O presente trabalho desenvolve uma proposta para a avaliação da redução da vazão de pico do hidrograma do método racional, no contexto de bacias hidrográficas topograficamente planas. Entendem-se como planas aquelas localidades, cujas declividades médias características e/ou projetadas são inferiores a 0,5%. Pretende-se também neste trabalho apresentar metodologias e práticas de projeto de drenagem usualmente adotadas em regiões de características topográficas semelhantes. No desenvolvimento do estudo, foram discutidas as bases teóricas do Método Racional e outros métodos de avaliação hidrológica que procuram levar em conta o amortecimento da vazão durante o seu escoamento sobre o leito das vias. Apresentam-se também as bases científicas para a criação de um modelo hidrodinâmico a ser usado no estudo para a determinação do fator de redução da vazão de pico do hidrograma racional. A capacidade de escoamento em vias urbanas é então discutida, de forma a se justificar as relações criadas como conclusão do trabalho. O resultado final apresentado é o estabelecimento de uma relação entre a variação do pico da vazão do Método Racional, com a capacidade de armazenamento ou amortecimento de cheias existente nessas vias. Relações estas que, para fins práticos, significam tanto o incremento positivo no período de retorno do projeto, quanto a redução da vazão para efeito de dimensionamento de galerias. Tais resultados são demonstrados de forma prática por meio do estudo de caso no município de Praia Grande, o litoral sul paulista. / This work presents a proposal for estimating the reduction of the Peak Flow Rate determined by the Rational Method, considering flat basins as a main characteristic. It is considered flat, all of those basins in which the average slope on the streets are smaller than 0,5 %. It is also intentions of this work discuss methods and practices adopted to flat areas as urban drainage solutions and best management practices. Within this work, we also present all the theoretical basis of the Rational Method, among others, that try to fuse the street storm water storage capacity whit the conveyance capacity of a usual street. It is also presented theoretical basis of hydrodynamic models to be used as the main tool to determine de peak flow reduction factor of the Rational Method Hydrogram. Conveyance capacity of a usual street is discussed, street storm water conveyance capacity is also discussed in order to justify the relations proposed as a conclusion of this work. As a result of this work it is established a relationship between the Peak flow rate determined by the Rational Method and the street storm water storage capacity. In addition, this peak reduction can be used as a positive increment on the Recurrence Interval or as flow rate reduction when designing the sewerage system, which means implementation costs reduction. An application to the city of Praia Grande, located the Sao Paulo State, is presented and used as a case of study.

Poucos estudos são reportados na literatura sobre o comportamento dinâmico do reator UASB submetido a variações cíclicas diárias, de cargas orgânicas e hidráulicas, em períodos curtos de duração - iguais ou menores que 24h, com os quais verifica-se queda na eficiência do reator, causada pela provável flotação dos grânulos, problemas com geração de odor e alta concentração de sólidos suspensos no efluente. Para melhor compreender a resposta dinâmica desses reatores submetidos a essas variações, foi desenvolvido o modelo MMS baseado no modelo hidrodinâmico de mistura completa em reatores em série, modelo cinético de primeira ordem para consumo de substrato e para crescimento da biomassa e equacionamentos empíricos reportados na literatura. Esse modelo indicou a capacidade do reator de amortecer as variações impostas e a influência da cinética na eficiência de remoção da matéria orgânica. Para calibrar e validar o MMS, foi avaliado o desempenho de um reator UASB (160 L) no tratamento de esgoto sanitário municipal da cidade de São Carlos. Durante o período de operação, o reator foi submetido a variações senoidais cíclicas, de cargas orgânica e hidráulica, em valores inferiores e superiores a 40% e 60% da vazão afluente de 16,0 L/h. A produção média de gás metano e a eficiência média de remoção de DQO alcançadas pelo reator foram de aproximadamente: 1,83 L/h e 61% para vazão afluente de 16 L/h, TDH de 10 h e velocidade ascensional de 0,23 m/h; 2,24 L/h e 48% para variação cíclica de 40% e 2,97 L/h e 40% para variação cíclica de 60%. O MMS indicou faixa de valores para a DQO efluente com diferença em relação aos resultados observados experimentalmente - de 37% para vazão afluente constante de 16 L/h e 59% e 56% para variações senoidais cíclicas de 40% e 60% da vazão afluente, respectivamente – devido à limitação do modelo em considerar o arraste de sólidos no efluente que ocorreu ao longo de toda a operação do reator e mais acentuadamente quando foram aplicadas variações da vazão afluente. O modelo ADM1 proposto por Batstone et al.