Styrene-butadiene rubber (SBR) copolymer nanosized latex particles were synthesized via differential microemulsion polymerization (DMP) in a 300ml bench-scale semi-batch reactor, equipped with a thermocouple and a magnetic four-blade stirrer. This approach employed a continuous and slow addition of styrene and butadiene monomers drop-wise into a continuous aqueous phase comprising DI water, an initiator, a surfactant and a chain transfer agent. It was found that this approach offered an efficient heterogeneous phase path to synthesize styrene-butadiene copolymer latices with a high-butadiene-level of the resulting latex particles. The latex nanoparticles were formed as the SBR copolymer monomers undergo a self-assembly process in the continuous phase and were stabilized by their surrounding surfactant particles. The size of the latex particles could be easily adjusted by alternating the monomer addition speed, the reaction temperature, the amount of chain transfer agent applied and the type and the amount of surfactant introduced in the process. Not surprisingly, a small amount of chain transfer agent introduced into the DMP system might facilitate micellar nucleation and reduction of gel content in the polymer dramatically and may also aid increasing the size of the SBR latex particles. Owing to the small size of SBR latices prepared by the DMP method, the glass transition temperature (Tg) of the latices is much lower than the SBR latices generated by conventional technique. Furthermore, the increase of Tg was observed with an increase of the SBR particle size.

Thesis (Ph. D.)--Lehigh University, 1998. / Includes vita. Includes bibliographical references.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 93-100). Also available in electronic version. Access restricted to campus users.

The objective of this study was to compare different modifiers in two asphalt cements, namely Cold Lake 80/100 obtained from the Edmonton, Alberta refinery of Imperial Oil Limited and a PG 58-28 obtained from a now closed refinery in the Montreal, Quebec area. The modifiers investigated were polyphosphoric acid (PPA), styrene-butadiene-styrene (SBS), and reactive ethylene terpolymer (Elvaloy® RET). The comparisons were done based on both unaged and laboratory-aged materials. The investigation covers high temperature grading using a dynamic shear rheometer (DSR), low temperature grading using a bending beam rheometer (BBR), ductile strain tolerance as measured in the double-edge-notched tension (DENT) test and percentage recovered strain using multiple shear creep recovery (MSCR) test. The Superpave® performance grade span was increased for all modifiers with substantial increases in the high temperature rutting parameter G*/sin while the BBR parameters, T(S = 300 MPa) and T(m = 0.3), remained largely unchanged. In the PG 58-28 base asphalt, Elvaloy® modifiers were able to reduce the intermediate Superpave® grade temperature by significant amounts. All polymer modifiers were good at improving the ductile strain tolerance as measured in the DENT test. In contrast, PPA alone reduces the strain tolerance due to the formation of extra asphaltenes and the likely gelation of the asphaltene-rich phase. Nearly all the modified samples passed the MSCR test except those with poor compatibility (i.e. SBS blended with Cold Lake without sulfur, Elvaloy® systems without acid catalyst, and pure PPA modified systems) or no modifier, which did not reach the required elastic recovery at high levels of non-recoverable compliance. In the BBR test done at low temperatures, all modified systems showed similar elastic recovery and viscous (non-recoverable) compliance. However, in the ductile-to-brittle range the Elvaloy® RET-modified binders showed a definite advantage of a few degrees over the unmodified base asphalts. Finally, chemical aging tendencies, as measured by weight gain and carbonyl formation, turned out to be very similar for all the investigated compositions. / Thesis (Master, Chemistry) -- Queen's University, 2010-12-13 13:29:45.173

Thesis (M.S.)--University of Akron, Dept. of Polymer Engineering, 2005. / "August, 2005." Title from electronic thesis title page (viewed 11/28/2005) Advisor, Lloyd Goettler; Faculty Reader, Avraam I. Isayev; Department Chair, Sadhan C. Jana; Dean of College, Frank N. Kelley; Dean of Graduate School, George R. Newkome. Includes bibliographical references.

