# Maleic Anhydride-Grafted Isotactic Polybutene-1 and Modified Polyamide 6
## 3 Results
### iPB-g-MAH Modified PA6  
The iPB-g-MAH (Gd = 1.5%, MFR = 15.1 g/10 min) or iPB-1 was used to modify the PA6.  
As shown in Figure 13, the elongation at break, notch impact strength, and tensile strength of PA6/iPB blends decreased significantly when the iPB-1 concentration increased. It suggested that iPB-1 should not be used to modify PA6. For PA6/iPB-g-MAH blends, the elongation at break and notch impact strength increased when iPB-g-MAH concentration increased, the elongation at break of blends (20% content of iPB-g-MAH) increased from 56.8% to 147%, while the tensile strength only slightly decreased. The result showed that the anhydride group in iPB-g-MAH reacted with the amide group in PA6, and improved the compatibility between iPB-g-MAH and PA6. This can be confirmed by the Figure 16. The iPB-g-MAH is an excellent modifier for PA6. This also explained the fact that  
Figure 11: Polarizing optical micrograph of iPB-1 at 85 \({}^{\circ}\)C with changing time.  
Figure 12: Polarizing optical micrograph of iPB-g-MAH (Gd = 1.563%) at 85 \({}^{\circ}\)C with changing time.  
iPB-1 had little effect on the hardness and heat resistance temperature of the blends, while iPB-g-MAH had relatively greater influence on them.  
The addition of iPB or iPB-g-MAH did not affect the Vicat softening point temperature of the blends (Figure 14). This can be explained by the fact that the heat resistance of iPB-1 and iPB-g-MAH were significantly lower than that of PA6. The MFR of PA6/iPB-g-MAH blends much lower than that of PA6/iPB, which greatly slowed the degradation of PA6 during processing. The reason was that the anhydride group in iPB-g-MAH reacted with the amide group in PA6 and formed crosslinking structure. This resulted in higher relative molecular weight of PA6 and improved its processability.  
The melting and crystallization curves of iPB-1, PA6, iPB-g-MAH, PA6/iPB-g-MAH (85:15), and PA6/iPB (85:15) are shown in Figure 15. In PA6/iPB blends, PA6 and iPB exhibited independent crystallization peaks because of weak interaction between two phases. The interference between two crystalline phases had a slight effect on the melting and crystallization temperature. Moreover, the crystallization of PA6 was affected by the addition of iPB, resulting in its degree of crystallinity decreasing (Table 3). However, only one melting and one crystallization peak were shown in DSC curves of PA6/iPB-g-MAH blends. The iPB-g-MAH crystallization peak disappeared, and the melting peak and crystallization peak of PA6 moved to low temperature. This indicated good compatibility  
Figure 14: Effect of content of iPB and iPB-g-MAH in blends on Vicat softening point (**a**) and MFR (**b**).  
Figure 13: Effect of content of iPB and iPB-g-MAH in blends on blends mechanical properties. (**a**) Tensile strength; (**b**) Elongation at break; (**c**) Noched impact strength; (**d**) Shore D.  
between PA6 and iPB-g-MAH. The reason may be that the chemical reaction between the acid anhydride group in iPB-g-MAH and the amide group in PA6 formed crosslinking structures. This was confirmed by the apparent decrease of its MFR. It was difficult to crystallize because of crosslinking structure causing the degree of crystallinity of PA6 to decrease (Table 3).  
The SEM of PA6/iPB (85:15) and PA6/iPB-g-MAH (85:15) blends are shown in Figure 16. In PA6/iPB blends, the interface was clear between the two phases, due to lack of cohesion. The iPB dispersion phase showed smooth spheroids or ellipsoids that were pulled out and left holes or remained as hemispherical protrusions on the fracture surface (Figure 16c,d). In PA6/iPB-g-MAH blends, the interface between two phases was obscure, and the dispersion phase iPB was virtually invisible, indicating that the interaction between them was enhanced and macroscopic two-phase compatibility was achieved. This also can be confirmed by the Figures 13-15.