The Application Of Two-dimensional X-ray Diffraction In The Study Of Polyester Industrial Yarn

Polyester industrial yarn has the advantages of high strength,large modulus,good mechanical properties and application performance.It is widely used as the submarine cable,conveyor belt,geogrid grid,canvas warp wire,membrane structure material,coating fabric(advertisement lamp box cloth,etc.),tire cord,seat belt and other fields.After decades of research,sustained and rapid development of polyester industrial yarn industry has been achieved in China.It has become an international competitive advantage industry,and its output has reached about 60% in the world.However,the independent research and development capability of the polyester industry in China are still weak.Meanwhile,the product quality and added value are not high enough to satisfy some personalized consumption.Therefore,we must combine the production process of the enterprise,the macroscopic performance of the polyester industrial silk and the microstructure of the fiber to develop high performance polyester industrial yarn and ensure the product stability.The basic research is to analyze the internal complex microstructure of polyester industrial yarn.In this work,we have studied the three polyester industrial yarn,included high tenacity type(HT),low shrinkage type(LS)and super low shrinkage type(SLS).The crystallinity of the yarn was measured by two-dimensional X-ray diffraction and differential scanning calorimetry.The orientation of the yarn was measured by sonic and two-dimensional X-ray diffraction.And the mechanical properties of three kinds of yarns were measured by universal testing machine.The results showed that the SLS with maximal crystallinity(55.6%)and minimum orientation(89.60%)had the smallest Dry heat shrinkage rate and the best dimension stability;The HT with minimum crystallinity(47.1%)and maximal orientation(92.64%)had the largest breaking strength(8.3 cN/dtex)and the minimum elongation at break(15%);LS between the two.Accordingly,it can be concluded that the crystallinity and grain size mainly affect the dry heat shrinkage rate of polyester industrial yarns,the crystal orientation mainly affects the breaking strength,elongation at break and elastic modulus of the fibers.This paper established an effective approach for the analysis of microcosmic structure of polyester industrial yarn.In the study of the same type of polyester industrial yarn in the different process,it can be found that microscopic analysis showed no difference between the apparent structure of two HT yarns.However,its mechanical performance has very big difference and some even appears strong loss phenomenon.To explore its causes,this paper tests the change of the production of different stages of polyester inherent viscosity.Through the two-dimensional X-ray diffraction method and other research methods,we study the microscopic structure,which showed that amorphous area orientation is the main reason of polyester industrial yarn breaking strength.In addition,the crystallinities of two kinds of polyester industrial yarns are different.The large crystallinity means that there are more regular structure characteristics inside the polyester industrial yarn.And its dry heat shrinkage rate is larger and it has better dimensional stability.In this paper,the microstructure changes of two HT yarns under different temperature and strain conditions were studied by thermal drawing and two-dimensional X-ray diffraction technology.And the research shows that the crystallinity of polyester industrial yarn increases after decreases first then decreases with the increasing temperature.But under the condition of different strain,the crystal surface orientation of two kinds of polyester industrial yarn shows different patterns of change.The degree of the(-110)crystal plane orientation increases first and decreases afterwards with the strain.The degree of the(010)and(100)crystal plane orientation increases with the strain.When strain continues to increase,all crystal plane orientation will decrease again.The reason is that the lower tension in the process of industrial production helps to improve the compactness of the product structure,while the higher tensile will damage the internal structure and make it loose.In this paper,two-dimensional X-ray diffraction technique and other methods of test crystallization are used to study the internal microstructure of polyester industrial yarn.And it has established a relationship between microstructure and macroscopic performance.It provides theoretical reference for the industrial production process of polyester industrial yarn and has great practical significance.