Yes / Polymer nanocomposites are usually characterized using various methods, such as small angle X-ray diffraction (XRD) or transmission electron microscopy, to gain insights into the morphology of the material. The disadvantages of these common characterization methods are that they are expensive and time consuming in terms of sample preparation and testing. In this work, near infrared spectroscopy (NIR) spectroscopy is used to characterize nanocomposites produced using a unique twin-screw mini-mixer, which is able to replicate, at ~25 g scale, the same mixing quality as in larger scale twin screw extruders. We correlated the results of X-ray diffraction, transmission electron microscopy, G′ and G″ from rotational rheology, Young’s modulus, and tensile strength with those of NIR spectroscopy. Our work has demonstrated that NIR-technology is suitable for quantitative characterization of such properties. Furthermore, the results are very promising regarding the fact that the NIR probe can be installed in a nanocomposite-processing twin screw extruder to measure inline and in real time, and could be used to help optimize the compounding process for increased quality, consistency, and enhanced product properties

Yes / Impact resistance of polypropylene fibre-reinforced concrete was investigated using the repeated drop weight impact test recommended by ACI Committee 544. The results were analysed based on a statistical approach. The variation in results was examined within the same batch and between different batches. Statistical parameters were compared with reported variations in impact resistance of concrete composites reinforced with other types of fibres such as carbon and steel fibres. Statistical analysis indicated that the results obtained from this test had large variations and it is necessary to increase the number of replications to at least 40 specimens per concrete mix to assure an error below 10%. It is concluded that this test with its current procedures and recommendations should not be considered a reliable impact test. This study has highlighted the need for modifying this test in such a way as that increases its accuracy and reduces the large variation in results.

No

Yes / Polypropylene has been oriented by solid-phase deformation processing to draw ratios up to ∼16, increasing tensile stiffness along the draw direction by factors up to 12. Nanoindentation of these materials showed that moduli obtained for indenter tip motion along the drawing direction (3) into to 1–2 plane (axial indentation) were up to 60% higher than for indenter tip motion along the 2 direction into the 1–3 plane (transverse indentation). In static tests, tensile and compressive determinations of elastic modulus gave results differing by factors up to ∼5 for strain along the draw direction. A material model incorporating both orthotropic elasticity and tension/compression asymmetry was developed for use with Finite Element simulations. Elastic constants for the oriented polypropylene were obtained by combining static testing and published ultrasonic data, and used as input for nanoindentation simulations that were quantitatively successful. The significance of the tension/compression asymmetry was demonstrated by comparing these predictions with those obtained using tensile data only, which gave predictions of indentation modulus higher by up to 70%.

The synthesis of molecularly designed poly(propylene oxide) was accomplished by using aluminum porphyrin initiator/catalysts to prepare controlled molecular weights, narrow molecular weight distributions, topologies, and functionalities. Poly(propylene oxide) has been an important intermediate in macromolecular synthesis. However, lack of control via the conventional potassium hydroxide initiated synthetic method limits the applications of this polymer. In the synthesis of poly(propylene oxide) by using aluminum porphyrin catalyst system, polymerization occurred by exclusive cleavage of the epoxide methylene oxygen bond via nucleophilic attack. This type of ring opening polymerization yields to head to tail configuration with asymmetric monomers. The aluminum porphyrin allowed the synthesis of poly(propylene oxide) with a high molecular weight of ca. 100,000 g/mole and narrow molecular weight distribution, indicating a living nature of this system. A variety of reactive functional end groups, including both primary and secondary hydroxyl and amine could be incorporated in the polymer chains through the modification of the original catalyst with chain transfer agents such as bisphenol A or p-nitro phenol. These reagents also permitted very significant reductions in the required concentration of the catalyst. The well defined poly(propylene oxide)s allowed the systematic study of effects of functional end groups on thermal degradation behavior. Interestingly, aromatic amine and aromatic nitro end groups significantly improved the thermal stability, whereas the presence of unsaturated end groups caused very adverse effects. Some of the functionally terminated poly(propylene oxide)s were utilized in the synthesis of block and segmented copolymers to examine the well defined structures as characterized by spectroscopic analysis. The aluminum porphyrin catalyst system was also used to produce statistical copolymers of propylene oxide and allyl glycidyl ether or caprolactone. / Ph. D.

