Papers by Keyword: Blooming

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Authors: Denise Ester O. Santiago, Bryan B. Pajarito, Mark John A. Aparre, Karl Joel E. Biolena, Yvette Celina W. Condez
Abstract: This study investigated the ambient blooming behavior of additives and mechanical properties of vulcanized natural rubber (VNR) loaded with non-ionic surfactants coco diethanolamide (CDEA) and glycerol monostearate (GMS). Taguchi method and analysis of variance (ANOVA) were used to determine the significant main effects of additives on bloom rates and mechanical properties of VNR. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectra of VNR surface confirm the presence of chemical functional groups of stearic acid, paraffin wax, used oil, CDEA, and GMS. The amount of bloom (MB) versus square root of time (t1/2) plot yields two linear regions corresponding to distinct bloom rates which suggest that the blooming behavior of additives follows a non-Fickian mechanism. High loadings of stearic acid, used oil, and paraffin wax increase the bloom rates due to migration of excess unreacted additives to the surface of VNR. Also, additives easily diffuse out of the VNR due to softening of the rubber matrix. High loadings of sulfur and CDEA consistently decrease the bloom rates because of the increase in crosslink density and increase in filler dispersion, making it difficult for additives to bloom out of rubber matrix. High loading of sulfur significantly improves the tensile and compression moduli of VNR. Meanwhile, high loadings of ZnO and used oil significantly decrease the tensile and compression moduli of VNR. Sulfur as a crosslinking agent increases the crosslink density which resulted to increase mechanical properties. Excess used oil and zinc stearate, reaction product of ZnO and stearic acid, on the VNR matrix resulted to rubber matrix softening and decrease in mechanical properties.
Authors: Bryan B. Pajarito, Jimyl Arabit
Abstract: Tensile properties of surfactant-loaded natural rubber (NR) vulcanizates are investigated in correlation with blooming. Rubber sheets are compounded using an L12 orthogonal array of Taguchi design of experiment, where ingredients are treated as factors varied at low and high loadings. Blooming experiments are carried out by placing NR sheets in a natural convection oven set at 50 °C for 20 days. The amount of bloom on the surface is removed using adhesive tape and is monitored with time. Tensile properties of rubber dogbone samples are also measured with time. Results show that 5 out of 12 formulations show blooming to be significantly related to tensile modulus (0.005 < p < 0.039). It is observed that the tensile modulus increases with blooming (0.898 < r < 0.973). Three formulations indicate significant correlation of blooming with tensile strength (0.022 < p < 0.047). As observed, tensile strength decreases with blooming (-0.884 < r < -0.930). Five formulations signify blooming to have significant correlation with maximum tensile strain (0.000 < p < 0.011), which decreases with blooming (-0.957 < r < -0.995). Two formulations imply significant negative (-0.960 < r < -0.963) correlation between blooming and tensile set (p= 0.009).
Authors: Ummu Qani’ah Yasin, Dzaraini Kamarun, Che Mohd Som Said, Azemi Samsuri
Abstract: Blooming is a diffusion process whereby compounding ingredients dispersed in rubber matrix migrate to the rubber surface and appears as a layer of white crystalline material. Blooming is a typical phenomenon observed in rubber compounds which could lead to problems such as discoloration and poor appearance of products as well as loss of adhesion. Cause of blooming was still unclear and this research was carried out to identify the effect of compounding ingredients and crosslink concentration on blooming rate in natural rubber compounds. In this project 6 natural rubber formulations based on three different types of compounding ingredients at two different concentrations of crosslinker were compounded and tested for their blooming characteristics. Sulphur, wax and dithiocarbamate as the compounding ingredients were mixed with natural rubber in the presence of 1 and 6 phr of peroxide as the vulcanizing agents. The effect of crosslink concentration on blooming rate of the compounded rubber was then determined. The blooming rate was determined by the weight of the blooming material on the rubber surface as a function of time. The blooming rate was found to be affected by the types of compounding ingredients and crosslink density of rubber. Wax with 6 phr of peroxide showed the highest amount of bloom and the highest blooming rate while the dithiocarbamate accelerator with 1 phr peroxide showed the lowest amount of bloom and the lower blooming rate. As expected, all the compounding ingredients showed an increase of crosslink concentration as the loading of peroxide increases. The blooming rate was also found to be affected by the crosslink concentration of rubber. As the crosslink concentration increases, the rate of blooming increases as were shown by wax and dithiocarbamate accelerator. However, sulphur showed the opposite trend whereby the crosslink concentration increases but the blooming rate decrease. This could be due to the high peroxide level retarding the sulphur blooming process.
Authors: Ludomir Ślusarski, Dariusz Bieliński, Piotr Głąb, Łukasz Kaczmarek, Jean-Paul Chapel, Gisèle Boiteux
Authors: Guo Hui Liu, Zheng Zhuang, Peng Liu, Li Yong Ni, Shi Yong Zhu, Jia Jia Chen, Hou Chao Lin, Long Hua Liu
Abstract: Forgings quality depends on the blooming processes and the deforming processes. The blooming processes are composed of upsetting and stretching, both of which influence the forgings quality very much. However, it is ignored. Methods are put forth to improve the forgings quality. It is surely of much significance.
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