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Adsorption and controlled release of agrochemicals has been studied widely using different nanomaterials and a variety of formulations. However, the potential for application of high surface-area metal–organic frameworks (MOFs) for the controlled release of agrochemicals has not been thoroughly explored. Herein, we report controlled and sustainable release of a widely used herbicide (2-methyl-4-chlorophenoxyacetic acid, MCPA) via incorporation in a range of zirconium-based MOFs and their biodegradable polymer composites. Three Zr-based MOFs, viz., UiO-66, UiO-66-NH2, and UiO-67 were loaded with MCPA either postsynthetically or in situ during synthesis of the MOFs. The MCPA-loaded MOFs were then incorporated into a biodegradable polycaprolactone (PCL) composite membrane. All three MOFs and their PCL composites were thoroughly characterized using FT-IR, TGA, SEM, PXRD, BET, and mass spectrometry. Release of MCPA from each of these MOFs and their PCL composites was then studied in both distilled water and in ethanol for up to 72 h using HPLC. The best performance for MCPA release was observed for the postsynthetically loaded MOFs, with PS-MCPA@UiO-66-NH2 showing the highest MCPA concentrations in ethanol and water of 0.056 and 0.037 mg/mL, respectively. Enhanced release of MCPA was observed in distilled water when the MOFs were incorporated in PCL. The concentrations of herbicides in the release studies provide us with a range of inhibitory concentrations that can be utilized depending on the crop, making this class of composite materials a promising new route for future agricultural applications.

Polypropylene (PP) reinforced with 2 and 4 wt% of multi-walled carbon nanotubes (MWNT) were melt-blended in twin screw extruder and then molded by compression or micromolding process. The impact of injection speed on the surface morphology, rheological and tensile characteristics was investigated by using a scanning electron microscope, parallel plate rheometry, and tensiometry. Results showed that the tensile properties of micro-molded specimens were remarkably higher than those of the compression molded sheets. Compared to compression molded sheets, micromolded specimens demonstrated up to 40 and 244% higher tensile stiffness and yield strength, respectively, most likely due to the alignment of polymer chain segments in the flow direction induced during the micromolding process. It was observed that the fast filling speed caused a drop in the tensile properties of the nanocomposites and polymer. Rheological examination revealed that the presence of a rheological percolation network in the nanocomposites produced by micromolding and the fast injection speed was beneficial for establishing the percolated network. Morphological examination revealed that the size of nanotube agglomerations that appeared in micromolded specimens was up to five times smaller than in compression molded sheets and the agglomeration size decreased with the increase of the injection speed.

It has been shown that seeded granules of calcium carbonate can be produced in commercial batch high shear granulators such as the Cyclomix high-shear impact mixer. Seeded granules are attractive to the pharmaceutical industry due to their high uniformity and good mechanical properties which can assist efficient tablet manufacture. In the current study, attempts to produce seeded granules of Durcal 65 and PEG 4000 binder using hot melt granulation are reported, in response to the recent shift towards continuous pharmaceutical manufacturing. Various screw configurations and rotation speeds were investigated in a series of experiments to determine the relationship between process conditions and granule properties. Particle size analysis, strength measurement and structural characterisation were used to quantify granule properties. It was found that using a series of kneading elements arranged at a 60° staggering angle located near to the feed section of the extruder screw generated strong, spherical granules. From structural characterisation approximately 5–15% of extruded granules were found to be seeded. Twin screw melt granulation is therefore considered to be a promising technique for continuous production of seeded granules, although a more detailed investigation is required to optimise yield and quality.

The present study demonstrates the application of decision tree algorithms to the cocrystallization process. 54 batches of Carbamazepine–Salicylic acid cocrystals embedded in poly(ethylene oxide) w...

Polymer extrusion is an important but an energy intensive method of processing polymeric materials. The rapid increase in demand of polymeric products has forced manufactures to rethink their processing efficiencies to manufacture good quality products with low-unit-cost. Here, analysing the operational conditions has become a key strategy to achieve both energy and thermal efficiencies simultaneously. This study aims to explore the effects of polymers’ rheology on the energy consumption and melt thermal quality (i.e., a thermally homogeneous melt flow in both radial and axil directions) of extruders. Six commodity grades of polymers (LDPE, LLDPE, PP, PET, PS and PMMA) were processed at different conditions in two types of continuous screw extruders. Total power, motor power, and melt temperature profiles were analysed in an industrial scale single-screw extruder. Moreover, the active power, mass throughput, torque, and power factor were measured in a laboratory scale twin-screw extruder. The results confirmed that the specific energy consumption for both single and twin screw extruders tends to decrease with the processing speed. However, this action deteriorates the thermal stability of the melt regardless the nature of the polymer. Rheological characterization results showed that the viscosity of LDPE and PS exhibited a normal shear thinning behaviour. However, PMMA presented a shear thickening behaviour at moderate-to-high shear rates, indicating the possible formation of entanglements. Overall, the findings of this work confirm that the materials’ rheology has an appreciable correlation with the energy consumption in polymer extrusion and also most of the findings are in agreement with the previously reported investigations. Therefore, further research should be useful for identifying possible correlations between key process parameters and hence to further understand the processing behaviour for wide range of machines, polymers and operating conditions.