<p> A computer model is developed to simulate the emulsion copolymerization of styrene/butadiene in perfectly stirred batch, semi-batch or continuous flow reactors. The model considers free radical initiation by a redox mechanism, micellar particle nucleation, radical concentration as -a function of particle size, radical entry rate and termination rate and diffusion controlled termination and propagation reactions. It predicts conversion, copolymer composition, particle number, number and mass average molecular masses and tri- and tetra-functional branch frequencies. A simple method of estimating the particle size distribution is included in the model. Heat balances over the reactor and cooling jacket are considered and proportional-integra control of the reactor temperature is simulated.</p> <p> The model is used to simulate SBR copolymerization and styrene homopolymerization experimental data from the literature. These simulations tested only certain parts of the model and it is concluded that a more complete verification of the model can only be achieved by running a series of designed experiments. Qualitatively, the molecular mass, particle size distribution and reactor temperature predictions appear to be reasonable. The lack of appropriate temperature dependent rate constants currently limits the molecular mass predictions to isothermal conditions.</p> <p> A comparison of semi-batch operating policies designed to control copolymer composition is presented to illustrate the potential application of the model.</p> / Thesis / Master of Engineering (ME)

Typical rubber compounds used to manufacture industrial products such as tyres, hoses, conveyor belts, acoustics, shock pads, and engine mountings contain up to eight classes of chemical additives· including curing agents, accelerators, activators, processing aids, and antidegradants. The cure systems in these articles often consists of primary and secondary accelerators, primary and secondary activators, and elemental sulphur. Recent legislation impacting upon the working environment, safety and health has imposed a considerable burden on the manufacturers of rubber compounds to meet various obligations. The selection of raw materials and manufacturing processes that do not harm the environment is of great importance. A novel technique for preparing rubber formulations using crosslinking nanofillers such as silanised precipitated silica has been developed in this research. The silica surfaces were pre-treated with bis[3-triethoxysilylpropyl-] tetrasulphane coupling agent (TESPT).· TESPT is a sulphur containing bifunctional organosilane which chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulphur-cure systems. The tetrasulphane groups of the TESPT are rubber reactive and react in the presence of accelerator at elevated temperatures, i.e.140 -260°C, with or without elemental sulphur being present, to form crossIinks in rubbers containing chemically active double bonds for example styrene-butadiene rubber (SBR) and polybutadiene rubber (BR) .. SBR and BR rubber compounds containing 60 phr of TESPT pre-treated silica nanofiller were prepared. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulphur in TESPT. The reaction between the tetrasulphane groups of TESPT and the rubbers was optimised by incorporating different accelerators and activators in the rubber. The mechanical properties of the rubber vulcanisates such as hardness, tear strength, tensile strength, elongation at break, stored' energy density at break, abrasion resistance, modulus and cyclic fatigue life were increased significantly when the treated silica filler was added. The need for the accelerator and activator was dependent on the composition of the rubber. Interestingly, the rubbers were fully cured without the use of elemental sulphur, secondary accelerator and secondary activator. As a result, a substantial reduction in the use of the curing chemicals was achieved without compromising the important properties of rubber compounds which are essential for maintaining long life and good performance of industrial rubber products in service. This approach has also helped to improve health and safety within the workplace and minimise harm to the enviromnent.Furthermore, a significant cost saving was achieved after reducing the number of curing chemicals in the rubber.

Thermal and fatigue cracking are pavement distresses that deteriorate asphalt pavements in Canada. However, the current AASHTO M320 standard specification protocol does not give satisfactory correlation between the properties measured in the laboratory to thermal and fatigue cracking performance of the asphalt in service. This thesis is aimed at validating the newly developed MTO LS-299 and LS-308 specification test methods for predicting pavement distress. A secondary objective is to determine how well laboratory-aged and field-aged binders correlate with each other in terms of their chemical and physical properties. Chemical testing using infrared (IR) spectroscopy and X-ray fluorescence (XRF), as well as physical and mechanical testing using the regular bending beam rheometer (BBR), extended BBR (eBBR), dynamic shear rheometer (DSR), and double edge notched tension (DENT) tests were performed on laboratory-aged and recovered binders from Highway 417. Asphalt cements with significant amounts of waste engine oil residues as determined by XRF data were found to have cracked severely due to their high tendency for chemical aging. Western Canadian binders modified with styrene-butadiene-styrene polymer showed low affinity for both chemical and physical aging as determined from their carbonyl indices. Asphalt binders with smaller paraffinic structures exhibited insignificant pavement deterioration while the opposite occurred to those with low aromatic indices according to their IR data. The DSR data show that chemical aging occurs much faster in the laboratory-aged binders than the field-aged binders. The DENT test is able to separate superior performing binders from inferior ones with 86% accuracy according to their CTOD data. The regular BBR gave poor correlation between the laboratory test methods and the performance of the pavements. Good correlation exists between the laboratory test methods and the performance of the pavements in service according to the eBBR data. Pavements without any cracks showed lower grade losses, while pavements with severe thermal cracking recorded higher grade losses after three days of conditioning prior to testing. The study has shown that the eBBR and DENT tests are better tools for predicting pavement performance and provide good specification tests for the control of thermal and fatigue cracking in modern pavements. / Thesis (Master, Chemistry) -- Queen's University, 2012-02-28 13:16:02.222