Yes / Polypropylene is one type of plastic that is widely used in our everyday life. This study focuses on the identification and justification of the optimum process parameters for polypropylene production in a novel pilot plant based fluidized bed reactor. This first-of-its-kind statistical modeling with experimental validation for the process parameters of polypropylene production was conducted by applying ANNOVA (Analysis of variance) method to Response Surface Methodology (RSM). Three important process variables i.e., reaction temperature, system pressure and hydrogen percentage were considered as the important input factors for the polypropylene production in the analysis performed. In order to examine the effect of process parameters and their interactions, the ANOVA method was utilized among a range of other statistical diagnostic tools such as the correlation between actual and predicted values, the residuals and predicted response, outlier t plot, 3D response surface and contour analysis plots. The statistical analysis showed that the proposed quadratic model had a good fit with the experimental results. At optimum conditions with temperature of 75 °C, system pressure of 25 bar and hydrogen percentage of 2%, the highest polypropylene production obtained is 5.82% per pass. Hence it is concluded that the developed experimental design and proposed model can be successfully employed with over a 95% confidence level for optimum polypropylene production in a fluidized bed catalytic reactor (FBCR).

As a preliminary starting point for the present study, physical and mechanical properties of polypropylene nanocomposites (PPNCs) for samples received from Queen's University Belfast have been evaluated. Subsequently, polymer/clay nanocomposite material has been produced at Bradford. Mixing and processing routes have been explored, and mechanical properties for the different compounded samples have been studied. Clay intercalation structure has received particular attention to support the ultimate objective of optimising tensile and fracture behaviour of isotropic and die-drawn PPNCs. Solid-state molecular orientation has been introduced to PPNCs by the die-drawing process. Tensile stress-strain measurements with video-extensometry and tensile fracture of double edge-notched tensile specimens have been used to evaluate the Young's modulus at three different strain rates and the total work of fracture toughness at three different notch lengths. The polymer composite was analyzed by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, wide angle x-ray diffraction, and transmission electron microscopy. 3% and 5% clay systems at various compatibilizer (PPMA) loadings were prepared by three different mixing routes for the isotropic sheets, produced by compression moulding, and tensile bars, produced by injection moulding process. Die-drawn oriented tensile bars were drawn to draw ratio of 2, 3 and 4. The results from the Queen's University Belfast samples showed a decrement in tensile strength at yield. This might be explained by poor bonding, which refers to poor dispersion. Voids that can be supported by intercalated PP/clay phases might be responsible for improvement of elongation at break. The use of PPMA and an intensive mixing regime with a two-step master batch process overcame the compatibility issue and achieved around 40% and 50% increase in modulus for 3% and 5% clay systems respectively. This improvement of the two systems was reduced after drawing to around 15% and 25% compared with drawn PP. The work of fracture is increased either by adding nanoclay or by drawing to low draw ratio, or both. At moderate and high draw ratios, PPNCs may undergo either an increase in the size of microvoids at low clay loading or coalescence of microvoids at high clay loading, eventually leading to an earlier failure than with neat PP. The adoption of PPMA loading using an appropriate mixing route and clay loading can create a balance between the PPMA stiffness effect and the degree of bonding between clay particles and isotropic or oriented polymer molecules. Spherulites size, d-spacing of silicate layers, and nanoparticles distribution of intercalated microtactoids with possible semi-exfoliated particles have been suggested to optimize the final PPNCs property.

The synthesis of ion-exchange resin which can be used in various separation and chemical purposes, such as diffusion dialysis, electro dialysis, electrolysis and fuel cells has of considerable interest. For all these applications, the interactions of the ionic groups and the resulted morphologies are critical for establishing the unique properties. Considerable researches have been continued to understand the microstructure of these materials. The aim of this study is to synthesize polypropylene (PP) based ion exchange resins and to investigate their ion-exchange properties. In the first part of this study polypropylene was functionalized by grafting maleic anhydride onto the polypropylene and the product was characterized by ATR. The effect of maleic anhydride introduced to the grafting medium and the effect of the radical initiator on the maleic anhydride content of the MA-g-PP samples were investigated. In the second part, neutralization of the MA-g-PP samples with Na+, K+, Mg2+ and Ca2+ ions and peroxide cross-linking of neutralized MA-g-PP samples were performed. Characterization of the neutralized MA-g-PP samples were performed by ATR and SEM-EDX. In the last part of the study, ion exchange properties of MA-g-PP resins towards Cu2+, Co2+, Cd2+, Pb2+ and Fe3+ ions at different pHs were investigated by batch equilibrium method. Rate of metal uptake, concentration effect on the metal uptake and regeneration of the MA-g-PP samples were also examined.

