Abstract The industries that have polymers as an important raw material in their production, such as the construction, automotive, electrical and electronic sectors, always seek innovations to cut costs, reduce weight, easiness of processing, maximizing mechanical properties, and recyclability. In this context, this work presents the study of the kinetic parameters and viscoelastic behavior of a new thermoplastic system initially liquid. Through differential scanning calorimetry (DSC) analysis, Brookfield viscosimetry; dynamic-mechanical analysis (DMA) and mathematical modeling with consolidated and standardized methods, it was possible to evaluate the polymerization kinetics and viscoelastic behavior of the material in solutions with different concentrations. The generated equations allow the prediction of the kinetic and gelation behavior of the material reducing the need for laboratory tests to determine polymer properties. The found results showed that concentrations of benzoyl peroxide initiator with 1wt% in the methyl methacrylate (MMA) copolymer solution have the best viscoelastic and dynamic-mechanical properties with a less expensive polymerization cycle. production construction automotive sectors costs weight processing recyclability context liquid DSC (DSC viscosimetry dynamicmechanical dynamic DMA (DMA methods 1wt wt MMA (MMA cycle

Abstract Among the engineering thermoplastics, poly(phenylene sulfide) (PPS) stands out for its excellent properties and mainly for processing at lower temperatures. The requirements requested by industries can be made by improving mechanical strength, weight reduction, and durable components by reinforcing the PPS matrix with fiberglass (FG) and carbon fiber (CF). This review intends to present the most current research related to the physical, mechanical, and thermal properties of PPS and the PPS/FG and PPS/CF composites most currently used by the aerospace, automotive, and energy industries. In addition to presenting the feasibility of mechanical and thermal recycling processes for PPS-based waste to reinsert a high market value thermoplastic into the industrial production cycle, thus contributing to the minimization of waste destined for landfills and incinerated or even improperly disposed of in the environment.

Abstract Polyamide (PA) is a well-known and researched thermoplastic due to its excellent mechanical and physical properties, making it developed in the automotive sector, suitable for lighter vehicles, and, consequently, lower fuel consumption. This review manuscript presents the applications of PA-based materials in the manufacture of vehicle parts, with a description of their processing, a discussion about their thermal properties and the crystallization of polymer structure, the challenges of machining PA-based composite materials, and the feasibility of recyclability. This work aims to revise literature about the use of polyamide 6 (PA6), polyamide 66 (PA66), and polyamide 12 (PA12) and their composites reinforced with fiberglass (FG) and carbon fiber (CF) focused on the potential that these materials have as alternative materials for the automotive industry.

Abstract This review provides valuable information about the general characteristics, processing conditions and physical properties of carbon nanotube buckypaper (BP) and its polymer composites. Vacuum filtration is the most common technique used for manufacturing BP, since the carbon nanotubes are dispersed in aqueous solution with the aid of surfactant. Previous works have reported that mechanical properties of BP prepared by vacuum filtration technique are relatively weak. On the other hand, the incorporation of polymer materials in those nanostructures revealed a significant improvement in their mechanical behavior, since the impregnation between matrix and BP is optimized. Electrical conductivity of BP/polymer composites can reach values as high as 2000 S/m, which are several orders of magnitude greater than traditional CNT/polymer composites. Also, BP can improve remarkably the thermal stability of polymer matrices, opening new perspectives to use this material in fire retardant applications.

Resumo Neste estudo, foram avaliadas as propriedades dinâmico mecânicas e a viscosidade de compósitos nanoestruturados de poli(sulfeto de fenileno) (PPS) reforçado com nanotubos de carbono de paredes múltiplas (MWCNT) obtidos através da técnica de mistura em fusão. O módulo de armazenamento (E') e a temperatura de transição vítrea (Tg) apresentaram aumentos de até 130% e 11 °C em relação ao PPS puro quando 2,0 m/m% do nanoreforço foi considerado. Além disso, para concentrações superiores a 1,0% em massa foi observado um aumento nos valores da viscosidade complexa (η*), o que sugere a formação de uma estrutura interconectada de nanotubos no interior da matriz polimérica.

Abstract In this work, dynamic mechanical properties and viscosity of multiwalled carbon nanotubes reinforced poly (phenylene sulfide) nanostructured composites obtained by melt mixing techinique were investigated. The storage modulus (E') and the glass transition temperature (Tg) showed increases up to 130% and 11 °C for concentrations of 2.0 wt% compared to neat PPS. In Addition, it was observed for concentrations above 1.0 wt% an increment of complex viscosity (η*), suggesting the formation of an interconnected nanotube structure within the polymeric matrix.