With good insulation, cross-linked polyethylene (XLPE) cables are widely used as an important basic material for power transportation. Due to being insoluble and infused, the cross-linked network structure caused a challenge in the recycling of waste XLPE, which is usually treated by incineration and landfilling. In this research, XLPE was part-de-cross-linked via solid-state shear milling (S

Long chain branches (LCB) are successfully grafted to linear poly(lactic acid) (PLA) using functional group reactions with pentaerythritol triacrylate (PETA) and tetraethylthiuram disulfide (TETDS)...

Solid state shear milling (S3M) is reported as a scalable, continuous, polymer-assisted cocrystallization technique. A specially designed milling pan was employed to provide high levels of applied shear, and the addition of a polymeric processing aid enabled generation of high stress fields. Carbamazepine–salicylic acid cocrystals were produced with 5–25 wt % of poly(ethylene oxide) (PEO). A systematic study was carried out to understand the effect of process variables on properties and performance of the cocrystals. S3M offers an important new route for continuous manufacturing of pharmaceutical cocrystals.

Novel natural fibre composites of nylon-6 reinforced with coconut shell (CS) particles and empty fruit bunch (EFB) fibres have been investigated. Fillers were alkali treated before melt compounding...

A series of rheological experiments was performed for a polypropylene (PP) melt to explore its elongation behavior through a capillary die. Using an advanced twin-bore capillary rheometer with dies measuring 1.0, 0.5, and 0.25 mm in diameter, the experiments were performed at 210, 220, and 230 °C. The results indicated that the temperature of the PP melt had a significant effect on its extensional viscosity. The different decreases in the extensional viscosity values in the tested dies revealed the geometry dependence of the extensional viscosity. In the case of PP in the 0.25 mm die at 210 °C, the extensional viscosity values under different extensional strain rates were much higher than those in the other dies. Only in the 1.0 mm die did the relationship between the extensional viscosity of PP and its temperature obey the Arrhenius equation due to the larger die size which related to a slight size effect on its elongation behavior. The calculated deviations of the extensional viscosity in the tested dies demonstrated that the increasing pressure applied to the PP melt in the micro channel was related to the geometry dependence of the elongation behavior of the PP melt. The change in the extensional viscosity eventually relied on the interaction of the die geometry, the temperature, and the extensional stress of the PP melt.

A green approach has been used for co-crystallization of noncongruent co-crystal pair of caffeine/maleic acid using water. Ultrasound is known to affect crystallization; hence, the effect of high power ultrasound on the ternary phase diagram has been investigated in detail using a slurry co-crystallization approach. A systematic investigation was performed to understand how the accelerated conditions during ultrasound-assisted co-crystallization will affect different regions of the ternary phase diagram. Application of ultrasound showed considerable effect on the ternary phase diagram, principally on caffeine/maleic acid 2:1 (disappeared) and 1:1 co-crystal (narrowed) regions. Also, the stability regions for pure caffeine and maleic acid in water were narrowed in the presence of ultrasound, expanding the solution region. The observed effect of ultrasound on the phase diagram was correlated with solubility of caffeine and maleic acid and stability of co-crystal forms in water.

Understanding structure-property relationships is critical for the development of new drug delivery systems. This study investigates the properties of Pluronic smart hydrogel formulations for future use as injectable controlled drug carriers. The smart hydrogels promise to enhance patient compliance, decrease side effects and reduce dose and frequency. Pharmaceutically, these systems are attractive due to their unique sol-gel phase transition in the body, biocompatibility, safety and injectability as solutions before transforming into gel matrices at body temperature. We quantify the structural changes of F127 systems under controlled temperature after flow, as experienced during real bodily injection. Empirical formulae combining the coupled thermal and shear dependency are produced to aid future application of these systems. Induced structural transitions measured in-situ by small angle x-ray and neutron scattering reveal mixed oriented structures that can be exploited to tailor the drug release profile.

