Abstract In this work, the rheological, mechanical and morphological behavior of immiscible blend poly (methyl methacrylate) with elastomeric particles (PMMAelast) and post-consumer poly (ethylene terephthalate) (PET) with and without the use of the interfacial compatibilizer poly (methyl methacrylate-co-glycidyl methacrylate-co-ethyl acrylate) (MGE) was studied. The significant increase in torque presented in rheological analyses has shown a indication of chemical reactions between the epoxy group of MGE with end groups of PET chains and also with the elastomeric phase of PMMAelast. The increased concentration of PET yielded an increase in maximum strength and elasticity modulus and a decrease in elongation at break. The PMMAelast/PET binary blend (50/50 wt%) and PMMAelast/PET/MGE compatibilized blend (65/30/5 wt%) showed pronounced results in elongation at break compared to PMMAelast, whereas, in the first results were due to the evidence of a co-continuous morphological structure and in the second, due to the efficiency of the dual reactive interfacial compatibilization of PMMAelast/PET blends. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that PMMAelast/PET/MGE blends exhibit complex phase morphology due to the presence of elastomeric particles in the PMMAelast copolymer and in the use of MGE terpolymer.

Poly(butylene terephthalate) (PBT)/ acrylonitrile-butadiene-styrene (ABS) terpolymer blends were prepared in a twin screw extruder and the use of methyl methacrylate-glycidyl methacrylate-ethyl acrylate (MGE) terpolymer as compatibilization additive was evaluated. The effect of different screw profiles and mixing conditions were evaluated on the crystallization of the blends. Differential scanning calorimetry (DSC) was used to evaluate melting and crystallization behaviors of the PBT/ABS blends. The binary PBT/ABS blend has shown a double melting peak when cooled at lower cooling rates, mainly due to its melt-recrystallization during the heating up step. ABS has not affected the melting characteristics of neat PBT. The presence of MGE, as a reactive compatibilizer, in the PBT/ABS blends has reduced its heat of fusion and has partially inhibited its melt-recrystallization under heating. As result, it has prevented the occurrence of double melting peak. The epoxy functional groups of the MGE may react in situ to the carbonyls and hydroxyls end groups of the PBT molecules, thereby hindering the mobility of PBT molecules during the crystallization process due to its grafting to the compatibilizer molecules. The melt mixed blends prepared at lower feeding rate have shown a higher degree of crystallinity for the PBT/ABS blend, probably due to degradation of PBT caused by longer residence time in the extruder. The highest shear stress imposed to the blends at higher screw speed increased the degree of crystallinity of PBT, also due to its degradation.

Os plásticos apresentam boa processabilidade, oferecendo uma grande liberdade de design. Porém, a fabricação de peças cada vez maiores e mais complexas tem exigido a busca por melhorias e desenvolvimento dos atuais processos de união e soldagem de polímeros. Friction Spot Welding (FSpW) é uma técnica de soldagem pontual por fricção inicialmente desenvolvida para ligas de alumínio, possibilitando soldas com excelentes propriedades mecânicas. Nesse trabalho a soldagem de termoplásticos através da técnica FSpW foi analisada. Para tal, utilizaram-se placas de polimetacrilato de metila (PMMA), um termoplástico amorfo com crescente importância na indústria automotiva e aeronáutica por seu bom balanço de propriedades, como baixa densidade, boa processabilidade, soldabilidade e resistência química e ao envelhecimento. As amostras soldadas foram analisadas por microscopia ótica, medições de microdureza Vickers e ensaio de resistência ao cisalhamento. Os resultados mostraram que a resistência mecânica ao cisalhamento alcançada (cerca de 9,5 MPa) é igual ou maior que a resistência de juntas sobrepostas de PMMA obtidas por outras técnicas convencionais como soldagem por ultra-som, por microondas e thermal bonding. O presente trabalho comprovou, dessa forma, a potencialidade da técnica FSpW para soldar termoplásticos.

