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Estudos da fotodegradação em compostos estabilizados de ABS ocasionada por ensaios de envelhecimento natural e acelerado
(Universidade Federal de São Carlos, 2012-11-22) Bosquetti, Péricles; Agnelli, José Augusto Marcondes; https://lattes.cnpq.br/7592090152400440; https://orcid.org/0000-0003-3637-8921; https://lattes.cnpq.br/7864244439911523; https://orcid.org/0000-0002-8678-2589
This work has made comparative assessments of the performance of ABS compounds in accelerated aging and natural exposure tests. The degradation was analyzed by measurements of the Color Variations (CIELab system), Brightness (60º) and Yellow Index (Index), besides the mechanical properties of traction and impact. These characterizations were related to the chemical composition of the ABS polymers and their structural characteristics, such as: free and total SAN contents, succulent phase grafting index and particle size distribution. Different ABS compounds formulated with the same pigments and additives were used, changing the amounts and type of stabilizers used. Some of the compounds have a primary antioxidant and a HALS such as Johoku's JF-90. In another system a HALS (Tinuvin 622) and a UV absorber (Tinuvin P) were used in addition to the primary antioxidant. These compounds were evaluated with 5 and 10% of a high flow SAN, to evaluate the effect of the degradation with the decrease of the rubbery phase of these compounds. In general, the compounds presented excellent physico-mechanical performance, with only mild surface changes over the exposures, even in QUV-B. The HALS efficiency was proportional to the amounts used, since the compounds with the lowest initial yellowing showed better results in the degradation rate, which was related to the use of higher HALS content in the formulation, since the other components were not altered. The HALS were more efficient at surface degradation when compared to the HALS system and UV absorber, without observing synergistic effect of stabilizers for the compounds. The rubbery phase content of ABS interferes with the degradation, since AG1000 compounds, with higher rubber content, presented higher degradation than AF3500, even with higher HALS content in the compound. The addition of SAN up to 10% showed less yellowing and less loss of mechanical properties, such as impact resistance, especially in ABS AG1000.
Os efeitos do laser terapêutico na cartilagem articular em modelo experimental de osteoartrite induzida por transecção do ligamento cruzado anterior
(Universidade Federal de São Carlos, 2012-11-22) Santos, Anderson Amaro dos; Renno, Ana Claudia Muniz; https://lattes.cnpq.br/4106611304688552; https://lattes.cnpq.br/0993071180356578
Objective: The aim of this study was to evaluate the effects of laser therapy on the degeneratives modifications in articular cartilage after anterior cruciate ligament transection (ACLT). Methods: We used eighty-male rats (Wistar), distributed into four groups: intact, injury control, injury laser treated, at 50 J/cm2 and injury laser treated, at 10 J/cm2. Animals were distributed into 2 subgroups, with different periods of sacrifice 5 and 8 weeks post-surgery. The animals were submitted to the surgery to induce OA by anterior cruciate ligament transection. Laser treatment started 2 weeks after the surgery and it was performed for 15 and 30 sessions. A laser 685 nm, at 10 and 50 J/cm2, 30mW was used. Results: Initial signs of tissue degradation could be observed 5 weeks post- ACLT, with the decrease of proteoglycans concentration and increase of thickness in the CG. After 8 weeks post-surgery, analysis showed a progression in the degenerative process in the CG, revealed by the increase of cellullarity and higher TNF- α, IL1 and MMP-13 immunoexpression. Laser therapy was able of modulating some of the aspects related to the degradative process, such as biomodulation of the number of condrocyte proliferation, prevention of proteogycans loss and decrease of MMP-13 immunoexpression. Conclusion: This study showed that 685nm laser, especially at 10 J/cm2 prevented features related to the articular degenerative process in the knees of rats.