Extruder Melt Temperature Control with Fuzzy Logic

In polymer extrusion, the delivery of a melt which is homogenous in composition and temperature is paramount for achieving high quality extruded products. However, advancements in process control are required to reduce temperature variations across the melt flow which can result in poor product quality. The majority of thermal monitoring methods provide only low accuracy point/bulk melt temperature measurements and cause poor controller performance. Furthermore, the most common conventional proportional-integral-derivative controllers seem to be incapable of performing well over the nonlinear operating region. This paper presents a model-based fuzzy control approach to reduce the die melt temperature variations across the melt flow while achieving desired average die melt temperature. Simulation results confirm the efficacy of the proposed controller.

Understanding the Performance of Melt-Extruded Poly(ethylene oxide)–Bicalutamide Solid Dispersions: Characterisation of Microstructural Properties Using Thermal, Spectroscopic and Drug Release Methods

In this article, we have prepared hot-melt-extruded solid dispersions of bicalutamide (BL) using poly(ethylene oxide) (PEO) as a matrix platform. Prior to preparation, miscibility of PEO and BL was assessed using differential scanning calorimetry (DSC). The onset of BL melting was signi?cantly depressed in the presence of PEO, and using Flory– Huggins (FH) theory, we identi?ed a negative value of -3.4, con?rming miscibility. Additionally, using FH lattice theory, we estimated the Gibbs free energy of mixing which was shown to be negative, passing through a minimum at a polymer fraction of 0.55. Using these data, solid dispersions at drug-to-polymer ratios of 1:10, 2:10 and 3:10 were prepared via hot-melt extrusion. Using a combination of DSC, powder X-ray diffractometry and scanning electron
microscopy, amorphous dispersions of BL were con?rmed at the lower two drug loadings. At the 3:10 BL to PEO ratio, crystalline BL was detected. The percent crystallinity of PEO was reduced by approximately 10% in all formulations following extrusion. The increased amorphous content within PEO following extrusion accommodated amorphous BL at drug to polymer loadings up to 2:10; however, the increased amorphous domains with PEO following extrusion were not suf?cient to fully accommodate BL at drug-to-polymer ratios of 3:10.

Hot-melt extrusion technology and pharmaceutical application

The use of hot-melt extrusion (HME) within the pharmaceutical industry is steadily increasing, due to its proven ability to efficiently manufacture novel products. The process has been utilized readily in the plastics industry for over a century and has been used to manufacture medical devices for several decades. The development of novel drugs with poor solubility and bioavailability brought the application of HME into the realm of drug-delivery systems. This has specifically been shown in the development of drug-delivery systems of both solid dosage forms and transdermal patches. HME involves the application of heat, pressure and agitation through an extrusion channel to mix materials together, and subsequently forcing them out through a die. Twin-screw extruders are most popular in solid dosage form development as it imparts both dispersive and distributive mixing. It blends materials while also imparting high shear to break-up particles and disperse them. HME extrusion has been shown to molecularly disperse poorly soluble drugs in a polymer carrier, increasing dissolution rates and bioavailability. The most common difficulty encountered in producing such dispersions is stabilization of amorphous drugs, which prevents them from recrystallization during storage. Pharmaceutical industrial suppliers, of both materials and equipment, have increased their development of equipment and chemicals for specific use with HME. Clearly, HME has been identified as an important and significant process to further enhance drug solubility and solid-dispersion production. © 2012 Future Science Ltd.

Determination of the drug solubility at the melt temperature in silicone intravaginal rings using dynamic mechanical analysis

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Preliminary Report of the 1 field season at Gubbio.:Malone, C.A.T. and S.K.F. Stoddart,

Xerox circulation to sponsors. Cambridge University.

Preliminary report of the 1984 field season at Gubbio.,

Malone, C.A.T., et al., in Xerox circulation to sponsors. 1984. Cambridge University.

Provisional report. 1986 Season. Gubbio Project.

Stoddart, S.K.F. and C. Malone, ProXerox circulation to sponsors. 1986.