Microstructure and Crystallization Kinetics of Polyurethane Thermoplastics Containing Trisilanol Isobutyl POSS

Abstract

The synthesis of thermoplastic polyurethanes (TPU) from the reaction of a NCO group-containing prepolymer and 0, 1.14, 1.71, and 2.28 wt% of trisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS) was carried out in an instrumented batch mixer. The samples were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM analysis shows that the incorporation of POSS promoted strongly aggregation through physical interactions (formation of POSS-rich domains). Modifications in the TPU microstructure and the reduction in the crystal size were observed in the XRD diffractograms. The incorporation of POSS equally altered the TPU crystallization, and samples bearing higher concentrations of POSS formed two distinct types of crystalline structures. The kinetics of crystallization showed that nucleation strongly depends on the balance between TPU crystal formation and POSS-rich domains.

Effects of Molecular Structure and Packing Order on the Stretchability of Semicrystalline Conjugated Poly(Tetrathienoacene‐diketopyrrolopyrrole) Polymers

“…[16,17] The crystalline packing arrangement and properties of conjugated polymers are both governed by the structure of the side chains and polymer backbones, which will affect the resulting thin film morphology of crystalline and amorphous regions. The presence of a modest fraction of crystalline domains (e.g., 12% for thermoplastic polyurethane and 10% for elastic polypropylene) is able to improve the tensile strength and elasticity of polymer thin films.…”

Carbon nanotube‐based thermoplastic polyurethane‐poly(methyl methacrylate) nanocomposites for pressure sensing applications

“…The addition of PMMA microbeads in the TPU‐CNT nanocomposites resulted in the decrease in Δ H m and χ c . It is also important to note that Δ H m and χ c also decreased with increasing size of PMMA microbeads; this reduction of Δ H m and χ c in case of nanocomposites with respect to the neat polymers is generally observed when there are specific interactions between the polymer components in the nanocomposites . It was also noticed that T m decreased slightly with the addition of PMMA microbeads.…”

Thermoplastic polyurethane synthesis with modified montmorillonite prepared by torque rheometry: Investigation of morphological, thermal, chemical, and physical properties

“…Four important diffraction peaks in the range 2θ = 10, 19, 21, and 23 ° ( L I , L II , L III , and LI v , respectively) can be noted in Figure for the TPU and nanocomposites. These diffraction peaks with interplanar spacings ( d ‐spacing) of 0.84, 0.46, 0.41, and 0.37 nm are reportedly related to hard crystallized segments . The peaks in the range of 2θ = 19 − 23 ° relate to the hard crystalline segments of TPU (hydrogen bonds between urethane groups) .…”

“…Peak separations were performed using Gaussian and Pseudo‐voigt deconvolution. The d spacings were calculated using the Bragg equation and the crystallite sizes ( L ) were calculated using the Scherrer equation …”

“…After cooling, the hydrogen bonds between the urea groups and urethane linkages are regenerated and the material once again behaves like an elastomer . TPU can be molded applying the traditional techniques used for thermoplastics, but the urethane group has low thermal stability, and these bonds dissociate and re‐associate simultaneously above the temperature of thermal stability …”