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Estudo da irradiação do polipropileno para possibilitar o controle de sua degradação ambiental / Study of polypropylene irradiation to ensure the control of its environmental degradationRomano, Rebeca da Silva Grecco 20 April 2017 (has links)
O PP é descartado em grande quantidade no meio ambiente, tendo em vista seu consumo muito elevado derivado de suas excelentes propriedades químicas e físicas, boa processabilidade e baixo custo. As radiações ionizantes, não ionizantes (UV e infravermelho), bem como o oxigênio e os poluentes podem causar a degradação do polipropileno (PP). A exposição à radiação ionizante pode causar na molécula de PP cisão de cadeia principal, reticulação e peroxidação (na presença de ar) entre outras. Este estudo tem como objetivo, o desenvolvimento de um PP oxidegradável por meio do controle da degradação induzida por radiação ionizante. As amostras foram processadas por injeção e expostas ao envelhecimento natural durante 180 dias e ao envelhecimento acelerado em estufa á 100°C por 192 dias e depois caracterizadas por avaliação visual, ensaios mecânicos, FTIR, SEM, DSC, TGA e DRX. As amostras de PP Grão 20 kGy, após o envelhecimento natural, apresentaram maior oxidação com presença de fissuras superficiais mais intensamente do que o PP d2w®. A resistência a tração do PP irradiado foi superior ao PP d2w® e os resultados do alongamento na ruptura mostraram uma diminuição intensa se compararmos o PP irradiado e o PP d2w® com o PP. Após a exposição natural espécies os índices de vinila e carbonila aumentaram ligeiramente devido as reações Norrish. O grupo carbonila promove uma oxidação contínua, junto à superfície fazendo com que o polímero diminua sua massa molar. O efeito da degradação natural foi evidente na ordem PP Grão 20 kGy > PP Grão 12,5 kGy = PP d2w® > PP. Por conseguinte, este conceito pode ser utilizado para produzir um PP com propriedades oxi-degradáveis de uma forma controlável. / UV light, heat, and pollutants can interact with Polypropylene (PP) molecules, mainly with the tertiary carbon producing free radicals which can react with oxygen producing changes in its properties. PP has outstanding chemical and physical properties and a good processability at very low market price. In addition, PP is extensively used for manufacturing various kinds of products, however due to its large-scale consumption a lot of waste is generated at the end of their life cycle to the environment with low rate degradation. Controlled degradation of PP can be achieved by exposing the polymers to well defined parameters, such as absorbed dose, intemperies, oxygen, etc. In this study, structural changes in PP macro-molecule are created upon exposure to ionizing radiation such as: main chain scission, crosslinking and peroxidation (in presence of air). This study has the objective of comparing the environmental and accelerated exposures of PP neat, PP irradiated with 12,5 kGy and 20 kGy and the incorporation of the commercial pro-degradant d2w®. Dumbbell samples were manufactured by injection molding and exposed to the environment during 180 days and to accelerated aging to 192 days. The samples were characterized by Mechanical Testing, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (DRX) and Differential Scanning Calorimetry (DSC). The samples previously irradiated, PP 20 kGy, after environmental aging showed higher oxidation and presence of surface cracks than the PP d2w® and PP neat. They also showed presence of carbonyl groups, decreases in elongation at break, increase in Strength Modulus and decrease of melting temperature corroborating with degradation.
