Rubber Deposits Research Articles

Interfacial coupling efficiency of functionalised rubbers on silica surfaces

Understanding filler-polymer interactions at the interfaces is an important aspect for rubber reinforcement development. Recent technology in the field of silica-rubber reinforcement has led to an increasing interest in functionalised rubbers, since they can directly react and enhance interactions with silica filler, and hence improved rubber reinforcement. The present work aims to better understand the role of different reaction variables, i.e. time, temperature, rubber concentration, solvent, surfactants, sonication, specific surface area of silica, rubber type, and catalyst, on rubber deposition on silica surface in a model reaction in solution of silica and functionalised rubbers. Results from the Design of Experiments (DoEs) study, i.e. One-Factor-At-a-Time (OFAT), Plackett-Burman (P-B) and Full-Factorial (FF) designs showed that all studied factors have a negligible effect on interfacial coupling efficiency of rubber to silica surface. Accessibility of the functional groups at the rubber molecules and the steric hindrance due to large polymeric molecular chains seem to be the most limiting factors, resulting in low coupling efficiency. Effects of the investigated reaction parameters and plausible mechanisms involved in rubber-silica coupling reactions are elucidated.

An analytical solution for friction coefficients of grooved pavements considering tire rubber-groove interaction

To reduce the loss of skid resistance of pavement in wet weather, pavement grooving is used to improve aircraft operation safety on runways. This study presents an analytical solution to analyze mechanical interactions between tire tread rubber and pavement surface grooves for calculating friction coefficients of aircraft tires on runway pavements. The energy dissipation theory is utilized to calculate the contribution of rubber-groove interlock and the friction on plane part of pavement surface due to surface texture is accounted using Brush model. The comparison of model results and field measurements proves the capability of the proposed method to predict friction coefficients of aircraft tire on runway pavements with various groove configurations. The evaluation of trapezoidal grooved pavement shows similar friction coefficients compared to the standard square grooved pavement regulated by the Federal Aviation Administration (FAA). The friction coefficients of grooved pavement vary depending on the inclined angles of groove and edge-to-edge spacing that are two important geometry parameters. The findings demonstrate the pronounced influences of rubber deposits and groove deterioration on skid resistance of runway pavements. The analysis results can be further used to design optimized groove configuration and determine maintenance threshold for safe operation of aircraft on runways.

Numerical analysis concerning the skid resistance of rubber-contaminated runway grooves

Runway grooves are essential for water drainage and skid resistance; although the skid resistance of runway grooves has been studied, research on the frictional properties of runway grooves remains limited. This study presents a numerical method for analyzing the skid resistance of runway grooves. A aircraft tire model was developed with rubber and belt layer materials. A grooved runway sample was obtained by simulating the grooves on a runway surface specimen. A numerical algorithm was employed on the runway sample to simulate groove closure caused by rubber deposits; the degree of closure was defined as the percentage of closed grooves resulting from rubber deposits. An interaction model was developed according to the power spectrum density of a grooved runway and the viscoelastic properties of tread rubber. The numerical simulation results were verified using a runway skid resistance field test. The effects of groove closure due to rubber deposit contamination and groove geometry were analyzed. Friction increased as groove depth and width increased, but friction decreased as groove spacing and degree of closure increased.

Design of an Expert System for Airport Rubber Removal

The most important parameter for airport operator is safety. Minimizing any possible risks for passengers, crew, and equipment is the main objective of applying safety management systems at airports. The rubber deposits that accumulate on the runway surface due to aircraft operations is one of the most critical factors that directly effects on the skid resistance value of the airport runway.Four common techniques are applied throughout the world for mitigating this rubber strip water blasting, chemical, shot blasting, and mechanical. Every technique has its pros and cons in terms of cost, efficiency, environmental effect, and damage to pavement surface. The current design involves developing an expert system that takes into account the parameters that may support choosing the optimal method for rubber removal in certain situations. These parameters include airport classification, cost involvement, accessibility, pavement damage concerns, environment damage or side effects, and any additional factors such as noise.The system is developed using webpage-based Expert System builder ES-Builder. Simple user interface, windows based, easy to build the decision tree are the major concerns for choosing this program to build the proposed expert system. The expert system follows a deduction process, until the expert system makes the final conclusion according to user selected answers. The proposed expert system works very well when selecting appropriate answers taking into consideration specific characteristics for each airport category. Faulty conclusions could be given if the user does not use the appropriate parameters related to the airport category. There is no optimum solution, every airport situation is different, and the solution or the recommended method varies from one airport to another.

