/genética , Neoplasias Maxilares/diagnóstico por imagem , Neoplasias Maxilares/genética , Odontoma/diagnóstico por imagem , Odontoma/genética , Osteoma/diagnóstico por imagem , Neoplasias dos Seios Paranasais/diagnóstico por imagem , Neoplasias dos Seios Paranasais/genética , Neoplasias Cranianas/diagnóstico por imagem , Erupção Ectópica de Dente/diagnóstico por imagem , Erupção Ectópica de Dente/genética , Dente Impactado/diagnóstico por imagem , Dente Impactado/genética , Adulto Jovem
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