Carbon fiber composites are used in several industries such as, aerospace, automotive, civil engineering, sports goods and technical applications due to its low-weight, strength and stiffness. However, the technology of recycling of these thermosetting polymer composites remains an engineering challenge because of their cross-linked structures that impede their reprocessing by simple heating. The aim of this work was to study the influence of the amount and dimensions of carbon fibers arising from composite waste into a new composite of polypropylene matrix. In order to carry out the study, the carbon fiber composite waste has been mechanically processed for the production of chopped fibers with two different lengths (4.5 mm and 3.0 mm). Thermoplastic composites made of chopped carbon fiber/ polypropylene at proportions 1%, 5% and 7% in fiber weight content were obtained by extrusion and injection process. Then, a series of laboratory test (mechanical, thermal and morphological) were performed in order to characterize the composite material obtained. The results showed that the fibers were capable of causing a reinforcing, even though the new composite presents a complex phase system with low adhesion between the recycled carbon fibers and the polypropylene matrix.

Resumo: O presente trabalho tem como principal objetivo avaliar a efetividade do processo de soldagem por resistência elétrica em compósitos de matriz poli (éterimida) reforçados com fibras contínuas de carbono, a partir do estudo das propriedades térmicas e mecânicas da junta soldada. Para a avaliação das propriedades térmicas, as amostras do material soldado foram submetidas às análises por termogravimetria e por análise termomecânica. Já com o intuito de se estudar a interface resultante da soldagem, estudos foram realizados a partir dos ensaios de cisalhamento ILSS e Iosipescu, assim como por End-Notched Flexure (ENF). Os resultados das análises térmicas em laminados de PEI/fibras de carbono não soldados mostram que o início da degradação para estes compósitos ocorre a 460 °C, e ainda é evidenciado que a temperatura de transição vítrea para amostras soldadas é aproximadamente 15% superior aos resultados provenientes de amostras não soldadas. Nos ensaios mecânicos mostram que houve um aumento de 32% e de 20%, respectivamente, nos resultados de cisalhamento interlaminar por ILSS e por Iosipescu nas amostras soldadas, quando estas são comparadas a amostras não soldadas. Os resultados do ensaio de ENF apresentam valores satisfatórios de tenacidade à fratura interlaminar nos compósitos soldados em relação aos valores encontrados em literatura.

Abstract: This study has as main objective to evaluate the effectiveness of the welding process by electrical resistance in composite poly (éterimida) matrix reinforced with continuous fibers of carbon, from the study of the thermal and mechanical properties of the welded joint. To evaluate the thermal properties of the welded material samples were subjected to analysis by thermogravimetry and by thermomechanical analysis. With the intention to study the resulting weld interface, studies were made from the shear tests ILSS and Iosipescu, as well as end-Notched Flexure (ENF). The results of the thermal analysis in laminated PEI / carbon fiber non-welded show that the beginning of degradation for these composites is 460 °C, and it is also evident that the glass transition temperature of welded samples is about 15% higher than the results from samples not welded. In the mechanical tests show that there was an increase of 32% and 20% respectively in interlaminar shear results for the ILSS and Iosipescu welded samples, when they are compared to samples not welded. The ENF test results show satisfactory values of interlaminar fracture toughness in the composite welded from the values found in literature.

RESUMO Frente à crescente necessidade de recuperar o meio ambiente e seus recursos naturais, atualmente a reciclagem e reutilização dos materiais torna-se uma das soluções sustentáveis mais visadas. Neste cenário, o processamento de compósitos particulados de alumínio em matriz termoplástica de polietileno de baixa densidade (PEBD), provenientes da reciclagem de embalagens longa vida, apresenta-se de maneira atrativa para a obtenção de matéria prima para a construção civil, na fabricação de telhas de baixo peso, associado a baixo custo e elevada disponibilidade, dentre outras aplicações. Este trabalho tem por objetivo estudar as propriedades e o comportamento do compósito de polietileno de baixa densidade/alumínio reciclados. Com este objetivo, foi realizada a avaliação morfológica do compósito a partir de microscopia óptica (MO), microscopia eletrônica de varredura (MEV) e espectroscopia por energia dispersiva de raios X (EDS), bem como avaliados os comportamentos térmico e mecânico deste material após estes terem sido submetidos à climatização higrotérmica e por radiação ultravioleta (UV). Para a avaliação térmica foram empregadas técnicas de análise termogravimétrica (TGA) e calorimetria exploratória diferencial (DSC). As propriedades mecânicas foram avaliadas por análise dinâmico-mecânica (DMA) e ensaios de tração e impacto. A partir dos resultados obtidos por meio deste trabalho pode-se concluir que o intemperismo envolvendo umidade e radiação UV pode influenciar nos desempenhos térmico e mecânico do compósito de Alumínio/PEBD, porém, foi observado que esta influência não é suficiente para inviabilizar a utilização destes materiais na construção civil, garantindo este mercado para o compósito de PEBD/Al.