Submicron surface roughening of aliphatic polyamide 6,6 fabric through low temperature plasma and its effect on interfacial bonding in rubber composite

The present study aims to produce submicron surface roughening of aliphatic polyamide 6,6 (nylon 6,6) fabric using dielectric barrier discharge-based atmospheric low temperature plasma for improving the adhesion bonding with rubber. The plasma treatment was done in the time ranging from 15 s to 300 s. Formation of surface roughness on the fabric due to plasma treatment and the associated chemical changes were studied through high-resolution scanning electron microscope, geometrical surface roughness by Kawabata evaluation system surface tester, contact angle measurements and Fourier transform infrared in Attenuated total reflectance mode. Scanning electron microscope micrographs revealed the presence of submicron roughness on the nylon 6,6 fibre surface with pores of around 100 nm (0.1 µm) for the optimum treatment time of 180 s above which the pore merging effect dominated resulting in the net low surface roughness. Geometrical roughness (SMD) results were also well in agreement with the scanning electron microscope results for the roughening and the optimum effect of the plasma treatment. The control and plasma treated nylon 6,6 samples were used as reinforcements for rubber composite. The peel strength of the rubber composite, which is a measure of interfacial bonding, increased to 150% as the maximum for the optimum plasma treatment time of 180 s. Intense rubber deposits over the 180 s plasma treated samples were observed while only a few deposits of rubber were observed on the control fabric when their interfaces were examined through scanning electron microscope after peeling test.

활주로 고무 퇴적물 제거를 위한 포장 파손 저감형 사전처리제 개발 연구

항공기 착륙 시 발생하는 고무퇴적물은 젖은 노면에서의 표면 마찰력을 감소시키는 주원인으로 안전한 항공기 착륙을 위해 주기적인 제거를 실시하고 있다. 제거작업에 주로 사용되는 고압살수 방법은 고압의 물로 직접 표면을 타격함에 따라 표면 재료 유실의 원인이 되고 있다. 본 연구에서는 고무 제거시 살수 압을 상대적으로 낮추어 표면 파손을 저감시키고, 저수압에도 효율적으로 고무퇴적물을 제거할 수 있는 사전 처리제 개발을 진행하였다. 이를 위해 사전 처리제에 적합한 기초재료를 선정하여 성능 평가, 침투율 평가, 현장 적용성 평가를 진행하였다. 이를 토대로 기초재료의 성능 개선에 필요한 첨가제의 비율을 1차적으로 선정하였고, 포장 영향성 평가를 통해 최적배합을 도출하여 고무제거 사전처리제 개발을 완료하였다. Rubber deposited during aircraft landing is known as the main cause of reducing surface friction force on wet surfaces. Thus, rubber deposits are removed at regular intervals for sae airplane landing. The high-pressure waterblast method, widely used for the removal of rubber deposits, is regarded as the main cause for the loss of surface material because in this method, water hits the surface directly at a high pressure. In this study, a rubber removal primer is developed to reduce surface damage by lowering the pressure of waterblast relatively during the removal of rubber deposits such that the deposits are removed efficiently even with a lower water pressure. To achieve this, basic materials appropriate for the primer were selected and their performance, penetration rate, and site applicability were evaluated. Based on the evaluations, the proportion of additive required for improving the performance of the basic materials was first determined. Then, the optimum mix ratio was derived through the evaluation of the effect on pavements, and the development of the rubber removal primer was completed.

FIELD MEASUREMENTS ON RUNWAY FRICTION DECAY RELATED TO RUBBER DEPOSITS

Surfaces of airport pavements are subject to contamination that can be very dangerous for the movement of aircraft particularly on the runway. A recurrent problem is represented by the deposits of vulcanized rubber of aircraft tires in the touchdown area during landings and lesser during take-offs. This causes a loss of grip that compromises the safety of aircraft movements in take-off and landing operations. This study deals with the surface characteristics decay phenomenon related to contamination from rubber deposits. The experiment was conducted by correlating the pavement surface characteristics, as detected by Grip Tester, to air traffic before and after de-rubberizing operation and two models were constructed for the assessment of functional capacity of the runway before and after the operations de-rubberizing.

