Ottimizzazione di progettazione stampi per materie plastiche attraverso prove simulative agli elementi finiti

La presente tesi ha come oggetto lo studio di metodologie di progettazione di stampi per iniezione di materie plastiche; in dettaglio essa si propone di fornire, attraverso una serie di simulazioni svolte al software CAE agli elementi finiti “Moldflow 2.0”, le dimensioni ottimali dei canali del sistema di alimentazione per una particolare tipologia di iniezione, quella sottomarina su espulsore. Al fine di dare allo studio una validità il più possibile generale e rendere applicabili nella pratica i risultati ottenuti, sono state effettuate simulazioni di iniezione con polimeri di viscosità e caratteristiche molto diverse tra loro per la produzione di elementi con lunghezza caratteristica variabile da 100 mm a 600 mm, con spessore pari a 3 mm (spessore più comune dell’iniezione di materie plastiche). L’obiettivo di tali simulazioni è mettere a disposizione del progettista di stampi, che si trovi a dover progettare un sistema di iniezione per un nuovo elemento, una banca dati contenente le dimensioni ottimali del sistema di iniezione per dati polimeri e lunghezze dei pezzi, nella quale egli troverà la combinazione materiale/lunghezza pezzo che più si avvicina al suo nuovo progetto da svolgere. I vantaggi della realizzazione di tale database sono evidenti dal momento in cui viene evitata, o comunque ridotta al minimo indispensabile, tutta la fase in cui vengono effettuati materialmente sugli stampi numerosi tentativi di “prova e correggi” delle dimensioni dei vari canali di iniezione, comportando ovviamente spreco di tempo e di denaro prima di trovare il dimensionamento ottimale. Risultano altresì vantaggi tangibili anche in fase di preventivazione delle nuove commesse, rendendo più snella la quantificazione dello spreco del materiale e del tempo di ciclo. Infine tale tesi affronta e riassume alcuni argomenti necessari a completare un manuale ad uso pratico del progettista quali cablaggi degli stampi, pistoni idraulici e movimentazioni interne di esso al fine di risolvere sottosquadri. The object of this thesis is the study of methodologies of moulds design for injection of plastics; in detail it proposes itself to supply, through a series of simulations developed on finite elements CAE software “Moldflow 2.0”, the optimal dimensions of the runner systems for a specified kind on injection, the submarine on ejector one. To the aim of giving the most possible general value at this study and make practical applicable the results, have been carried out simulations of injection with polymers having various viscosity and physical characteristics for the production of elements with variable characteristic length from 100 to 600 mm, with thickness of 3 mm (the most common thickness of the injection of plastics). The objective of those simulations is to create a database, containing the optimal dimensions of the system of injection for data polymers and lengths of pieces, available to the developer of moulds when he have to develop the system of injection for a new element; in this database he will find the combination material/piece length nearest its new project. The advantages of the realization of such database are evident in the moment which its avoided, or however minimized, all the phase called “try and correct”, that is when materially are corrected the dimensions of the running systems on the mould, involving money and time waste before finding the optimal dimensions. There also resulting tangible advantages even in budgeting phase of new projects, making faster the quantification of the material waste and the time of cycle. At last this thesis face up and synthesize some arguments necessary to complete a practical use handbook for the developers of moulds, treating wirings of the moulds, hydraulic pistons and inners movement

Iniziative imprenditoriali in Usa e Cina: Stategie di intervento

L’elaborato si propone di fornire un quadro significativo sulle varie opportunità di ampliamento del mercato definendo le diverse tipologie commerciali, contrattuali e societarie a disposizione dell’operatore italiano che intende operare in Usa e Cina

Microbiological valorisation of bio-composites based on polylactic acid and wood fibres

The use of wood fibres for production of bio-based composites has attracted interest in various application sectors ranging from packaging to automotive components and in other high value applications. In the course of the present research activity, several bio-based composites were developed using wood fibres with a compostable polymeric matrix such as polylactic acid (PLA) and a flexible biodegradable polymer such as poly(butylene adipate-co-terephthalate) (PBAT). The developed materials were used for the manufacture of several prototypes for food packaging (trays, boxes for refrigerated or frozen fish, egg box), agricultural applications (pots and yarns), automotive components (spoiler and seats) as well as containers for cosmetics and chemicals. Biodegradability and compostability are desired properties, allowing bio-recycling as end of life scenario, mainly for materials used in food packaging and agricultural applications. Thus, they may be recycled at the end of their life time service producing compost as a value-added by-product. Composting is the main option for bio-recycling but also other valuable pathways can be pursued. Because lignocellulose is one of the components of developed materials, several by-products such as enzymes, reducing sugars, proteins, amino acids, carbohydrates, organic acids, etc. may be obtained from the bio-composites produced. Alternatively, the bio-composites can be also used for the production of yeast biomass. This is important as another recyclability way of the new produced materials. In the present research the bio-composites produced were investigated as substrates for the production of the methylotrophic yeast Pichia pastoris, a potential source of single-cell protein (SCP), β-carotene, and Rhodotorula sp. as potential source of food and feed grade colorant. This is another more valuable alternative to the composting considering also that composting cannot be used to dispose of large quantities of bio-plastics, and in the future it will become more and more important to find alternative routes of valorisation for bio-plastics disposal

