Quantification of Volatile Residuals in Polydioxanone by Gas Chromatography: Method Development, Validation and Implementation

Bioresorbable polymers are increasingly utilized for implantable medical devices to avoid complications related to explant and/or long term responses to foreign materials. As with all polymeric materials, residual levels of unreacted monomer, and other volatiles, drastically affect the mechanical and chemical properties as well as the parameters required to process the material into a device. The 1,4-dioxane-2-one (PDO) monomer is a six membered ring that forms an ether-ester polymer via ring-opening polymerization (ROP) with intermediate absorption rate properties that are ideal for numerous implant situations. Developing devices using poly(1,4-dioxane-2-one) (PPDO, PDO, PDX, PPDX, or PDS) is complicated by residual levels of the unreacted, ring-form of the monomer causing the material to be toxic to biologic tissue in addition to the typical negative effects of excessive residual monomer in polymers, especially bioresorbable polymers. It is required to quantify the residual monomer content of PDO polymer throughout the manufacturing and storage of polymer or devices to ensure proper and repeatable processing in addition to the safety aspects related to the end use of the material. This work describes the application and comparison of known gas chromatography techniques, multiple headspace extraction and classical vaporization injection, to separate the residual monomer from the polymer matrix and allow for quantification. Accuracy and repeatability evaluations were used to determine the ideal testing methods to be used in industry as regulated by governing agencies such as the Food and Drug Administration (FDA)

Powder bed fusion metrology for additive manufacturing design guidance

The benefits afforded by the use of additive manufacturing (AM) are diminished due to limited understanding of the various AM processes. Design for additive manufacturing (DFAM) guidelines can be generated through metrology studies using test parts to characterize specific processes and inform designers. Polymer selective laser sintering (SLS) is an AM process that can be used to create geometrically complex, end-use parts. However, no DFAM guidelines exist for polymer SLS that are both comprehensive and statistically robust. A test part is designed for polymer selective laser sintering (SLS) that incorporates an array of geometric features. The part is comprehensive, including a variety of different features of interest to a designer. Many copies of the test part are built in a factorial-style metrology study, while varying different input parameters. The part is built in multiple materials, build orientations, locations within the build chamber, and on different machines to assess the variation attributed to each processing parameter. Multiple replicates are created at each point in the experimental design to add statistical robustness to the results. Both resolution and accuracy are investigated based on the features of the test part. Upon measurement of the test parts, tolerances and design allowables could be established and compiled into a set of design guidelines for SLS. The design guidelines are structured to include varying levels of detail depending on the intent of the designer implementing them. Lastly, the guidelines are assembled into an online web-based tool that allows them to be accessed freely. Using the web tool, designers can realize parts with fewer mistakes and iterations in the design process.Mechanical Engineerin

Análise Multivariada do Sistema de Medição de um Processo de Solda a Ponto por Resistência Elétrica utilizando Componentes Principais Ponderados.

O processo de soldagem a ponto por resistência elétrica (RSW) apresenta ampla aplicabilidade na indústria, principalmente no setor automotivo, devido à sua rápida execução, não utilização de consumíveis e adequação a operações automáticas. Sendo um processo de grande destaque, a busca pela melhoria da qualidade do produto é incessante e em um processo já capaz, não deve haver erro de medição. O RSW apresenta diversas características da qualidade e a análise de múltiplas grandezas correlacionadas pode ser melhor abordada utilizando-se técnicas multivariadas. Assim, esta dissertação busca aplicar o estudo de repetitividade e reprodutibilidade de caráter multivariado (GR&Rm) com o objetivo de analisar o sistema de medição de um processo de soldagem a ponto por resistência elétrica fazendo uso de uma estratégia por componentes principais ponderados, que se caracteriza por um método que trabalha com o escores dos componentes principais, ponderando-os pelo seus autovalores, a partir de grandezas correlacionadas. Para o estudo fora selecionado sete características da qualidade, duas respostas para ensaios mecânicos destrutivos e cinco para caracterização geométrica do ponto soldado. Para complementar as análises, realizou-se a comparação com os instrumentos convencionais de metrologia para duas características da qualidade distintas. No que diz respeito aos resultados, os ensaios destrutivos identificaram uma falta de repetitividade nas medições de uma das máquinas, favorecendo à realização de possíveis melhorias neste sistema. Para a caracterização geométrica do ponto soldado, o ndcm apresentou-se como aceitável, porém o estudo GR&Rm se classificou como marginal, podendo variar para um valor até 6,94, mostrando que este SM tem capacidade de apresentar melhorias e ter classificação aceitável, diante ao intervalo de confiança estabelecido. Na análise comparativa com instrumentos convencionais de metrologia, verificou-se que a coerência das medições através do analisador de imagens se apresentou superior em ambos os casos avaliados

