Papers by Keyword: Redispersible Polymer Powder

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Authors: Igor I. Rudenko, Oleksandr P. Konstantynovskyi, Artem V. Kovalchuk, Marharyta V. Nikolainko, Dmytro V. Obremsky
Abstract: Properties of dry mixes for anchoring application (increasing of mortars strength, adhesion, volume stability etc.) based on alkali activated Portland cement (AAPC) are influenced by different factors. One of them is application of chemical admixtures with different functionality. Adhesive properties are mainly achieved by redispersible polymer powders (RPP). The main problem in choice of RPP’s type is destruction of their molecules with ester links due to alkaline hydrolysis.The purpose of work was investigation of RPP’s molecular structure influence on properties of mortar for anchoring application based on AAPC and determination of the most effective.Efficiency of RPP based on copolymer of versatile acid ester was shown. The application of this RPP provides adhesion of 1.1 MPa and consistency of 190 mm. Positive effect of copolymer of ethylene and vinyl acetate was shown despite of partial destruction of RPP’s molecule as a result of alkaline hydrolysis of vinyl acetate at early terms of hardening. Negative effect of RPP is in decreasing of mortar strength. Thus this problem solving is decreasing of powder content to values which provide necessary physical-mechanical properties (strength, adhesion).
Authors: Zheng Mao Ye, Wen Chen, Xin Cheng
Abstract: The impermeability and other performance of sulphoaluminate cement were studied, which mixed with redispersible polymer powders. With the help of SEM and mercury intrusion apparatus, the morphology of the hydrates and the pore structure of the cement mortars were observed. The impermeability mechanism of redispersible polymer powders in sulphoaluminate cement mortar was analyzed. The results show that sulphoaluminate cement mortar could be modified by adding redispersible polymer powders. The flexural strength of sulphoaluminate cement mortar could be increased by adding redispersible polymer powders, and compressive strength of sulphoaluminate cement mortar could also be increased to a certain extent. When the mass fraction of redispersible polymer powders was 0.9%, the flexural strength and compressive strength reached 9.2 MPa and 52.5 MPa. When small amount of redispersible polymer powders was added, the impermeability of modified sulphoaluminate cement mortar was improved significantly. When the mass fraction of redispersible polymer powders exceeded 0.9%, impermeability of Sulphoaluminate cement mortar would not be improved significantly. Due to redispersible powders gap filling and film forming, the interface of cement and aggregate is more closed, total porosity decreased and unharmful porosity increased when redispersible polymer powders is added.
Authors: Jian Xu, Zhong Jun Feng, Le Feng Fu, Bai Cun Zheng
Abstract: Acrylate polymer emulsion was synthesized by semi-continuous seeded emulsion polymerization with methacrylic acid (MAA) as the hydrophilic shell monomer. The redispersible polymer powder was prepared by spray drying method. The effects of the amount of MAA, styrene (St) stoichiometry equivalents to methyl methacrylate, and two kinds of spray drying methods on size distribution of the redispersible polymer powder were further systematically investigated. The Malvern laser particle size analyzer, transition electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimeter were employed to characterize the redispersible polymer powder. Results showed that the redispersible polymer powder obtained by pneumatic spray drying with excellent re-dispersibility could be synthesized at 10 % of MAA, 50 % of St stoichiometry equivalents. The final copolymer emulsion with “perfect” core-shell morphology was approved by TEM, and the comparable film forming ability of the redispersible polymer powder with the original emulsion was observed by SEM, which could form a dense and smooth membrane.
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