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Estudo da irradiação do polipropileno para possibilitar o controle de sua degradação ambiental / Study of polypropylene irradiation to ensure the control of its environmental degradationRebeca da Silva Grecco Romano 20 April 2017 (has links)
O PP é descartado em grande quantidade no meio ambiente, tendo em vista seu consumo muito elevado derivado de suas excelentes propriedades químicas e físicas, boa processabilidade e baixo custo. As radiações ionizantes, não ionizantes (UV e infravermelho), bem como o oxigênio e os poluentes podem causar a degradação do polipropileno (PP). A exposição à radiação ionizante pode causar na molécula de PP cisão de cadeia principal, reticulação e peroxidação (na presença de ar) entre outras. Este estudo tem como objetivo, o desenvolvimento de um PP oxidegradável por meio do controle da degradação induzida por radiação ionizante. As amostras foram processadas por injeção e expostas ao envelhecimento natural durante 180 dias e ao envelhecimento acelerado em estufa á 100°C por 192 dias e depois caracterizadas por avaliação visual, ensaios mecânicos, FTIR, SEM, DSC, TGA e DRX. As amostras de PP Grão 20 kGy, após o envelhecimento natural, apresentaram maior oxidação com presença de fissuras superficiais mais intensamente do que o PP d2w®. A resistência a tração do PP irradiado foi superior ao PP d2w® e os resultados do alongamento na ruptura mostraram uma diminuição intensa se compararmos o PP irradiado e o PP d2w® com o PP. Após a exposição natural espécies os índices de vinila e carbonila aumentaram ligeiramente devido as reações Norrish. O grupo carbonila promove uma oxidação contínua, junto à superfície fazendo com que o polímero diminua sua massa molar. O efeito da degradação natural foi evidente na ordem PP Grão 20 kGy > PP Grão 12,5 kGy = PP d2w® > PP. Por conseguinte, este conceito pode ser utilizado para produzir um PP com propriedades oxi-degradáveis de uma forma controlável. / UV light, heat, and pollutants can interact with Polypropylene (PP) molecules, mainly with the tertiary carbon producing free radicals which can react with oxygen producing changes in its properties. PP has outstanding chemical and physical properties and a good processability at very low market price. In addition, PP is extensively used for manufacturing various kinds of products, however due to its large-scale consumption a lot of waste is generated at the end of their life cycle to the environment with low rate degradation. Controlled degradation of PP can be achieved by exposing the polymers to well defined parameters, such as absorbed dose, intemperies, oxygen, etc. In this study, structural changes in PP macro-molecule are created upon exposure to ionizing radiation such as: main chain scission, crosslinking and peroxidation (in presence of air). This study has the objective of comparing the environmental and accelerated exposures of PP neat, PP irradiated with 12,5 kGy and 20 kGy and the incorporation of the commercial pro-degradant d2w®. Dumbbell samples were manufactured by injection molding and exposed to the environment during 180 days and to accelerated aging to 192 days. The samples were characterized by Mechanical Testing, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (DRX) and Differential Scanning Calorimetry (DSC). The samples previously irradiated, PP 20 kGy, after environmental aging showed higher oxidation and presence of surface cracks than the PP d2w® and PP neat. They also showed presence of carbonyl groups, decreases in elongation at break, increase in Strength Modulus and decrease of melting temperature corroborating with degradation.
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Envelhecimento ambiental acelerado em PRF a base de tecidos h?bridos kevlar/vidro: propriedades e instabilidade estruturalFelipe, Renata Carla Tavares Santos 14 September 2012 (has links)
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Previous issue date: 2012-09-14 / There are a number of damaging mechanisms that various materials can suffer in service.
However, when working with polymer composite materials, this is something that requires
analysis, especially when exposed to adverse environmental conditions. Thus, the objective
of the present thesis is the study of the direct influence of environmental aging and the
form of hybridization of the reinforcement woven on the structural stability,
surfacedegradation and fracture process of polymer composites laminates. For this, the
development of two polymer composite laminates was necessary, where one of them was
reinforced with a bi-directional woven with hybrid strandsofkevlar-49/glass-Efibers, and
the other also with a bi-directionalwoven, however with weft and warpformed of
alternating strandsof Kevlar-49 fibers and glass-E fiber The reinforcementwoven are
industrially manufactured. Both laminates use a polyester resin as a matrixand are made up
of four layers each. All laminates were industrially prepared by the hand lay-up method of
manufacturing. To do this, test specimens were manufactured of the respective laminates
and submitted to environmental aging accelerated through the aging chamber. They were
exposed to alternating cycles of UV radiation and moisture (heated steam) for a standard
defined period. At the end of the exposure period the specimens were subjected to
mechanical tests of uniaxial tensile and bending in three points and to the
characterizationsof the fracture and surface deterioration. In addition, they were submitted
to a structural degradation assessment by the measurement of mass variation technique
(MMVT) and the measurement of thickness variation technique (MTVT), this last
technique being developed in this thesis. At the end of the analysis it was observed that the
form of hybridization of the reinforcement woven and the aging process directly influence
with losses or gain in mechanical properties, with losses in the structural degradation and
in the formation and propagation of damage mechanism of the developedcomposite
laminates / S?o v?rios os mecanismos de danos que os diversos materiais podem sofrer em servi?o. No
entanto, ao se trabalhar com os materiais comp?sitos polim?ricos isso ? algo que necessita
de an?lises principalmente quando expostos a condi??es ambientais adversas. Logo, a
respectiva tese objetiva o estudo da influ?ncia direta do envelhecimento ambiental e da
forma de hibridiza??o dos tecidos de refor?o no comportamento mec?nico, degrada??o
estrutural (dimensional e de massa) de laminados comp?sitos polim?ricos. Para tanto se fez
necess?rio o desenvolvimento de dois laminados comp?sitos polim?ricos, onde um deles ?
