Thermal, Chemical, and Morphological Characterization of Microcellular Polyurethane Elastomers

Abstract

In this study, three different microcellular polyurethane elastomers (MPUE) based on 4,4'-diphenylmethane diisocyanate with different rigid segment contents are prepared (Formulations 1, 2, and 3 with 32, 35, and 42% of rigid segment content, respectively). The MPUE are obtained through a two-step method using a prepolymer system. The samples are analyzed to determine their thermal, morphological, and chemical properties. The thermogravimetric analysis indicates the presence of two degradation stages, referring to the rigid and flexible phases, respectively. The differential scanning calorimetry tests indicate that for the MPUE there was an increase in the glass transition temperature of the flexible phase with an increase in the percent of the rigid phase. An increase in the quantity of the rigid phase present in the MPUE results in greater values for the crosslink density, which in turn results in an increase in the rigidity of the material. The scanning electron microscopy micrographs indicated a large number of closed cells and that a higher rigid segment content give a better cell homogeneity of the samples.

Influence of dynamic crosslinking on the morphology, crystallization, and dynamic mechanical properties of PA6,12/EVA blends

“…The solubility parameters of EVA [9.27 (cal/cm 3 ) 1/2 ] and PA6,12 [9.54 (cal/cm 3 ) 1/2 ] used in this work were approximated from Fedors’ molar volume . The EVA phase was dissolved in xylene, selected for its similar solubility (8.80 cal/cm 3 ) to EVA . The samples were placed in the 120‐mesh wire cage containing approximately 0.3 g of polymer and washed in a round‐bottomed flask containing boiling xylene for 8 h. After solvent extraction, all samples were dried at 60 °C for 48 h. The continuity of one phase is defined as the fraction of the continuous phase.…”

Effect of chain extenders on the hydrolytic degradation of soybean polyurethane

“…The films were initially dried at 80°C for 24 h; subsequently, they were immersed in xylene solvent (8.88 cal cm −3 solubility parameter, 123.31 cm 3 mol −1 molar volume, and 0.861 g cm −3 density) until reaching the equilibrium (30 days). The swelling degree was determined through Equation () 22 : where, Q is the swelling coefficient, m i is the swollen polymer mass at equilibrium (g), m 0 is the polymer mass before swelling (g), ρ P is the polymer density (g cm −3 ), and ρ s is the solvent density (g.cm −3 ). Thus, the crosslinking density ( ν ) for all SPUs was determined by Equation () 23 : where, is the polymer volume fraction in the swelled polymer, χ is the polymer‐solvent interaction parameter (usually, the χ value is 0.34) 20 .…”

“…The films were initially dried at 80 C for 24 h; subsequently, they were immersed in xylene solvent (8.88 cal cm À3 solubility parameter, 123.31 cm 3 mol À1 molar volume, and 0.861 g cm À3 density) until reaching the equilibrium (30 days). The swelling degree was determined through Equation ( 1) 22 :…”

Effect of the partially hydrolyzed EVA‐h content on the morphology, rheology, and mechanical properties of PA12/EVA blends

“…The elastomeric phase was dissolved in xylene, solvent selected for its similar solubility parameter (18.0 (J/cm 3 ) 1/2 ) [28]. The samples were placed in the 120-mesh wire cage containing $0.3 g of polymer and washed in a round-bottomed flask containing boiling xylene for 8 h. After solvent extraction, all samples were dried at 608C for 48 h.…”