Comparative Study of Water-Blasting Equipment for Airfield Surface Decontamination

Runway rubber removal is a maintenance function employed to ensure safe landing areas for aviation operations. Rubber deposits accumulate on runway areas where aircraft tires touchdown and braking occurs. This tire-rubber build-up occludes pavement microtexture and macrotexture, causing a significant loss in available skid resistance during wet conditions. Reduction of available pavement microtexture in a wet environment prevents the development of adhesional friction, which can result in viscous hydroplaning. Reduction of pavement macrotexture prevents the removal of bulk water from the tire–pavement contact area and also prevents the development of the hysteresis frictional component. To restore friction to safe levels for aircraft operations, rubber must be periodically removed. Several techniques for rubber removal are available. Water-blasting is a proven surface decontamination technique which employs the use of high-pressure or ultra-high-pressure water (UHPW) to blast rubber deposits from the runway surface. This effort provides a performance-based comparison between three commercially available UHPW water-blasting systems. The evaluation was conducted on an ungrooved portland cement concrete (PCC) runway with heavy rubber contamination along the touchdown and breaking zones. Several types of testing equipment such as a circular track meter (CTM) and dynamic friction tester (DFT) were used to characterize the surface properties of the runway before and after rubber removal. The measurements were used for statistical pairwise comparative analysis of International Friction Index (IFI), speed constant and mean profile depth (MPD). Treatment effect analysis of premeasured and postmeasured data revealed that UHPW systems improved the surface texture properties by at least 40% regardless of the decontamination equipment.

Macroscopic and microscopic evaluation of surface friction of airport pavements

Rubber deposits accumulated on the runway surface pose a distinct threat to the operational safety of aircraft during landings and take-offs in adverse weather. This paper is to evaluate the microscopic and macroscopic effect of rubber deposits on the friction characteristics of runway pavements. A concrete runway at Kaohsiung International Airport was chosen for friction and texture measurements on the pavement surface for analyses. This study comprised field testing and laboratory testing. The surface friction tester, the British Pendulum Test and the grease-patched method were regularly conducted on site for runway pavements over a 24-month period of time. An optical microscope and a scanning electron microscopy (SEM) were used for the microscopic evaluation of rubber deposits taken from runway pavements. Results indicated that runway friction characteristics changed over time primarily due to the buildup of rubber deposits. The accumulation of rubber filled the macrotexture of the pavement surface and caused loss of the skid-resistance of a runway. An increased macrotexture led to a rise in the friction value. The difference between friction values measured in the forward direction and those measured in the backward direction was significant. The directional distribution of rubber deposits as observed by SEM was shown to raise friction level.

Effect of Rubber Deposits on Runway Pavement Friction Characteristics

This purpose of this paper is to evaluate the effect of rubber deposits on pavement friction characteristics on the basis of macroscopic and microscopic measurements. Runway pavement sections at the Kaohsiung (Taiwan) International Airport were chosen for field and laboratory testing over a 16-month period. In the first step of the field testing, the monthly variation in friction was established by using the Saab surface friction tester (SFT) and British pendulum testing. In the second step, macro-texture measurements were made by the grease patch method. The last step of field testing was to take samples of rubber deposits for laboratory analyses by optical microscope and scanning electron microscopy. Results showed that rubber deposits had strong effects on runway surface friction. An aircraft landing appeared to result in an increase in the thickness of rubber deposits by approximately 0.05 μm. The microstructure of rubber deposits was shown to be accumulated by the directional distribution of multiple layers of polymer scale. The friction value measured in the backward direction was higher than that measured in the forward direction. The rate of decrease in the SFT friction value was found to be about 0.05 for an increase in rubber thickness of 0.1 mm.

Mould fouling of elastomers during injection moulding

A systematic study of mould fouling during elastomer injection moulding is presented. Moulding was undertaken principally using nitrile rubber compound and purpose built tooling with interchangeable mould inserts. Rubber metal interactions between treated and untreated Stavax steel surfaces were characterised by a variety of analytical techniques to study factors influencing the onset of mould fouling and its origins. Preliminary simulation and supporting experimental investigation suggested that the design and location of the gate influenced both mould filling pattern and the position of rubber deposition within the cavity.

