There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Progress on the morphological control of conductive network in conductive polymer composites and the use as electroactive multifunctional materials

This review provides a critical assessment of the use of cellulosic materials for reinforcement in polymer composites. The review focuses on structure–property interrelationships and the compatibilization of cellulosic materials for optimal performance of the resulting composite materials. Optimal material and physical properties are characterized on the basis of the reinforcement’s physical dimension and the nature of the interface between reinforcement and matrix. We explore how very different cellulosic materials—bacterial, microcrystalline, microfibrillated or nanocrystalline—can cause distinctly different reinforcment.

Cellulose reinforced polymer composites and nanocomposites: a critical review

Pharmaceutical cocrystals and poorly soluble drugs.

Strength and toughness of crystalline polymer systems

To explore hot melt extrusion (HME) as a scalable, solvent-free, continuous technology to design cocrystals in agglomerated form. Cocrystal agglomerates of ibuprofen and nicotinamide in 1:1 ratio were produced using HME at different barrel temperature profiles, screw speeds, and screw configurations. Product was characterized for crystallinity by XRPD and DSC, while the morphology was determined by SEM. Dissolution rate and tabletting properties were compared with ibuprofen. Process parameters significantly affected the extent of cocrystallization which improved with temperature, applied shear and residence time. Processing above eutectic point was required for cocrystallization to occur, and it improved with mixing intensity by changing screw configuration. Product was in the form of spherical agglomerates, which showed directly compressible nature with enhanced dissolution rate compared to ibuprofen. This marks an important advantage over the conventional techniques, as it negates the need for further size modification steps. A single-step, scalable, solvent-free, continuous cocrystallization and agglomeration technology was developed using HME, offering flexibility for tailoring the cocrystal purity. HME being an established technology readily addresses the regulatory demand of quality by design (QbD) and process analytical technology (PAT), offering high potential for pharmaceuticals.

Cocrystalization and Simultaneous Agglomeration Using Hot Melt Extrusion

Experimental observations of melt temperature profiles and melting performance of extruder screws are reported. A novel temperature sensor consisting of a grid of thermocouple junctions was used to take multiple temperature readings in real time across melt flow in a single screw extruder. Melt pressure in the die and power consumption were also monitored. Three extruder screws at a range of screw speeds were examined for a commercial grade of low density polyethylene. Results showed melt temperature fields at low throughputs to be relatively independent of screw geometry with a flat-shaped temperature profile dominated by conduction. At high throughputs, melting performance and measured temperature fields were highly dependent upon screw geometry. A barrier-flighted screw with Maddock mixer achieved significantly better melting than single flighted screws. Low temperature “shoulder” regions were observed in the temperature profiles of single-flighted screws at high throughput, due to late melting of the solid bed. Stability of the melt flow was also dependent upon screw geometry and the barrier-flighted screw achieving flow with lower variation in melt pressure and temperature. Dimensionless numbers were used to analyze the relative importance of conduction, convection, and viscous shear to the state of the melt at a range of extrusion conditions. Polym. Eng. Sci. 46:1706–1714, 2006. © 2006 Society of Plastics Engineers

The effect of screw geometry on melt temperature profile in single screw extrusion

The growth in Micro Electro-Mechanical Systems (MEMS) and demand for functional devices at smaller and smaller length scales has placed increasing demands on industry for product miniaturisation. Consequently, the micro-injection moulding (micromoulding) technology has evolved for the mass production of minute, intricate, polymer and composite components. Although there has been significant growth in the technology, there is little understanding of the effects of the process dynamics on product properties. This paper presents details of a programme of work conducted within these laboratories with the objectives of enhancing the understanding of polymer processing–property interaction. More particularly, the effects of microscale processing on the rheological, mechanical and tribological properties of engineering and commodity polymers, nanocomposites, metal and ceramic injection moulded feedstock and biomaterials are being explored. Simple analysis reveals that process conditions are potentially m...

Micromoulding: process measurements, product morphology and properties.

Over the last decade, there has been an increased drive in the polymer industry toward the development of in-line monitoring techniques for analysis of melt processing. Manufacture of high material volumes combined with stringent quality-control restrictions and the requirement for tailored end-user products, have made the implementation of analytical methods essential for measurement of material characteristics. This paper presents the application of a range of spectroscopic techniques for in-line analysis of polymer extrusion processes. Fourier transform near-infrared (FT-NIR), Raman and fluorescence spectroscopy have been successfully implemented as tools to monitor a range of processing characteristics including copolymer melt and additive composition, material residence time distribution and degree of polymerization. In combination with partial least squares (PLS) chemometric analysis, these spectroscopic techniques are demonstrated to be sensitive and robust tools for monitoring a wide range of chem...

Philip D. Coates

Papers

Cocrystalization and Simultaneous Agglomeration Using Hot Melt Extrusion

The effect of screw geometry on melt temperature profile in single screw extrusion

Micromoulding: process measurements, product morphology and properties.

Process monitoring of polymer melts using in-line spectroscopy:

Application of an elastic model to the large deformation, high temperature stretching of polypropylene