Polymers are one of the major classes of raw materials available for many aspects of production. Extrusion is a fundamental method for processing polymeric materials to form a wide range of products. Being poor thermal conductors these materials are difficult to heat and cool and also exhibit high viscosity in their molten state. Hence, heat transfer and rheology are major aspects of polymer processing applications. Also, polymer melts usually exhibit a non-Newtonian behaviour and hence are quite complicated to model. This work aims to observe the thermal behaviour/quality of a number of industrially common polymeric materials under a wide range of processing conditions using a capillary die with a specifically designed thermocouple mesh sensor. The melt temperature is considered as the main parameter in determining the thermal quality of the melt. Materials were processed under different screw speeds and set temperature conditions using three different screw geometries. The results showed that the uniformity of temperature across the melt flow varied considerably with increase in screw rotational speed whilst it was also shown to be dependent upon process settings, screw geometry and material properties. Moreover, it appears that the effects of the material, machine and process settings on the quantity and quality of the process output are heavily coupled with each other and this may cause the process to be difficult to predict and variable in nature. In terms of the flow behaviour, regardless of the processing conditions used, the highest melt temperature was observed always in the middle of the melt flow. At lower processing speeds, the lowest melt temperature was close to the die wall where this position shifted a few millimetres away from the die at higher speeds by forming low temperature shoulder regions (making the melt flow highly thermally inhomogeneous). Moreover, a discussion was made on the possible effects of materials’ properties on viscous heat generation during processing. Additionally, the importance of the use of the appropriate thermal monitoring techniques can also be highlighted in determining the actual melt thermal quality during polymer processing applications.

The aim of this study was to evaluate the choice of polymer and polymer level on the performance of the microstructure and wettability of hot-melt extruded solid dispersion of Glyburide (Gly) as a model drug. The produced solid dispersion were characterised using scanning electron microscopy (SEM), image analysis using a focus variation instrument (FVI), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), X-ray microtomography (XµT), dynamic contact angle measurement and dissolution analysis using biorelevant dissolution media (FASSIF). SEM and focus variation analysis showed that the microstructure and surface morphology was significantly different between samples produced. This was confirmed by further analysis using XµT which showed that an increase in polymer content brought about a decrease in the porosity of the hot-melt extruded dispersions. DSC suggested complete amorphorisation of Gly whereas XRPD suggested incomplete amorphorisation. The static and dynamic contact angle measurement correlated with the dissolution studies using FASSIF media indicating that the initial liquid imbibition process as captured by the dynamic contact angle directly affects the dissolution performance.

The use of near infra red spectroscopy to predict the concentration of two pharmaceutical co-crystals; 1:1 ibuprofen–nicotinamide (IBU-NIC) and 1:1 carbamazepine–nicotinamide (CBZ-NIC) has been evaluated. A partial least squares (PLS) regression model was developed for both co-crystal pairs using sets of standard samples to create calibration and validation data sets with which to build and validate the models. Parameters such as the root mean square error of calibration (RMSEC), root mean square error of prediction (RMSEP) and correlation coefficient were used to assess the accuracy and linearity of the models. Accurate PLS regression models were created for both co-crystal pairs which can be used to predict the co-crystal concentration in a powder mixture of the co-crystal and the active pharmaceutical ingredient (API). The IBU-NIC model had smaller errors than the CBZ-NIC model, possibly due to the complex CBZ-NIC spectra which could reflect the different arrangement of hydrogen bonding associated with the co-crystal compared to the IBU-NIC co-crystal. These results suggest that NIR spectroscopy can be used as a PAT tool during a variety of pharmaceutical co-crystal manufacturing methods and the presented data will facilitate future offline and in-line NIR studies involving pharmaceutical co-crystals.

A transflectance near infra red (NIR) spectroscopy approach has been used to simultaneously measure drug and plasticiser content of polymer melts with varying opacity during hot melt extrusion. A high temperature reflectance NIR probe was mounted in the extruder die directly opposed to a highly reflective surface. Carbamazepine (CBZ) was used as a model drug, with polyvinyl pyrollidone-vinyl acetate co-polymer (PVP-VA) as a matrix and polyethylene glycol (PEG) as a plasticiser. The opacity of the molten extrudate varied from transparent at low CBZ loading to opaque at high CBZ loading. Particulate amorphous API and voids formed around these particles were found to cause the opacity. The extrusion process was monitored in real time using transflectance NIR; calibration and validation runs were performed using a wide range of drug and plasticiser loadings. Once calibrated, the technique was used to simultaneously track drug and plasticiser content during applied step changes in feedstock material. Rheological and thermal characterisations were used to help understand the morphology of extruded material. The study has shown that it is possible to use a single NIR spectroscopy technique to monitor opaque and transparent melts during HME, and to simultaneously monitor two distinct components within a formulation.