A general environmentally friendly access to long chain fatty acid ionic liquids (LCFA-ILs)

The development of bio-based ionic liquids (ILs) has attracted a great deal of interest in recent years. The so called long chain fatty acid ionic liquids (LCFA-ILs) represent a bio-based subfamily of hydrophobic ionic liquids. Here, a new preparation of the three major classes of LCFA-ILs (phosphonium, ammonium, imidazolium) is presented with the aim to overcome previous environmental synthetic issues. The undeniable interesting properties and potential applications of the LCFA-ILs often led to the underestimation of the drawbacks related to their synthetic pathways. Pure LCFA-ILs as well as cheaper mixture of LCFA-ILs have been obtained in a single step, in almost quantitative yields, and without production of waste water. The rheological and thermal stability properties of the prepared ILs have been analyzed

Terbuthylazine and desethylterbutylazine : recent occurrence, mobility and removal techniques

The herbicide terbuthylazine (TBA) has displaced atrazine in most of EU countries, becoming one of the most regularly used pesticides and, therefore, frequently detected in natural waters. The affinity of TBA for soil organic matter suggests prolonged contamination, once present; degradation leads to the release of the metabolite desethylterbuthylazine (DET), which has a higher water solubility and binds more weakly to organic matter compared to the parent compound, resulting in higher associated risk for contamination of groundwater resources. Additionally, TBA and DET are chemicals of emerging concern because of their persistence and toxicity towards aquatic organisms; moreover, they are known to have significant endocrine disruption capacity to wildlife and humans. Conventional treatments applied during drinking water production do not lead to the complete removal of these chemicals; activated carbon provides the greatest efficiency, whereas ozonation can generate by-products with comparable oestrogenic activity to atrazine. Hydrogen peroxide alone is ineffective to degrade TBA, while UV/H2O2 advanced oxidation and photocatalysis methods are the most effective processes for oxidation of TBA, with efficiencies above 90%. It has been determined that direct photolysis gives the highest degradation efficiency of all UV/H2O2 treatments, while most of the photocatalytic degradation efficiency is attributed to OH radicals, and TiO2 solar-photocatalytic ozonation can lead to almost complete TBA removal in ~30 min. Biomixtures could also be highly effective in preventing groundwater pollution due to TBA and DET, while constructed wetlands provide a valuable buffer capacity, protecting downstream surface waters from contaminated agricultural runoff

Development of Fibres-Reinforced Biodegradable Composites

In this work, blends of poly(3-hydroxybutyrate) (PHB), the most widespread member of the polyhydroxyalkanoates (PHAs), with wood fibres were investigated to assess the feasibility of producing biodegradable materials suitable for applications in packaging and agricultural environment. Due to its high crystallinity, PHB is stiff and brittle resulting in very poor mechanical properties with low extension at break, which limits its range of application. PHB was compounded successfully with wood fibres up to 30 % by weight in presence of polyethylene glycol (PEG) by extrusion. The composites were characterized by differential scanning calorimetry (DSC) and by scanning electron microscopy (SEM). Their mechanical properties were tested by dynamic mechanical thermal analysis (DMTA) and tensile tests. Preliminary tests in soil were carried out on the samples with wood fibres in order to investigate their biodegradation behavior, and further tests were performed in compost. Polyethylene glycol resulted effective as lubricating agent for the production of composites based on PHB and fibres. The good preliminary biodegradability results in soil showed that the blends PHB/wood fibres appear suitable for the production of natural fibre-reinforced thermoplastic items degradable in agricultural environment

