Segmented Polyurethane Nanocomposites:  Impact of Controlled Particle Size Nanofillers on the Morphological Response to Uniaxial Deformation

Abstract

A series of TPU nanocomposites were prepared by incorporating organically modified layered silicates with controlled particle size. To our knowledge, this is the first study into the effects of layered silicate diameter in polymer nanocomposites utilizing the same mineral for each size fraction. The tensile properties of these materials were found to be highly dependent upon the size of the layered silicates. A decrease in disk diameter was associated with a sharp upturn in the stress−strain curve and a pronounced increase in tensile strength. Results from SAXS/SANS experiments showed that the layered silicates did not affect the bulk TPU microphase structure and the morphological response of the host TPU to deformation or promote/hinder strain-induced soft segment crystallization. The improved tensile properties of the nanocomposites containing the smaller nanofillers resulted from the layered silicates aligning in the direction of strain and interacting with the TPU sequences via secondary bonding. This phenomenon contributes predominantly above 400% strain once the microdomain architecture has largely been disassembled. Large tactoids that are unable to align in the strain direction lead to concentrated tensile stresses between the polymer and filler, instead of desirable shear stresses, resulting in void formation and reduced tensile properties. In severe cases, such as that observed for the composite containing the largest silicate, these voids manifest visually as stress whitening.

Development of an image-based numerical model for predicting the microstructure–property relationship in alumina trihydrate (ATH) filled poly(methyl methacrylate) (PMMA)

“…However, at high filler volume fractions, the possible agglomeration of smaller particles can lead to non-uniform distributions, and thereby, creating weak regions which cause a decrease in mechanical properties (Dasari et al 2006;Finnigan 2005).…”

Dynamics of Uniaxially Oriented Elastomers Using Broadband Dielectric Spectroscopy

“…[14][15][16] Segments in the soft phase (soft segments and dissolved hard segments) will first become oriented in the deformation direction due to the lower modulus of the soft phase and stress will be ultimately be exerted on the hard domains. If anisotropic in shape, the hard domains are expected to align with their long axis in the deformation direction.…”

Effects of ionic interactions between clay and waterborne polyurethanes on the structure and physical properties of their nanocomposite dispersions

“…For many solvent-based PU/clay nanocomposites with the absence of ions in PU moieties, the electrostatic forces between the clay platelets have a tendency to squeeze the PU polymer chains out and subsequently result in an intercalated structure. 8,[19][20][21]26,35 The clay intercalated with the PU polymer exhibits a reflection at 2h ¼ 2.58 for a certain solvent-based PU/clay nanocomposite. 21 In the WPU/clay system studied in this work, the aforementioned squeeze effect has been overcome by the ionic attractions between anionic WPUs and cationic clay platelets.…”

“…The morphology of PU/clay nanocomposites has also been examined. [26][27][28] In the literature, most PU/clay nanocomposites have been prepared in various organic solvents, so a lot of organic solvent needs to be removed. The PU moieties of these nanocomposites are solvent-based.…”