One of the current problems faced by mankind is the problem of safe disposal of waste rubber. Statistics show that the number of waste tires is continuously increasing at a very rapid rate. Since rubber materials do not decompose easily (due to their crosslinked structure), they end up being a serious ???environmental problem???. An intuitive solution to prevent the accumulation of the scrap tires is to continuously reuse them. A new patented reclamation method was discovered in our laboratory, which makes use of a twin screw extruder (TSE) in order to produce reclaimed rubber (referred as devulcanized rubber (DR) from here on) of very high quality. Also, this method has proven to be more economical than other commercial reclaiming methods. Products made solely from a reclaimed material face challenges from those made by virgin materials because of relatively poor properties. However, the striking advantage of using reclaimed rubbers is the cost reduction. Hence, it is important to work on establishing methods by which these reclaimed rubbers could be efficiently used and incorporated into present day products. The deterioration of properties could be minimized by blending them with varying amounts of other materials. A possibility in this direction is manufacturing of thermoplastic vulcanizates (TPVs) using reclaimed rubber and general purpose thermoplastics. In accordance with this idea, the focus of this research is to prepare DR and polypropylene (PP) based TPVs. DR is unique as the rubber itself consists of two phases- one phase consisting of uncrosslinked (including devulcanized rubber molecules), and the other phase consisting of crosslinked (un-devulcanized) rubber. These un-devulcanized crumbs act as stress concentrators because they do not break-up easily, and lead to poor physical properties. Hence, this project tries to find out ways to increase the interfacial adhesion between the rubber and PP by using reactive and non-reactive techniques. Preliminary experiments were carried out in a batch mixer to compare DR and rubber crumb (CR). DR based TPVs showed better properties than CR based TPVs, however, the properties were not useful for commercial applications. Sulphur based dynamic vulcanization was studied in a batch mixer and found to be not effective in improving the properties of DR based blends. On the other hand, DCP/ sulphur based curing system was found to show significant improvement in properties. Therefore, DCP/sulphur based curing package was studied in detail on the blends consisting of DR and PP. The optimum ratio of DCP/sulphur was found to vary depending on the ratio of DR/PP. A hypothesis regarding the mechanism of DCP/sulphur curing has been proposed, which seem to correlate well with the experimental results observed. Additionally, it was determined that DR prepared from tire rubber (DRT) performed better than DR prepared from waste EPDM (DRE) for the curing system used. Accordingly, experiments on a TSE were carried out using DRT and a combination of compatibilizing resins and curatives. This combination showed a drastic improvement in blends properties and once again the optimum ratio of compatibilizing resins seemed to depend on the ratio of DRT/PP. As a result of the work, successful strategies based on reactive compatibilization techniques were developed in order to prepare useful TPVs having up to 70% DR. A series of compatibilization techniques has been evaluated using design of experiments and various characterization techniques such as mechanical tests, scanning electron microscopy, thermal analysis and crosslink density measurements. This led to the development of a formulation, which could improve the blend properties significantly. A tensile strength of around 10 MPa and an elongation-at-break of 150-180 % could be achieved for devulcanized rubber (70%) based TPVs, which has broadened the scope for its commercial applications. In addition to that, the process was established on a TSE that has enabled a continuous and steady production of these TPVs with reasonable throughputs.

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