Night temperature, rubber production, and carbon exchange in guayule

Guayule ( Parthenium argentatum Gray), a native of the Chihuahuan desert, produces the majority of its rubber during the winter months. Increased rubber production is thought to be induced by cold night temperatures, but the factors involved in rubber induction are not completely understood. The purpose of this study was to answer three questions about rubber production in the winter: (1) how do immature plants (<180 days) respond to cold night temperatures?; (2) how is rubber production in mature plants (≈1 year) related to night temperature?; and (3) what is the relationship between carbon exchange and rubber production under cold night temperatures? Plants were grown in differentially heated enclosures over three consecutive winters. The warm-night plants were exposed to simulated summer night temperatures and the cold-night plants to ambient winter night temperatures. Plant responses to different night temperatures were monitored by measuring growth, carbon exchange, fresh and dry weight, and resin and rubber production. Immature plants exposed to cold nights had higher rubber concentration than the warm-night plants only in the first year, which had the lowest night temperatures. For the mature plants, dry weight was not significantly different between treatments, but rubber concentration and yield were significantly greater in the cold-night than the warm-night plants. Plants in both treatments had similar carbon exchange rates. Therefore, the similarity in dry weight between treatments was most likely due to increased growth in the warm-night plants and increased rubber deposition in the cold-night plants. Rubber concentration was significantly related to night temperature in both mature and immature plants and appears to be stimulated most by temperatures below 10 °C.

Influence of Process Conditions on the Rate of Activation of Chars Derived from Pyrolysis of Used Tires

Used tires were pyrolyzed in a nitrogen-purged 3 kg static bed, batch reactor. The char was subsequently activated in an equimolar mixture of either steam and nitrogen or carbon dioxide and nitrogen. Activation was a two-stage process, with an initial more rapid gasification of carbonized rubber deposits followed by less rapid gasification of carbon black. The activation energy in steam was 201 kJ mol-1. The burnoff achieved by carbon dioxide under otherwise identical conditions to that of steam was on average 72% of that found when steam was used. The reactivity of acid-demineralized char in steam was around 22% less than that of raw char. It was suggested that calcium ions in the raw tire char catalyzed the gasification reactions. The tire pyrolysis temperature had an unclear influence on the rate of activation of the derived chars. The influence of particle size on the rate of activation was also investigated, and the results are discussed in terms of ash content and distribution. The outflow gas composition and gross calorific value of the gas were also determined in relation to activation conditions. BET surface areas of the derived activated carbons reached a maximum of 640 m2 g-1.

Geosynthetic containment beneath Stockholm-Arlanda Airport

Arlanda International Airport in Stockholm, Sweden, is in the process of constructing a new, third runway. Through extensive siting studies and economic evaluation, the alignment of this runway and the associated taxiway has been located over an esker, a ridge-like glacio-fluvial formation common in Sweden. This esker is an aquifer and constitutes a water supply for the airport as well as a back-up water supply for more than 250,000 residents of the area. The use of approximately 100 tonnes (110 tons) of deicing products per runway each year, and the periodic use of solvents to remove rubber deposits from the pavement have resulted in the need for a protection system for this valuable water resource. As a result, design of a lining system was commissioned to minimize the impact of these constituents on the groundwater. Based on the preliminary design, select portions of the new runway and taxiway are to be lined with a geomembrane. Sensitive and critical areas will include the use of a geosynthetic clay liner (GCL) beneath the geomembrane to form a composite liner, and/or a geotextile above the geomembrane as a protective cushion. The geomembrane lined area totals approximately 330,000 m 2 (3,550,000 ft 2), making the project one of the largest installations of this nature in northern Europe.

Cyclic patterns of growth and rubber deposition in guayule Parthenium argentatum. Suggestions for a management programme

As the natural pattern of development and rubber synthesis in guayule (Parthenium argentatum) is cyclic any treatments to improve growth and rubber production should be synchronized with the normal sequence of events pertaining to growth and metabolism. Starting with 25-week-old seedlings an attempt has been made to acquire information about rubber deposition, growth and defoliation. Observations were made in the field as well as at the light and electron microscope level. Rubber is deposited mainly in the bark during winter. The highest deposits were found in the secondary stem tissue. S. Afr. J. Plant Soil 1986, 3: 21–26

CO 2 Fixation and Rubber Deposition in the Bark and Leaves of Guayule during Winter

Summary The chloroplasts found in the stem tissue of Parthenium argentatum (guayule) which had passed through one winter fixed a considerable amount of CO 2 and a relatively large proportion was incorporated into rubber. In this region of the stem the cells were not completely filled with rubber and new cells were still generated by the vascular and cork cambia. While the cells in the oldest part of the two-year-old plants appeared to be filled to capacity with rubber, 14 C was still incorporated into cis -polyisoprene. This indicated that despite the presence of copious amounts of rubber some of these cells still had the ability to synthesize rubber. In the parts of the stem produced by the current season's growth most of the 14 C was incorporated into the aqueous extract and not into rubber which suggests that it was used for general metabolism. At present it is not known which precursors, if any, are obtained directly from the chloroplasts and are used as substrate for rubber production. This aspect is currently receiving attention.