ABSTRACT Face the growing need to restore the environment and its natural resources, currently the recycling and reuse of materials becomes one of the most important sustainable solution. In this scenario, the processing of aluminum particulate composite with low density polyethylene thermoplastic matrix (LDPE) from recycling packages, presents an attractive way to obtain raw materials for the building industry, in the manufacturing of lightweight roof tiles, associated with low cost and high availability, among other applications. This work aims to study the properties and behavior of recycled low density polyethylene/aluminum composite. In order to do this, they were performed composite morphology assessment through optical microscopy (OM), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS), as well as were evaluated the thermal and mechanical behavior of this material after being subjected to hygrothermal and ultraviolet conditioning (UV). For the thermal evaluation was performed thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mechanical properties were evaluated by dynamic mechanical analysis (DMA) and tensile and impact tests. From the results obtained from this study it can be concluded that the moisture involving weathering and UV radiation can influence the thermal and mechanical performance of the composite aluminum / LDPE, but it was observed that this influence was not enough to prevent the use of these materials in construction, ensuring this market for LDPE / Al composite.

Atualmente, muitos componentes destinados à indústria aeronáutica, que anteriormente utilizavam compósitos com matriz termorrígida, vêm sendo substituídos por aqueles que apresentam matriz termoplástica, devido principalmente às melhores propriedades mecânicas obtidas, possibilidade de reaproveitamento do mesmo e a facilidade na fabricação de peças grandes e complexas, que serão integradas para formar o componente final desejado, assim como a sua temperatura de serviço mais elevada. Entretanto, um dos principais problemas da utilização de compósitos poliméricos em aplicações estruturais consiste em sua união efetiva para a integração de componentes. Nos últimos anos, a soldagem por resistência elétrica vem sendo considerada como uma das mais promissoras técnicas para a união de compósitos, pois se trata de um processo com pouca preparação de superfície e com qualidade aceitável no setor industrial. O principal objetivo deste trabalho consiste no estudo de parâmetros de soldagem por resistência elétrica para o compósito polimérico PEI poli (éter-imida) reforçado com fibras de carbono e de vidro (sistema híbrido) para aplicações aeronáuticas. As amostras do compósito foram soldadas e submetidas ao ensaio de lap shear para obtenção de tensão de ruptura ao cisalhamento de juntas simples. A partir deste ensaio foram estabelecidas as variáveis mais adequadas para utilização neste processo. O método utilizado foi um planejamento experimental fatorial completo que permitiu, com um número menor de experimentos, explorar todo o espaço experimental de interesse, estabelecendo os valores mais adequados de corrente elétrica, pressão e tempo para o processo de soldagem estudado.

Nowadays, many components applied in the aerospace industry, which had been previously used with thermoset matrix composites, are being replaced by those with thermoplastic matrix, which is mainly due to having better mechanical properties, the possibility of reuse and ease in manufacturing large and complex parts which will be integrated to form the desired component with higher service temperature. However, a major problem concerning the use of polymer composites for structural applications consists in its effective integration of components. Electrical resistance welding has been considered as one of the most promising techniques for bonding thermoplastic composites because it is a quick process with little surface preparation. The main objective of this work is to study the resistance welding parameters for PEI (polyether imide), and carbon and glass (hybrid) fibers laminates for aeronautical applications. The composite specimens were welded and subjected to the lap shear test in order to establish the most suitable variable in this process. It was used a full factorial design that allowed, with fewer experiments, exploring the whole experimental area of interest, establishing values of electric current, pressure and time for the studied welding process.

Neste trabalho o comportamento de cristalização e a condutividade elétrica de compósitos nanoestruturados de poli(sulfeto de fenileno) reforçado com nanotubos de carbono de paredes múltiplas obtidos através da técnica de mistura em fusão foram estudados. A incorporação do nanoreforço na matriz polimérica foi responsável por um aumento da cristalinidade devido ao fenômeno de nucleação heterogênea. A condutividade elétrica do PPS apresentou um aumento de 11 ordens de magnitude quando 2,0 m/m% de MWCNT foram adicionados a matriz polimérica. Além disso, o limite de percolação elétrica encontrado para este sistema foi de 1,4 m/m% de MWCNT, revelando a formação de uma rede condutiva tridimensional no interior da matriz polimérica.

