Ring-opening polymerization in molten PEEK: transient reduction of melt-viscosity by macrocyclic aromatic thioetherketones

Blends of PEEK with macrocyclic thioether-ketones show initial melt-viscosities reduced by more than an order of magnitude relative to the polymer itself, enabling more facile processing and fabrication. On raising the temperature of the melt, however, the macrocycle undergoes spontaneous, entropically-driven ring-opening polymerization (ED-ROP), so that the properties of the final polymer should not, in principle, be compromised by the presence of low-MW macrocyclic material.

A Comparison of Deep Drawing and Ironing of Metal Alloy Strip Produced conventionally and Non-conventionally via Semi Solid Material Processing

A semi solid thin strip continuous casting process was used to obtain 50%wt Pb/50%wtSn strip by single and twin roll processing at speed of 15 m/min. A 50%wt Pb/50%wtSn plate ingot was also cast for rolling conventionally into strips of 1.4 mm thickness and 45 mm width for comparison with those achieved non-conventionally. This hypoeutectic alloy has a solidification interval and fusion temperature of approximately 31 degrees C and 215 degrees C respectively. The casting alloy temperature was around 280 degrees C as measured by a type K immersion thermocouple prior to pouring into a tundish designed to maintain a constant melt flow on the cooling slope during semi solid material production. A nozzle with a weir ensures that the semi solid material is dragged smoothly by the lower roll, producing strip with minimum contamination of slag/oxide. The temperatures of the cooling slope and the lower roll were also monitored using K type thermocouples. The coiled semi solid strip, which has a thickness of 1.5 mm and 45 mm width, was rolled conventionally in order to obtain 1.2 mm thick strip. The coiled thixorolled strip had a thickness of 1.2 mm and achieved practically the same width as the conventional strips. Blanks of 40 mm diameter were cut from the strips in a mechanical press, ready for deep drawing and ironing for mechanical characterization. All the strips achieved from non-conventional processing had the same mechanical performance as those achieved conventionally. The limiting drawing ratio (LDR) achieved was approximately 2.0 for all strips. Microscopy examination was made in order to observe phase segregation during processing.

Sintering of tin oxide and its applications in electronics and processing of high purity optical glasses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efficient fabrication of polymer nanocomposites with effective exfoliation and dispersion by solid-state/melt extrusion

In this communication, solid-state/melt extrusion (SSME) is introduced as a novel technique that combines solid-state shear pulverization (SSSP) and conventional twin screw extrusion (TSE) in a single extrusion system. The morphology and property enhancements in a model linear low-density polyethylene/organically modified clay nanocomposite sample fabricated via SSME were compared to those fabricated via SSSP and TSE. The results show that SSME is capable of exfoliating and dispersing the nanofillers similarly to SSSP, while achieving a desirable output rate and producing extrudate similar in form to that from TSE.

Characterization of Biodegradable Polymer Nanocomposites Fabricated via Solid-State Processing

Biodegradable polymer/clay nanocomposites were prepared withpristine and organically modified montmorillonite in polylactic acid (PLA) and polycaprolactone (PCL) polymer matrices. Nanocomposites were fabricated using extrusion and SSSP to compare the effects of melt-state and solid-state processing on the morphology of the final nanocomposite. Characterization of various material properties was performed on prepared biodegradable polymer/clay nanocomposites to evaluate property enhancements from different clays and/or processing methods.

The Crystallization Kinetics of Polylactic Acid (Pla) Processed Through Solid-State/Melt Extrusion

