| The polyimide with stable aromatic heterocyclic structure in the molecule makes it exhibit excellent high temperature resistance and low temperature resistance,and its excellent flame retardancy and low smoke rate can satisfy most fields that need flame retardant requirements;in addition,polyimide fiber that has been industrially produced in China has high-strength and high-modulus physical properties.Therefore,the use of polyimide fiber to develop fire-fighting outer fabric has broad market prospects.However,since the polyimide fiber belongs to the chemical fiber,there are some problems such as low moisture regain and serious electrostatic phenomenon,which is not suit to the smooth progress of the spinning process;in addition,the development of the outer fabric of the fire-fighting suit requires strict implementation of the corresponding industry standards,therefore,it is necessary to solve problems such as mechanical properties during the development of the fabric.This paper analyzed polyimide from three aspects of fiber,yarn and fabric.Firstly,compared with cotton,viscose and aramid fiber,some characteristics of the polyimide fiber were tested,including the length and fineness,tensile properties,specific resistance and moisture regain of the fiber,and summarized the characteristics of polyimide fiber;then,according to the characteristics of the polyimide fiber,the pure spinning process design was developed,the pre-spinning process adopts the principle of “light weight,low speed,big spacing”,and the post-spinning process adopts the principle of “large gauge,heavy pressurization,medium speed and small twist”,three kinds of polyimide pure-spun yarns of 14.8tex,19.7tex and 29.6tex were spun,and in order to explore the quality of pure spinning,three yarns were tested and analyzed,including tensile properties,strip uniformity and hairiness;finally,the plain weave fabric with 14.8tex linear density yarn was developed,the mechanical properties,wearing comfort and flame retardancy were tested,then the fabric structure of the polyimide fabric was optimized,developed a plain weave fabric by 29.6tex single yarn and 14.8tex × 2 double strands yarn,and 4/4 square fabric by 14.8tex × 2 double strands yarn,which the square fabric can fully meets the requirements of the industry standard for fire-fighting outer fabrics,then,the thermal performance of 4/4 square plain weave fabric were tested such as limiting oxygen index,smoke density,thermogravimetric infrared(TG-FITR)and cone calorimeter,and compared with flame retardant cotton and aramid IIIA fabrics which commonly used in the market.The experimental results show that:(1)Polyimide fiber has smooth surface,irregular section,high fiber strength and good toughness;but compared with cotton fiber,viscose fiber and other fibers,polyimide fiber has low moisture regain,the specific resistance of fiber is larger.And there is a serious electrostatic phenomenon in the spinning process.Therefore,in the pre-spinning stage,it should be sprayed with oil to prevent static electricity.(2)The post-spinning process adopted the suitable principles.The mechanical properties of three different yarns by the spinning method of siro spinning are excellent,and can meet the weaving process.(3)Compared with flame retardant cotton and aramid IIIA fabrics,polyimide fabrics have the highest limiting oxygen index,the best heat resistance,the lowest heat release rate and total heat release,and its pyrolysis begins at around 528 °C,the sample quality is still about 60% until 800℃,but the smoke density after pyrolysis is larger.Through the above three aspects of research,it can be concluded that the use of polyimide fiber to develop high-grade fire-fighting outer fabrics can fully meet industry standards and has great advantages. |
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