Constipation in infants: influence of type of feeding and dietary fiber intake

Objective: To study the relationship between breast-feeding, dietary fiber intake and constipation in infants. Methods: The study population consisted of 275 infants consecutively enrolled in two Primary Care Clinic in the city of Embu, in the Great São Paulo. The feeding pattern were classified in predominantly breast-feeding, partially breast and cow s milk feeding and artificial feeding. Constipation was defined by the elimination of hard stool associated with one of the following: painful or difficult defecation, hard or round cracked stools and less than three defecations a week. False constipation was defined by the elimination of soft stools without pain or difficulty but with less than three defecations a week. Results: Constipation was found in 25.1% (69/275). False constipation was found only in the first semester of life in 5.1% of 159 infants. The prevalence of constipation was higher between 6 and 24 months (38.8%, 45/116) than in the first semester of life (15.1%, p=0.000). A model of logistic regression demonstrated that infants under artificial feeding were 4.53 times more liable to develop constipation than infants who were predominantly breastfed. The daily dietary fiber intake (g/day) was similar (p=0.57) among the constipated (median=9.0 g; 25th and 75th percentiles: 6.9-13.1g) and non-constipated (median = 8.8 g; 25th and 75th percentiles: 6.1-12.9 g). Conclusions: Dietary fiber intake was similar in constipated and non-constipated infants. Breast-feeding serves as a protection factor against the development of constipation in the first semester of life.Objetivo: estudar a associação entre tipo de aleitamento, consumo de fibra alimentar e ocorrência de constipação em lactentes. Métodos: foram estudados 275 lactentes atendidos consecutivamente em unidade básica de saúde. O tipo de aleitamento foi classificado como predominante, misto e artificial. Constipação foi caracterizada pela eliminação de fezes duras, associada a uma das seguintes características: dor ou dificuldade ao evacuar, fezes em cíbalos ou cilíndrica, com rachaduras, e intervalo entre as evacuações maior ou igual a 3 dias. Pseudoconstipação foi caracterizada quando ocorria a eliminação de fezes amolecidas, sem dor ou dificuldade, em intervalo maior ou igual a 3 dias. Resultados: constipação foi observada em 25,1% dos lactentes. Pseudoconstipação ocorreu exclusivamente nos primeiros 6 meses de vida, em 5,1% dos 159 lactentes desta faixa etária. Constipação entre os 6 e 24 meses (38,8%; 45/116) foi mais freqüente do que no primeiro semestre de vida (15,1%, p=0,0000). A análise de regressão logística evidenciou que, no primeiro semestre, os lactentes em aleitamento artificial demonstram chance 4,5 vezes maior de apresentar constipação do que os em aleitamento predominante. Entre os de 6 a 24 meses, a estimativa de consumo de fibra alimentar (gramas/dia) foi semelhante (p=0,57) nos lactentes com constipação (mediana=9,0g; percentis 25 e 75: 6,9-13,1g) e naqueles com hábito intestinal normal (mediana=8,8; percentis 25 e 75: 6,1-12,9g). Conclusões: o consumo de fibra alimentar por crianças menores de dois anos foi semelhante entre os grupos com e sem constipação intestinal. O aleitamento natural predominante é fator de proteção contra constipação no primeiro semestre de vida.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo (UNIFESP) Escola Paulista de MedicinaUniversidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Departamento de PediatriaUNIFESP, EPM, Depto. de PediatriaSciEL

New Bio-Composites Based on Polyhydroxyalkanoates and Posidonia oceanica Fibres for Applications in a Marine Environment

Bio-composites based on polyhydroxyalkanoates (PHAs) and fibres of Posidonia oceanica (PO) were investigated to assess their processability by extrusion, mechanical properties, and potential biodegradability in a natural marine environment. PHAs were successfully compounded with PO fibres up to 20 wt%while, at 30 wt%of fibres, the addition of 10 wt%of polyethylene glycol (PEG 400) was necessary to improve their processability. Thermal, rheological, mechanical, and morphological characterizations of the developed composites were conducted and the degradation of composite films in a natural marine habitat was evaluated in a mesocosm by weight loss measure during an incubation period of six months. The addition of PO fibres led to an increase in stiffness of the composites with tensile modulus values about 80% higher for composites with 30 wt % fibre (2.3 GPa) compared to unfilled material (1.24 GPa). Furthermore, the impact energy markedly increased with the addition of the PO fibres, from 1.63 (unfilled material) to 3.8 kJ/m2 for the composites with 30 wt % PO. The rate of degradation was markedly influenced by seawater temperature and significantly promoted by the presence of PO fibres leading to the total degradation of the film with 30 wt % PO in less than six months. The obtained results showed that the developed composites can be suitable to manufacture items usable in marine environments, for example, in natural engineering interventions, and represent an interesting valorisation of the PO fibrous wastes accumulated in large amounts on coastal beaches

A monocenter retrospective study of serological,histological and genetic characteristics of celiac disease in Northern Central Italy

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