Polylactic acid (PLA) is a bio-derived, biodegradable polymer with a number of similar mechanical properties to commodity plastics like polyethylene (PE) and polyethylene terephthalate (PETE). There has recently been a great interest in using PLA to replace these typical petroleum-derived polymers because of the developing trend to use more sustainable materials and technologies. However, PLA¿s inherent slow crystallization behavior is not compatible with prototypical polymer processing techniques such as molding and extrusion, and in turn inhibits its widespread use in industrial applications. In order to make PLA into a commercially-viable material, there is a need to process the material in such a way that its tendency to form crystals is enhanced. The industry standard for producing PLA products is via twin screw extrusion (TSE), where polymer pellets are fed into a heated extruder, mixed at a temperature above its melting temperature, and molded into a desired shape. A relatively novel processing technique called solid-state shear pulverization (SSSP) processes the polymer in the solid state so that nucleation sites can develop and fast crystallization can occur. SSSP has also been found to enhance the mechanical properties of a material, but its powder output form is undesirable in industry. A new process called solid-state/melt extrusion (SSME), developed at Bucknell University, combines the TSE and SSSP processes in one instrument. This technique has proven to produce moldable polymer products with increased mechanical strength. This thesis first investigated the effects of the TSE, SSSP, and SSME polymer processing techniques on PLA. The study seeks to determine the process that yields products with the most enhanced thermal and mechanical properties. For characterization, percent crystallinity, crystallization half time, storage modulus, softening temperature, degradation temperature and molecular weight were analyzed for all samples. Through these characterization techniques, it was observed that SSME-processed PLA had enhanced properties relative to TSE- and SSSP-processed PLA. Because of the previous findings, an optimization study for SSME-processed PLA was conducted where throughput and screw design were varied. The optimization study determined PLA processed with a low flow rate and a moderate screw design in an SSME process produced a polymer product with the largest increase in thermal properties and a high retention of polymer structure relative to TSE-, SSSP-, and all other SSME-processed PLA. It was concluded that the SSSP part of processing scissions polymer chains, creating defects within the material, while the TSE part of processing allows these defects to be mixed thoroughly throughout the sample. The study showed that a proper SSME setup allows for both the increase in nucleation sites within the polymer and sufficient mixing, which in turn leads to the development of a large amount of crystals in a short period of time.

Processing and mechanical properties of cast aluminum containing scandium, zirconium, and ytterbium

A series of aluminum alloys containing additions of scandium, zirconium, and ytterbium were cast to evaluate the effect of partial ytterbium substitution for scandium on tensile behavior. Due to the high price of scandium, a crucible-melt interaction study was performed to ensure no scandium was lost in graphite, alumina, magnesia, or zirconia crucibles after holding a liquid Al-Sc master alloy for 8 hours at 900 °C in an argon atmosphere. The alloys were subjected to an isochronal aging treatment and tested for conductivity and Vickers microhardness after each increment. For scandium-containing alloys, peak hardnesses of 520-790 MPa, and peak tensile stresses of 138-234 MPa were observed after aging from 150-350 °C for 3 hours in increments of 50 °C, and for alloys without scandium, peak hardnesses of 217-335 MPa and peak tensile stresses of 45-63 MPa were observed after a 3 hour, 150 °C aging treatment. The hardness and tensile strength of the ytterbium containing alloy was found to be lower than in the alloy with no ytterbium substitution.

Processing and Characterization of Nano-biocomposites Based on Mater-Bi® with Layered Silicates

The development of new nano-biocomposites has been one of the main research areas of interest in polymer science in recent years, since they can combine the intrinsic biodegradable nature of matrices with the ability to modify their properties by the addition of selected nano-reinforcements. In this work, the addition of mineral nanoclays (montmorillonites and sepiolites) to a commercial starch-based matrix is proposed. A complete study on their processing by melt-intercalation techniques and further evaluation of the main properties of nano-biocomposites has been carried out. The results reported show an important influence of the nano-biocomposites morphology on their final properties. In particular, the rheological and viscoelastic characteristics of these systems are very sensitive to the dispersion level of the nanofiller, but it is possible to assess that the material processing behaviour is not compromised by the presence of these nano-reinforcements. In general, both nanofillers had a positive influence in the materials final properties. Mechanical performance shows improvements in terms of elastic modulus, without important limitations in terms of ductility. Thermal properties are improved in terms of residual mass after degradation and low improvements are also observed in terms of oxygen barrier properties.