refor?ado com um tecido bidirecional com mecha h?brida de fibras de kevlar-49/vidro-E e
o outro com um tecido tamb?m bidirecional, por?m com trama e urdume formadas com
mechas alternadas de fibras kevlar-49 e fibras de vidro-E. Os tecidos de refor?o s?o de
fabrica??o industrial. Ambos os laminados utilizam como matriz a resina de poli?ster,
sendo constitu?dos de quatro camadas cada. Todos os laminados foram confeccionados
industrialmente pelo m?todo de fabrica??o handlay-up. Desta forma, foram fabricados
corpos de provas (CP s) dos respectivos laminados e submetidos ao envelhecimento
ambiental acelerado atrav?s da c?mara de envelhecimento. Os mesmos foram expostos aos
ciclos alternados de radia??o UV e umidade (vapor aquecido) por um per?odo definido em
norma. Ao t?rmino do per?odo de exposi??o os CP s foram submetidos aos ensaios
mec?nicos de tra??o uniaxial e flex?o em tr?s pontos e ?s caracteriza??es da fratura e da
deteriora??o superficial. Al?m disso, foram submetidos ? avalia??o da degrada??o
estrutural mediante a t?cnica de media??o de varia??o de massa (TMVM) e a t?cnica de
medi??o de varia??o de espessura (TMVE), sendo essa ?ltima desenvolvida nesta tese. Ao
t?rmino das an?lises foi observado que a forma de hibridiza??o dos tecidos de refor?o e o
processo de envelhecimento influenciam diretamente, seja com perdas ou ganho
naspropriedades mec?nicas, com perdas na degrada??o estrutural e na forma??o e
propaga??o do mecanismo de dano dos laminados comp?sitos desenvolvidos
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Envelhecimento ambiental em comp?sitos polim?ricos ? base de tecidos de refor?os h?bridosBatista, Ana Cla?dia de Melo Caldas 25 July 2013 (has links)
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Previous issue date: 2013-07-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The utilization of synthetic fibers for plastic reinforcement is more and more frequent and this growing interest requires that their mechanic behavior under the most variable conditions of structural applications be known. The use of such materials in the open and exposed to the elements is one of them. In this case, it becomes extremely necessary to study their mechanical properties (strength, stiffness) and the mechanism of fracture by which the environment aging them out. In order to do that, the material must be submitted to hot steam and ultraviolet radiation exposure cycles, according to periods of time determined by the norms. This study proposal deals with the investigation of accelerated environmental aging in two laminated polymeric composites reinforced by hybrid woven made up of synthetic fibers. The configurations of the laminated composites are defined as: one laminate reinforced with hybrid woven of glass fibers/E and Kevlar fibers/49 (LHVK) and the other laminate is reinforced with hybrid tissue of glass fibers/E and of carbon fibers AS4 (LHVC). The woven are plane and bidirectional. Both laminates are impregnated with a thermofix resin called Derakane 470-300 Epoxy Vinyl-Ester and they form a total of four layers. The laminates were industrially manufactured and were made through the process of hand-lay-up. Comparative analyses were carried out between their mechanical properties by submitting specimen to uniaxial loading tractions and three-point flexion. The specimen were tested both from their original state, that is, without being environmentally aging out, and after environmental aging. This last state was reached by using the environmental aging chamber / O interesse na utiliza??o dos pl?sticos refor?ados por fibras sint?ticas ? cada vez mais crescente e esse grande interesse na utiliza??o dos mesmos faz com que seja necess?rio o conhecimento do comportamento mec?nico desses materiais sob as mais variadas condi??es de aplica??o estrutural. Dentre estas pode ser destacada a aplica??o desses materiais em situa??es em o elemento encontra-se exposto ? intemp?rie, e nesse caso os estudos das propriedades mec?nicas (resist?ncia, rigidez) al?m do mecanismo fratura frente ao envelhecimento ambiental s?o de extrema necessidade. Para tanto, submeter o material ? per?odos c?clicos de exposi??o ao vapor aquecido e ? de radia??o ultravioleta, por tempo definido em norma, se faz necess?rio. A presente proposta de