An experimental study has been performed to examine the crystallisation rate of poly(L)lactic acid (PLLA) blended with poly(D) lactic acid (PDLA) in order to reduce injection moulding cycle time. Optically pure PLLA was melt blended with up to 15wt% of its enantiomer PDLA in a twin screw extruder. Flow properties, melt strength and thermal properties of the blends were assessed. PLLA/PDLA blends were then injection moulded and allowed to crystallise using two different methods, either non-isothermally in a high temperature injection mould tool or isothermally by annealing moulded samples in a hot oven after conventional injection moulding. Mechanical and thermomechanical properties of the moulded samples were investigated and optical measurement of crystal formation using polarised light microscopy was performed at conditions representative of both crystallisation methods. Addition of PDLA was found to accelerate crystallisation rate by up to 80% and the resulting morphology demonstrated increased heat resistance, melt strength and stiffness, with a corresponding reduction in strain at break.

A study has been carried out to investigate controlled release performance of caplet shaped injection moulded (IM) amorphous solid dispersion (ASD) tablets based on the model drug AZD0837 and polyethylene oxide (PEO). The physical/chemical storage stability and release robustness of the IM tablets were characterized and compared to that of conventional extended release (ER) hydrophilic matrix tablets of the same raw materials and compositions manufactured via direct compression (DC). To gain an improved understanding of the release mechanisms, the dissolution of both the polymer and the drug were studied. Under conditions where the amount of dissolution media was limited, the controlled release ASD IM tablets demonstrated complete and synchronized release of both PEO and AZD0837 whereas the release of AZD0837 was found to be slower and incomplete from conventional direct compressed ER hydrophilic matrix tablets. The results clearly indicated that AZD0837 remained amorphous throughout the dissolution process and was maintained in a supersaturated state and hence kept stable with the aid of the polymeric carrier when released in a synchronized manner. In addition, it was found that the IM tablets were robust to variation in hydrodynamics of the dissolution environment and PEO molecular weight.

A systematic identification of the degradation products of hydroxypropyl methylcellulose phthalate (HPMCP) during hot melt extrusion (HME) has been performed. A reverse phase HPLC method was developed for the extrudates of both hydroxypropyl methylcellulose acetate succinate (HPMCAS) and HPMCP polymers to quantify their thermal hydrolytic products: acetic acid (AA), succinic acid (SA) for HPMCAS and phthalic acid (PA) for HPMCP, without hydrolysing the polymers in strong alkaline solutions. The polymers were extruded in the temperature range of 160-190 °C at different screw rotation speeds and hydrolytic impurities were analysed. Investigation of extruded HPMCP showed an additional thermal degradation product, who is structural elucidation revealed to be phthalic anhydride (PAH). Moreover, two environmental analytical impurities, dimethyl phthalate and methyl benzoate formed in situ were recorded on GC-MS and their origin was found to be associated with PAH derivatization. Using the experimental data gathered during this study, a degradation mechanism for HPMCP is proposed.

highlights � This paper discusses the energy conservation of an extruder. � This describes the energy and thermal efficiencies in polymer extrusion. � This explores the correlation between energy demand and thermal stability. � This explores radial temperature fluctuations of the melt flow in extrusion. � This models the total power demand in polymer extrusion empirically. abstract Thermal stability is of major importance in polymer extrusion, where product quality is dependent upon the level of melt homogeneity achieved by the extruder screw. Extrusion is an energy intensive process and optimisation of process energy usage while maintaining melt stability is necessary in order to pro- duce good quality product at low unit cost. Optimisation of process energy usage is timely as world energy prices have increased rapidly over the last few years. In the first part of this study, a general dis- cussion was made on the efficiency of an extruder. Then, an attempt was made to explore correlations between melt thermal stability and energy demand in polymer extrusion under different process settings and screw geometries. A commodity grade of polystyrene was extruded using a highly instrumented sin- gle screw extruder, equipped with energy consumption and melt temperature field measurement. More- over, the melt viscosity of the experimental material was observed by using an off-line rheometer. Results showed that specific energy demand of the extruder (i.e. energy for processing of unit mass of polymer) decreased with increasing throughput whilst fluctuation in energy demand also reduced. How- ever, the relationship between melt temperature and extruder throughput was found to be complex, with temperature varying with radial position across the melt flow. Moreover, the melt thermal stability dete- riorated as throughput was increased, meaning that a greater efficiency was achieved at the detriment of melt consistency. Extruder screw design also had a significant effect on the relationship between energy consumption and melt consistency. Overall, the relationship between the process energy demand and thermal stability seemed to be negatively correlated and also it was shown to be highly complex in nat- ure. Moreover, the level of process understanding achieved here can help to inform selection of equip- ment and setting of operating conditions to optimise both energy and thermal efficiencies in parallel. 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://

