Understanding the deformation mechanism of amorphous
polymeric
materials is indispensable for their applications but is quite challenging.
Here, with amorphous plasticized poly(vinyl butyral) (PVB) as a model
system, we studied its structural change in situ during
uniaxial deformation with ultrasmall-angle X-ray scattering (USAXS).
We observed a stretch-induced phase separation behavior characterized
by a butterfly scattering pattern in plasticized PVB for the first
time. This phase separation, featured by a concentration fluctuation
along the stretch direction, is a result of stress–concentration
coupling under stretch. The phase size at its formation is around
100 nm, which increases almost linearly with strain. The strain rate
has a weak effect on the phase size. This suggests that the elastic
deformation of the network, cross-linked by entanglements and hydrogen-bonding
clusters, governs the phase size. We proposed a tentative model to
explain the deformation behavior of plasticized PVB, where the breaking
and reforming of hydrogen bonds, the formation and growth of phase
separation against osmotic pressure, and the plastic deformation and
rupture of phase structure dissipate a large amount of energy and
endow the plasticized PVB with excellent mechanical performance. We
believe our findings are general and should be applicable to other
amorphous polymers with solvents or plasticizers.
As a key component in laminated glass, plasticized polyvinyl butyral (PVB) interlayer is a kind of impact‐resistant polymer material with high toughness. Recently, by using ultrasmall angle X‐ray scattering (USAXS) technique, Stretch‐induced phase‐separated structure on the scale of hundreds of nanometers formed in plasticized PVB for the first time is reported. In this work, the multiscale relaxation behavior of plasticized PVB is further investigated. The relaxation behavior of deformed plasticized PVB is studied from macroscopic stress, mesoscopic phase‐separated structure, and microscopic chain segment by combining USAXS, and birefringence with in situ stretching device. The contributions of chain segments and hydrogen bonding clusters for the multiscale relaxation behavior are discussed.
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