(2002a,b)apresentou menor similaridade com os resultados observados experimentalmente por não contemplar a variação horária e diária de alguns parâmetros de entrada, mas apenas a média aritmética dos valores. / There are no extensive reports on the dynamic behaviour of UASB reactor submitted to cyclical daily variations of organic and hydraulic loads of short periods of time - equal to or shorter than 24 hours - that can damage the reactor efficiency due to probable granule flotation, odor generation and high concentration of suspended solids in the effluent. Aiming to understand the dynamic response of these reactors when submitted to these variations, it was developed the MMS model based on the N-continuous flow stirred tank reactors (CSTR) in series model, first order kinetics model for substrate consumption and biomass growth and empirical equations reported in the literature. The model indicated the reactor capacity on dampening the imposed flow rate variations and the influence of the kinetics in the organic matter removal efficiency. It was evaluated the response of a UASB in bench scale (160 L) treating sanitary sewage of São Carlos city in order to calibrate and validate the MMS. During the operation, the reactor was submitted to cyclical sinusoidal variations of organic and hydraulic loads in lesser and higher values of 40% and 60% of the influent flow rate of 16 L/h. The reactor achieved mean methane production and mean COD removal efficiency of: 1,83 L/h and 61% to influent flow rate of 16 L/h, HRT of 10 h and upflow velocity of 0,23 m/h; 2,24 L/h and 48% to sinusoidal variation of 40%; 2,97 L/h and 40% to sinusoidal variation of 60%. The MMS model results indicated a range of effluent COD values with a difference of 37% to influent flow rate of 16 L/h, 59% and 56% to sinusoidal variations of 40% and 60%, respectively, in comparison with the experimental observed data. This probably occurred due to the model limitation in considering and predicting the solids washout in the effluent that was verified during all the operation, and also more significant when the sinusoidal variations were applied. The ADM1 reported by Batstone et al. (2002a,b) presented lesser similarity with the experimental observed results due to the fact that it does not consider hourly and daily variations of some input parameters, but only the arithmetical mean of the values.

O presente trabalho desenvolve uma proposta para a avaliação da redução da vazão de pico do hidrograma do método racional, no contexto de bacias hidrográficas topograficamente planas. Entendem-se como planas aquelas localidades, cujas declividades médias características e/ou projetadas são inferiores a 0,5%. Pretende-se também neste trabalho apresentar metodologias e práticas de projeto de drenagem usualmente adotadas em regiões de características topográficas semelhantes. No desenvolvimento do estudo, foram discutidas as bases teóricas do Método Racional e outros métodos de avaliação hidrológica que procuram levar em conta o amortecimento da vazão durante o seu escoamento sobre o leito das vias. Apresentam-se também as bases científicas para a criação de um modelo hidrodinâmico a ser usado no estudo para a determinação do fator de redução da vazão de pico do hidrograma racional. A capacidade de escoamento em vias urbanas é então discutida, de forma a se justificar as relações criadas como conclusão do trabalho. O resultado final apresentado é o estabelecimento de uma relação entre a variação do pico da vazão do Método Racional, com a capacidade de armazenamento ou amortecimento de cheias existente nessas vias. Relações estas que, para fins práticos, significam tanto o incremento positivo no período de retorno do projeto, quanto a redução da vazão para efeito de dimensionamento de galerias. Tais resultados são demonstrados de forma prática por meio do estudo de caso no município de Praia Grande, o litoral sul paulista. / This work presents a proposal for estimating the reduction of the Peak Flow Rate determined by the Rational Method, considering flat basins as a main characteristic. It is considered flat, all of those basins in which the average slope on the streets are smaller than 0,5 %. It is also intentions of this work discuss methods and practices adopted to flat areas as urban drainage solutions and best management practices. Within this work, we also present all the theoretical basis of the Rational Method, among others, that try to fuse the street storm water storage capacity whit the conveyance capacity of a usual street. It is also presented theoretical basis of hydrodynamic models to be used as the main tool to determine de peak flow reduction factor of the Rational Method Hydrogram. Conveyance capacity of a usual street is discussed, street storm water conveyance capacity is also discussed in order to justify the relations proposed as a conclusion of this work. As a result of this work it is established a relationship between the Peak flow rate determined by the Rational Method and the street storm water storage capacity. In addition, this peak reduction can be used as a positive increment on the Recurrence Interval or as flow rate reduction when designing the sewerage system, which means implementation costs reduction. An application to the city of Praia Grande, located the Sao Paulo State, is presented and used as a case of study.

