Preparation And Flame Resistance Property Of Clay Coated Polymer

High-temperature resistance flame-retardant protective suit is composed by three layers: out layer, vapor barrier layer and heat insulation layer. The heat insulation layer is the most important layer that prevents the penetration of external heat into wearer’s skin, and the key which is related to the characteristic of flame-retardant protective suit. Currently, heat insulation performance of the insulation layer can not meet the needs of users. It has always been an important issue for academia and industry that producing a kind of excellent flexible and fire retardant material to be used as insulation layer for flame-retardant suit. Although there has been a variety of high-temperature resistance organic fibers to be used as thermal insulation layer of fire-retardant uniform, the fire resistance of these fibers is too poor to achieve the need of the uniform. In spite of the excellent high-temperature resistance performance of ceramic fiber and glass fiber, the limited weaving property and flexibility of the fibers make them not suitable to be used as insulation layer of flame-retardant protective suit. Therefore, the exploitation of organic/inorganic composite materials has become the important issue. The composites of organic and inorganic material could achieve the complementary advantages, and both mechanical behavior and fire retardant property of the material.This study was part of the State863Project "Design and realization of flexibility and high temperature resistance protective coating of organic fiber"(Project NO.2001AA03Z336), aimed at developing a kind of material with wonderful mechanical behavior and flame retardant. This study focused on analyzing the structure and film-forming property of vermiculite and montmorillonite (MMT), and preparing the exfoliated vermiculite coated polyimide(PI) composite, MMT coated PI composite and PNBD(poly(N-benzyloxycarbonyl-3,4-dihydroxyphenylalanine))- MMT coated PI composite. Then the fire resistance and thermal insulation property of those composites was discussed. The main work of the study were as follows:(1) Study the preparation of exploited vermiculite, exploited vermiculite coated PI composite, and discuss the fire retardant properties of the composites.A. Preparation and characteristic of exploited vermiculite. First, chemical and physical method was used to prepare exfoliated vermiculite. Scanning electron microscope (SEM) was used to analyze vermiculite samples, the results showed that the layered structure of vermiculite was almost cleavage and the aspect ratio of lamellae became larger after intercalation and exfoliated treatment. Finally, exfoliated vermiculite lamellae with uniform size was selected to prepare inorganic vermiculite film. The structure of the film was layered. This could indicate the film-forming property of exploited vermiculite.B. Study the preparation and thermal insulation property of exfoliated vermiculite coated PI composite. Exfoliated vermiculite lamellae with uniform size were used to coat on PI fiber material to prepare a new type of organic/inorganic composite material. The composite material was characterized by SEM, the result shown that with the increasing weight of vermiculite, more lamellae were covered on PI fibers. When the weight gain of vermiculite reached a certain value, the inorganic clay coating could also form between fibers. The exploited vermiculite coated PI composite was tested at600℃for480s to evaluate the heat-insulation performance of the composites, the results indicated that the temperature difference between the inner and outer surfaces of composites (weight gain,90wt.%) was220℃, and that of uncoated PI was less than100℃under the same condition. It suggested that the vermiculite coating could enhance heat-insulating property of PI, and the insulation performance of the composite material was stronger with the increase of vermiculite weight addition. In addition, the deformation rate for uncoated PI fiber material was38%after heated at600℃for480s, and that of the composites (weight gain,90wt.%) was only15%under the same condition. This could also indicate that the vermiculite coating could enhance the thermal stability of the composites.(2) Study the preparation of MMT coated PI composite, discuss the fire retardant and heat insulation property of the composites.A. Preparation of MMT film. Different kinds of MMT dispersion were prepared with different pH value and different dispersing medium, in order to prepare MMT films. The optimum process which was used to prepare MMT film was determined by investigating the structure and flexibility of those MMT films.B. Study the preparation and characteristic of MMT coated PI composite. MMT-PI composites were prepared by coating MMT on the surface of PI material. The arrangement of MMT lamellae on the surface of PI fiber was analyzed by SEM, the result indicated the MMT lamellae coated on the surface of PI fiber by forming a kind of inorganic film. TG, cone calorimeter, open flame ablation, temperature difference of internal and external surface test were used to investigate the thermal stability property, fire hazard performance, resistance to open flame performance and thermal insulation property of the composites. The results showed that those characteristics of the composites were more excellent than pure PI. For example, the thermal insulation property of MMT-PI composite and PI material was tested at800℃for600s, the temperature difference between outer surface and inner surface of MMT-PI was400℃, and that of PI material was just100℃under the same condition. In addition, mechanical property of the composites was tested and the result indicated that, compared with pure PI, the mechanical strength of MMT-PI was improved.(3) Study the preparation of PNBD-MMT composite film, and discuss the fastness between PNBD-MMT film and PI fiber, and the fire resistance of the composites.A. Preparation PNBD-MMT composite film. Na-MMT (CEC=90mmol/100g) and homemade PNBD (6000g/mol) were used to prepare composite film by LbL self-assembly method on the surfaces of glass slides. The test result of thermal stability property and interlayer distance of composite film indicated that the weight loss of the composite films and d001of MMT lamellae in the composite films were increased with the increase of PNBD solution concentration.B. Study preparation and characteristic of PNBD-MMT coated PI composite material. PNBD solution (concentration,0.02wt%,0.04wt%,0.10wt%) and MMT dispersion (0.02wt%) were used to coat on PI fiber by LbL method to prepare composite materials. The flame resistance of PNBD-MMT coated PI and fastness between PNBD-MMT composite film and PI fibers was investigated. The result indicated that there was more PNBD-MMT coating on the surface of PI than MMT coating after20times standard washing. The thermal stability and flame resistance of PNBD-MMT coated PI composite was still excellent after20times standard washing. However, those properties of MMT-PI was decreased after20times standard washing. For example, the result of vertical burning test showed that, the burning length of PNBD-MMT coated PI were about7-9mm and7-14mm before and after20times standard washing, and that of MMT-PI were8mm and17mm. Those result indicated that the combination fastness between PNBD-MMT composite film and PI fiber was stronger than that of MMT film, so as to endue durable fire retardant property to the composites. The mechanical strength testing of PNBD-MMT composite film coated PI showed that the mechanical strength of the composites was stronger than that of pure PI.In summary, the combination fastness between MMT lamellae and PI fiber was improved greatly by PNBD. So as to endue durable fire retardant property and mechanical properties to the PNBD-MMT coated PI composite material. The composites could meet the need of thermal insulation layer of high-temperature resistance and flame-retardant protective suit. So it was another breakthrough of the thermal-insulation materials research and development.