Applications of thermal processing in pharmaceutical drug product development

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Quantifying ice-shelf basal melt and ice-stream dynamics using high-resolution DEM and GPS time series

Thesis (Ph.D.)--University of Washington, 2016-06

Yield behaviour of a melt-compounded polyethylene-intercalated montmorillonite nanocomposite

The yield behaviour of a series of melt-mixed polyethylene-modified montmorillonite nanocomposites has been studied as a function of temperature and strain rate and compared to the behaviour of the base polymer. The processing conditions used gave an intercalated structure as assessed by X-ray diffraction. Although there was a modest improvement in stiffness with clay content, the yield behaviour was insensitive to the addition of the clay. Both the base polymer and the nanocomposites showed double yield points. These were analysed as activated rate processes, with the activation energies consistent with the low strain yield point being associated with the alpha(2) molecular relaxation and the higher strain yield point with W axis slip. (C) 2003 Society of Chemical Industry.

Reactive processing methods for functionalisation of polymers and in-situ compatibilisation of poly(ethylene terephthalate)-based blends

One of the main objectives of this study was to functionalise various rubbers (i.e. ethylene propylene copolymer (EP), ethylene propylene diene terpolymer (EPDM), and natural rubber (NR)) using functional monomers, maleic anhydride (MA) and glycidyl methacrylate (GMA), via reactive processing routes. The functionalisation of the rubber was carried out via different reactive processing methods in an internal mixer. GMA was free-radically grafted onto EP and EPDM in the melt state in the absence and presence of a comonomer, trimethylolpropane triacrylate (TRlS). To optinuse the grafting conditions and the compositions, the effects of various paranleters on the grafting yields and the extent of side reactions were investigated. Precipitation method and Soxhlet extraction method was established to purifY the GMA modified rubbers and the grafting degree was determined by FTIR and titration. It was found that without TRlS the grafting degree of GMA increased with increasing peroxide concentration. However, grafting was low and the homopolymerisation of GMA and crosslinking of the polymers were identified as the main side reactions competing with the desired grafting reaction for EP and EPDM, respectively. The use of the tri-functional comonomer, TRlS, was shown to greatly enhance the GMA grafting and reduce the side reactions in terms of the higher GMA grafting degree, less alteration of the rheological properties of the polymer substrates and very little formation of polyGMA. The grafting mechanisms were investigated. MA was grafted onto NR using both thermal initiation and peroxide initiation. The results showed clearly that the reaction of MA with NR could be thermally initiated above 140°C in the absence of peroxide. At a preferable temperature of 200°C, the grafting degree was increased with increasing MA concentration. The grafting reaction could also be initiated with peroxide. It was found that 2,5-dimethyl-2,5-bis(ter-butylproxy) hexane (TIOI) was a suitable peroxide to initiate the reaction efficiently above I50°C. The second objective of the work was to utilize the functionalised rubbers in a second step to achieve an in-situ compatibilisation of blends based on poly(ethylene terephthalate) (PET), in particular, with GMA-grafted-EP and -EPDM and the reactive blending was carried out in an internal mixer. The effects of GMA grafting degree, viscosities of GMAgrafted- EP and -EPDM and the presence of polyGMA in the rubber samples on the compatibilisation of PET blends in terms of morphology, dynamical mechanical properties and tensile properties were investigated. It was found that the GMA modified rubbers were very efficient in compatibilising the PET blends and this was supported by the much finer morphology and the better tensile properties. The evidence obtained from the analysis of the PET blends strongly supports the existence of the copolymers through the interfacial reactions between the grafted epoxy group in the GMA modified rubber and the terminal groups of PET in the blends.

Investigation of the oxidative degradation mechanisms and melt stabilisation of a new generation metallocene polytehylene