A aplicação de filmes finos em diferentes setores da indústria tem aumentado consideravelmente nos últimos anos. Dentre os diversos tipos de revestimentos, filmes finos cerâmicos tem se destacado por melhorarem as propriedades mecânicas, tribológicas e superficiais dos componentes industriais. Dentre os mais variados filmes finos cerâmicos, o Nitreto de Titânio (TiN) é um dos mais conhecidos e aplicados. Caracteriza-se principalmente por possuir alta dureza, resistência à corrosão, estabilidade química e resistência ao desgaste. Essas e outras características são extremamente sensíveis ao processo e, principalmente, aos parâmetros de deposição. Entender a influência da variação dos parâmetros de deposição em busca de melhorar as propriedades é um dos desafios da Ciência e Engenharia de Superfícies. O objetivo deste trabalho é obter, caracterizar e avaliar as propriedades mecânicas e adesivas de filmes finos de TiN obtidos via deposição física a vapor (PVD, Physical Vapour Deposition). Os filmes foram depositados em substratos de alumínio AA 1000, utilizando a técnica Triodo Magnetron Sputtering. Variou-se o fluxo de N2 durante a deposição e comparou-se com a condição de fluxo de N2 constante, sendo verificada a viabilidade de produção de filmes funcionalmente gradados. Os filmes obtidos foram caracterizados por Nanoindentação instrumentada, Difração de Raios-X por ângulo rasante, Teste de riscamento (scratch test), TEM (Transmission Electron Microscopy), Microscopia de Varredura de Alta Emission Gun) e Ensaio de tração em escala reduzida. Como resultado, os filmes depositados com fluxo de N2 variável possuíram melhor comportamento mecânico/adesivo e quando comparados com os filmes depositados sob fluxo de N2 constante. Portanto, a obtenção de filmes finos de TiN gradados funcionalmente com propriedades superiores aos filmes finos de TiN obtidos de modo convencional é possível, e sua aplicação em diferentes áreas da indústria tendem a ser melhor exploradas. / The application of thin films in different industry sectors has increased considerably in recent years. Among the various types of coatings, thin ceramic films have been distinguished by improving the mechanical, tribological and surface properties of industrial components. Among the ceramic thin films, titanium nitride (TiN) is one of the most known and applied. It is characterized by its high hardness, corrosion resistance, chemical stability and wear resistance. These characteristics are extremely sensitive to the deposition process.Understanding the influence of the variation of deposition parameters to improve properties is one of the challenges of Surface Science and Engineering. The films were deposited on AA 1000 aluminum substrates by Triode Magnetron Sputtering. N2 flow was varied during deposition and compared to the constant N2 flow condition and the viability of production of functionally graded films was tested. The obtained films were characterized by instrumented Nanoindentation, Grazing Incidence X-Ray Diffraction (GIXRD), scratch test, TEM (Transmission Electron Microscopy), Field Emission Gun (FEG) and Tensile Test on a reduced scale. As a result, films deposited with variable N2 flow had better mechanical / adhesive behavior when compared to films deposited under constant N2 flow. Therefore, obtaining thin films of functionally graded TiN with properties superior to the TiN thin films obtained in conventional manner is possible, and their application in different areas of industry tend to be better explored.

