Broadening the damping temperature range of viscoelastic microporous polyurethane elastomers (MPUE) is a challenge to break the limits of practical applications in damping field. Based on the molecular reaction kinetics and the molecular structure design of MPUE, different molecular weight suspension chain extenders were synthesized from polyethylene glycol monomethyl ether (MPEG), isophorone diisocyanate (IPDI) and 2-amino-1,3-propanediol via end-controlling oriented synthesis. The effect of molecular weight and dosages of suspension chain extenders on the damping property of MPUE was studied. It was demonstrated that strong intermolecular hydrogen bonds can be formed between MPUE molecules due to the carbamate groups and urea groups of the suspension chain extenders. The transformations of various motion modes of the suspended chain were driven by the existence of a large number of ether bonds, which can reduce the micro-phase separation degree in the material matrix, resulting in higher kinetic friction between molecular chains. The damping properties of the material were significantly improved, presenting a maximum increase of 62.3% in the effective damping temperature domain, and a maximum increase of 34.0% in the peak loss factor (tan δ), which was attributed to the synergistic compound effect of multiple motion modes. This high damping MPUE has great application prospects in the fields of acoustic noise reduction and household appliances damping.
Bo Wen,Gaopeng Wang,Renze Xu,Chenglong Weng,Jintao Yang
With the growing global emphasis on environmental protection, supercritical CO 2 foaming technology for biodegradable materials such as polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), poly (butylene succinate) (PBS) and their blends has emerged as a research and application hotspot. However, the low melt strength and poor compatibility of these polymers often lead to low nucleation efficiency, cell wall rupture and coalescence, exhibiting inferior foaming performance. In this work, aiming to enhance the foamability of PLA and PLA/PBAT blends, a fluorinated chain extender, F-CE (GMA-co-DFHA-co-MMA), was designed and synthesized. Through the reactive melt blending, F-CE effectively enhanced the melt strength of PLA and interfacial adhesion between PLA and PBAT, leading to a significant improvement in foaming performance. Additionally, the fluorine groups in DFHA demonstrated high affinity for CO 2 , providing additional heterogeneous nucleation sites for bubble formation, thereby increasing both foam expansion ratio and cell density. Notably, the F-CE/PLA foam exhibited a cell diameter of ∼13.8 μm with an exceptionally high expansion ratio of ∼35. As a contrast, pristine PLA foam shows an expansion ratio of ∼30, but with large cell diameter (∼118 μm). Although PLA foam containing CE without fluorine (CE/PLA foam) exhibits small cells with an average cell diameter of ∼13.6 μm, the expansion ratio is low (∼23). In addition, F-CE also exhibits superior performance in improving the foamability of PLA/PBAT blends. This work presents a chain extender specifically engineered for foaming applications, which functions as a highly efficient foaming additive to holistically enhance the foaming performance of polymers.
危险品化学品经营许可证（带存储）