trabalho de investiga??o consiste no estudo do envelhecimento ambiental acelerado em dois laminados comp?sitos polim?ricos refor?ados por tecidos h?bridos ? base de fibras sint?ticas. As configura??es dos laminados comp?sitos s?o definidas como: um laminado refor?ado com tecido h?brido de fibras de vidro/E e de fibras kevlar/49 (LHVK) e outro laminado refor?ado com tecido h?brido de fibras de vidro/E e de fibras de carbono AS4 (LHVC). Os tecidos s?o dos tipos planos e bidirecionais. Ambos os laminados foram impregnados a base de resina termofixa Derakane 470-300 Ep?xi Vinil-Ester e constitu?dos com quatro camadas no total. Os laminados t?m fabrica??o industrial e foram obtidos atrav?s do processo de lamina??o manual (Hand-lay-up). Foram realizados estudos comparativos entre as propriedades mec?nicas sob a a??o dos carregamentos de tra??o uniaxial e flex?o em tr?s pontos, nas condi??es dos corpos de prova sem o efeito do envelhecimento ambiental (estado original) e sob o efeito desse envelhecimento (estado envelhecido). O envelhecimento ambiental foi acelerado atrav?s do uso da c?mara de envelhecimento
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Evaluating Thermal and Mechanical Properties of Electrically Conductive Adhesives for Electronic ApplicationsXu, Shuangyan 26 April 2002 (has links)
The objective of this study was to evaluate and gain a better understanding of the short-term impact performance and the long-term durability of electrically conductive adhesives for electronic interconnection applications. Three model conductive adhesives, designated as ECA1, ECA2 and ECA3, supplied by Emerson & Cuming, were investigated, in conjunction with printed circuit board (PCB) substrates with metallizations of Au/Ni/Cu and Cu, manufactured by Triad Circuit Inc.
Effects of environmental aging on the durability of conductive adhesives and their joints were evaluated. All the samples for both mechanical tests and thermal tests were aged at 85%, 100%RH for periods of up to 50 days. Studies of bulk conductive adhesives suggested that both plasticization, which is reversible and further crosslinking and thermal degradation, which are irreversible, might have occurred upon exposure of ECAs to the hot/wet environment. The durability of electrically conductive adhesive joints was then investigated utilizing the double cantilever beam (DCB) test. It was observed that the conductive adhesive joint was significantly weakened following hydrothermal aging, and there was a transition from cohesive failure to interfacial failure as aging continued. A comparative study of the durability of different conductive adhesive and substrate metallization combinations suggested that the resistance of the adhesive joints to moisture attack is related to the adhesive properties, as well as the substrate metallizations. It was noted that the gold/adhesive interface had better resistance to moisture attack than the copper/adhesive interface. A reasonable explanation of this phenomenon was given based upon the concept of surface free energy and interfacial free energy. XPS analysis was performed on the fractured surfaces of DCB samples. For adhesive joints with copper metallization, copper oxide was detected on the failed surfaces upon exposure of the conductive adhesive joints following aging. XPS analysis on the fractured surfaces of adhesive joints with Au metallization suggested that diffusion of Cu to the Au surface might have happened on the Au/Ni/Cu plated PCB substrates during aging.
The impact performance of conductive adhesives was quantitatively determined using a falling wedge test. This unique impact resistance testing method could serve as a useful tool to screen conductive adhesives at the materials level for bonding purpose. Moreover, this test could also provide some useful information for conductive adhesive development. This study revealed that the viscoelastic energy, which is a result of the internal friction created by chain motions within the adhesive material, played an important role in the impact fracture behavior of the conductive adhesives. This study also demonstrated that the loss factor, evaluated at the impact environment conditions, is a good indicator of a conductive adhesive's ability to withstand impact loading. / Ph. D.