Studies on the translocation system of guayule (Parthenium argentatum Gray)

Observations at ultrastructural level have been added to earlier descriptions of the vascular tissue inParthenium argentatum (guayule). Large transfer cells with pronounced cell wall projections were found in the phloem of the minor veins in the leaves. These cells have every appearance of being modified for the purpose of collecting photosynthates. In the large veins of the leaf the elements of the phloem, engaged in bulk transport of solutes, showed reduced transfer cell characteristics. Within these larger veins of the leaf nacreous thickenings of the sieve tubes was very common. Similar thickenings were found in the petiole and the stem and these persisted to maturity. Histochemical tests indicated a high level of pectic substances in these walls. In the stem, particularly in regions where rubber deposition was significant, the companion cells in the phloem had elaborate cell wall ingrowths. The adjacent parenchyma cells were adequately provided with pits. Occasionally transfer cells were found in the xylem.

Cis-Polyisoprene Synthesis in Guayule Plants (Parthenium argentatum Gray) Exposed to Low, Nonfreezing Temperatures

Exposure of guayule plants (Parthenium argentatum Gray) to 6 months of a night temperature of 7 degrees C results in a 2-fold stimulation of cis-polyisoprene (rubber) formation over that of control plants exposed to 21 to 24 degrees C night temperature. Control and cold-treated plants contained 2.18% and 5.69% rubber, respectively. Examination of the stem apices by transmission electron microscopy showed extensive formation of rubber particles in the cold-treated plants compared to the control plants. The rubber particles in guayule are formed in the cytoplasm and fuse to form large globular deposits. The surface area of the rubber particles and globules range from 4 x 10(-6) to 2.9 x 10(-3) square micrometers. The deposition of rubber in the cytoplasm of the cortical parenchyma cells differs from rubber deposition in the vacuoles of laticifers of Asclepias syriaca. Electron micrographs of stem cortical parenchyma in control plants show mature cells with large central vacuoles, thin layers of parietal cytoplasm, and smaller numbers of rubber particles. Radioactive acetate and mevalonate are incorporated into rubber at a faster rate in stem slices from cold-treated plants compared to slices from control plants. A faster rate of these reactions may account for the increase in rubber synthesis in the cold-treated plants.

Detection of Rubber in Guayule (Parthenium argentatum Gray) at the Ultrastructural Level

Summary Guayule tissue from stems of one-year-old plants was fixed with osmium tetroxide and glutaraldehyde and embedded in araldite resin to trace the deposition of rubber with the electron microscope. The rubber appeared as electron opaque membrane bound particles. They were most abundant in the meristematic cells of bud and shoot primordia and in the epithelial cells of the resin canals which also may be very active metabolically. Smaller vesicles filled with rubber were apparent in the parenchyma cells of the cortex, pith and vascular rays. There was usually no central vacuole, and as the rubber particles increased the organelles became disorganised. These findings suggest that rubber particles are part of the cytoplasm and must be regarded as inclusions in the same sense as protein bodies. Chloroplasts were sparse in the stem tissue where most of the rubber occurs.

The resistance of electrodeposited layers of rubber and resins

The electrical resistance per unit deposition charge per unit area (p,ΩC−1 cm−2) has been calculated from current-time data for the anodic deposition of polymers in the following systems: (a) resin deposition on mild steel and copper coated mild steel, (b) rubber deposition on mild steel and aluminium, and (c) two resin systems of two concentrations on mild steel and brass. The values ofp are analyzed in detail and it is concluded thatp can be qualitatively related to the electrical conductivity of the electrode material and the adhesion of the electrodeposits, taking into consideration the different mechanism for the stability of rubber latex and the resin system. For a given value ofp, electrodeposits on aluminium are 40% more adherent than those on mild steel. Further, for the same adhesion, values ofp are lower by about 20% when aluminium is used instead of mild steel as the anode. It has also been concluded that the study ofp versus the current density during the electrodeposition of the resins is a convenient and useful method of approach to the study of electrophoresis in its practical application to the preparation of electro-coatings of industrial value.