No abstract

In this work, a biphenyl liquid crystalline small molecule (BLCM) containing flexible units was synthesized by one-step condensation reaction of 4,4'-dihydroxybiphenyl (BP) and 1,6'-dibromohexene. Then the commercially available bisphenol A...

Ancient architectures are an important part of immovable cultural heritage and the largest surviving amount of tangible cultural heritage in the world. However, the increasingly serious noise pollution will not only affect the sanctity of ancient architectures, but damage the internal structure caused by continuous mechanical vibration, and affect their lifetime. In this paper, diaminodiphenyl ether and pyromellitic dianhydride were used as monomers, modi ed by triethylamine to synthesize water-soluble polyamide acids, and calcium carbonate (CaCO 3 ) was used as ller to prepare CaCO 3 /polyimide (CaCO 3 /PI) composite aerogels by homogeneous mixing, freeze-drying and thermal imidization. CaCO 3 can effectively adjust the pore wall roughness of CaCO 3 /PI composite aerogels, so as to improve their sound absorption performance. When the amount of CaCO 3 is 4 wt%, CaCO 3 /PI composite aerogels exhibit optimal sound absorption performance, excellent mechanical properties, thermal insulation and heat resistance. The corresponding noise reduction coe cient is 0.327 and the average sound absorption coe cient is 0.903 in the frequency range of 2000 ~ 6300 Hz. Young's modulus is 4.03 kPa, stress loss and plastic deformation after 100 compression cycles with a maximum strain of 50% are 3.27% and 2.17%, respectively. The energy loss coe cient is 0.248, thermal conductivity is 0.038 W/(m•K), and heat resistance index is 334.1 o C. The CaCO 3 /PI composite aerogels show momentous application prospects in the eld of ancient architectures protection.

Ancient architectures are an important part of immovable cultural heritage and the largest surviving amount of tangible cultural heritage in the world. However, the increasingly serious noise pollution will not only affect the sanctity of ancient architectures, but damage the internal structure caused by continuous mechanical vibration, and affect their lifetime. In this paper, diaminodiphenyl ether and pyromellitic dianhydride were used as monomers, modified by triethylamine to synthesize water-soluble polyamide acids, and calcium carbonate (CaCO3) was used as filler to prepare CaCO3/polyimide (CaCO3/PI) composite aerogels by homogeneous mixing, freeze-drying and thermal imidization. CaCO3 can effectively adjust the pore wall roughness of CaCO3/PI composite aerogels, so as to improve their sound absorption performance. When the amount of CaCO3 is 4 wt%, CaCO3/PI composite aerogels exhibit optimal sound absorption performance, excellent mechanical properties, thermal insulation and heat resistance. The corresponding noise reduction coefficient is 0.327 and the average sound absorption coefficient is 0.903 in the frequency range of 2000 ~ 6300 Hz. Young’s modulus is 4.03 kPa, stress loss and plastic deformation after 100 compression cycles with a maximum strain of 50% are 3.27% and 2.17%, respectively. The energy loss coefficient is 0.248, thermal conductivity is 0.038 W/(m·K), and heat resistance index is 334.1oC. The CaCO3/PI composite aerogels show momentous application prospects in the field of ancient architectures protection.