The two main objectives of the research work conducted were firstly, to investigate the processing and rheological characteristics of a new generation metallocene catalysed linear low density polyethylene (m-LLDPE), in order to establish the thermal oxidative degradation mechanism, and secondly, to examine the role of selected commercial stabilisers on the melt stability of the polymers. The unstabilised m-LLDPE polymer was extruded (pass I) using a twin screw extruder, at different temperatures (210-285°C) and screw speeds (50-20rpm) and was subjected to multiple extrusions (passes, 2-5) carried out under the same processing conditions used in the first pass. A traditional Ziegler/Natta catalysed linear low density polyethylene (z-LLDPE) produced by the same manufacturer was also subjected to a similar processing regime in order to compare the processability and the oxidative degradation mechanism (s) of the new m-LLDPE with that of the more traditional z-LLDPE. The effect of some of the main extrusion characteristics of the polymers (m-LLDPE and z-LLDPE) on their melt rheological behaviour was investigated by examining their melt flow performance monitored at two fixed low shear rate values, and their rheological behaviour investigated over the entire shear rates experienced during extrusion using a twin-bore capillary rheometer. Capillary rheometric measurements, which determine the viscous and elastic properties of polymers, have shown that both polymers are shear thinning but the m-LLDPE has a higher viscosity than z-LLDPE and the extent of reduction in viscosity of the former when the extrusion temperature was increased from 210°C to 285°C was much higher than in the case of the z-LLDPE polymer. This was supplied by the findings that the m-LLDPE polymer required higher power consumption under all extrusion conditions examined. It was fUliher revealed that the m-LLDPE undergoes a higher extent of melt fracture, the onset of which occurs under much lower shear rates than the Ziegler-based polymer and this was attributed to its higher shear viscosity and narrower molecular weight distribution (MWD). Melt flow measurements and GPC have shown that after the first extrusion pass, the initial narrower MWD of m-LLDPE is retained (compared to z-LLDPE), but upon further multiple extrusion passes it undergoes much faster broadening of its MWD which shifts to higher Mw polymer fractions, paliicularly at the high screw speeds. The MWD of z-LLDPE polymer on the other hand shifts towards the lower Mw end. All the evidence suggest therefore the m-LLDPE undergoes predominantly cross-linking reactions under all processing conditions whereas z-LLDPE undergoes both cross-linking and chain scission reactions with the latter occurring predominantly under more severe processing conditions (higher temperatures and screw speeds, 285°CI200rpm). The stabilisation of both polymers with synergistic combinations of a hindered phenol (Irganox 1076) and a phosphite (Weston 399) at low concentrations has shown a high extent of melt stabilisation in both polymers (extrusion temperatures 210-285°C and screw speeds 50-200rpm). The best Irganox 1076/Weston 399 system was found to be at an optimum 1:4 w/w ratio, respectively and was found to be most effective in the z-LLDPE polymer. The melt stabilising effectiveness of a Vitamin E/Ultranox 626 system used at a fraction of the total concentration of Irganox 1076/Weston 399 system was found to be higher in both polymers (under all extrusion conditions). It was found that AOs which operate primarily as alkyl (Re) radical scavengers are the most effective in inhibiting the thermal oxidative degradation of m-LLDPE in the melt; this polymer was shown to degrade in the melt primarily via alky radicals resulting in crosslinking. Metallocene polymers stabilised with single antioxidants of Irganox HP 136 (a lactone) and Irganox E201 (vitamin E) produced the highest extent of melt stability and the least discolouration during processing (260°C/1 OOrpm). Furthermore, synergistic combinations of Irganox HP I 36/Ultranox 626 (XP-60) system produced very high levels of melt and colour stability (comparable to the Vitamin E based systems) in the mLLDPE polymer. The addition of Irganox 1076 to an Irganox HP 136/Ultranox 626 system was found not to result in increasing melt stability but gave rise to increasing discolouration of the m-LLDPE polymer. The blending of a hydroxylamine (lrgastab FS042) with a lactone and Vitamin E (in combination with a phosphite) did not increase melt stability but induced severe discolouration of resultant polymer samples.

