Preparation Of Acid Catalyzed Polyvinyl Alcohol Carbonate Portiforium Foaming Materials And Property Research

Foaming materials can be divided into portiforium forming material and obturator foaming material. Due to the portiforium foaming material has excellent absorption liquid performance, penetrating performance and so on, so far it has been widely used in water, filtering, sound-absorbing, ventilation and other fields. The preparation of the conventional polyvinyl alcohol as substrate portiforium foaming material generally needs to undergo two processes of condensation reaction and foaming. The condensation reaction process means that polyvinyl alcohol(PVA) and aldehydes are condensed to polyvinyl acetal compounds under acid catalysis. The foaming process means that polyvinyl acetal compounds are foamed to polyvinyl acetal portiforium foaming material through the action of aerating powder. Aldehydes are a class of high toxic organic compound. The polyvinyl acetal portiforium foaming material prepared by aldehydes often contains free aldehydes which can cause some damage to human health. In order to reduce the influence of free aldehydes inside polyvinyl acetal portiforium foaming material on human health, the purpose of this dissertation is to prepare a portiforium foaming material without free aldehydes. Therefore, dimethyl carbonate(DMC) is used to replace aldehydes, and the transesterification is used to replace the condensation reaction, and polyvinyl alcohol carbonate portiforium foaming material is prepared through transesterification-foaming technology; meanwhile, DMC is used to replace aldehydes, and the transesterification is used to replace the condensation reaction, and expanded graphite is used to replace sulfuric acid, and expanded graphite/polyvinyl alcohol carbonate composite portiforium foaming material is prepared through transesterification-doping-foaming technology. The research of entire dissertation consists of the following three aspects.1. Preparation and characterization of polyvinyl alcohol carbonate portiforium foaming materialUnder the catalysis of sulfuric acid, polyvinyl alcohol carbonate was synthesized via a transesterification of PVA and DMC; and then, the polyvinyl alcohol carbonate was foamed to polyvinyl alcohol carbonate foaming material under the action of n-pentane used as the aerating powder; at last, the structure of polyvinyl alcohol carbonate was confirmed by IR, and the polyporous morphology of polyvinyl alcohol carbonate foaming material was also confirmed by SEM. In order to screen the optimum condition which prepared polyvinyl alcohol carbonate foaming material, the effects of PVA, DMC and n-pentane of the use level and the reaction temperature and the foaming temperature on the water absorption ratio of polyvinyl alcohol carbonate foaming material were investigated, and the effects of PVA, DMC and n-pentane of the use levels and the foaming temperature on the density of polyvinyl alcohol carbonate foaming material were also investigated. On the basis of the investigations, it was confirmed that polyvinyl alcohol carbonate foaming material belonged to the portiforium foaming material; otherwise, the optimum condition which used transesterification-foaming technology to prepare polyvinyl alcohol carbonate portiforium foaming material was also screened in accordance with the maximum water absorption ratio and the minimum density. The optimum condition was obtained as follows: the use level of PVA was 10.00 g; the use level of DMC was 7.50 mL; the use level of n-pentane was 4.00 mL; the foaming temperature was 50 ℃; the reaction temperature was 75 ℃.2. Preparation of acidic expanded graphite-100 mesh of flake graphite as raw material, the mixed inorganic compounds as oxidizing agents and the mixed inorganic and organic compounds as intercalation agents were used to the acidic expanded graphite via the chemical oxidation and the thermal expansion(chemical oxidation method).3. Preparation and characterization of expanded graphite/polyvinyl alcohol carbonate composite portiforium foaming materialUnder the catalysis of acidic expanded graphite, polyvinyl alcohol carbonate was synthesized via a transesterification of PVA with DMC, and expanded graphite and polyvinyl alcohol carbonate were mixed together to form expanded graphite/polyvinyl alcohol carbonate composite; then, the expanded graphite/polyvinyl alcohol carbonate composite was foamed to expanded graphite/polyvinyl alcohol carbonate composite foaming material under the action of n-pentane used as the aerating powder; lastly, the cross-linked structure of expanded graphite and polyvinyl alcohol carbonate was confirmed by IR, and the polyporous morphology of expanded graphite/polyvinyl alcohol carbonate composite foaming material was also characterized by SEM. In order to screen the optimum use level of acidic expanded graphite which prepared expanded graphite/polyvinyl alcohol carbonate composite foaming material, the influence of the use level of acidic expanded graphite on the water absorption ratio of expanded graphite/polyvinyl alcohol carbonate composite foaming material was investigated, and the influence of the use level of acidic expanded graphite on the density of expanded graphite/polyvinyl alcohol carbonate composite foaming material was also investigated. On the basis of the investigations, it was confirmed that polyvinyl alcohol carbonate composite foaming material belonged to the portiforium foaming material; otherwise, the optimum use level of acidic expanded graphite which used transesterification-doping-foaming technology to prepare expanded graphite/polyvinyl alcohol carbonate composite portiforium foaming material was also screened in accordance with the maximum water absorption ratio and the minimum density. The optimum condition was obtained as follows: the use level of PVA was 10.00 g; the use level of DMC was 7.50 mL; the use level of n-pentane was 4.00 mL; the reaction temperature was 75 ℃; the foaming temperature was 50 ℃; the use level of acidic expanded graphite was 1.20 g.