In this thesis, fluid flow and solute transport in heterogeneous aquifers and particularly in frac-tured rock have been investigated using Lagrangian Stochastic Advective-Reaction (LaSAR) framework. The heterogeneity of the aquifer structure or fracture configuration, as well as the various reaction/retention processes have been considered in the modelling approach. Advection and retention processes are considered to be the dominant transport processes. Monte-Carlo simulation results for transport of nonreactive tracers in 2D generic heterogeneous aquifers indicate that the travel time τ can be well approximated by a lognormal distribution up to a relative high degree of heterogeneity of the aquifers. Comparison between the Monte-Carlo simulation results and the results of first-order approximation reveals that the analytical solutions of the statistical moments of τ are valid only when the variability of the aquifer properties is small. For reactive tracers, Monte-Carlo simulations have been conducted by accounting for spatial variability of both hydraulic conductivity and one sorption parameter simultaneously. The simulation results indicate that the reaction flow path μ is a nonlinear function of distance for shorter distance, linear function for longer distance, and also that μ and τ are well correlated over the considered parameter range. The parameter β, which is purely determined by the flow condi-tions, quantifies the hydrodynamic control of retention processes for transport of tracers in frac-tures. Numerical simulations have been performed to study the statistical properties of the pa-rameter β, travel time τ and flow rate Q in a single heterogeneous fracture and in a sequence of fractures. The results of Monte-Carlo simulations indicate that the parameter β and τ are corre-lated with a power-law relationship β ∼ τm. The correlation between β and the flow rate Q have also been studied and an inverse power-law relationship β ∼ Q-m is proposed. The establishment of these relationships provides a link between the parameter β and measurable parameters τ (or Q). The LaSAR approach has been applied for prediction, evaluation and interpretation of the results of a number of tracer tests (TRUE-1, TRUE Block Scale and TRUE Block Scale Continuation) conducted by SKB at the Äspö site for tracer transport in fractures. The breakthrough curves may be predicted reasonably well, provided that the retention parameters, boundary conditions and hydraulic properties of the domain are given. The evaluation of TRUE tests indicates that the retention occurs mainly in the rim zone on site characterization time scales, while on the per-formance assessment time scale, diffusion and sorption in the unaltered rock matrix are likely to become dominant retention mechanisms. / QC 20100624

Ett undersöknings- och utvecklingsarbete för att lösa ett problem med att dränkbara pumpar i ett vattenavrinningssystem gick sönder med perioder på två år i genomsnitt, utfördes i samarbete med Cementa AB i Skövde. Orsak till pumpars haveri söktes och fanns vara bristande rutiner och kunskap om det underhåll pumparna krävde. För att lösa detta problem utvecklades riktlinjer för nyinköp av torruppställda pumpar för att möjliggöra kontinuerligt underhåll. Då möjligheter för placering av torruppställd pump saknades utvecklades ett pumpfundament för placering av torruppställd pump. Krav för utvecklingsarbetet togs fram i samarbete med Cementas underhållsavdelning och teoretisk dimensionering av dränkbara länspumpars dåvarande volymflödeskapacitet utfördes. Krav utvärderades och viktades med hjälp av parvis jämförelse. Dimensionering och kontroll av hållfasthet för utvecklat pumpfundamentet utfördes med hjälp av Finita Element Analyser i programvaran Pro/Engineer Creo 1.0 Mechanica. Kontroll av hållfasthet i infästning av pumpfundamentet samt svetsfogar utfördes analytiskt. Arbetet resulterade i en rekommendation till Cementa AB i Skövde att ta in offerter på nya torruppställda pumpar med hjälp av utvecklade riktlinjer och att tillverka det pumpfundament som tagits fram inom ramen för examensarbetet, för att placera nya pumpar på. Att noggrant följa de underhållsinstruktioner som pumpar har och att underlätta för personal att utföra detta underhåll ansågs kunna bidra till att pumpar skulle få en längre och mer ekonomisk livslängd. / A development project to solve problems with why submersible pumps in a run-off system broke down with periods of two years, on average, was performed in collaboration with Cementa AB in Skövde. Reason for the pumps breakdowns was searched and found to be inadequate procedures and missing knowledge of the maintenance required on the pumps. To solve this problem, guidelines for the purchase of new dry pit pumps were developed to allow for continuous maintenance. As the possibilities of placing a dry well pump did not exist at Cementa, a pump foundation was developed. Requirements for the development work were produced in cooperation with Cementas maintenance department and theoretical dimensioning of the submersible bilge pumps volume flow capacity was performed. Requirements were evaluated and weighted using Pairwise comparison. The design and control of the strength of the developed pump foundation was performed using finite element analysis in the software Pro/Engineer Creo 1.0 Mechanica. Controls of the strength of the attachment of the pump foundation and welds were performed analytically. The work resulted in a recommendation to Cementa AB in Skövde to bring in quotes on the new dry-pit pumps using the developed guidelines and to manufacture the pump foundation developed within the framework of the thesis. Cementa was also recommended to carefully follow the maintenance instructions for pumps and make it easier for staff to perform this maintenance. This was recommended to ensure that new pumps would have a longer and more economical lifetime.

