Enhancement And Identification Of Amber

Because of unique texture,amber become the most popular gem in China,loved by all consumers.However,the quality and price of amber are highly influenced by opacity and crack defects.Opaque beeswax containing a large number of tiny pores and pure a crack-free amber are more favored by consumers.In this study,based on the plasticity and foamability of supercritical carbon dioxide（CO2）,the internal structure and crack of amber have been successfully changed by supercritical CO₂ treatment.This is a new attempt of the development of the amber enhancement process.First of all,this paper explores the processibility of scCO₂ treatment of Baltic amber.The results showed that amber is an amorphous polymer with a glass transition temperature of 126.1℃.CO₂ gas can effectively diffuse and adsorbed in the amber matrix,and the gas adsorption capacity and diffusion coefficient can be controlled by the process conditions to change,indicating that amber has good foamability.At a temperature higher than the glass transition temperature,the amber reaches the gas saturated adsorption state within 5h,and the matrix is in the non-ductile elastomeric state with large melt strength and small viscosity and deformability.Secondly,the supercritical CO2 foam method successfully transforms the transparent amber into the opaque beeswax with high-density delicate cells and high-quality appearance.Saturation pressure,saturation temperature,saturation time and foaming pressure mainly affect the polymer viscoelasticity,CO₂ gas adsorption capacity and diffusion rate,and finally affect the amber cell structure and appearance quality.The experimental results show that the optimum conditions for supercritical CO₂ foaming are as follows:the saturation pressure is12MPa,the saturation time is 5h,the saturation temperature is 120℃,and the foaming temperature is 130℃.The average cell size of this process is 56.12μm,Cell density of112618 cell/cm3,high appearance quality modified samples.In this study,supercritical CO₂ was also used as plasticizer,and amber crack was successfully bridged by supercritical CO₂ permeation method.T The results show that the increase of saturation temperature,saturation time and saturation pressure can decrease the viscosity and surface tension of the amber system,and promote the diffusion and reentanglement of the polymer chain.The optimum permeation and healing process is as follows:saturation pressure is 12MPa,saturation temperature is 240℃,saturation time is 9h.Finally,by comparing and analyzing the gemstone and spectral characteristics of the samples before and after supercritical CO₂ treatment,the special distinguishing feature of supercritical CO₂ modified samples was obtained:1)the density of supercritical CO₂ foamed samples was low,it can float on the surface of the water,and the coarse flat elongated bubbles with directional arrangement are observed in the interior.2)in solid ¹³C NMR,the modified amber exhibits a new chemical shift δ=48×10^-6,and the peak type and peak intensity ratio of the secondary carbon absorption peak change significantly.The IR and Raman spectra showed that the supercritical CO₂ treatment had no effect on the basic chain structure of amber,and the treatment was a physical modification process.