The Effect of Molecular Parameters on the Thermal Behavior of Recycled and Virgin Polyamides and Their Glass Fiber Composites

Abstract

The Effect of Molecular Parameters on the Thermal BehaviorofR ecycled and Virgin Polyamides and Their Glass Fiber CompositesAs tudy was carried out to evaluate the effects of molecular weight and molecular structure on non-isothermal crystallization behavior of recycled and virgin polyamides (PA) and their corresponding glass fiber (GF) composites. Two different recycled polyamides( PA), namely post-industrial waste (PIW) and post-consumer waste (PCW) were used. The former was obtained from af iber manufacturer and the latter was recycled from used carpets. The molecular weights of the resins were measured by intrinsic viscosity (IV) measurements and 13 carbon nuclear magnetic resonance ( 13 C-NMR).The NMR technique also provided information on PA structure, cis and trans amide conformers content and residual unreacted monomer. Non-isothermal crystallization of the resins was studied using differential scanning calorimetry (DSC). The molecular weights of recycled materials were higher than that of virgin injection molding grade PA-6. However, the crystallization rates (indicated by t 1/2 )ofrecycled resins were faster. It could be attributed to the presence of TiO 2 in recycled materials. Moreover, the higher cis-amide conformer content of recycled resins suggested higher segmentalmobility. On the other hand, the crystallization rate of composites based on recycled PA-6 was slower than that of composites based on the virgin PA-6. The suppression of crystallization rate was apparently due to PA-66 added during the preparation of reinforced recycled resins. This behavior was confirmed by model compounds based on PA-6/PA-66 blends.

Effect of Polypropylene Contamination on Weld Strength of Recycled Polyamide 6

“…Previous studies have confirmed that the molecular weights of these two compounds are similar. 8 This difference is therefore likely due to the higher inorganic contamination of PCW. Figure 2(a) shows the storage modulus (E') for both compounds as a function of temperature.…”