China
Africa
Explore chapters and articles related to this topic
Radial Tire Compound Polymer Blends
Published in Brendan Rodgers, Tire Engineering, 2020
NR or synthetic elastomers can be blended with a range of additional materials which can be defined as secondary polymer systems. This would include such materials as resin systems, high-molecular-weight green strength promoters, and polymeric antioxidant systems. Of these types of compounding materials, resins are the most important. Resins used in rubber compounding can be classified into one of three groups (15,16): Tackifying resins, which remain predominantly unchanged during the vulcanization process,Reinforcing resins, where the resin, when mixed with a catalyst or hardening agent, react with one another during vulcanization to form an interpenetrating network and do not participate in other crosslinking reactions to any significant degree,Curing resins, where the resin reacts with the polymer, thereby crosslinking it. There are exceptions to all three definitions. For example, C5 tackifying resins can exhibit a significant level of unsaturation, which can crosslink at curing temperatures of 160°C.
Applications of Electron Beam Radiation
Published in Jiri George Drobny, Radiation Technology for Polymers, 2020
Body plies of a tire are various rubber-coated cord fabrics (see Figure 9.7). These are subjected to stresses when the tire is built. If a body ply does not have sufficient green (i.e., uncured) strength, the cords will push through the rubber coating (skim) during the building and vulcanization of the tire, resulting in irregular cord placement or defect in the tire. For example, damage can occur from turning the ply around the bead during the building of the tire when the skim compound does not have adequate green strength. Green strength may be defined as that level of cohesive strength that allows an essentially uncross-linked polymer-based composition to deform uniformly, under stress, without sagging or nonuniform thinning (necking).
Application of Inverse Gas Chromatography to the Study of Rubber Reinforcement
Published in Michel Nardin, Eugène Papirer, Powders and Fibers, 2006
Green strength is important during the building of rubber products. For example, in the construction of radial-ply tires, the uncured compounds between the cords in the carcass may be subject to extensions of up to three times their original dimension during the building process [46]. Moreover, a high green strength is necessary to prevent the uncured tires from creep and distortion prior to molding. Compared to NR, the low green strength of certain types of synthetic rubber such as SBR and BR has been attributed to their lack of strain-induced crystallization. However, fillers also have an important effect on the stress–strain behavior of uncured compounds [47,48]. It was found that besides filler morphology, the filler surface energy is another important factor influencing green strength. The green strengths of filled compounds, based on a blend of SBR and BR, are shown in Table 3.2. While the green strength is higher for the silica-filled compound, its yield strain is much lower. Whereas the high green strength of carbon-black-filled rubber is related to higher polymer-filler interaction, the high green strength of the silica-filled compound originates from a strong filler network that is rigid, brittle, and characterized by very low yield strain. The lower green strength and yield strain of the compound filled with the TESPT-modified silica is, of course, associated with weaker polymer-filler and filler–filler interactions (i.e., the low specific and dispersive components of surface energy of this silica). This effect is partially compensated for by its high bound rubber content and possible precrosslinking between silica surface and polymer during mixing.
A review on recent developments in binder jetting metal additive manufacturing: materials and process characteristics
Published in Powder Metallurgy, 2019
Asier Lores, Naiara Azurmendi, Iñigo Agote, Ester Zuza
The use of the appropriate binder is essential to ensure good part green strength. This will allow the manipulation of green parts after the curing stage without damaging them. That is not completely true since the selection of powder particle size is sometimes much more determinant than binder composition. Towards improving green part integrity, a research work developed by Kathy Lu et al. [92,93] determine that smaller powder particle sizes improve green part strength, due to the reduced binder spreading rate variations, and the faster and the better binder spreading due to the higher capillarity forces. Nevertheless, the selection of binder system for BJ is critical as it determines the success of creating satisfactory green parts and affects the final properties of the sintered parts [94].
Reasons for crack propagation and strength loss in refractory castables based on changes in their chemical compositions and micromorphologies with heating: special focus on the large blocks
Published in Journal of Asian Ceramic Societies, 2019
After sintering at higher temperatures (>1000°C), however, the conditions change and castables containing sol acquire greater mechanical strength than castables containing a hydraulic binder (Figure 3); the green strength has great importance in large blocks (e.g. electric arc furnace roofs). For this reason, many scientists are investigating ways of increasing the green strength of castables containing colloidal binders. One of the factors that can affect the strength of castables containing colloidal binders is the amount of solid contents available in the sol or in the composition as well as the average particle size of the sol. It is recommended that a colloidal binder with an average particle size smaller than 14 nm and a high solid content should not be used in a castable, because these factors cause drying shrinkage and may lead to internal stresses and crack formation [15,20,23–25].
Experimental study of the feasibility of using groundnut shell ash and ant hill powder in foundry application
Published in Journal of the Chinese Advanced Materials Society, 2018
Patrick C. Okonji, Chidozie C. Nwobi-Okoye, Philip N. Atanmo
The green strength of the foundry sands depends on a number of factors such as: clay, water content, sand size distribution, temperature of the sand, amount and type of additive, degree of mulling or mixing, extent of compaction (number of rams of a testing machine), etc. In this work, the main factor responsible for the increase is the fine particle size of the GSAp and the high alumina content of the AHp. From Figure 9, it can be observed that the green strength obtained from 8/15%, 10/20%, 12/25%, 14/30% GSAp/AHp addition meets the requirement strength for casting ferrous and non-ferrous metal.[18]