Ya-Nan Wang

Preparation of oxidized sodium alginate with different molecular weights and its application for crosslinking collagen fiber

A series of periodate oxidized sodium alginate (OSA) were prepared as green polysaccharide-based crosslinkers. The molecular weight of OSA decreased, while their aldehyde group content increased with increasing dosage of sodium periodate. A typical OSA was further fractionated to four fractions by ethanol with a narrower molecular weight distribution. Then the crosslinking performances of OSAs/fractions on collagen fiber (CF) were investigated. DSC and SEM analyses showed that the thermal stability and dispersion degree of crosslinked CF was considerably enhanced with decreasing molecular weight of OSA. The effect of aldehyde group content of OSA on its crosslinking performance was less obvious than that of molecular weight, probably because the aldehyde group content in each OSA sample was higher than the amino group content of CF involved in the crosslinking reaction. In general, molecular weight of OSA plays a decisive role in improving properties of the crosslinked CF.

Preparation of highly-oxidized starch using hydrogen peroxide and its application as a novel ligand for zirconium tanning of leather

A series of highly-oxidized starch (HOS) were prepared using H2O2 and a copper-iron catalyst as a desired ligand for zirconium tanning of leather. The effects of catalyst and H2O2 dosages, and reaction temperature on the oxidation degree (OD, represented as the amount of carbonyl and carboxyl groups derived) of starch were investigated. The OD reached 76.2% when oxidation was conducted using 60% H2O2 and 0.015% catalyst at 98°C for 2h. 13C NMR and FT-IR illustrated carbonyl and carboxyl groups were formed in HOS after oxidation. GPC and laser particle size analyses indicated the decrease of HOS molecular size with increasing H2O2 dosage and OD. HOS with moderate OD and molecular weight was able to coordinate with zirconium and remarkably improve tanning process. Leather tanned by Zr complexes using HOS-60 (60% H2O2, Mn 3516g/mol) as ligand presented considerably better physical and organoleptic properties than those of traditional Zr-tanned leather.

Effect of structure features of polysaccharides on properties of dialdehyde polysaccharide tanning agent

Sodium alginate (SA), tara gum (TG), starch (ST) and cyclodextrin (CD) were oxidized to dialdehyde polysaccharides (DAPs) using equivalent sodium periodate. The effects of polysaccharide structure features on aldehyde group content, molecular size and tanning performance of DAPs were investigated. Each DAP had abundant aldehyde groups (>7 mmol/g) for fur tanning in the experimental conditions, and DAP with higher aldehyde group content was obtained when polysaccharide with lower molecular weight and linear chain was used. Lower crystallinity and β-(1→4) glycosidic linkage of polysaccharide benefited its degradation. Compared with dialdehyde ST (Mw>150,000) and dialdehyde CD (Mw<500), DAPs prepared from β-(1→4)-linked amorphous SA and TG had moderate molecular sizes (Mw 15,000-30,000) and exhibited satisfactory penetrability and crosslinking reactivity in collagen fiber network, and thus performed more favorable tanning properties in terms of higher shrinkage temperature and whiteness of fur. This suggests the suitability of β-(1→4)-linked amorphous polysaccharides for preparing dialdehyde tanning agents.