Study On The Preparation And Properties Of PA6/12powder Applied In Selective Laser Sintering

Selective Laser Sintering(SLS)is a special rapid prototyping technology in which a three-dimensional object is created layer by layer from heat-fusible powdered materials with LASER.This paper mainly developed polyamide 6/12(PA6/12)powder applied in SLS.A novel method has been developed for the synthesis of polyamide(PA)powder with lactam(caprolactam-CL,lauryllactam-LL)and polystyrene(PS)via anionic ring-opening polymerization.Aiming at developing the good SLS parts,the recipe,the SLS process and the properties of SLS parts are further discussed with various characterization methods,such as SEM,DSC,TG,GPC and so on.The main results are as follows:(1)The effect of the polymerization temperature,the types of catalytic systems and CL/LL ratio on the conversion and the thermal properties of PA powders are studied.Polymerization temperature has a certain influence on the conversion of lactam in PA,but no influence on the thermal properties.The melting point and conversion of PA decreased and then increased with increasing the content of LL in monomer.(2)The effect of the polymerization temperature,the types of catalytic systems and monomer feed on morphology of PA powders is studied.With the variation of the polymerization temperature,the morphology varied as well.The PA powder has more irregalar morphology size when the polymerization temperature rises in both EtMgBr/ACL and NaOH/ACL catalytic systems.The difference is PA powder of EtMgBr/ACL catalytic systems to be irregular particles when the polymerization temperature rises to 190℃.The average size of the PA powder in EtMgBr/ACL catalytic systems is smaller than the PA powder in NaOH/ACL catalytic systems,when in the same condition.(3)The dynamic powder behavior of PA6/12 powder has been qualitatively analyzed with some Parameters,such as Bulk/Tap Density,voidage fraction,internal friction angle,etc.According to the process of melting-crystallizing of PA6/12 powder by SEM,pre-heating at a proper temperature before sintering is an effective method to ease the phenomenon of warpage.(4)The effect of process parameters of SLS like the laser power on the property of SLS parts of PA powders is studied.The results showed that,the strength of SLS parts varied with the increase of laser power,reached its highest strength at the laser power was 30 W.Overhigh laser power accelerated the oxidation of SLS parts,enlarged the border of the SLS parts.The strength and the dimension precision of the SLS parts decreased with the higher temperature.Moreover,the property of SLS parts also has been affected by scan spacing and atmosphere of SLS.