Hot melt extrusion has been used to produce a solid dispersion of the thermolabile drug artemisinin. Formulation and process conditions were optimized prior to evaluation of dissolution and biopharmaceutical performance. Soluplus®, a low Tg amphiphilic polymer especially designed for solid dispersions enabled melt extrusion at 110 °C although some drug-polymer incompatibility was observed. Addition of 5% citric acid as a pH modifier was found to suppress the degradation. The area under plasma concentration time curve (AUC0–24h) and peak plasma concentration (Cmax) were four times higher for the modified solid dispersion compared to that of pure artemisinin.

In this work, a highly instrumented single screw extruder has been used to study the effect of polymer rheology on the thermal efficiency of the extrusion process. Three different molecular weight grades of high density polyethylene (HDPE) were extruded at a range of conditions. Three geometries of extruder screws were used at several set temperatures and screw rotation speeds. The extruder was equipped with real-time quantification of energy consumption; thermal dynamics of the process were examined using thermocouple grid sensors at the entrance to the die. Results showed that polymer rheology had a significant effect on process energy consumption and thermal homogeneity of the melt. Highest specific energy consumption and poorest homogeneity was observed for the highest viscosity grade of HDPE. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. In particular, specific energy consumption was lower using a barrier flighted screw compared to single flighted screws at the same set conditions. These results highlight the complex nature of extrusion thermal dynamics and provide evidence that rheological properties of the polymer can significantly influence the thermal efficiency of the process.

An infrared temperature sensor has been used to provide real time quantification of the thermal homogeneity of polymer extrusion. The non-intrusive sensor was located in the barrel of a single screw extruder, positioned such that it provided a measurement of melt temperature in the channel of the metering section of the extruder screw. The rapid response of the technique enabled melt temperature within the extruder screw channel to be monitored in real time, allowing quantification of the thermal stability of the extrusion process. Two polyethylenes were used in experiments with three extruder screw geometries at a range of screw speeds. Data generated by the infrared sensor was found to be highly sensitive to thermal fluctuations relating to the melting performance of the extruder screw. Comparisons made with an intrusive thermocouple grid sensor located in the extruder die suggested that the infrared technique was able to provide a similar level of information without disturbing the process flow. This application on infrared thermometry could prove highly useful for industrial extrusion process monitoring and optimization. POLYM. ENG. SCI., 55:1059–1066, 2015. © 2014 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers

Polymer extrusion, in which a polymer is melted and conveyed to a mould or die, forms the basis of most polymer processing techniques. Extruders frequently run at non-optimised conditions and can account for 15–20% of overall process energy losses. In times of increasing energy efficiency such losses are a major concern for the industry. Product quality, which depends on the homogeneity and stability of the melt flow which in turn depends on melt temperature and screw speed, is also an issue of concern of processors. Gear pumps can be used to improve the stability of the production line, but the cost is usually high. Likewise it is possible to introduce energy meters but they also add to the capital cost of the machine. Advanced control incorporating soft sensing capabilities offers opportunities to this industry to improve both quality and energy efficiency. Due to strong correlations between the critical variables, such as the melt temperature and melt pressure, traditional decentralized PID (Proportional–Integral–Derivative) control is incapable of handling such processes if stricter product specifications are imposed or the material is changed from one batch to another. In this paper, new real-time energy monitoring methods have been introduced without the need to install power meters or develop data-driven models. The effects of process settings on energy efficiency and melt quality are then studied based on developed monitoring methods. Process variables include barrel heating temperature, water cooling temperature, and screw speed. Finally, a fuzzy logic controller is developed for a single screw extruder to achieve high melt quality. The resultant performance of the developed controller has shown it to be a satisfactory alternative to the expensive gear pump. Energy efficiency of the extruder can further be achieved by optimising the temperature settings. Experimental results from open-loop control and fuzzy control on a Killion 25 mm single screw extruder are presented to confirm the efficacy of the proposed approach.

