Studies And Synthesis On The Ramie Fiber's Modifying Agents Of Used In Automobile's Inner Decoration

Energy saving and environmental protection is always the developmental motive of automotive industry. Light, cheap, recycled and biodegradable nature ramie fiber reinforced polypropylene composite used in automobile's inner decorations has many advantages than other thermoses composites. Ramie fiber is hydrophilic and polar material because of containing many hydroxyl groups, but polypropylene is hydrophobic and nonpolar material, so essentially hydrophilic nature ramie fiber and hydrophobic polypropylene can't be consistent. Unmodified ramie fiber and resin matrix have weak interface condition in interfacial contact, so ramie fiber should be treated to reduce its hydrophilic and water absorption before preparation of ramie fiber reinforced polypropylene composite for improving the composite's interface bonding capability.In this paper several species of modifying agents were selected to treat ramie fiber which could reduce its water absorption. And after treated with the melamine formaldehyde resin synthesized by ourselves, the amount of water absorption ramie fiber was significantly decreased. However, unmodified melamine formaldehyde resin was not convenient to use because it could be stored for only few days. Thus the storage stability of Melamine formaldehyde resin modified by polyvinyl alcohol was researched. The influences of the amount of polyvinyl alcohol, mol ratio of formaldehyde and melamine, reaction temperature and pH value were investigated by uniform design and optimized method. And the melamine formaldehyde resin whose storage life could last two months long was synthesized. The optimal conditions of synthesis are as follows, the molar ratio of formaldehyde/melamine is 3:1, the temperature of reaction is 95℃, pH value is between 9-10, and the amount of polyvinyl alcohol is 1 percent of formaldehyde in weight.During the process of melamine formaldehyde resin's synthesis, the contents of different groups and the structure of the resin varied with the change of reaction condition, which was showed through the storage stability and the composite's service performances. Through our exploratory experiment, the amount of free formaldehyde, hydroxymethyl, dimethylene ethers, methyl ethers and methylene in melamine formaldehyde resin were analyzed, which would support the further research for improving the resin's storage stability.Ramie fiber needled fabric felt was treated and modified by different modifying agents such as the melamine formaldehyde resin synthesized by ourselves, sodium hydroxide, silica sol binder, polyvinyl acetate, polyvinyl alcohol, mixture of melamine formaldehyde resin and silica sol binder, mixture of melamine formaldehyde resin and polyvinyl alcohol. The water absorption of treated ramie fiber was studied. The result showed that concentrations of the modifying agents have a large effect on the water absorption and all modifying agents mentioned above were efficient in decreasing water absorption. Among these modifying agents melamine formaldehyde resin showed the best performance in decreasing the ramie fiber's water absorption. After treated by melamine formaldehyde resin the water absorption of ramie fiber decreased from 14% to 2% in weight.