Thesis--Brunswick. / In Periodical Room.

Paderborn, Universiẗat-Gesamthochsch., Fachber. Maschinentechnik, Diss. 1985.

Universiẗat, Diss., 2003--Essen.

Quantitative design of extruder dies for rubber compounds and thermoplastics requires a knowledge of the pumping performance of the extruder, for an appropriate extruder-die interaction. The dies are generally formed from a succession of convergent, circular or noncircular ducts with axial varying geometrical dimensions. The design and operation of dies of these types is then a matter of sufficient importance to justify a detailed analysis of the factors involved.

Solvent-free extrusion emulsification (SFEE) is new top-down technique specially suited to high viscosity polymers (100-1000 Pa.s) for producing sub-micron (100-500 nm) particles inside a twin screw extruder (TSE) without the use of hazardous solvents. SFEE has been difficult to implement in industry due to process sensitivities and a lack of mechanistic knowledge on how the polymer-water morphology must develop prior to inversion. To devise a mechanistic explanation of the critical stages of the process, an inline orifice-plate type viscometer was developed to monitor rheological changes previously witnessed in early batch studies. The general variables of study throughout the thesis included the manner by which sodium hydroxide (NaOH) can be added as well as the NaOH content necessary, resin-to-water (R/W) ratio, and surfactant content. The last study in the thesis explores the influence of matrix viscosity, which was accomplished by crosslinking the polyester. The striated lamellae morphology of the polyester-water system, critically controlling the final particle size, depended on two factors, specifically surface energy (determined by endgroup conversion and added surfactant) and matrix viscosity. Analysis of the rheological response indicated that a higher polar surface energy contribution had the greatest influence on the morphological state, demonstrating a steeper viscosity transition due to more favourable and more rapid incorporation of water within the polyester matrix. A strong correlation was repeatedly found between particle size and this viscosity transition, which has been related to the thickness of striated lamellae through a theory of lamellae coarsening (or thinning as is more relevant to the current process). The reported lamellae coarsening model in the literature, which shows the predominant effects of interfacial energy and viscosity on lamellae thickness in a mixed phase system showed excellent correspondence to the results in this thesis. Among the variables of study in this thesis, the dissolution of the sodium hydroxide species (when added as a solid particle) and the kinetics of end-groups conversion proved to be rate-limiting phenomena to generating thinner striated lamellae. The ionic strength of the system was notably important to the viscosity change occurring in the process as water was added for the first time and subsequently influenced the particle size produced, particularly when additional surfactant was not added and the system relied exclusively on the carboxylate endgroups present. Finally, with mounting evidence that SFEE showed significant sensitivity to the matrix viscosity, a final study examined the effectiveness of SFEE in the face of ever increasing viscous force by blending a crosslinked polyester into the neat resin at different weight fractions. With higher viscosity there was a corresponding decrease in interfacial area growth between the polyester and water, resulting in increased particle size but even with a viscosity near 800 Pa.s, far above a traditional oil-in-water system, it was still found possible in this study to create nano-sized particles by SFEE. / Thesis / Doctor of Philosophy (PhD)

This thesis covers a systematic examination of wet granulation in a twin screw extruder. Granulation of the excipient, (alpha)-lactose monohydrate, was done with the aid of PVP in an aqueous solution which acted as a binding agent. The influences on agglomeration by the following processing parameters were studied: screw elements design, screw rotational speed, binding solution concentration, and binder addition method. Qualitative efforts had also been made in modeling the process to gain valuable insight into how the elements affected agglomeration and granule rupture. A commercial software package PFC^2D, based on the Discrete Element Method (DEM), was used to simulate the dynamic behavior of the screw elements in the barrel. Within the optimal range of 7.5 -10wt% binder concentration, all the screw profiles were studied for their capacity to produce desirable granules suited to solid oral dosage form production. By increasing the rotational speed from 30 RPM to 80 RPM, the granules size of the conveying, discharging and chopping elements decreased whereas this operating parameter had little effect on granule size within kneading blocks. The nominal particle size produced by a screw element increased from 300(mu)m to 1mm when dispersive mixing was its dominant purpose (i.e. the kneading block), thereby meeting our criteria for a suitable granule in tab letting. Similar size development of the granules was not found with the other conveying or distributive mixing elements. In regards to particle shape, the kneading blocks produced elongated shape granules while other elements tested in this study produced smaller, more spherical agglomerates. Either shape was found effective in tabletting. Wet granulation was not feasible with more extreme concentrations of the aqueous binder (i.e. 5 wt% or 12 wt%) in this project, and the hand pre-blend method was the only approach found suitable for metering this additive into the system while maintaining steady feeding rates and output. / Thesis / Master of Applied Science (MASc)

Syftet med detta arbete är att förbättra ett verktyg för strängsprutning (extrudering). Arbetet består av tre faser (konstruktion, tillverkning och statistiska analyser). Omkonstruktionen sker med hänsyn till en del områden som har potential för optimering. Man börjar med en förstudie för att lära sig mer om verktyget och produktionscykeln och för att få en bättre helhetsbild. Innan arbetets start fastläggs en del avgränsningar, så att studenterna får en ram att jobba inom. Idéer i konstruktionsfasen utvecklas till tänkbara förslag, som sedan verkställs grafiskt i en datorstyrd programvara. Vidare tillverkas förslagen utifrån ritningar till riktiga detaljer med hjälp av bland annat metoder för skärande bearbetning. Slutligen monteras och mäts komponenterna och sedan provkörs verktyget för att se faktiska förbättringar.

Zugl.: Paderborn, Univ., Diss., 2008

Universiẗat, Diss.--Paderborn, 2000.

Universiẗat, Diss., 2008--Kassel.