Synthesis Of Silicon Based Dendritic- Linear Polymer And Its Application In Leather Fatliquoring Process

In current study, the new dendritic-linear fatliquor was prepared with polysiloxane and dendritic polyamide-amine, and was applied to fatliquoring process. The mechanism of action between branched molecular and leather was also discussed preliminarily.Firstly, ethylenediamine and methyacrylate were mixed in methanol to synthesize 1G polyamide-amine (1G PAMAM) and 2G polyamide-amine (2G PAMAM) by Michael addition reaction and amidation reaction in turn. Then the single epoxy-terminated polydimethylsiloxane (SEPDMS) was prepared with hydrogen-terminated polydimethylsiloxane (HTPDMS) and allyl glycidyl ether (AGE) using chloroplatinic acid as catalyst by hydrosilylation reaction. Finally, two silicon based dendrtic-linear polymers (1G PAMAM-Si and 2G PAMAM-Si) were obtained by grafting SEPDMS onto 1G PAMAM and 2G PAMAM, respectively. The results of FT-IR and’H-NMR showed that the reactions were carried out in accordance with the experiment design. Taken the preparation of 1G PAMAM-Si for instance, the influences of reaction temperature, reaction time and solvent percent on the grafting ratio of PAMAM grafted by SEPDMS were investigated by single-factor experiments, and the optimum grafting conditions were obtained through a series of orthogonal experiments:the mole ratio of SEPDMS and PAMAM is 0.95:1, the reaction temperature is 60 ℃, the reaction time is 5.5 h and the solvent percent is 60%.The emulsion properties of 1G and 2G PAMAM-Si were studied. The results showed that the emulsions of PAMAM-Si have excellent stability for dilution (1:9) and centrifugation and resistance of chromium salt, acid, alkali, thermal and cold. The distribution emulsion particle sizes are narrow and the average particle sizes are only 35.78 nm and 26.73 nm, which are far less than the collagen fiber spacing. So PAMAM-Si molecules can penetrate into the leather, γcmc of PAMAM-Si is around 30 mN/m, and pC20 is near 2.90, indicating that their ability and efficiency to reduce the water surface are excellent. In addtion, the average stability in hard water is the grade of 5, which reveales that PAMAM-Si has excellent stability of hard water resistance. Based on the object of castor oil, the emulsifying ability of 2G PAMAM-Si was found to 33.39%, which was better than 26.93% of 1G PAMAM-Si.Through being applied PAMAM-Si in leather fatliquoring process, it was found that the properties of leather can be greatly improved. The softness of leather fatliquored with 1G PAMAM-Si is improved obviously, which is increased by 1.63 mm than that of blank leather. However the tensile strength of leather fatliquored with 2G PAMAM-Si is increased by 10.62 MPa and the tear strength is increased by 45.85 N/mm. It should be noticed that the fatliquoring effect of PAMAM-Si combined with castor oil is more outstanding. The properties of leather fatliquored with different mass ratios of PAMAM-Si and castor oil were investigated. The maximum softness value will be obtained when the mass ratio of PAMAM-Si and castor oil is 3:7, and the physical and mechanical properties of the fatliquored leather increase with the content of PAMAM-Si in the mixture.The PAMAM-Si distribution, collagen fiber loose degree and thermal performance of fatliquored leather were characterized by EDS, SEM, XRD and TG. It was shown that PAMAM-Si can be uniformly distributed in leather. The distribution of collagen fiber with 1G PAMAM-Si is looser. However, the arrangement of collagen fiber fatliquored with 2G PAMAM-Si is closer. PAMAM-Si can penetrate into the fibers, increase their spacing and cross-link disorder, without destroying their molecular structure.2G PAMAM-Si has larger molecular volume, more amino content and stronger interaction with fiber, so that the obvious change has not been observed in the distance of fiber. Moreover,2G PAMAM-Si significantly increases the thermodynamic stability of leather, in which T10% is 224.40℃ and CR600℃ is 26.66%.The interaction forces of PAMAM-Si and leather mainly comprise of the hydrogen bond. And a certain amount of electrovalent bond, covalent bond and physical adsorption may also exist. According to the analysis, the hydrogen bond is made by the interaction of PAMAM-Si peripheral amino and hydroxyl, amino and carboxyl of leather. The formation of electrovalent bond is due to the way in which the partial amino with a positive charge (NH3+) attracted the references in the collagen side chain or ionized carboxyl with negative charge (COO-) at the selected conditions.