Polyurethane (PU) flexible foams were synthesized by substituting a portion of base polyether polyol with soybean oil-derived polyol (SBOP) as well as well-known substituent: crosslinker polyol and styrene acrylonitrile (SAN) copolymer-filled polyol. Increases in compression modulus were observed in all substituted foams and the most substantial increase was found in the 30% SBOP-substituted sample. Scanning electron microscopy (SEM) was used to examine cellular structure, in particular cell size. Polymer phase morphology, i.e., interdomain spacing and microphase separation, was studied using small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). Hydrogen bonding was investigated via Fourier transform infrared (FTIR) spectroscopy. Thermal and mechanical behaviors of foams were examined using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Compression properties were tested and compared via a 65% indentation force deflection (IFD) test. It was found that substituting SAN-filled polyol slightly reduced foam cell size and had no effect on polymer phase morphology. Crosslinker and SBOP polyols, on the other hand, had appreciable influence on polymer phase morphology. Crosslinker polyol disrupted hydrogen bonding between hard segments and was mixed with hard domains. SBOP polyol reduced hard domain size and soft domain fraction, and showed a broad distribution of interdomain spacings. Compression modulus increases in foams correlated well with shear modulus by DMA and could be associated with the polymer phase morphology changes.
Bibliographical noteFunding Information:
The authors would like to acknowledge Cargill Incorporated for financial support. Throughout this work, many researchers have provided help with instrumentation and shared their expertise. Among them we would especially like to thank Tim Abraham, Cargill Inc. for providing us with technical information, Tomy Widya of University of Minnesota for his help with SEM images and Greg Haugstad of University of Minnesota for his assistance with AFM and helpful discussions. Parts of this work were carried out in the University of Minnesota IT Characterization Facility, which receives partial support from NSF through the National Nanotechnology Infrastructure Network (NNIN) program.
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- Polyurethane foam
- Soybean oil polyol