Compatibilisation of heterogeneous polymer blends by reactive processing

Functionalisation of polystyrene, PS, and ethylene-co-propylene-co-cyclopentadiene terpolymer, EPDM, with acrylic acid, AA, in a melt reactive processing procedure, in the presence of peroxide, trigonox 101, and coagents, Divinyl benzene, DVB (for PS), and trimethylolpropane triacrylate, TRIS (for EPDM), were successfully carried out. The level of grafting of the AA, as determined by infrared analysis, was significantly enhanced by the coagents. The grafting reaction of AA takes place simultaneously with homopolymerisation of the monomers, melt degradation and crosslinking reactions of the polymers. The extent of these competing reactions were inferred from measurements of melt flow index and insoluble gel content. Through a judicious use of both the peroxide and the coagent, particularly TRIS, unwanted side reactions were minimized. Five different processing methods were investigated for both functionalisation experiments; the direct addition of the pre-mixed polymer with peroxide and reactive modifiers was found to give optimum condition for grafting. The functionalised PS, F-PS, and EPDM, F-EPD, and maleinised polypropylene carrying a potential antioxidant, N-(4-anilinophenyl maleimide), F-PP were melt blended in binary mixtures of F-PS/F-EPD and F-PP/F-EPD in the presence (or absence) of organic diamines which act as an interlinking agent, e.g, Ethylene Diamine, EDA, and Hexamethylene Diamine, HEMDA. The presence of an interlinking agent, particularly HEMDA shows significant enhancement in the mechanical properties of the blend, suggesting that the copolymer formed has acted as compatibiliser to the otherwise incompatible polymer pairs. The functionalised and amidised blends, F and A-PSIEPDM (SPOI) and F and A-PPIEPDM (SPD2) were subsequently used as compatibiliser concentrates in the corresponding PSIEPDM and PPIEPDM blends containing various weight propotion of the homopolymers. The SPD1 caused general decreased in tensile strength, albeit increased in drop impact strength particularly in blend containing high PS content (80%). The SPD2 was particularly effective in enhancing impact strength in blends containing low weight ratio of PP (<70%). The SPD2 was also a good thermal antioxidant albeit less effective than commercial antioxidant. In all blends the evidence of compatibility was examined by scanning electron microscopy.

The chemical modification of polymer blends by reactive processing

The primary objective of this research was to examine the concepts of the chemical modification of polymer blends by reactive processing using interlinking agents (multi-functional, activated vinyl compounds; trimethylolpropane triacrylates {TRIS} and divinylbenzene {DVD}) to target in-situ interpolymer formation between immiscible polymers in PS/EPDM blends via peroxide-initiated free radical reactions during melt mixing. From a comprehensive survey of previous studies of compatibility enhancement in polystyrene blends, it was recognised that reactive processing offers opportunities for technological success that have not yet been fully realised; learning from this study is expected to assist in the development and application of this potential. In an experimental-scale operation for the simultaneous melt blending and reactive processing of both polymers, involving manual injection of precise reactive agent/free radical initiator mixtures directly into molten polymer within an internal mixer, torque changes were distinct, quantifiable and rationalised by ongoing physical and chemical effects. EPDM content of PS/EPDM blends was the prime determinant of torque increases on addition of TRIS, itself liable to self-polymerisation at high additions, with little indication of PS reaction in initial reactively processed blends with TRIS, though blend compatibility, from visual assessment of morphology by SEM, was nevertheless improved. Suitable operating windows were defined for the optimisation of reactive blending, for use once routes to encourage PS reaction could be identified. The effectiveness of PS modification by reactive processing with interlinking agents was increased by the selection of process conditions to target specific reaction routes, assessed by spectroscopy (FT-IR and NMR) and thermal analysis (DSC) coupled dichloromethane extraction and fractionation of PS. Initiator concentration was crucial in balancing desired PS modification and interlinking agent self-polymerisation, most particularly with TRIS. Pre-addition of initiator to PS was beneficial in the enhancement of TRIS binding to PS and minimisation of modifier polymerisation; believed to arise from direct formation of polystyryl radicals for addition to active unsaturation in TRIS. DVB was found to be a "compatible" modifier for PS, but its efficacy was not quantified. Application of routes for PS reaction in PS/EPDM blends was successful for in-situ formation of interpolymer (shown by sequential solvent extraction combined with FT-IR and DSC analysis); the predominant outcome depending on the degree of reaction of each component, with optimum "between-phase" interpolymer formed under conditions selected for equalisation of differing component reactivities and avoidance of competitive processes. This was achieved for combined addition of TRIS+DVB at optimum initiator concentrations with initiator pre-addition to PS. Improvements in blend compatibility (by tensiles, SEM and thermal analysis) were shown in all cases with significant interpolymer formation, though physical benefits were not; morphology and other reactive effects were also important factors. Interpolymer from specific "between-phase" reaction of blend components and interlinking agent was vital for the realisation of positive performance on compatibilisation by the chemical modification of polymer blends by reactive processing.