Plastisol foaming process. Decomposition of the foaming agent, polymer behavior in the corresponding temperature range and resulting foam properties

The decomposition of azodicarbonamide, used as foaming agent in PVC—plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min−1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g−1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol−1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse.

Social determinants of sexual satisfaction in Spain considered from the gender perspective

Aims: To describe gender- and social class-related inequalities in sexual satisfaction and analyze their relationship with self-perceived health status. Methods: This population-based, cross-sectional study included 7384 sexually active people aged 16 years and over residing in Spain in 2009 (3951 men and 3433 women). The explanatory variables were gender, age, social class, share in performing domestic tasks, spend time looking after oneself, collaborate economically in supporting the family, caring for children, self-perceived health status, and the desire to increase or decrease frequency of having sexual relations. Bivariate and multivariate logistic regression models were fitted. Results: Among women, sexual satisfaction declines progressively after age 45. Sexual satisfaction is 1.7 times higher among women who look after themselves and who feel good compared with those who do not. The odds of wanting to increase sex is 3.3 times higher for women who are satisfied compared with women who desire a lower frequency of sexual intercourses; and good perceived health was associated with sexual satisfaction. In satisfied men, the corresponding odds is 1.9 times that of men desiring to reduce their frequency of sex. Conclusions: Gender and social class inequalities are found in sexual satisfaction. This is associated with perceived health status, adding evidence in support of the World Health Organization definition of sexual health.

How can an invasive grass affect fire behavior in a tropical savanna? A community and individual plant level approach

Some invasive grasses have been reported to change fire behavior in invaded plant communities. Urochloa brizantha is an aggressive invasive grass in the Brazilian Cerrado, an ecosystem where fire is a common disturbance. We investigated the effects of U. brizantha on fire behavior in an open Cerrado physiognomy in Central Brazil. Using experimental burnings we compared fire behavior at both the community and the individual plant level in invaded (UJ) and non-invaded (NJ) areas burned in July. We also assessed the effect of fire season in invaded areas by comparing July (UJ) and October (UO) burnings. We evaluated the following variables: fuel load, fuel moisture, combustion efficiency, maximum fire temperature, flame height, and fire intensity. Additionally, we evaluated the temperatures reached under invasive and native grass tussocks in both seasons. Fuel load, combustion efficiency, and fire intensity were higher in NJ than in UJ, whilst flame height showed the opposite trend. Fuel amount and fire intensity were higher in October than in July. At the individual plant level, U. brizantha moisture was higher than that of native species, however, temperatures reaching ≥600 °C at ground level were more frequent under U. brizantha tussocks than under native grasses. At the community level, the invasive grass modified fire behavior towards lower intensity, lower burning efficiency, and higher flame height. These results provide essential information for the planning of prescribed burnings in invaded Cerrado areas.