Blends of poly butylene terephthalate (PBT) and polycarbonate (PC) form a very important class of commercial blends in numerous applications requiring materials with good chemical resistance, impact resistance even at low temperatures, and aesthetic and flow characteristics. PC and PBT are usually blended in a twin screw extruder (TSE). Product melt volume flow rate (MVR) is a property used to monitor product quality while blending the PC/PBT in a twin screw extruder. It is usually measured off line in a quality control laboratory using extrusion plastometer on samples collected discretely during the compounding operation. Typically a target value representing the desired value of the quality characteristics for an in-control process, along with upper and lower control limits are specified. As long as the MVR measurement is within the control limits, the sample is approved and the whole compounded blend is assumed to meet the specification. Otherwise, the blend is rejected. Because of infrequent discrete sampling, corrective actions are usually applied with delay, thus resulting in wasted material. It is important that the produced PC/PBT blend pellets have consistent properties. Variability and fault usually arise from three sources: human errors, feed material variability, and machine operation (i.e. steady state variation). Among these, the latter two are the major ones affecting product quality. The resulting variation in resin properties contributes to increased waste products, larger production cost and dissatisfied customers. Motivated by this, the objective of this project was to study the compounding operation of PC/PBT blend in a twin screw extruder and to develop a feasible methodology that can be applied on-line for monitoring properties of blends on industrial compounding operations employing available extruder input and output variables such as screw speed, material flow rate, die pressure and torque. To achieve this objective, a physics-based model for a twin screw extruder along with a MVR model were developed, examined and adapted for this study, and verified through designed experiments. This dynamic model for a TSE captures the important dynamics, and relates measurable process variables (screw speed, torque, feed rates, pressure etc.) to ones that are not being measured (material holdups and compositions at the partially and filled section along a TSE barrel). This model also provides product quality sensors or inferential estimation techniques for prediction of viscosity and accordingly MVR. The usefulness of the model for inferential MVR sensing and fault diagnosis was demonstrated on experiments performed on a 58 mm co-rotating twin-screw extruder for an industrial compounding operation at a SABIC Innovative Plastics plant involving polycarbonate – poly butylene terephthalate blends. The results showed that the model has the capability of identifying faults (i.e., process deviation from the nominal conditions) in polymer compounding operations with the twin screw extruder. For instance, the die pressure exhibited a change as a function of changes in raw materials and feed composition of PC and PBT. In the presence of deviations from nominal conditions, the die pressure parameters are updated. These die pressure model parameters were identified and updated using the recursive parameter estimation method. The recursive identification of the die pressure parameters was able to capture very well the effects of changes in raw material and/or composition on the die pressure. In addition, the developed MVR model showed a good ability in monitoring product MVR on-line and inferentially from output process variables such as die pressure which enables quick quality control to maintain products within specification limits and to minimize waste production.

In this work, the compounding of polycarbonate (PC) / poly-butylene terephthalate (PBT) blends was studied for the purpose of improving quality of products with reduced wastage and finally to satisfaction of end users. The effect of material rheological characteristics and processing conditions on compounding of PC /PBT was investigated through statistical experiments carried out on a 58 mm twin-screw extruder at SABIC Innovative Plastics Limited (formerly GE Plastics Limited) in Cobourg, Ontario. Melt Volume-Flow Rate (MVR) is the most commonly used property to monitor the quality of products of PC/PBT blends. The MVR was studied with different sampling times and correlations between product properties (melt flow) and processing conditions (screw speed, flow rates) were discussed. The rheological behavior of PC/PBT blends was investigated by dynamic and capillary rheometers. The effects of processing conditions (screw speed, feed rate) on viscosity were measured and it was found that the Cox-Merz rule is not valid for PC/PBT blends. The change of morphology of PC/PBT blends was observed under a scanning electron microscope (SEM) by using different types of samples. Those samples were (i) PC/PBT blends pellets, (ii) PC/PBT blend samples, but collected after completing the rheological tests in the parallel plate rheometer, and (iii) PC/PBT blend samples, but collected after completing the rheological tests in the capillary rheometer. There was evidence that the samples collected after completing the tests in the parallel and capillary rheometer might be degraded due to temperature and time.

