Low Shrinkage Polyester Industrial Yarn Structure And Molding Conditions

In spinning and drawing processes of polyethylene terephthalate(PET)industrial yarn,the effect of some technologically processingparameters on the thermal shrinkage has been investigated.Underspinning rate 3000m/min.,the structural transformation in differenttechnolo gical processes,and the related variation sinphysicalperformances were observed,and the improvement of mechanicalproperties, such as strength,modulus,and shrinkage, may beexperimentally coordinated for preparing PET industrial yarn withhigh modulus and low thermal shrinkage. As the experimental data shown,the higher the spinning rate,thebetter the orientation of winding yarn,and as a result,the thermalshrinkage is lowered. Furthermore, an increase in drawingtempera ture and over - feed ingmay also decrease the thermalshrinkage respectively under the operational conditions.In drawing,the variations in both orientation and crystallinity are mainly carriedout at the first step and second one,and the relation between fibreshrinkage and oriented structure of amorphous region isdemonstrated. According to the known regularity of structure transformationduring spinning and drawing process,the most of orientation has beengot in the first drawing step,and a little crystallizatiOn take place inthis step.In the second drawing step,the crystallinity is tiigh and thecrystal is made perfected.In succeeding thermosetting,the crystal ismade even more perfect and the orientation is lowe redin theamorphous region,SO that to make the industrial yarn with lowersthermal shrinkage and higher modulus. It is known,spinning the as-spun yarn at a speed 3 000m/min.,after being properly drawn and thermoseted,the industrial yarn canbe with properties:tenacity--7.1 cN/dtex,modulus(tenacity at 5%elongation)--higher than 4.4cN/dtex,thermal shrinkage in 1 77℃hotair for 10 min.--Iess than 2.9%.