ABSTRACT
The development of a dynamic network for commodity polymer systems via feasible methods has been explored in the context of a society-wide focus on the environment and sustainability. Herein, we demonstrate an adaptive post-curing method used to build a self-healable network of waterborne polyurethane-acrylate (WPUA) composite latex. The composite latex was synthesized via the miniemulsion polymerization of acrylates in the dispersion of waterborne polyurethane (PU), with commercial acetoacetoxyethyl methacrylate (AAEM) serving as the functional monomer. Then, a dynamic disulfide (S-S)-bearing diamine was applied as the crosslinking agent for the post-curing of the hybrid latex via keto-amine condensation, which occurred during the evaporation of water for film formation. It was revealed that the microphase separation in the hybrid films was suppressed by the post-curing network. The mechanical performance exhibited a high reliability as regards the contents of the crosslinking agents. The reversible exchange of S-S bonds meant that the film displayed associative covalent-adaptive networks in the range of medium temperature in stress relaxation tests, and ≥95% recovery in both the stress and the strain was achieved after the cut-off films were self-healed at 70 °C for 2 h. The rebuilding of the network was also illustrated by the >80% recovery in the elongation at break of the films after three crushing-hot pressing cycles. These findings offer valuable insights, not only endowing the traditional WPUA with self-healing and reprocessing properties, but broadening the field of study of dynamic networks to polymer hybrid latex.
ABSTRACT
To investigate the epidemic characteristics and prevention strategies of main infectious diseases. From 2010 to 2012, 23 notifiable diseases were reported in Yantai with average reported cases of 17,376. The morbidity was the highest in 2012 and the lowest in 2011. The accumulated death toll was 101 with the highest death rate in 2011 and the lowest in 2012. Major class A and B infectious diseases included viral hepatitis, phthisis, syphilis, clap and dysentery. The major class C infectious disease was hand-foot-and-mouth disease every year. The distribution of transmission routes of HIV/AIDS among patients with HIV and AIDS in Yantai were investigated. The overall condition of phthisis in Yantai showed stable with slight decrease. The occurrence rate of phthisis every season had fluctuation with higher rate in middle two seasons and lower rate at the beginning and end. The major type of viral hepatitis was still hepatitis B. Patients with hand-foot-and-mouth disease were children under 5 years old accounting for 90.56%, mainly reported in May, June, July and August. At present, the condition of plague prevention for infectious diseases in Yantai is not optimistic with both new and old infectious diseases.
ABSTRACT
BACKGROUND: High levels of dietary sodium are associated with raised blood pressure and adverse cardiovascular health. To determine baseline salt intake, we investigated the average dietary salt intake from 24-hour urinary sodium excretion with a small sample of Yantai adults in the Shandong province of China. METHODS: One hundred ninety one adults aged 18-69 years were randomly selected from the Yantai adult population. Blood pressure, anthropometric indices and sodium excretion in a 24-hour urine collection were measured. Consumption of condiments was derived from 3-day weighted records. Completeness of urine collections was verified using creatinine excretion in relation to weight. RESULTS: The mean Na and K outputs over 24 hours were 201.5 ± 77.7 mmol/day and 46.8 ± 23.2 mmol/day, respectively (corresponding to 11.8 g NaCl and 1.8 g K). Overall, 92.1% of the subjects (96.9% of men and 87.1% of women) had intakes of over 6 g salt (NaCl)/d. The main sources of salt intake from weighed condiments records were from home cooking salt (74.7%) followed by soy sauce (15.0%). Salt intake from condiments and salt excretion were weakly correlated((r = 0.20, p = 0.005).A positive linear correlation between salt intake was associated with systolic blood pressure in all adjusted and unadjusted model (r = 0.16, p = 0.01). Each 100 mmol/day increase in sodium intake was associated with a 4.0 mmHg increase in systolic blood pressure. CONCLUSION: Dietary salt intake in Yantai adults was high. Reducing the intake of table salt and soy sauce used in cooking will be an important strategy to reduce sodium intake among Yantai adults.
