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Synthesis and Application of Highly Branched Polymers as Filling-Retanning Agents

Highly branched polymers (HBPs) were prepared via free-radical polymerization of methacrylic acid (MAA) with polyfunctional allyl co-monomer (Mono-trimethylolpropane trimaleate, MTPTM) at various n(MAA)/n(MTPTM) ratios. HBPs were employed in retanning wet-blue pigskins and the retanned leathers were evaluated by their physical properties such as tensile strength, tear strength, extension at break and organoleptic properties including softness, fullness, smoothness and tightness. The results showed that HBPs did well in filling and retanning leather and especially in the case of n(MAA)/n(MTPTM) = 12:1 (HBP-4). HBP-4 was characterized by 1 HNMR, SEC, DSC and TGA, the results indicated that the polymer showed polydispersity (PDI = 1.456, M w 27,024, M n 18 566), its TG/DTG curves showed two-stage decomposition with two weight loss temperature maxima (206.38°C and 429.57°C), the single glass transition on the DSC curve and the Tg (209.98°C) which was lower than that of poly-methacrylic acid (227.85°C) implies that HBP-4 molecules have better flexibility than PMAA and there is no phase separation in the polymer.