Papers by Author: Jian Ping Duan

Abstract: Effect of polycarboxylate superplasticizer (PCs) with different bond between side chain and truck chain on hydration of cement in early period was studied. The performance of PCs in concrete was investigated by setting time, TGA and SEM. PC-based superplasticizer with ester bonding between side chain and truck chain. Although they had the proximate structure parameters in density of side chain and absorption group (carboxyl groups), the setting time of cement paste was significantly different when different PCs were employed in the preparation of cement. Decomposing of this bond in alkali environment may lead to a shorter setting time. On the other hand, same difference in hydration production was observed in early period hydration of cement paste when two different PCs was incorporated, which indicated that the different bond structure in PCs affected the hydration of cement in a different manner. The result of SEM indicated that the morphological phase of hydrated product was different when PC was applied, this may be related with the different result in the TG and TGA

Abstract: Maleic anhydride modified polycarboxylates superplasticizes (MPC) was synthesized from allylic poly (ethylene oxide ether) (APEG), maleic anhydride (MAH), sodium methylallyl sulfonate (SMAS) using ammonium persulfate (APS) as initiator. The optimal MPC with best fluidity was got at 90 °C when molar ratio of MAH, APEG, SAMA was 2.75∶1∶0.4 in the present of 4.5 mol% APS of all the monomer molars. MPC which possessed hydroxyl terminated side chains shows some difference in fluidity retarding related to the conventional superplasticizers possessed methoxy terminated side chains.

Abstract: Sulfonated chitosan (SCS) was prepared from chitosan and sulfuric acid via sulfation reaction. SCS was used as superplasticizer in cement. The test showed that the maximum fluidity of the cement paste was 232 mm with dosage of 0.75 wt % at water to cement ratio (w/c) of 0.29. Meanwhile, lesser loss of fluidity and slump over 60 mins were observed comparing to naphthalene sulfonated formaldehyde condensates (NSF). A well-distribution of cement particles can be seen from the image of SEM in the sample of mortar prepared by SCS. The water reduce ratio of SCS reach 19.2 %. The applied results showed that SCS could slightly improve the mechanical properties of mortar. The paste fluidity, mechanical properties and slump loss of the cement paste incorporated SCS indicated that it can be used as superplasticizer in concrete.

Abstract: The effect of sodium sulfate on the dispersion of polycarboxylate superplasticizer (PC) was studied in this paper. The study of fluidity of cement paste shown that the carboxyl groups did more to improve the fluidity of cement paste than the sulfonic groups, and a quick loss of fluidity was much more likely arisen by slufonic groups in PC comparing with the carboxyl groups. The methods of zeta potential and fluidity of cement paste were applied to investigate the dispersal ability of cement particles when different PC used in the present of different concentration of sodium sulfate. The result showed that the sulfonic group was more sensitive to sodium sulfate than carboxyl groups in PC.

Abstract: Superplasticizers with various of length of side chains, density of the carboxylic (-COO-) and sulfonic groups (-SO3-) have been synthesized based on different monomers and ratios. The effects of these structural factors on the properties of cement pastes were investigated though measurements of paste fluidity, adsorption amount and Zeta potential (ζ-potential). The results indicated that the higher density of -COO^- and -SO₃^- and the longer of polyoxyethylene (PEO) side chains contributed to the dispersion and adsorption amount of cement pastes in the presence of the same dosage of polycarbosylate superplasticizer. The results indicate that -COO^- and -SO₃^- mainly provide electrostatic repulsion effects and PEO side chains contribute to the steric hindrance repulsion during the process of hydration of cement.

Abstract: A graft copolymer was synthesized by means of radical copolymerization of degraded starch, phloroglucinol(PG) and sulfanilic acid (SA) and the reaction was catalyzed by horseradishperoxidase (HRP)/H₂O₂. It was discussed that the effectsof monomer composition, the temperature and system pH on the graft copolymerization. The ideal copolymer was synthesized in the pH 7.0 at 30°C when the molar ratio of PG and SA was 5:6. The structure of the copolymer was characterized by Fourier Transform Infrared (FTIR) spectroscopy. Meanwhile, the graft copolymer has been used in tanning process. The retanned leather exhibits excellent increase ratio in leather thickness and good dyeing ability which indicate that the graft copolymer has retanning and assisting dyeing properties.

Abstract: Modified starch tannage was synthesized by two steps. First step, a graft starch was synthesized by graft copolymerization of degraded starch with p-aminobenzene sulfonic acid and nekal using horseradish peroxidase (HRP)/H₂O₂ catalyze system. The effects of system pH, reaction temperature and amount of HRP on the graft efficient (GE) and graft percent (GP) were investigated and the maximum GE and GP of modified starch were obtained using 4 mg HRP/2.24 g H₂O₂ as catalyst at 35 for 3h under pH 7. The second step, the graft starch was oxidized by periodic acid to prepare modified starch tannage with dial dehyde.The effect of periodic acid on aldehyde groups content of graft starch was studied and it was found that the maximum content was at periodic acid concentration of 4 mol/L. The structure of modified starch tannage was characterized by FTIR, NMR and GPC. The shrink temperature (T_s)of tanned leather is 80.6 °C and the retanned leather has distinctive style of softness and flexibility.

Abstract: A modified polycarboxylate superplasticizer was synthesized by copolymerization of polyethylene glycol monomethyl ether methacrylate (MPEG-MA), β–Cyclodextrins grafted maleic anhydride (MAH-β-CD), methacrylic acid (MAA) and methallyl sulfonic acid (MAS). The excellent superplasticizer was obtained at the molar ratio of n(MAH-β-CD) : n(MAS) : n(MAA) : n(MPEG-MA) was 0.05:0.1:3:1 using ammonium persulfate (APS) as initiator at 90°C for 5 h. The applied results show that the product had many advantages, such as lower dosage, longer setting time, better flow-keeping ability and better compatibility with different cement. Meanwhile, the structure and relative molecular weight were characterized by FTIR and GPC respectively.

Abstract: Two grafting starch was obtained by grafting copolymerization of two synthetical vinyl monomers using HRP/H2O2 as catalyst. The structure of vinyl monomers was verified by 1H-NMR.The grafting polymer was proof by structures were verified by FTIR. The effect of mass ratio of starch and vinyl monomer on the grafting efficiency (GE) and grafting percentage (GP) was studied. The highest GE and GP of the first grafting starch was 35% and 32%, 59% and 50% for the second grafting starch when the vinyl monomer ratio was 9%. The molecular mass tested by GPC for the two kinds grafting starch with highest GE and GP were 54 600 and 63 970. The two mostly grafted starches were used as retanning agent. The increase ratios in thickness were 18.1% and 18.6% respectively and the tanned leather has excellent softness and flexibility.

Abstract: The copolymer of phenol and acrylamide was synthesized by copolymerization using horseradish peroxidase (HRP)/H2O2 as catalyst. The effect of monomer composition on the copolymer tanning agent properties was investigated. The structure of the copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy. The molecular weight was determined by gel permeation chromatography (GPC). The result shows that the average molecular weight of the copolymer is about 1900. Its molecule distribution index is much narrower. The copolymer was used as tanning agent, the result shows that the applied leather is excellent in softness and dyeing.