Development Of UHMWPE Nascent Fiber Dynamic Rolling Equipment And Study On Its Spinning Characteristics

As an embodiment of a country's comprehensive strength and innovation capabilities,high-performance fiber has the advantages of high strength,high modulus,and corrosion resistance.It is an important strategic basic raw material in the fields of national defense,military industry and aerospace.It is used in national defense construction and national economy play an irreplaceable role.At present,the raw materials of high-performance fibers are mainly derived from refractory and difficult-spinning polymers.Because of their special molecular structure,these polymers have a melting temperature higher than the decomposition temperature or the melt flow is difficult and the melt is easily broken during processing.It is difficult to realize melt spinning.Scholars have found that introducing a vibration force field into the polymer processing process can effectively reduce melt viscosity and improve melt fluidity.Therefore,this article developed a dynamic rolling spinning forming equipment,by introducing a vibration force field into the melt spinning process to improve the fluidity of the refractory and difficult to spin polymer melt and reduce the difficulty of melt spinning processing.This article expounds the structure and principle of the dynamic rolling device,and introduces the structure and design of the core components in detail.The influence of the plane piston and the obliquely curved piston on the melt flow rate distribution is analyzed through simulation and comparison,and it is found that the obliquely curved rolling piston can better achieve the consistency of the melt flow rate and guide the melt to fill the entire rolling cavity.By establishing a simplified dynamic model,the displacement response,amplitude-frequency characteristics and phase-frequency characteristics of the rolling piston under forced vibration with a single degree of freedom are solved.The research results show that as the frequency ratio increases,the vibration amplification coefficient first increases and then decreases,and as the damping rate increases,the vibration amplification coefficient curve gradually becomes flat,and its maximum value is gradually reduced.Through the establishment of the melt flow model,the melt flow characteristics in the rolling cavity and the spinning hole under the vibration field are obtained.The research results show that the introduction of the vibration field can effectively reduce the melt flow regardless of whether in the rolling cavity or in the spinning hole.The pressure drops of the body and the transmission power improve the flow rate of the melt.As the vibration intensity increases,the melt pressure drops and transmission power decrease,and the melt flow rate increases accordingly.And under the condition of high vibration intensity,the tendency of melt pressure drop,transmission power and melt flow rate to increase or decrease is more obvious than under low vibration conditions.Taking ultra-high molecular weight polyethylene(UHMWPE)as the research object,the influence of process parameters on die pressure,spinning power,spinning output and UHMWPE nascent fiber performance was studied through experiments.The research results showed that the dynamic rolling device passed the introduction of vibration force field can effectively reduce die pressure and spinning power,and increase spinning output.Compared with the steady state,the die pressure and spinning power are reduced by 8.9% and 5.1% at the maximum,and the spinning output is increased by 4.7% at the maximum.The apparent quality test shows that vibration can reduce the surface roughness of UHMWPE fiber and improve the apparent quality of the fiber.The mechanical performance test showed that the fracture strength of UHMWPE fiber increased by 12.4% after the introduction of the vibration field,and as the vibration frequency or vibration amplitude increased,the increase in fiber fracture strength continued to increase.DSC analysis results show that the crystallinity of UHMWPE fiber increases with the increase of vibration intensity.TG analysis results show that the temperature of UHMWPE fiber's thermal weight loss begins to decrease after the introduction of the vibration field,but the decrease range is very small,within 2 ?.As the spinning temperature increases,the die pressure and spinning power decrease,and the spinning output increases.The apparent quality,breaking strength and crystallinity of UHMWPE fiber increased first and then decreased with the increase of spinning temperature,while the thermal stability continued to decrease with the increase of spinning temperature.The research results of this paper enrich the theory and technology of polymer dynamic forming and processing,reveal the influence of vibration on UHMWPE melt flow and fiber properties during dynamic rolling,and provide experimental and theoretical basis for process control and equipment design.The further promotion of rolling technology and the green and efficient manufacturing of high-performance fibers have important theoretical and practical significance.