A novel, green, and continuous method for solid-state polymorphic transformation of artemisinin by high temperature extrusion has recently been demonstrated. This communication describes attempts to understand the mechanisms causing phase transformation during the extrusion process. Polymorphic transformation was investigated using hot stage microscopy and a model shear cell. At high temperature, phase transformation from orthorhombic to the triclinic crystals was observed through a vapor phase. Under mechanical stress, the crystalline structure was disrupted continuously, exposing new surfaces and accelerating the transformation process.

Polymer extrusion is regarded as an energy-intensive production process, and the real-time monitoring of both energy consumption and melt quality has become necessary to meet new carbon regulations and survive in the highly competitive plastics market. The use of a power meter is a simple and easy way to monitor energy, but the cost can sometimes be high. On the other hand, viscosity is regarded as one of the key indicators of melt quality in the polymer extrusion process. Unfortunately, viscosity cannot be measured directly using current sensory technology. The employment of on-line, in-line or off-line rheometers is sometimes useful, but these instruments either involve signal delay or cause flow restrictions to the extrusion process, which is obviously not suitable for real-time monitoring and control in practice. In this paper, simple and accurate real-time energy monitoring methods are developed. This is achieved by looking inside the controller, and using control variables to calculate the power consumption. For viscosity monitoring, a ‘soft-sensor’ approach based on an RBF neural network model is developed. The model is obtained through a two-stage selection and differential evolution, enabling compact and accurate solutions for viscosity monitoring. The proposed monitoring methods were tested and validated on a Killion KTS-100 extruder, and the experimental results show high accuracy compared with traditional monitoring approaches.

Objectives To compare the properties of solid dispersions of felodipine for oral bioavailability enhancement using two different polymers, polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose acetate succinate (HPMCAS), by hot-melt extrusion (HME) and spray drying. Methods Felodipine solid dispersions were prepared by HME and spray drying techniques. PVP and HPMCAS were used as polymer matrices at different drug : polymer ratios (1 : 1, 1 : 2 and 1 : 3). Detailed characterization was performed using differential scanning calorimetry, powder X-ray diffractometry, scanning electron microscopy and in-vitro dissolution testing. Dissolution profiles were evaluated in the presence of sodium dodecyl sulphate. Stability of different solid dispersions was studied under accelerated conditions (40°C/75% RH) over 8 weeks. Key findings Spray-dried formulations were found to release felodipine faster than melt extruded formulations for both polymer matrices. Solid dispersions containing HMPCAS exhibited higher drug release rates and better wettability than those produced with a PVP matrix. No significant differences in stability were observed except with HPMCAS at a 1 : 1 ratio, where crystallization was detected in spray-dried formulations. Conclusions Solid dispersions of felodipine produced by spray drying exhibited more rapid drug release than corresponding melt extruded formulations, although in some cases improved stability was observed for melt extruded formulations.

The shear viscosity of polymethylmethacrylate (PMMA) melt is particularly investigated by using a twin-bore capillary rheometer at four temperatures of 210, 225, 240, and 255 � C with different capillary dies. Experimental results show that the geomet- rical dependence of shear viscosity is significantly dependent on melt pressure as well as melt temperature. The measured shear vis- cosity increases with the decrease of die diameter at lower temperatures (210 and 225 � C) but decreases with the decrease of die diameter at higher temperatures (240 and 255 � C). Based on the deviation of shear viscosity curves and Mooney method, negative slip velocity is obtained at low temperatures and positive slip velocity is obtained at high temperatures, respectively. Geometrical depend- ence and pressure sensitivity of shear viscosity as well as temperature effect are emphasized for this viscosity deviation. Moreover, shear viscosity curve at 210 � C deviates from the power law model above a critical pressure and then becomes less thinning. Mecha- nisms of the negative slip velocity at low temperatures are explored through Doolittle viscosity model and Barus equation, in which the pressure drop is used to obtain the pressure coefficient by curve fitting. Dependence of pressure coefficient on melt temperature suggests that the pressure sensitivity of shear viscosity is significantly affected by temperature. Geometrical dependence of shear vis- cosity can be somewhat weakened by increasing melt temperature. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3384-3394, 2013

Polymer extrusion is an energy intensive process, which is often run at less than optimal conditions. The extrusion process consists of gradual melting of solid polymer by thermal conduction and viscous shearing between a rotating screw and a barrel; as such it is highly dependent upon the frictional, thermal and rheological properties of the polymer. Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers, but in practice this is rarely achieved due to the lack of understanding of the process. Here, in-process monitoring techniques have been used to characterise the thermal dynamics of the extrusion process. Novel thermocouple grid sensors have been used to measure melt temperature fields within flowing polymer melts at the entrance to an extruder die in conjunction with infra-red thermometers and real-time quantification of energy consumption. A commercial grade of polyethylene has been examined using three extruder screw geometries at different extrusion operating conditions to understand the process efficiency. Extruder screw geometry, screw rotation speed and set temperature were found to have a significant effect on the thermal homogeneity of the melt and process energy consumed.

