Lingqi Jian

Nonisothermal Crystallization Kinetics of Nylon 66/Montmorillonite Nanocomposites

Polyamide 66(PA66)/montmorillonite nanocomposites were prepared via direct melt compounding. The nonisothermal crystallization of PA66 and PA66/MMT nanocomposites were investigated by differential scanning calorimetry. The results show that MMT platelets play a competing role in the crystallization process of nylon 66. On the one hand, they can act as a nucleator for the PA66 matrix, accelerating the crystallization rate; on the other hand, they retard the crystal/spherulite growth, especially for nanocomposites with higher MMT content. The analysis results using Jeziorny and Mo equations verify the dual actions of the nucleation and the obstruction of crystallization of MMT in the PA66 matrix. Kissingers method was used to obtain the activation energy of the crystallization process; the results confirm that the incorporation of MMT causes the above actions.

Non-isothermal crystallization kinetics of PA6/attapulgite composites prepared by melt compounding

The non‐isothermal crystallization behaviors of neat polyamide 6 (PA6) and PA6/attapulgite (ATB) composites were examined using differential scanning calorimetry. The results show that ATB acts as a nucleator for PA6 matrix, accelerating the crystallization, and simultaneously obstructs the crystallization especially for the composites with higher ATB content. The analysis results using the Jeziorny and Liu equations verify the dual actions of the nucleation and the obstruction of crystallization of the ATB in the PA6 matrix. Kissingers method is employed to obtain the activation energy of the crystallization processes; the results further indicate that the addition of ATB may also cause the above actions. It is speculated that there is a very complicated crystallization mechanism in the PA6/ATB composites based on the analysis of Avrami exponents obtained by the Jeziorny model.

Morphological, Thermal and Mechanical Properties of Compatibilized Nylon 6/ABS Blends

Super‐tough nylon 6/ABS blends were prepared by using styrene/acrylonitrile/maleic anhydride co‐polymer (SAM) as a compatibilizer. The variations in morphology, mechanical behavior, and crystallinity associated with the reaction of the SAM with the nylon were characterized. The results showed that the addition of SAM to nylon 6/ABS blends enhanced the interfacial adhesion between nylon 6 and ABS, and this led to the decrease of ABS domain size and the improvement of mechanical properties of their blends. Moreover, it could be found that the crystallinity and phase morphology changed with the variation of SAM.

Preparation, Characterization, and Properties of Polyamide 66/Maleic Anhydride -grafted-polypropylene/Clay Ternary Nanocomposites

Polyamide (PA) 66/PP-g-MA/Organic-modified MMT (OMMT) ternary composites were prepared by direct melt compounding. The FESEM results showed that the PP-g-MA phase dispersed homogeneously in the PA matrix due to the interfacial chemical reactions between the two phases. The mechanical properties of the composites were evaluated. The tensile and bending properties decreased and the notched impact strength increased with the increase of PP-g-MA. The tribological behaviors of the ternary composites were studied by means of a ball-on-disk apparatus. The ternary composites exhibited better tribological properties compared with the PA/OMMT system. This was probably due to the fact that the PP has good flexibility and a transferring film could be formed easily on the counterpart. Combining the results of the mechanical and tribological properties, the optimal mass fraction of PP-g-MA was 10 wt. %.

Friction and Wear Behavior of Polyamide 66/Poly(vinylidene fluoride) Blends

The tribological performance of PA66 and PVDF blends was investigated by a block‐on ring sliding friction and wear tester. The appropriate amount of PVDF can decrease the friction coefficient and improve the wear resistance of PA66. Moreover, the appropriate amount of PA66 can improve the wear resistance of PVDF. SEM analysis shows that PVDF is noncompatible with PA66, and the blend presents a two‐phase structure. A smooth worn surface is a main reason for improving the frictional and wear properties of the PA66/PVDF blend. Besides, slight debris is an important factor in improving the wear resistance of the PA66/PVDF blend. FT‐IR analysis shows that the oxidation and degradation behavior of PVDF is effectively controlled in the PA66/PVDF blends. Therefore, the blend of PA66 and PVDF is a potential polymer material for tribological applications.

Structure and Micromorphology of Wear Debris of MC Nylon 6 under Dry Sliding: Correlation with Wear Mechanisms

The structure and micromorphology of wear debris of MC nylon 6 under dry sliding were investigated by FTIR, XRD, DSC, and FESEM, and the 3D surface topographies of friction materials before and after the friction test were observed, which will be helpful in understanding the friction and wear processes. The primary crystalline phase of both the unworn MC nylon 6 and the wear debris were α crystal, but the crystallinity of the latter was higher than that of the former. The proportion of α 2 (002 + 202) planes increased and the reflection from the α 1 (200) planes was suppressed in the wear debris, indicating a preferential arrangement of α 2 (002 + 202) on the surface of the wear debris. The transition in structure of the wear debris originated from the activation of the chain segments due to the thermodynamic effects. The thermodynamic effects and high chain segment mobility resulted in the hydrogen bonding whose interchain distance is a larger rupture or even chain scission. MC nylon 6 was severely worn due to the contribution of the tearing force that resulted from the combined action of the tribo-interface adhesion and the shearing effect during friction, whereas no damage happened on the worn surface of the counterpart steel pin even if under severe sliding conditions.