Blends of poly butylene terephthalate (PBT) and polycarbonate (PC) form a very important class of commercial blends in numerous applications requiring materials with good chemical resistance, impact resistance even at low temperatures, and aesthetic and flow characteristics. PC and PBT are usually blended in a twin screw extruder (TSE). Product melt volume flow rate (MVR) is a property used to monitor product quality while blending the PC/PBT in a twin screw extruder. It is usually measured off line in a quality control laboratory using extrusion plastometer on samples collected discretely during the compounding operation. Typically a target value representing the desired value of the quality characteristics for an in-control process, along with upper and lower control limits are specified. As long as the MVR measurement is within the control limits, the sample is approved and the whole compounded blend is assumed to meet the specification. Otherwise, the blend is rejected. Because of infrequent discrete sampling, corrective actions are usually applied with delay, thus resulting in wasted material. It is important that the produced PC/PBT blend pellets have consistent properties. Variability and fault usually arise from three sources: human errors, feed material variability, and machine operation (i.e. steady state variation). Among these, the latter two are the major ones affecting product quality. The resulting variation in resin properties contributes to increased waste products, larger production cost and dissatisfied customers. Motivated by this, the objective of this project was to study the compounding operation of PC/PBT blend in a twin screw extruder and to develop a feasible methodology that can be applied on-line for monitoring properties of blends on industrial compounding operations employing available extruder input and output variables such as screw speed, material flow rate, die pressure and torque. To achieve this objective, a physics-based model for a twin screw extruder along with a MVR model were developed, examined and adapted for this study, and verified through designed experiments. This dynamic model for a TSE captures the important dynamics, and relates measurable process variables (screw speed, torque, feed rates, pressure etc.) to ones that are not being measured (material holdups and compositions at the partially and filled section along a TSE barrel). This model also provides product quality sensors or inferential estimation techniques for prediction of viscosity and accordingly MVR. The usefulness of the model for inferential MVR sensing and fault diagnosis was demonstrated on experiments performed on a 58 mm co-rotating twin-screw extruder for an industrial compounding operation at a SABIC Innovative Plastics plant involving polycarbonate – poly butylene terephthalate blends. The results showed that the model has the capability of identifying faults (i.e., process deviation from the nominal conditions) in polymer compounding operations with the twin screw extruder. For instance, the die pressure exhibited a change as a function of changes in raw materials and feed composition of PC and PBT. In the presence of deviations from nominal conditions, the die pressure parameters are updated. These die pressure model parameters were identified and updated using the recursive parameter estimation method. The recursive identification of the die pressure parameters was able to capture very well the effects of changes in raw material and/or composition on the die pressure. In addition, the developed MVR model showed a good ability in monitoring product MVR on-line and inferentially from output process variables such as die pressure which enables quick quality control to maintain products within specification limits and to minimize waste production.

In this work, the compounding of polycarbonate (PC) / poly-butylene terephthalate (PBT) blends was studied for the purpose of improving quality of products with reduced wastage and finally to satisfaction of end users. The effect of material rheological characteristics and processing conditions on compounding of PC /PBT was investigated through statistical experiments carried out on a 58 mm twin-screw extruder at SABIC Innovative Plastics Limited (formerly GE Plastics Limited) in Cobourg, Ontario. Melt Volume-Flow Rate (MVR) is the most commonly used property to monitor the quality of products of PC/PBT blends. The MVR was studied with different sampling times and correlations between product properties (melt flow) and processing conditions (screw speed, flow rates) were discussed. The rheological behavior of PC/PBT blends was investigated by dynamic and capillary rheometers. The effects of processing conditions (screw speed, feed rate) on viscosity were measured and it was found that the Cox-Merz rule is not valid for PC/PBT blends. The change of morphology of PC/PBT blends was observed under a scanning electron microscope (SEM) by using different types of samples. Those samples were (i) PC/PBT blends pellets, (ii) PC/PBT blend samples, but collected after completing the rheological tests in the parallel plate rheometer, and (iii) PC/PBT blend samples, but collected after completing the rheological tests in the capillary rheometer. There was evidence that the samples collected after completing the tests in the parallel and capillary rheometer might be degraded due to temperature and time.