Polymer extrusion is an energy intensive production process andprocess energy efficiency has become a key concern in the currentindustry with the pressure of reducing the global carbonfootprint. Here, knowledge of the pattern of energy usage andlosses of each component in the plant is highly useful in theprocess energy optimization. Moreover, it is essential to maintainthe melt quality while improving the energy efficiency in polymerprocessing. In this work, an investigation was made on the totalenergy consumption, drive motor energy consumption, power factorand the melt temperature profile across the die melt flow (as anindication of the melt thermal quality) of an industrial scaleextruder with three different screw geometries, three polymertypes and wide range of processing conditions (altogether 135different processing situations were observed). This aims to widenthe knowledge on process energy and thermal behaviors whileexploring possible correlation/s between energy demand and meltquality (in terms of melt temperature fluctuations across the meltflow). The results showed that the level and fluctuations of theextruder's power factor is particularly dependent upon thematerial being processed. Moreover, it seems that there is arelation between the level of energy demand of the heaters and thelevel of melt temperature fluctuations. While the extruderspecific energy consumption decreases with increasing screw speed,specific energy consumption of the drive motor may have eitherincreasing or decreasing behavior. Overall, this study providesnew insights in a wide range on process energy demand and meltthermal quality in polymer extrusion. Moreover, further researchis recommended to establish strong correlation/s between processenergy consumption and melt thermal quality which should help toenhance process control and hence the product quality in singlescrew polymer extrusion.

The rheological characterization of polymer melts is strongly related to their material properties. In this study, we focused on the rheological behaviors of a polypropylene (PP) melt through a capillary die. With an advanced twin-bore capillary rheometer with dies measuring 1.0, 0.5, and 0.25 mm in diameter, experiments were performed over a shear-rate range of 3 × 102 to 5 × 103 s−1 at three temperatures, 210, 220, and 230 °C. The results demonstrate that the geometry dependence of the PP viscosity relied on the die diameter and the temperature of the PP melt. The viscosity values of the PP melt in the 0.25-mm diameter die were higher than were those in the 0.5- and 1.0-mm dies at 220 and 230 °C. However, the viscosity values in all of the tested dies were similar at 210 °C. The tendency for the viscosity to decrease as the temperature of the polymer melt increased weakened in the 0.25-mm diameter die. As a result, the pressure applied to the PP melt in the 0.25-mm diameter die increased; this caused a decrease in the free volume between molecules. On the basis of the Barus equation, the contribution of pressure to the changed viscosity in each die at each of the tested temperatures was calculated and was found to be as high as 32.86% in the 0.25-mm die at 230 °C. Additionally, the effect of the wall slip on the geometry dependence of the PP viscosity in the tested dies was investigated with a modified Mooney method. The values of the slip velocity revealed that wall slip occurred only in the 0.25-mm die at 210 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43459.

Melt temperature is one of the key variables in polymer extrusion which determines process thermal stability and hence melt quality. Therefore, melt temperature is commonly measured in polymer processing and point/bulk melt temperature measurement methods are widely used in the present industry. Some thermal profile measurement methods have also been attempted in research. This study presents a review of melt temperature measurements in polymer extrusion in research and industry, and describes the results of an experimental evaluation carried out to explore the performance of five melt temperature measurement techniques. In addition, an investigation was carried out on the fully developed melt temperature profile of a cylindrical rod die. Moreover, the existing challenges and possible future applications for extrusion thermal monitoring are discussed. The results confirmed that melt temperature varied significantly at different radial locations within the die. Point/bulk melt temperature measurements were found to provide relatively limited information on process thermal quality close to the die wall. Hence, information provided by these sensors is less representative of actual thermal conditions as they are unable to capture thermal information from the whole melt flow cross-section. Therefore, the importance of the development of industrially compatible thermal profile measurement techniques is emphasised.

