Preparation And Properties Of Ultrahigh Molecular Weight Polyethylene Monofilament

Ultra-high molecular weight polyethylene(UHMWPE)fiber,together with carbon fiber and aramid fiber,is called "three high-tech fibers of the world".It is a new generation of high-performance fiber after carbon fiber and aramid fiber,and has been applied in the fields of military protection,medical,sporting goods and civilian ropes due to its excellent overall performance.The technique of industrial production of UHMWPE fiber is usually jelly spinning method,which makes the fiber diameter small and cannot satisfy the requests of some special fields such as high wear-resistant ropes and composites demanding large surface area.Therefore,the monofilament preparation method can effectively improve the knitting efficiency of the rope net and improve the wear resistance of the final product,and reinforce the interface adhesion by increasing the surface area.Besides,the use of a large amount of extractant in the spinning process will result in an increase of production costs as well as environmental pollution.Therefore,it is one of the hot topics to seek a new technique requiring less extractants.In this paper,three kinds of domestic UHMWPE were tested to characterize their molecular weights,thermal properties,crystallization properties,particle sizes and surface morphology.The swelling effect was determined by swelling ratio.And the influence of temperature and swelling time on the swelling effect was analyzed.The influence of the physical properties of the raw material resin on the pre-swelling and spinning stability was researched.The results show that the molecular weight of a,b and c resin is 3.75×106,5.11×106 and 2.49×106,respectively.The average size of b and c resin particles is about 220?m,while the average size of a resin is 108?m,and the size distribution is larger.The surfaces of b and c resin contain hemispherical secondary structures,which connect with each other by fibrous silks.The relationship between swelling ratio and temperature is divided into four stages,and the optimum swelling temperature is a temperature range.131°C is the best swelling temperature of the three kinds of resins.The relationship between swelling ratio and time is divided into two stages.After a certain period of time the swelling process enters a relative equilibrium stage.The spinning stability of b and c are similar,but thin necks occasionally appear in the spinning process of b resin.The spinning stability of a resin is worst,and the extruded fibers are significantly uneven.The results show that the melting point of a,b and c raw materials is 136.5 ?,142.6 ? and 138.2 ?,respectively,after the extraction process,corresponding to the properties of raw resin.The physical properties of the resin in the extraction process there is a certain memory effect.The optimum extraction mass ratio was 1:20 and the optimum extraction time was 15 min.The extraction efficiency was 11.6% higher than that of standing extraction by ultrasonic extraction,and the extraction efficiency was improved.The secondary extraction could remove 99% solven,and the extraction time is reduced.The crystallinity of the silk with strength after the extraction was 68.53%,and the internal regularity was good,which was beneficial to the smooth drawing.The preparation of flat extraction yarns can remove 26.5% by mass of the solvent in the yarn at the press,reduce the amount of xylene used in the solvent mass fraction of 530%,reduce the environmental pollution and reduce the extraction cost.The effects of the stretching method,the raw material resin and the extraction state on the mechanical properties of the prepared UHMWPE monofilament were studied.It has been found that increasing the draw ratio is one of the effective ways to improve the strength and modulus of monofilaments,The maximum tensile modulus of the monofilament can be improved by three stretching methods,and the mechanical properties of the monofilament can be improved.The maximum tensile strength of monofilament A,B and C samples were 1.95 GPa,3.69 GPa and 3.10 GPa,the maximum tensile modulus were 128.05 GPa,133.15 GPa,138.07 GPa,the optimal elongation at break was 1.9%,2.6% and 2.3%,respectively.B monofilament has the best comprehensive mechanical properties,the maximum tensile strength of B monofilament is 3.69 GPa,19% higher than C monofilament,90% higher than A monofilament.So resin b is suitable raw materials the preparation of high-strength high-modulus monofilament;Tensile strength of flat monofilament is up to 1.95 GPa after single stretching,being similiar to the strength of monofilament A.DSC and XRD test showed that the melting point and crystallinity of monofilaments increased with the increase of the draw ratio,and the crystallinity increased rapidly at low magnification(less than 30 times),then the crystallinity tends to balance,increase the speed slowed down(higher than 30 times),while the occurrence of crystal phase transition,the study show that the regularity of the monofilaments internal chain improvement is the intrinsic factors of increased tensile strength.