Identification of viable vat dye candidates of a trichromatic series (compatible red, yellow and blue colorants) plus an orange based on the developed single-stage acid leuco vat dyeing process for unmodified polypropylene (PP) flat woven fabrics has been achieved with adequate fastness properties to washing, crocking and dry-cleaning: C. I. Vats Orange 1, Yellow 2 and Red 1 have been certified, whereas Vat Blue 6 is a marginal candidate. Vat Blue 1 has been demonstrated to be a viable colorant for dyeing of PP fiber as a single colorant. Molecular dynamics simulation and solubility parameter (SP) approaches have been utilized to screen the potential vat dye candidates for generic PP coloration. Experimental K/S results have exhibited good correlation with the predicted mixing energy of acid leuco vat dyes-PP fiber and the calculated dyes' SP's. The low SP/mixing energy acid leuco vat dyes (e.g., C. I. Vat Red 1) have shown better color-yield/fastness properties than the high SP/mixing energy vat dyes (e.g., C. I. Vat Brown 1), exhibiting that increasing difference of SP between the vat dye and the PP fiber, coupled with a higher mixing energy of dye-PP blend, resulted in decreased interactions between the two. For example, C.I. Vat Brown 1 with its high SP and calculated mixing energy with PP gave least color yield than the certified vat dyes, all with lower SP's and mixing energies. Cross-section micrographs of the dyed fibers revealed the absence of "ring-dyeing". Experimentally determined kinetic parameters such as affinity of dyeing and heat of dyeing quantified the presence of interaction between acid leuco vat dyes and PP fiber. Tensile test and X-ray crystallinity results have confirmed that dyeing process did not alter the tensile strength and modulus of the dyed PP textiles significantly. PP Fabrics dyed with simulated continuous dyeing processes (pad-steam and pad-dry heat) demonstrated good color yields and levelness with adequate fastness to crocking, washing and dry cleaning.

Les fibres naturelles ont récemment attiré l'attention des scientifiques en raison de leurs propriétés : faible coût, faible densité, renouvelables, biodégradables et non abrasives. Dans cette étude, trois types de fibres de bambou sont étudiées. La modification chimique des fibres par la soude est utilisée pour enlever l'hémicellulose et la lignine. Puis, la surface de la fibre est modifiée par acétylation ou silane avant élaboration de composites PP. Les propriétés mécaniques des composites augmentent avec le diamètre des fibres et avec l'utilisation d'un agent d'ensimage. Des mélanges amidon/PVA/plastifiant/agent de couplage sont également étudiés. Les composites préparés par réticulation avec l'acide citrique ont d'excellentes propriétés mécaniques. La résistance à la traction et la déformation à rupture de ces composite augmentent avec la teneur en PVA. La présence d'argile et de fibres ont toutes deux un effet considérable sur les propriétés mécaniques des composites. / Natural fibers have recently attracted the attention of scientists because of their properties of low-cost, low density, renewable, biodegradable and nonabrasive. In this study, three types of bamboo fibers are prepared. Chemical modification of fibers by alkali is used to remove hemicellulose and lignin. Then, fiber surface is modified by acetylation and silane before processing composite materials with polypropylene. As expected, the mechanical properties of the composites increase with the average fibre diameter. Tensile strength and Young's modulus increase when using a coupling agent. Starch/PVA blends are also prepared with glycerol and water as plasticizer. The composite prepared by citric acid crosslinking has excellent mechanical properties. Tensile strength and elongation at break of starch/ PVA composite increase with the content of PVA. The presence of clay and fiber are both found to have considerable effect on the mechanical properties of the composites.