Estudo sobre o efeito de vibrações axiais sobre a formação e remoção de tortas de filtração gás-sólidos

Many studies related to the filtration of gases for the control and recovery of particulate materials have been developed with the aim of making the filtration system, both in the gas filtration operation as in the cleaning operation, more effective, with a longer useful life of the fabric filters and with greater ease of removal of cake filtration, tanking into account the currente laws regarding the emission of pollutants not environment and reduction of maintenance and operation costs. In this context, in order to make the gas filtration operation more efficient, the objective of this work was to adapt a filtration system with vibration motor coupled axially to the gaseous flow that would allow the detachment of the filter cake without the need to stop the operation filtration, and to evaluate the influences of mechanical vibration frequencies in the formation of cakes as the forces of drag on the filter medium, the thickness of cakes filtration, specific resistance of cake, porosity of cake compared with the static system. The manioc starch powder, pure talcum powder and phosphate rock were used as particulates in order to verify the influence of vibration on particulates with different morphologies and granulometric distribution. The surface filtration velocity of the gaseous stream was 10 cm / s at a mass flow rate of 0.183 g / s and the maximum pressure drop was 10000 Pa. The porosities of the cake filtration were determined by correlations found in the literature. The results showed that the frequencies of mechanical vibration 12, 17 and 18Hz influenced the structure of the cake and its removal for the rock phosphate particulate material, whose circularity was of 0.60, causing a formation of thinner of cake filtrantion, more resistant cake filtration and less porous cake filtrantion when compared to the static system. As adhesion forces of material also higher for vibration frequencies than the static system. It was concluded that the mechanical vibrations caused a denser packing of the phosphate rock particles in the filter medium. As for the particulate material, pure talcum powder, , whose circularity was of 0.67, the mechanical vibrations to both the independent system and the intermittent system provide behavior similar to the static system, it is not feasible to use. For the particles of manioc starch, whose circularity approaches a perfect circle, 0.98, for the independent vibration frequency of 12 Hz allowed the formation of cake filtration with greater thicknesses, smaller specific resistances of the cake filtrantion and larger porosities when compared to the static system, as well as lower adhesion force when compared to the static system. This may be related to the appearance of gaps in the cake filtration and the distribution of the particles in the layers of the cake filtration. Finally, the system of independent and intermittent mechanical vibration did not allow the detachment of the filter cake, but influenced the structure of the cake formation.Tese (Doutorado)Com o intuito de tornar a operação de filtração de gases mais eficiente, o objetivo desse trabalho foi adaptar um sistema de filtração com motor vibrador acoplado axial ao fluxo gasoso que possibilitasse o desprendimento da torta de filtração sem a necessidade de parar a operação de filtração, além de avaliar a influências das frequências de vibração mecânica na formação das tortas quanto às forças de arraste no meio filtrante, espessuras das tortas, resistências específicas das tortas, porosidades das tortas em comparação com o sistema ausente de vibração. Foram utilizados como materiais particulados o polvilho doce, o talco puro e a rocha fosfática moída, a fim de verificar a influência da vibração em materiais particulados com diferentes morfologias e distribuição granulométrica. A velocidade de filtração superficial do fluxo gasoso foi de 10 cm/s, a uma vazão mássica de 0,183 g/s e queda de pressão máxima estabelecida de 10000 Pa. As porosidades das tortas de filtração foram determinadas por correlações encontradas na literatura. Os resultados mostraram que para as frequências de vibrações mecânicas de 12, 17 e 18 Hz influenciaram na estrutura da torta e em sua remoção para o material particulado rocha fosfática moída, cuja circularidade era de 0,60, causando a formação de tortas menos espessas, mais resistentes e menos porosas quando comparadas ao sistema estático. As forças de adesão desse material também foram maiores para as frequências de vibração que o sistema estático. Concluiu-se que as vibrações mecânicas causaram um empacotamento mais denso das partículas de rocha moída no meio filtrante. Já para o material particulado, o talco puro, cuja circularidade era de 0,67, as vibrações mecânicas tanto para o sistema independente quanto ao sistema intermitente proporcionam comportamentos semelhantes ao sistema estático, não sendo viável sua utilização. Para as partículas de polvilho doce, cuja circularidade se aproxima de um círculo perfeito, 0,98, para a frequência de vibração de 12 Hz independente possibilitou a formação de tortas com maiores espessuras, menores resistências específicas das tortas e maiores porosidades quando comparadas ao sistema estático, além de menor força de adesão quando comparadas ao sistema estático. Isso possivelmente estar relacionado ao surgimento de lacunas nas tortas e à distribuição das partículas nas camadas das tortas. Enfim, o sistema de vibração mecânica independente e intermitente não possibilitou o desprendimento das tortas de filtração, porém influenciou a estrutura de formação das tortas

