Identification and quantification of cell gas evolution in rigid polyurethane foams by novel GCMS methodology

Producción CientíficaThis paper presents a new methodology based on gas chromatography-mass spectrometry (GCMS) in order to separate and quantify the gases presented inside the cells of rigid polyurethane (RPU) foams. To demonstrate this novel methodology, the gas composition along more than three years of aging is herein determined for two samples: a reference foam and foam with 1.5 wt% of talc. The GCMS method was applied, on one hand, for the accurate determination of C5H10 and CO2 cell gases used as blowing agents and, on the other hand, for N2 and O2 air gases that diffuse rapidly from the surrounding environment into foam cells. GCMS results showed that CO2 leaves foam after 2.5 month (from 21% to 0.03% for reference foam and from 17% to 0.03% for foam with 1.5% talc). C5H10 deviates during 3.5 months (from 28% up to 39% for reference foam and from 29% up to 36% for foam with talc), then it starts to leave the foam and after 3.5 year its content is 13% for reference and 10% for foam with talc. Air diffuses inside the cells faster for one year (from 51% up to 79% for reference and from 54% up to 81% for foam with talc) and then more slowly for 3.5 years (reaching 86% for reference and 90% for foam with talc). Thus, the fast and simple presented methodology provides valuable information to understand the long-term thermal conductivity of the RPU foams.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grants MAT2015-69234-R and RTC-2016-5285-5)Junta de Castilla y Leon (grant VA275P18)Agencia austriaca para la promoción de la investigación (grant 850697

Rigid polyurethane foams with infused nanoclays: Relationship between cellular structure and thermal conductivity

Producción CientíficaA water blown rigid polyurethane (PU) formulation has been used to manufacture cellular nanocomposites containing different concentrations of montmorillonite nanoclays. The PU foams have been produced using a low shear mixing technique for dispersing the nanoclays and by reactive foaming to generate the cellular structure. A detailed characterization of the cellular structure has been performed. The effect of the nanoparticles on the reaction kinetics and the state of intercalation of the nanoparticles in the foams has been analyzed. The thermal conductivity and extinction coefficient of the different materials has been measured and the results obtained have been correlated with the materials structure. A strong reduction of cell size and modifications on cell size distribution, anisotropy ratio and fraction of material in the struts has been detected when the clays are added. In addition, a reduction of the thermal conductivity has been observed. Different theoretical models have been employed to explain thermal conductivity changes in terms of structural features. It has been found that, in addition to the modifications in the cellular structure, changes in the extinction coefficient and thermal conductivity of the matrix polymer play an important role on the final values of the thermal conductivity for these materials.We would like to acknowledge to Mr. Vela and Mr. Ferrer, from BASF Española S.L., for supplying the PU formulation employed in this research. The authors are grateful to the Spanish Ministry of Science and Education which supported this work with a FPU Grant Ref-AP-2008-03602 given to Mr. Estravís. In addition, Financial assistance from the Spanish Ministry of Science and Innovation, FEDER program (MAT 2012 – 34901 and MAT2015-69234-R), the Junta de Castile and Leon (VA035U13) and the EU Commission (FP7 program, EC project NanCore number 214148) is acknowledged