Polycarboxylates are linear polymers with a high molecular mass (Mr ≤ 100 000) and with many carboxylate groups. They are polymers of acrylic acid or copolymers of acrylic acid and maleic acid. The polymer is used as the sodium salt (see: sodium polyacrylate).
Polycarboxylate ethers (PCE) are used as superplasticizers in concrete production.
Polycarboxylates are used as builders in detergents. Their high chelating power, even at low concentrations, reduces deposits on the laundry and inhibits the crystal growth of calcite.
Polycarboxylate ethers (PCE) are used as superplasticizers in concrete production.
Polycarboxylates are poorly biodegradable but have a low ecotoxicity. In the sewage treatment plant, the polymer remains largely in the sludge and is separated from the wastewater.
Polyamino acids like polyaspartic acid and polyglutamic acid have better biodegradability but lower chelating performance than polyacrylates. They are also less stable towards heat and alkali. Since they contain nitrogen, they contribute to eutrophication.
Polycarboxylate superplasticizers (PCEs) are comb-shaped polymers with an anionic backbone and several nonionic pendant chains, which typically are comprised of polyethylene glycols. In this study, the synthesis of a new type of superplasticizer is presented, which does not exhibit the typical comb-shaped form of PCEs but is built up from a linear polyetheramine and a hyperbranched polyglycerol scaffold, which was carboxymethylated in the periphery. 1H/13C NMR and FT-IR spectroscopy and size exclusion chromatography were employed for the characterization of the polymers. Furthermore, their dispersing performance and “slump retention” capability were investigated in cement pastes. Adsorption and zeta potential measurements as well as heat flow calorimetry were conducted to gain more insight into the interaction of the polymers with cement. It was found that such non-comb-shaped polymers are highly effective cement dispersants. Moreover, the hyperbranched superplasticizers exhibited high robustness toward alkali sulfates and maintained the fluidity much longer, compared to a conventional comb-shaped PCE.
Polycarboxylate superplasticizers (PCEs) emerged as one of the most important superplasticizers for concrete due to their superior performance.Compared to other products like polycondensates, they fluidize cement even at low water to cement ratios, require relatively low dosages, and exhibit a long slump retention capability.The high dispersing efficacy of PCEs can be ascribed to the nonionic side chains, which stretch out into the pore solution and act as a steric barrier to keep the cement particles apart.Moreover, due to the adsorption of the PCEs, a negative surface charge is induced, which also provokes electrostatic repulsion between cement particles. However, a key parameter for effective dispersion represents the adsorbed layer thickness of the PCEs on the cement surface. According to the Ottewill Walker equation, a high steric stabilization of particulate suspensions especially can be achieved by polymers which adsorb by forming a particularly thick layer. Therefore, it is assumed that bulky, outstretched, and sterically demanding polymers might produce an even stronger steric effect than comb-shaped PCEs. This hypothesis was confirmed by Liu et al., who showed that star-shaped PCEs are superior over comb-shaped analogues due to their multi-arm structure composed of acrylic acid-co-isoprenyloxy polyethylene glycol ether (IPEG), which allows the polymer to reach out far more into the pore solution, thus creating a higher layer thickness. Similar results were also reported for PCEs with a branched topological structure synthesized by free radical copolymerization of acrylic acid, polyethylene glycol methallyl ether (HPEG), and a branched monomer, which was prepared in a two-step synthesis from diallylamine, methyl acrylate, and trimethylolpropane. Even the incorporation of branched lateral chains into comb-shaped PCEs can effectuate a higher steric hindrance effect as was demonstrated by Li and co-workers. They found that the dispersing performance of IPEG-PCEs was considerably improved after the introduction of hyperbranched polyamidoamine side chains synthesized from ethylene diamine and methyl acrylate. All these previous findings suggest that branched structures seem to be very beneficial for the steric stabilization, which is why such motifs are attractive elements for the development of new superplasticizers. Unfortunately, their preparation often involves multiple synthesis steps being tedious and time-consuming. Hence, branched polymer structures are needed, which can be formed in just a few reaction steps.
In light of this, hyperbranched polyglycerols represent a promising candidate as they can be obtained in one single step. They are synthesized by anionic ring opening multibranching polymerization (ROMP) of glycidol yielding branched polyether polyols with a globular structure and numerous hydroxyl functionalities in the inner and outer sphere. Hyperbranched polyglycerols have gained much attention over the last years due to their outstanding properties. They are nontoxic and highly water-soluble and exhibit a high chemical stability and low intrinsic viscosity, and their molecular weight can be tuned over a broad range. From a chemical perspective, they are highly interesting because the hydroxyl groups in the periphery can be derivatized by various functional groups. Owing to their excellent biocompatibility, hyperbranched polyglycerols are widely used in biomedical and pharmaceutical applications such as in polymer therapeutics, for controlled drug release, in the fabrication of antifouling surfaces, in tissue engineering, or as imaging agent. Meanwhile, they were also applied for other purposes such as for the biomimetic crystallization of calcium carbonate or as an additive in aqueous printing inks to improve the color fastness. Hitherto, hyperbranched polyglycerols have not been considered as a structural motif for superplasticizers. Therefore, this study aims to present the synthesis of a new type of superplasticizer, which contains a hyperbranched polyglycerol scaffold, and to evaluate the dispersing properties of such moieties in cement. On the basis of previous work from Frey and co-workers, the hyperbranched polymer was synthesized from a polyether monoamine (Jeffamine) and glycidol using the slow monomer addition approach. Thereafter, some of the hydroxyl groups in the periphery of the polyglycerol scaffold were carboxymethylated to facilitate the adsorption of the polymer on cement. In this way, a polymer was obtained whose structure resembles a jellyfish made up from a linear polyetheramine side chain and a hyperbranched polyglycerol unit. To ascertain the steric effect of this superplasticizer, additionally, a carboxymethylated hyperbranched polyglycerol without any side chain as well as a linear non-hyperbranched molecule with two carboxylate groups were synthesized as reference compounds. The dispersing performance and slump retention ability of all synthesized polymers were investigated via mini-slump tests and compared with the results obtained for a conventional comb-shaped PCE. Isothermal heat flow calorimetry as well as adsorption and zeta potential measurements were performed to elucidate the working mechanism of the novel hyperbranched superplasticizer. The overall goal of this study was to find out whether hyperbranched polyglycerols can provoke a sufficient steric hindrance effect.
DK-100 is a specifically designed polycarboxylate superplasticizer which exhibits excellent dispersion performance while maintaining good retention effects due to our cutting-edge processing technique; it has a wide range of applications as used in the industrial fields of normal concrete, pumping concrete, as well as self-compacting with high strength & durable concrete projects.
Traditional ones including high speed railways, highways, (air)ports, (hydro)power plants in forms of pre-cast concrete, reinforced concrete and pre-stressed concrete Excellent performance in dispersion and good slump retention Good compatibility with various concrete material components Low application dosage and contraction rate No corrosion effects Environmentally friendly
|Water Reducing Rate||%||≥25|
|Atmospheric Pressure Bleeding Rate||%||≤20|
|Pressure Bleeding Rate||%||≤90|
|Chlorine Ion（based on solids)||%||≤0.1|
|Alkali Content（based on solids)||%||≤5.0|
|Sodium Sulphate Content||%||≤5.0|
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