The modern thermoplastics show a wide range of engineering applications, mainly due to its good processability and properties, such as stress-to-weight ratio and toughness. However, the manufacturing of larger products with complex geometries require advanced polymer welding techniques. Friction Spot Welding (FSpW) is a joining technique allowing the fabrication of joint with good mechanical properties. In this work, the feasibility of the FSpW of thermoplastics was investigated in polymethyl-methacrilate (PMMA), an amorphous thermoplastic with increasing importance in the airspace and automotive industry due to its good processability, weldability, aging and chemical resistance. The welded samples were analyzed by optical microscopy and Vickers microhardness measurements and mechanically tested. Lap-shear testing showed ultimate shear resistance values of about 9,5 MPa, which were similar or higher than values obtained through current PMMA welding techniques, such as microwave welding, ultrasonic welding and thermal bonding. Therefore, the present work was able to demonstrate the potential of FSpW as an alternative welding process for thermoplastics.

The aim of this work was to evaluate the interfacial tension from the poly(butylene terephtalate) and poly(styrene-co-acrylonitrile) (PBT/SAN) interface region using the drop retraction method. SAN filaments were sandwiched between two PBT films; the whole system was heated up to 240 °C, in a hot stage coupled to an optical microscope. The rheological parameters of the PBT/SAN system were obtained by parallel plates rheometry. An increase of the interfacial tension with the PBT molecular weight was observed with values between 0.57 and 1.06 mN/m, depending on the molecular weight. Theoretical values were calculated using the geometric-mean and harmonic-mean equations and were found to be similar to the experimental results. Viscosity measurements showed that the higher the SAN/PBT viscosity ratio, the lower the interfacial tension of these blends.

A poliamida 6 (PA6) é um polímero termoplástico semicristalino que apresenta alta susceptibilidade ao entalhe quando solicitado mecanicamente. Apesar de apresentar um comportamento dúctil sob deformação e sob fratura quando solicitado sem entalhes, torna-se essencialmente frágil e quebradiço quando entalhado. Assim, o comportamento pseudo-dúctil dessas poliamidas requer cuidados especiais na confecção do entalhe e da pré-trinca para análise de seu comportamento mecânico. Devem ser observadas ainda as dimensões ideais dos corpos de prova para garantir a condição de estado de tensão plana no ensaio de tração uniaxial para aplicação do método EWF (Trabalho Essencial de Fratura). Neste trabalho, o método EWF foi utilizado para a avaliação da tenacidade à fratura de blendas poliméricas com uma matriz PA6 modificada com ABS e também a eficiência de um compatibilizante acrílico reativo (MMA-MA) sintetizado em laboratório, na tenacificação da blenda PA6/ABS. Através da aplicação do método observou-se que a simples incorporação do ABS à poliamida aumenta o termo relativo ao trabalho específico de fratura e reduz a sensibilidade ao entalhe da blenda embora com perda na capacidade de absorção de energia plástica. A incorporação do copolímero MMA-MA à blenda refletiu-se nos acréscimos do trabalho específico e recuperação da capacidade de absorção de energia plástica em relação à blenda não-compatibilizada. Os resultados ilustram a aplicabilidade do método EWF para determinação da tenacidade à fratura de blendas poliméricas em relação aos polímeros puros, bem como a avaliação do efeito do compatibilizante reativo na tenacidade da blenda PA6/ABS.

Polyamide 6 or polycaprolactam is a semi-crystalline thermoplastic whose toughness is very notch sensitive and consequently the material presents extreme susceptibility to stress concentrations. Thus, although such polyamides may fracture on a typical ductile manner on mechanical testing without notches, it will become brittle after being notched. The pseudo-ductile behavior in polyamides poses a task on notch and pre-crack preparation, for accurate assessment of their toughness. Furthermore, it must be observed the ideal specimen dimensions to guarantee plane stress conditions on tensile testing for application of the EWF (Essential Work of Fracture) method. In the present work, the EWF method was employed to evaluate the fracture toughness of PA6 blends modified with ABS and also to assess the efficiency of a self-made reactive acrylic compatibilizer (MMA-MA), on the toughness of the PA6/ABS blend. The EWF parameters have shown that by simply melt blending ABS with PA6 it increases the specific work of fracture owing to reduced notch sensitivity of the blend, although at the expenses of the blend capacity to absorb plastic energy. The addition of the compatibilizer MMA-MA to the blend has been reflected on increments of the specific work of fracture and recovery of the blend capacity to absorb plastic energy. The results have illustrated the applicability of the EWF method for determination of the fracture toughness parameters of polymer blends as well as evaluation of the effect of the reactive MMA-MA compatibilizer on the toughness of the PA6/ABS blend.