The effect of maleic anhydride grafted polypropylene (MA-g-PP) compatibilizer on the mechanical and electrical properties of a polypropylene-carbon nanotube composite is presented. Commercially available grades of polypropylene homopolymer (PP) and multiwalled CNT (MCNT) were used to prepare composites (PP/MCNT) by melt compounding. The effects of maleic anhydride graft level and loading on material properties were investigated. The addition of MCNT without compatibilizer enhanced the mechanical properties of PP, whereas addition of both grades of MA-g-PP alone had a detrimental effect. When MA-g-PP was added as a compatiblizer to the PP/MCNT composite, flexural and tensile moduli increased, indicating that enhanced levels of MCNT dispersion within PP had been achieved. Strength of the nanocomposite decreased with the addition of both grades of MA-g-PP, possibly due to the deterioration of the mechanical properties of the polymer in the presence of lower molecular weight MA-g-PP. Electrical resistivity improved with both grades of MA-g-PP, with higher maleic anhydride graft levels having the most significant effect. Scanning electron microscopy analysis confirmed that the optimum state of dispersion was for the nanocomposite prepared with MA-g-PP with highest grafting level. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

The purpose of this work was to explore NIR spectroscopy as a PAT tool to monitor the formation of ibuprofen and nicotinamide cocrystals during extrusion based solvent free continuous cocrystallization (SFCC). Drug and co-former were gravimetrically fed into a heated co-rotating twin screw extruder to form cocrystals. Real-time process monitoring was performed using a high temperature NIR probe in the extruder die to assess cocrystal content and subsequently compared to off-line powder X-ray diffraction measurements. The effect of processing variables, such as temperature and mixing intensity, on the extent of cocrystal formation was investigated. NIR spectroscopy was sensitive to cocrystal formation with the appearance of new peaks and peak shifts, particularly in the 4800–5200 cm−1 wave-number region. PXRD confirmed an increased conversion of the mixture into cocrystal with increase in barrel temperature and screw mixing intensity. A decrease in screw rotation speed also provided improved cocrystal yield due to the material experiencing longer residence times within the process. A partial least squares analysis in this region of NIR spectrum correlated well with PXRD data, providing a best fit with cocrystal conversion when a limited range of process conditions were considered, for example a single set temperature. The study suggests that NIR spectroscopy could be used to monitor cocrystal purity on an industrial scale using this continuous, solvent-free process.

Reproducible control of stoichiometry and difficulties in large scale production have been identified as two of the major challenges to commercial uptake of pharmaceutical co-crystals. The aim of this research was to extend the application of SFCC to control stoichiometry in caffeine: maleic acid co-crystals. Both 1:1 and 2:1 caffeine: maleic acid co-crystals were produced by control of the feedstock composition and process conditions. It was also observed that formation of 2:1 stoichiometry co-crystals involved formation of a 1:1 cocrystal which was subsequently transformed to 2:1 co-crystals. The investigation of stoichiometric transformation revealed that although 1:1 co-crystals could be converted into 2:1 form with addition of excess caffeine, the reverse was not possible in the presence of excess maleic acid. However, conversion from 2:1 into 1:1 was only achieved by melt seeding with the phase pure 1:1 co-crystals. This investigation demonstrates that stoichiometric control can be achieved by SFCC by control of parameters such as extrusion temperature.

A comparison of high rate extrusion rheometry was undertaken to assess the reproducibility of shear viscosity results obtained using standard laboratory extrusion rheometers and a Fanuc Roboshot injection moulding machine. Lower shear rate measurements were carried out using oscillatory and rotational rheometers to provide independent comparison of shear viscosity values in the regions of overlap between the methods. Shear viscosities were obtained at shear rates in the range 13 s-1 to 2.6 x 10^6 s-1 by capillary extrusion rheometry and up to 6 x 10^6 s-1 using a Fanuc Roboshot moulding machine. A significant source of error due to leakage of sample past the piston at the high pressures accounting for a factor of x10 error in measured shear viscosity was addressed through modification of the piston head to provide better sealing. The high shear rate results generally demonstrated an overall good level of agreement for shear viscosities up to a shear rate of 2 x 10^5 s-1, with results varying typically by up to no more than approximately ± 20%. This level of reproducibility is considered to be favourable compared with the reproducibility value of ± 28% (95% confidence level) identified for capillary extrusion rheometry measurements at lower shear rates in ISO 11443 [1]. At higher shear rates, e.g. above a shear rate of 360,000 s-1 for polystyrene, deviations in the shear thinning behaviour were apparent, potentially linked to the pressure dependence of viscosity [2]. The effect of the Rabinowitsch correction on true shear viscosity - shear rate data has been highlighted with reference to the high density polyethylene that had a low value for its shear thinning coefficient n. This correction introduces a potentially large degree of uncertainty in the corrected shear viscosity values at high shear rates.