Crystallization, Structures, and Properties of Different Polyolefins with Similar Grafting Degree of Maleic Anhydride

Abstract

Maleic anhydride (MAH) grafting to different polyolefins with similar grafting degree can have different effects on crystallization, crystal structure, and mechanical and thermal properties. The grafting leads to a smaller crystal size, less ordered lamellar structure, and a shorter long period for HDPE, LLDPE, and PP. The grafting makes PP lamellar packing less ordered the most and almost no effect to LLDPE. The grafting does not have that much impact on the crystallization ability of the HDPE, LLDPE, and HDPE/PP blend, but appreciably reduces the crystalline ability of PP-g-MAH, due to a dramatical drop in its molecular weight during the grafting process. As a result, the grafting makes PP a very brittle material with a lowered average melting point than the corresponding neat PP, but the grafting has almost no effect on elongation at break for LLDPE and some effect on HDPE (decreased by one-third). However, the PP degradation due to MAH grafting can be avoided in the presence of PE component, i.e., making the grafting of PP and PE at the same time with HDPE/PP blend. The grafted HDPE/PP blend shows a significantly improved compatibility, which leads to overall appreciably better mechanical properties than the neat HDPE/PP blend.Polymers 2020, 12, 675 2 of 13 slightly with addition of small amount of PP-g-MAH, while mechanical dampening decreased with addition of PP-g-MAH.It is well known that the degree of MAH grafting can have significant impact on the crystallization and structure of polyolefins. The melting temperature of HDPE-g-MAH decreases as increase in grafting content from 0.2% to 0.8%, [14] but increases with further increase in grafting degree. The crystallization, melting behavior and structures of PP with different maleic anhydride contents (AC = 0.5 mass%, 1 mass%, 3 mass%) was investigated by Menyhárd et al. [15] Liu et al. prepared and studied maleic anhydride/styrene-grafted PPR (polypropylene random copolymer) with grafting degrees of 1.38%, 2.25%, and 2.42%, respectively, and it is found that the crystallization rate of this MPP is higher than the neat PP and increases with the increase in grafting degree [16].Although there are quite a number of studies on MAH grafted polyolefins-including PP [15,16], high-density polyethylene (HDPE) [14], and linear low-density polyethylene (LLDPE) [17]-the different effects of similar MAH grafting degree on crystallization, structures, and properties of different polyolefins have not been explored. In the present work, a series of MAH grafted polyolefins are studied, including maleic anhydride grafted high-density polyethylene (HDPE-g-MAH), maleic anhydride grafted low-density polyethylene (LLDPE-g-MAH), PP-g-MAH and maleic anhydride grafted polypropylene/maleic anhydride grafted high-density polyethylene (PP-g-MAH/HDPE-g-MAH) blends (1:1). The crystallization kinetics, thermal behavior, crystal structure, lamellar packing, and crystal size of these grafted polyolefins, together with the corresponding non-grafted polymers, are discussed, which provides a ...

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“…It can be observed that PP-gAPP shows higher modulus and tensile strength than PP and PP-gMA. This could be attributed to the significant decrease in molecular weight and increase in melt index when MAH is grafted into PP as was reported elsewhere 41 and to the more rigid structure of APP. It also can be seen that the composite samples compatibilized with PP-gAPP show better mechanical properties with higher modulus and tensile strength.…”

Innovative high-density polyethylene/waste glass powder composite with remarkable mechanical, thermal and recyclable properties for technical applications

“…XRD measurements were conducted to study the structure of the RHDPE, WGP and MAgPE raw materials in addition to the RHDPE/MAgPE/WGP composite at the optimum mixture (78.5 wt.% RHDPE,1.5 wt.% MAgPE and 20 wt.% WGP) before and after the thermal milling consolidation process, as shown in Figure 7 (d) . As shown, the two characteristic diffraction peaks of HDPE at 2 θ = 21.4° and 23.9° corresponding to the 110 and 200 orthorhombic crystalline planes [ 33 ], respectively, were observed in RHDPE, suggesting that the crystal structure of RHDPE remained unchanged after cold milling. Similarly, the amorphous structure of WGP and semicrystalline structure of MAgPE were not affected by milling.…”

Nanosilicates in Compatibilized Mixed Recycled Polyolefins: Rheological Behavior and Film Production in a Circular Approach

“…In fact, as extensively reported in the literature for virgin polyethylene/polypropylene blends [ 19 , 20 ] and, as also successfully implemented by means of the reactive extrusion of Fil-s [ 6 ], the maleic anhydride is able to stabilize the macro-radicals’ sites formed during the reaction of the polymer with a peroxide. In other words, it creates an inter-chain block or graft copolymers, leading to enhanced compatibility and improved mechanical properties [ 21 ] of the obtained material.…”

“…The alternative strategy for Fil-s upgrading, which foresees the addition of a PE/PP-g-MA compatibilizer, instead of the direct, reactive grafting/compatibilization with maleic anhydride of the recycled material, offers the twofold advantage of providing the plastics converters with a ready-to-use compatibilizer and of more easily tuning the compatibilization process. Concerning this latter issue, while it is well known that the inherent complexity of conducting free radical reactions for grafting MA on virgin polyolefin matrices, without extensive side reactions [ 20 , 21 ], many further difficulties arise when the material comes from the post-consumer polymeric waste stream, due to the unpredictable presence of several types of contaminants [ 6 ], which might affect the yield and effectiveness of the reaction.…”