In this work, the crystallization behavior and electrical conductivity of multiwalled carbon nanotubes reinforced poly (phenylene sulfide) nanostructured composites obtained by melt mixing were investigated. The incorporation of nanofiller in polymeric matrix was responsible for an increase in crystallinity due heterogeneous nucleation phenomenon. The electrical conductivity of PPS showed an increase by 11 orders of magnitude when 2.0 wt% of MWCNT was considered. Moreover, the electrical percolation threshold found on this system was 1.4 wt%, suggesting the formation of three-dimensional conductive network within the polymeric matrix.

The non-isothermal thermogravimetric methods have been used extensively for the determination of kinetic parameters in polymers. The poly (ether ketones) are used as matrix in advanced high performance composites due its high thermal stability, excellent environmental performance and superior mechanical properties. In this work, the non-isothermal decomposition kinetics of the polymer poly (ether ether ketone) (PEEK) was evaluated in nitrogen and synthetic air atmospheres, using the Flynn-Wall-Ozawa and Coats Redfern models. The results showed that the necessary time for the material decomposes in 5% is approximately 216 years if it is submitted to temperatures of 350 °C in nitrogen atmosphere. On the other hand, if the material is submitted to air atmosphere, this decomposition time drops to about 1,05 years in the same temperature and for the same conversion rate. The decomposition kinetics study by Coats Redfern showed that the D3 mechanism (three-dimensional diffusion (Jander equation)) had better adjustment to the decomposition kinetics of the material in nitrogen atmosphere, while in synthetic air the R1 mechanism (phase boundary controlled reaction (one-dimensional movement)) has better adjustment to the decomposition kinetics of the material.

Nanostructured polymer composites have opened up new perspectives for multifunctional materials. In particular, carbon nanotubes (CNTs) present potential applications in order to improve mechanical and electrical performance in composites with aerospace application. The combination of epoxy resin with multiwalled carbon nanotubes results in a new functional material with enhanced electromagnetic properties. The objective of this work was the processing of radar absorbing materials based on formulations containing different quantities of carbon nanotubes in an epoxy resin matrix. To reach this objective the adequate concentration of CNTs in the resin matrix was determined. The processed structures were characterized by scanning electron microscopy, rheology, thermal and reflectivity in the frequency range of 8.2 to 12.4 GHz analyses. The microwave attenuation was up to 99.7%, using only 0.5% (w/w) of CNT, showing that these materials present advantages in performance associated with low additive concentrations.

Nanostructured polymer composites have opened up new perspectives for multi-functional materials. In particular, carbon nanotubes (CNTs) have the potential applications in order to improve mechanical and electrical performance in composites with aerospace application. This study focuses on the viscoelastic evaluation of phenolic resin reinforced carbon nanotubes, processed by using two techniques: aqueous-surfactant solution and three roll calender (TRC) process. According to our results a relative small amount of CNTs in a phenolic resin matrix is capable of enhancing the viscoelastic properties significantly and to modify the thermal stability. Also has been observed that when is used TRC process, the incorporation and distribution of CNT into phenolic resin is more effective when compared with aqueous solution dispersion process

ABSTRACT: The aim of this study was to investigate the effects of hygrothermal exposure, ultraviolet (UV) radiation, salt spray and thermal shock aging on the thermomechanical behavior of glass fiber reinforced by poly (ether-imide) (PEI) composites. Dynamic mechanical (DMA) and Thermomechanical (TMA) analyses have been performed on the aged PEI composites after being submitted to the climatic chambers. Additional techniques have been used to characterize the laminates, such as optical microscopy and infrared spectroscopy (FT-IR) in order to evaluate possible structural changes in these materials. Slight changes were observed both in glass transition temperature and in thermal expansion coefficient as a result from the environmental conditioning used (hygrothermal, salt spray, UV radiation and thermal shock conditioning). Thus, when exposed to these conditions, PEI/glass fiber laminates maintain its compromise with the performance component.

Abstract: Reinforced thermoplastic structural detail parts and assemblies are being developed to be included in current aeronautic programs. Thermoplastic composite technology intends to achieve improved properties and low cost processes. Welding of detail parts permits to obtain assemblies with weight reduction and cost saving. Currently, joining composite materials is a matter of intense research because traditional joining technologies are not directly transferable to composite structures. Fusion bonding and the use of thermoplastic as hot melt adhesives offer an alternative to mechanical fastening and thermosetting adhesive bonding. Fusion bonding technology, which originated from the thermoplastic polymer industry, has gained a new interest with the introduction of thermoplastic matrix composites, which are currently regarded as candidate for primary aircraft structures. This paper reviewed the state of the art of the welding technologies devised to aerospace industry, including the fields that Universidade Estadual Paulista Júlio de Mesquita Filho and Universidade de São Paulo are deeply involved.