A study of mechanical and optical properties of samples of transparent plastic Polyethylene terephthalate glycol (PETG) manufactured by additive technology Fused Filament Fabrication (FFF) was carried out. PETG plastic is used in medicine, particularly in dentistry due to its unique set of properties: strength, elasticity, resistance to aggressive environments, transparency. Preserving the complex of properties of PETG plastic, including transparency, during 3D-printing is an important technical task. In order to solve this task a set of studies of PETG laboratory samples was carried out. The optimum modes of 3D printing were determined to provide PETG samples with increased strength properties, preservation of elastic properties and optical transparency of the material. The increase in the optical transparency of the material is provided by an additional post-treatment of the printed samples surface with a chemical reagent. The influence of technological parameters of the post- treatment mode on the mechanical and optical properties of the printed samples has been investigated. The novelty of the work consists in a comprehensive study of the modes of manufacturing products from PETG by technology FFF with subsequent post-treatment, allowing to preserve the transparency of the polymeric material.

Glassy PMMA samples are plastically deformed at room temperature in the uniaxial compression regime to residual strains of e res = 25%. Dielectric spectra of the initial and deformed samples are recorded via the method of broadband dielectric spectroscopy in the frequency range f = (5 × 10 -4 ) -10 7 Hz. The results are compared with the dynamic mechanical spectra of samples deformed under the same condi tions. Dielectric and mechanical spectra are noticeably distorted by deformation. As a result, dielectric per mittivity ε' increases, shear modulus G' decreases, and the intensity of dielectric β losses slightly increases, while dielectric and mechanical α losses increase appreciably. In addition, the "anomaly" of total dielectric Δε tot and total mechanical ΔG tot dispersions (Δε tot = ε 0 -ε ∞ ≈ Δε α + Δε β and ΔG tot = G 0 -G ∞ ≈ ΔG α + ΔG β ) occurs, that is, the polymer is transformed from the state with Δε α Δε β and ΔG α < ΔG β into the state with Δε α > Δε β and ΔG α > ΔG β . The described phenomenon is related to a strong gain in α dielectric and mechan ical losses in the deformed material. It is found that α losses increase owing to an anelastic deformation com ponent arising during glass loading. This component is responsible for an increase in the internal energy of the glass during its anelastic deformation. Possible causes of the observed effects are discussed.

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