Design Of Anti-weathering Material For Relics And Its Applicability In Modern Environment

A number of historic cultural relics are badly damaged; their weathering and corrosion state is badly serious due to natural and human factors. Modern environmental issue such as acid deposition is speeding up corrosion for cultural relics. If effective measures should not be taken to minimize damage from circumstances and slow down the ageing process of relics, a mass of unique and rare historic cultural relics will be fading way. However, hardly any protective materials satisfy all requirements now. Consequently, it is a matter of great urgency to explore novel method for material design and find new protective materials with a good performance.The historical relic protection relates to many science disciplines such as physics, chemistry, material science, mineralogy, geology, environmental science, archeology, history, art. Firstly, weathering, protective materials and measurement for the historic stone and metal relics, and state and issue for acid deposition are summarized in this dissertation. Secondly, the feasibility analysis is discussed, which the current international advanced numerical modeling and theoretical methods is used to materials design on historical relic protection. The author takes into account the characteristic and applications of paraxylene in heritage preservation. Targeting on poly (chloro-p-xylylene), quantum chemistry, quantitative relationship between structures (QSPR), molecular dynamics and Monte Carlo are used to predict molecular structure, physical and chemical prosperities of poly (chloro-p-xylylene). The author is interesting in its nature of transport gas. Poly (chloro-p-xylylene) is evaluated whether can be used in historical relics. In accordance with the evaluation criteria for polymer and plastic, poly (chloro-p-xylylene) is strictly evaluated. Meanwhile, advanced synchrotron radiation small angle X-ray scattering device was employed to explore information for ageing poly (chloro-p-xylylene). The results obtained from experiments and theoretical studies are as follows:1. Combining knowledge of geochemistry with analysis of data in literature, we found that the main reason is environmental pollution such as acid deposition, which speed up weathering and corrosion for historical relics in recent decades. With the development of industry, harmful chemical from emission of industrial waste increases.2. Basing on experimental and simulation results, and geochemical kinetic, the author concluded that poly (chloro-p-xylylene) film can separate historic relic from harmful active matter such as acid deposition and harmful gas so that the film can protect historic relic and decelerate weathering and corrosion for relic. The experimental results show that poly (chloro-p-xylylene) film satisfies transparency and keeping original appearance and structure.3. Atomic index and bonding index for poly (chloro-p-xylylene) and poly (para-xylylene) are calculated on the basis of the definition of the molecular topology index. These indices are used to calculate the chain index of polymer unit. The equations which describe polymeric quantitative structure property relationship (QSPR) between the chain index and density, dielectric constant, refractive index, the Young′s modulus and permeability, etc. can be fitted by the multiple linear regressions, respectively. These QSPR equations can be used to predict physical and chemical properties of polymer. Comparing with the experimental data in literature, predicting values of the properties are smaller than the experimental values. Apart from mechanical properties and bulk resistance, the maximum error for the other prediction properties of is less than 7%. Therefore, QSPR is valuable for prediction properties of polymeric materials for protection relics. Accurate density is basis for building polymeric membrane model in molecular simulation.4. Molecular dynamics was used to explore molecular conformation of poly (chloro-p-xylylene) with different chain length. Molecular dynamics simulations are able to achieve equilibrium with various chain lengths under different temperature. All polymeric chains are linear in simulation results. The chain in simulation is consistent with the experimental conclusion in the literature. In molecular dynamics simulation, bonding energy more than non-bonding energy consisting of van der waals energy and electrostatic energy affects achieving equilibrium.5. The linear chain structure of poly (para-xylylene) also is confirmed by the first principle calculation. We found there are the linear relationship between degree of polymerization and the zero point energy, heat capacity, entropy, enthalpy and free energy. The energy gap between the frontier orbits implied that poly (para-xylylene) is insulator. These results are consistent with the experimental facts and confirm conclusion obtained from molecular dynamics simulation.6. The model of poly (chloro-p-xylylene) membrane was built on the basis of self-avoiding walk Monte Carlo method. The model was used in molecular dynamics simulation. The diffusion coefficient of Helium and small molecules in poly (chloro-p-xylylene) membrane was calculated by using the trajectory data and Einstein's fluid equation. The activation energy and prefactor of diffusion coefficient was obtained on the basis of diffusion coefficients under different temperature. These values are in agreement with the experimental data. The membrane model also was used to simulate isothermal adsorption. The results for adsorption are satisfactory, too. The author thought the methods can be used in design new polymeric materials for protection relics.7. The organic and inorganic chemicals were utilized to etch poly (chloro-p-xylylene). And specimen of poly (chloro-p-xylylene) was heated over 15 months under 323K. Only specimens etched by HNO3 and acetone showed few mass changes. Comparing with the original specimen and the specimen heated and etched by chemicals, difference of XRD and RAMAN spectroscopy is slight. Difference in synchrotron radiation small angel X-ray scatter is little, too. These results implied that poly (chloro-p-xylylene) is very stable for chemicals. Poly (chloro-p-xylylene) is made by chemical vapor deposition. The author inferred that poly (chloro-p-xylylene) can be used for long-term protection of cultural relics, especially in indoor environment. Therefore, poly (chloro-p-xylylene) can be used to protect metal, stone relics and to repair paper and silk relics.In short, the study confirms that poly (chloro-p-xylylene) has prefect charactistic for preventing corrosion from chemical. The modeling methods in the paper are expected to design polymeric materials for protection relics. The author has not found similar study during literature search. These achievements have important practical significance for developing new materials to protect cultural relics. The study broadens the field of materials for protection.