Lactose is a common component found in many foods and dairy products. In this study, the vibrational signatures in the crystalline structure of α -, β -, and α -lactose monohydrate were calculated based on quantum chemistry calculation (QCC), whilst the vibrational spectra in freeze-dried lactose equilibrated at various a w and pre-humidified amorphous lactose (0.33 a w ) stored from 25 to 95 °C were determined by using Raman and FT-IR spectroscopies. The vibrational signatures of crystalline lactose were affected by the presence of water according to QCC results. Water plasticization, involving water insertion, exposure of H-bonding sites, and structure disruption, was accelerated by storage temperature based on Raman and FT-IR spectra analysis. Raman spectra indicated that the crystal formation of lactose was affected by a w and storage temperature. Moreover, the spectral changes assigned in OH group provided useful information for determining the critical a w or temperature when T g -related molecular mobility occurred in lactose-containing products.
Xiaowen Yan,Ruoyu Zhang,Chunjun Zhao,Lijing Han,Shuai Han
With the development of self-healing materials and the increasing demands from complicated application environment, underwater self-healing is attracting more and more attention. However, until now, the effects of different dynamic chain extender and water molecular on the self-healing of polyurethanes have not been investigated yet. In this work, we synthesized two types of polyurethanes with 2,4-pentanedione dioxime (DMG) and bis(4-hydroxyphenyl) disulfide (HPS) as the chain extenders, respectively. Furthermore, PDMS was adopt as the soft segment and isophorone diisocyanate (IPDI) was used the hard segment. It is found that they all have good flexibility, probably due to the low Tg of PDMS soft segment. Interestingly, the five samples own a similar Tg at ∼ -112 °C, which belongs to PDMS. Due to the hydrophilicity of the majority component of PDMS, the five polyurethanes have water contact angle larger than 90°. Nevertheless, the water absorption experiment clearly show that they can absorb water until saturation. The self-healing experiments were carried out in both air and water, which proved that the underwater self-healing speed of DMG polyurethanes was increased significantly. It is deduced that the water could plasticize these hydrophobic polymers and accelerate the self-healing speed underwater.
危险品化学品经营许可证（带存储）