Abstract
We have performed a systematical investigation on the glass transition behavior of amorphous polymers with different solvent concentrations. Acrylate-based amorphous polymers are synthesized and treated by isopropyl alcohol to obtain specimens with a homogenous solvent distribution. The small strain dynamic mechanical tests are then performed to obtain the glass transition behaviors. The results show that the wet polymers even with a solvent concentration of more than 60 wt.% still exhibit a glass transition behavior, with the glass transition region shifting to lower temperatures with increasing solvent concentrations. A master curve of modulus as a function of frequency can be constructed for all the polymer–solvent systems via the time–temperature superposition principle. The relaxation time and the breadth of the relaxation spectrum are then obtained through fitting the master curve using a fractional Zener model. The results indicate that the breadth of the relaxation spectrum has been greatly expanded in the presence of solvents, which has been rarely reported in the literature. Thus, this work can potentially advance the fundamental understanding of the effects of solvent on the glass transition behaviors of amorphous polymers.
Highlights
Amorphous polymers exhibit a glass transition behavior, across which the thermomechanical properties, such as modulus, heat capacity, coefficient of thermal expansion, etc., all exhibit a tremendous change
The glassy modulus for polymers with 2 wt.% crosslink density decreases by almost 10 times from dry state to fully saturated state
It has been shown that the rubbery modulus in the wet state is scaled with that of dry state as E = E /J /, where J is the ratio of volume after swelling and that of the initial dry state [26]
Summary
Amorphous polymers exhibit a glass transition behavior, across which the thermomechanical properties, such as modulus, heat capacity, coefficient of thermal expansion, etc., all exhibit a tremendous change. It is important to investigate glass transition behavior of amorphous polymer systems, which mainly depends on the chemical composition of polymers. It can be affected by other factors, such as aging [1] and plasticization effects [2,3,4,5,6]. Plasticizers are known for the ability to modify mechanical behaviors of polymers. The effects of a plasticizer depend on the concentration as well as its compatibility with the polymer matrix [9]. Da Silva et al [10] adopted X-ray diffraction, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy to characterize the change in mechanical properties of polyvinylchloride (PVC)
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