Preparation And Characterization Of Monomer Casting Nylon 6 And Its Composition With SEBS Elastomer

Anionic ring-opening polymerization ofε-caprolactam was studied with NaOH as initioator and TMI (or TDI) as activator. Ubbelohde Viscometer, Gel Permeation Chromatography (GPC), and Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) were employed to characterize the molecular weight and molecular weight distribution of oligomers in the monomer casting(MC) nylon 6. The results show that bifunctional activator yield a product with higher molecular weight than monofunctional one, that the activator functionality does not affect the molecular weight of oligomers in MC nylon 6, that the formation of oligomers is remarkable at medium-high conversions indicating the oligomer-forming mechanism is a fast one other than the classical one applied to typical ring-opening polymerization, and that oligomers higher than M₉ do not remain in solution and are separated together with the higher polymer. MALDI-TOF-MS analyses reveal that mono- and bifunctional activator system give different oligomer molecular weight distribution with TMI the maximum abundance at 1266 Da while TDI at 1040 Da, that with increasing the polymerization time the absolute abundance of ions gradually increases and the most abundant oligomeric species change from M₈ to M₉ and M₁₁, and that annealing of the samples does not affect the composition of oligomers at temperature either lower or higher than the melting point of MC nylon 6.Composition of Monomer Casting Nylon 6(PA6) with SEBS-g-TMI was investigated in this paper. FTIR analysis revealed the evidence of the chemical reaction between the end groups of PA6 and SEBS-g-TMI. Thermal, rheological, morphological, and mechanical properties of the resultant system were investigated. DSC analysis indicated that the crystallization of PA6 in SEBS-g-TMI/PA6 blends was inhibited, due to the chemical reaction that occurs at the interface of PA6 and SEBS-g-TMI. A comparison with the blends obtained from ungrafted SEBS and PA6 shows that complex viscosity and storage modulus of SEBS-g-TMI/PA6 were dramatically enhanced and the increase was strongly dependent upon the grafting degree of TMI. After examining the morphology of both blending systems, smaller particle size, more homogeneous distribution of domains and improved interfacial adhesion between matrix and domains were observed in the compatibilized system. Mechanical properties such as tensile strength, Young's modulus, flexural strength and modulus, as well as notched and un-notched impact strength of SEBS-g-TMI/PA6 blends were also found to improve gradually with increasing the content of grafted TMI.