The thesis aims to study the effects of the mixing of immiscible polymers on the frictional properties of rubber compounds. The novelty of this work is to consider the rubber as a heterogeneous material in which the microscopic inhomogeneities are the domains generated from the mixing of immiscible compounds. Systematic experimental tests are performed to investigate the frictional properties of two different groups of tyre compounds, both provided by Pirelli Tyre S.p.A. The first group is represented by the homogeneous compounds realized by using Natural Rubber (NR) or Styrene Butadiene Rubber (SBR) and different amounts of filler and Sulphur. The second group considers heterogeneous compounds, generated by mixing in different percentages the homogeneous compounds, to obtain compounds characterized by microscopic domains of NR and SBR. The experimental outcomes proved that the presence of domains increases the friction coefficients. A Dynamic Mechanical Analysis (DMA) is performed to correlate the dynamic properties of the specimens with the friction coefficient. The results of the DMA of the homogeneous compounds agree with the frictional properties while the heterogeneous compounds show intermediate dynamical properties in contrast with the frictional results. The DMA is not able to recognize the microscopic domains of the heterogeneous compounds interpreting the system as a uniform material, suggesting that more complex dynamics arise during the sliding. The dependence of friction on the composition of the material is also investigated by using a numerical approach. For this purpose, a straightforward model is chosen to investigate numerically the frictional behaviour of a rubber material starting from the microscopic properties. The model is discretized as a chain of blocks connected by springs and dampers. Playing with the microscopic parameters of the model, such as the elastic modulus and the damping coefficient, it is possible to link the macroscopic frictional response of the bulk to the microscopic characteristics that locally describes the interactions between the blocks. Firstly, the frictional properties of compounds characterized by i) uniformly distributed viscoelastic or elastic elements and ii) a combination of purely elastic and viscoelastic elements randomly distributed is compared. The numerical outcomes reveal an increase of the frictional properties for samples realized by mixing elastic and viscoelastic elements pointing out that the presence of different domains due to the mixing of two immiscible materials, affects the macroscopic frictional response. Secondly, a comparison between the experiments and the numerical simulations is performed to verify if the 1D model can correctly predict the observed experimental behaviour. The 1D model, in its simplicity, is unable to predict the increase of frictional properties observed experimentally testing the heterogeneous compounds, confirming that more complex interactions influence the friction as suggested by the DMA.

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A study was conducted on the measurement of skin friction, the least under-stood component of drag. Skin friction is considered the "last frontier" in drag reduction for supersonic flight, but to understand skin friction, it must be accurately measured. This study utilized the direct measuring technique for skin friction. A small de-vice, termed a skin friction gage, measures the stress on a cantilever beam topped with a movable surface piece as a shear flow passes over the flush surface. The improvement of these devices for various flow fields is ongoing. A problem that arose with many designs was leakage of a gap-filling liquid. The typical direct measuring skin friction gage uses oil in a gap between the cantilever beam and the encasement to dampen vibrations, to create an even flow over the surface, and for temperature compensation. In high speed testing the oil leaks out; therefore, a gage with rubber to fill the gap instead of oil was introduced This study employed a finite element method model to fully understand the strains involved with the rubber and the skin friction gage. The development of a calibration device, called the Calibration Rig, for the rubber skin friction gages was constructed. The Calibration Rig was successful, but deemed to be more cumbersome than initially expected. This led to the development of a thin rubber sheet to cover the face of the gage instead of rubber filling the entire gap. More finite element method modeling was done to finalize the design of a gage with a rubber sheet. The design consisted of a plastic skin friction gage with an approximately 0.015 in. thick rubber sheet, a 0.0625 in. wide gap between the floating head on the cantilever beam and the encasement to be filled with oil, and semi-conductor strain gages to measure the beam deflection. Vibration tests were performed to determine if the rubber sheet produced the required damping. These tests were successful, and so much so, that the oil for damping was not necessary. However, supersonic wind tunnel tests at Mach 2.4 which were done at Virginia Polytechnic Institute and State University, initially yielded unfavorable results. The rubber sheet failed during the violent process of starting and unstarting of the tunnel. More study on the adhesive mounting of the rubber sheet to the skin friction gage face is needed. / Master of Science

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In Taiwan, the rubber industry began to bloom from the Japanese Colonial Era, and most of the rubber technologies were originated from Japan. Its evolution began from the rubber parts to the synthetic rubber manufacturing. The most of synthetic rubber manufacturers are cooperated with companies from Japan and US, the rubber industry was allowed to develop vigorously in a short period of time. In contrary to Taiwan, China could only obtain the obsolete rubber technologies and management skills from the Former USSR due to economy sanction during the Cold War period. The rubber industries lagged behind in terms of quality, production efficiency, and management. As China embraced the Socialist Planned Economy after the Communist Victory in Civil War, the marketing and sales made subject to state control and development was being dragged. After the Reform and Opening-Up, although there were a bunch of rubber manufacturers from Japan and western countries started to establish local production activities in China, the foreign investment bogged down after the Tiananman Square Protest in 1989. Only the Taiwanese manufacturers moved their steps to China against the tide with modern production technologies and management skills. The complementary development brought by Taiwan and China contributed significant improvement in quality of Chinese rubber goods and became a story on everybody¡¦s lips on the cooperation of the rubber industries between two sides of Taiwan Strait. Rubber industries are closely related to national defense and consumer goods, which makes themselves equally import to plastic industries. However, due to the labor-intensive nature of rubber industries and the serious lack of labor force in Taiwan in 1990¡¦s, the Taiwanese rubber industries began to move their production sites to China and accelerated the inosculation of the rubber industries in Taiwan and China. As the main raw material of rubber industries, the synthetic rubber is no exceptional either. In the end of 20th Century, China has successfully become the ¡§World Factory¡¨ and the consumption and capacity of synthetic rubber became the top of the world. Then the financial crisis in 2008 turned the China¡¦s policies to concentrate the development of the domestic demand, which made China the ¡§World Market¡¨. In recent years, the relationships between Taiwan and China have been substantially improved. The Economy Cooperation Framework Agreement (ECFA) is officially signed and taking effects, the economical activities and relationships between both sides are expected to be more liberalized than the past. The study is specially focused on the evolution of the marketing channel of the synthetic rubber between Taiwan and China, and how ECFA is going to possibly affect the synthetic rubber industries. The study will integrate the writer¡¦s points of view and the various ideas abstracted from the interviews with the several Associations and main agents/distributors in Taiwan and China in order to infer the trends of future development of rubber industries. With this study, the readers who are in the business are allowed to be more clear about the evolution of the marketing channel of the synthetic rubber industries and the trends of future development, so that the readers can take the initiatives to prepare for the future.