System Analysis Using Simulation for Manufacturing Gauge R&R Study

Manufacturing environment relies on fulfillment of product specifications and customer satisfaction. Quality characteristics of products are measured for assessing its accordance to requirements, but measurement error might mask true process performance. Measurement system variability must be small with respect to product specifications as well to process variation. Total variation in a manufacturing process is a combination of part-to-part variation and measurement variation. Prior to endeavor in process analysis and enhancement it is highly recommended to perform a measurement system capability study. The analysis of the measurement system has to take into account three basic components, appraiser, equipment and product. Measurement system analysis (MSA) relies on statistical tools, such as Gauge R&R study, to ensure that the measurement system is in acceptable conditions to monitor the manufacturing process. Main objective of the thesis is to analyze how sensitive are the confidence intervals of variability components and capability criteria to the design of a Gauge R&R study. We conducted extensive numerical experiments using simulation. Findings will be of help as guidance to practitioners when dealing with parameter allocation decisions in a Gauge R&R study

Modélisation et quantification 3D de la taille des superficies corporelles brûlées

Pour des patients grands brûlés, une estimation précise du pourcentage des superficies brûlées (%TBSA) est cruciale pour l’évaluation du pronostic vital et fonctionnel, la planification appropriée de traitements et pour minimiser les complications médicales et chirurgicales. Les méthodes cliniques actuelles manquent de précision et de fiabilité pour estimer des patients de morphologies différentes. Les approches de modélisation 2D/3D des brûlures approximent l’évaluation du %TBSA et sont imprécises. Seule la modélisation paramétrique satisfait aux exigences cliniques particulières aux grands brûlés (temps limité, patients inconscients, environnement restreint). Afin de répondre au besoin de personnalisation 3D de la morphologie des patients, il est suggéré d’utiliser le logiciel open source MakeHuman (MH). Ainsi, cette thèse propose une approche de modélisation 3D personnalisée de la morphologie des patients à partir d’un nombre de mesures anthropométriques limité pour l’estimation précise du %TBSA. D’abord, avec des performances prédictives supérieures à 98%, plusieurs analyses de régression ont permis de démontrer qu’un nombre limité de mesures anthropométriques est suffisant pour une modélisation 3D de la surface corporelle (BSA) précise. Ensuite, la pertinence de personnaliser les modèles 3D MH à la morphologie du patient pour une meilleure évaluation du %TBSA a été démontrée. En utilisant une interface de rendue 3D développée pour la représentation et le calcul du %TBSA, six patrons de brûlures ont été appliqués automatiquement à l’ensemble de 15 paires de modèles 3D ayant la même BSA, mais des morphologies différentes. Des petites variations dans la morphologie de 0.04 m2 ± 0.01 (caractérisée par le pourcentage de surface brûlée) ont induit des surestimations dans le %TBSA. 8 experts et 6 non-experts ont évalué le %TBSA de patrons de brûlures simulés sur 4 mannequins commerciaux avec la méthode clinique puis en 3D avec l’interface. La méthode clinique a obtenu une erreur moyenne de 34 % ± 11 tandis que l’approche proposée est plus précise, plus répétable et reproductible avec une erreur moyenne de 5 % ± 1. Enfin, à partir d’un échantillon stratifié de 50 000 morphologies générées aléatoirement, plusieurs algorithmes d’apprentissage machine ont été utilisés afin d’identifier les ensembles de 3 à 4 mesures anthropométriques les plus pertinentes pour une modélisation 3D précise de la morphologie. La précision de la modélisation 3D a été validée sur 8 sujets saints. Les algorithmes d’apprentissage machine ont mis en évidence la taille et les circonférences du buste, du cou, des hanches et du tour de taille comme étant les meilleures mesures anthropométriques pour une modélisation 3D des surfaces corporelles. Les modèles 3D des sujets saints modélisés à partir de 3 à 4 mesures anthropométriques ont montré une géométrie proche de celle des scans 3D avec une distance d’erreur moyenne de 1.1 cm ± 0.4 et une distance maximale moyenne de 7.4cm ± 1.1. La contribution de ce projet est de réduire à terme les complications médicales et chirurgicales des grands brûlés en diminuant l’erreur d’estimation du %TBSA. Ainsi, il est possible d’améliorer les chances de survie du patient et de son pronostic par la personnalisation de sa prise en charge et de son pronostic