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Laminados comp?sitos de PRFV: efeitos da descontinuidade geom?trica e do envelhecimento ambiental aceleradoTin?, S?rgio Renan Lopes 07 February 2014 (has links)
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Previous issue date: 2014-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The growing demand in the use of composite materials necessitates a better understanding of
its behavior related to many conditions of loading and service, as well as under several ways
of connections involved in mechanisms of structural projects. Within these project conditions
are highlighted the presence of geometrical discontinuities in the area of cross and
longitudinal sections of structural elements and environmental conditions of work like UV
radiation, moisture, heat, leading to a decrease in final mechanical response of the material. In
this sense, this thesis aims to develop studies detailed (experimental and semi-empirical
models) the effects caused by the presence of geometric discontinuity, more specifically, a
central hole in the longitudinal section (with reduced cross section) and the influence of
accelerated environmental aging on the mechanical properties and fracture mechanism of
FGRP composite laminates under the action of uniaxial tensile loads. Studies on
morphological behavior and structural degradation of composite laminates are performed by
macroscopic and microscopic analysis of affected surfaces, in addition to evaluation by the
Measurement technique for mass variation (TMVM). The accelerated environmental aging
conditions are simulated by aging chamber. To study the simultaneous influence of
aging/geometric discontinuity in the mechanical properties of composite laminates, a semiempirical
model is proposed and called IE/FCPM Model. For the stress concentration due to
the central hole, an analisys by failures criteria were performed by Average-Stress Criterion
(ASC) and Point-Stress Criterion (PSC). Two polymeric composite laminates, manufactured
industrially were studied: the first is only reinforced by short mats of fiberglass-E (LM) and
the second where the reinforced by glass fiber/E comes in the form of bidirectional fabric
(LT). In the conception configurations of laminates the anisotropy is crucial to the final
mechanical response of the same. Finally, a comparative study of all parameters was
performed for a better understanding of the results. How conclusive study, the characteristics
of the final fracture of the laminate under all conditions that they were subjected, were
analyzed. These analyzes were made at the macroscopic level (scanner) microscope (optical
and scanning electron). At the end of the analyzes, it was observed that the degradation
process occurs similarly for each composite researched, however, the LM composite
compared to composite LT (configurations LT 0/90? and LT ?45?) proved to be more
susceptible to loss of mechanical properties in both regarding with the central hole as well to
accelerated environmental aging / A crescente demanda na utiliza??o dos materiais comp?sitos torna imprescind?vel uma melhor
compreens?o do seu comportamento frente ?s mais diversas condi??es de carga e servi?o, bem
como sob as variadas formas de conex?es envolvendo mecanismos nos projetos estruturais.
Dentro dessas condi??es de projeto destaque se faz para a presen?a de descontinuidades
geom?tricas na ?rea de se??es transversal e ou longitudinal dos elementos estruturais, assim
como, condi??es ambientais de servi?o como a radia??o UV, a umidade, o calor, que levam a
um decr?scimo na resposta mec?nica final do material. Neste sentido, essa tese tem como
objetivo o desenvolvimento de estudos (experimental e modelos semi-emp?ricos) detalhados
dos efeitos causados pela presen?a de descontinuidade geom?trica, mais especificamente um
furo conc?ntrico na se??o longitudinal (com redu??o da se??o transversal), assim como, da
influ?ncia do envelhecimento ambiental acelerado nas propriedades mec?nicas e mecanismo
de fratura de laminados comp?sitos de PRFV sob a a??o de cargas uniaxiais de tra??o.
Estudos referentes ao comportamento morfol?gico e de degrada??o estrutural dos laminados
comp?sitos s?o realizados, atrav?s de an?lises macrosc?picas e microsc?picas das superf?cies
afetadas, al?m da avalia??o mediante a T?cnica de Media??o de Varia??o de Massa (TMVM).
As condi??es de envelhecimento ambiental acelerado ser?o simuladas atrav?s da c?mara de
envelhecimento. Para avalia??o da influ?ncia simult?nea do envelhecimento/descontinuidade
geom?trica nas propriedades mec?nicas dos laminados comp?sitos, um modelo semi-empirico
? proposto e denominado de Modelo IE/FCPM. Para o caso da presen?a da concentra??o de
tens?o devido ao furo conc?ntrico, a mesma ? avaliada a partir do uso dos crit?rios de falhas
da Tens?o M?dia (Average-Stress Criterion) e da Tens?o Pontual (Point-Stress Criterion).
Dois laminados comp?sitos polim?ricos, confeccionados industrialmente, foram estudados: o
primeiro ? unicamente refor?ado com mantas de fibras curtas de vidro/E (LM) e o segundo
onde o refor?o de fibras de vidro/E vem na forma de tecido bidirecional (LT). Na concep??o
das configura??es dos laminados a presen?a da anisotropia ? fundamental para a resposta
mec?nica final dos mesmos. Por fim, um estudo comparativo entre todos os par?metros foi
realizado para uma melhor compreens?o dos resultados. Como estudo conclusivo, as
caracter?sticas da fratura final dos laminados sob todas as condi??es que os mesmos foram
submetidos, foram analisadas. Essas an?lises foram feitas em n?veis macrosc?pico (scanner) microsc?pico (?ptico e eletr?nico de varredura). Ao t?rmino das an?lises foi observado que o
processo de degrada??o se d? de forma semelhante para cada comp?sito pesquisado, no
entanto, o laminado comp?sito LM quando comparado ?s configura??es LT 0/90? e LT ?45?
do laminado comp?sito LT, se mostrou mais suscept?vel a perda de propriedades mec?nicas
tanto em rela??o ? presen?a do furo conc?ntrico como em rela??o ao envelhecimento
ambiental acelerado
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