Remarkably Improved Impact Fracture Toughness of Isotactic Polypropylene via Combining the Effects of Shear Layer-Spherulites Layer Alternated Structure and Thermal Annealing

Abstract

The effect of thermal annealing on the mechanical properties and microstructure of polymers has been studied intensively. Nevertheless, sparse work investigated the influence of annealing on the mechanical properties of materials with alternated structure. In this work, the evolution of properties and microstructure of iPP samples with different structure after annealing were discussed. Note that annealing plays a little role on microstructure of all the specimens, whereas its effect on the variation of impact strength of different samples does not show the similar trend. For sample CIM and V1, impact fracture toughness does not improve significantly after annealing within the range of temperature used. But the promotion of the impact strength of sample V2 is extremely remarkable (from 29 KJ/m2 to 90.5KJ/m2), which can be attributed to better interfacial adhesion, resulting in violent crack deflection and plastic deformation, the formation of microfibers and the better ability of load transfer.

Unique Slow Crack Growth Behavior of Isotactic Polypropylene: The Role of Shear Layer-Spherulites Layer Alternated Structure

“…It should be noted here that the thickness of shear layer of samples V 1 and V 2 is almost the same (about 55%), indicating the same content of shish-kebab for these two samples, because it was speculated that the shear layer consisted fully of shish-kebab structure. More detailed information about the microstructure of all the samples, such as crystalline morphologies, orientation degree, the content of β crystal, have been reported in our previous literature [29]. Here, we can reasonably conclude that manipulated microstructures with different shear layer distributions could be obtained for the parts through MFVIM.…”

“…It has been reported that the Izod impact strength could be remarkably enhanced for the products with the alternated structure [ 27 , 28 ], and it could be further improved by thermal annealing at a suitable temperature for a certain time. The highest value climbed up to 90 KJ/m 2 for isotactic polypropylene (iPP), while the value of the sample prepared by CIM is lower than 5 KJ/m 2 [ 29 ]. However, the influence of the distribution of shear layer on the long-term mechanical properties has never been investigated.…”

Annealing‐induced high impact toughness of immiscible isotactic polypropylene/poly(acrylonitrile‐butadiene‐styrene) blend

“…However, the formation of β-iPP induced by ABS was suppressed simultaneously, due to the fact that ABS dispersed phase was surrounded by PP-g-MAH. 27 Except for the introduction of rigid particles, some effective techniques were also employed to elevate the impact toughness of iPP without the cost of stiffness, such as supercritical carbon dioxide treatment, 36 shearing, 37 and thermal annealing. [38][39][40][41][42][43] In recent decades, plethora of researches have been reported for annealed iPP, mainly focused on the changes in microstructure and mechanical properties upon annealing treatment.…”

Development of Unstable Flow and Morphological Analysis of Flow Marks in Injection Molding of Polypropylene and Polyolefin Elastomer Blend

“…Polypropylene (PP) is one of the most widely used thermoplastic polymers across the world and has been employed in the fields of construction, textile, packaging, electrical, and automotive industries – owing to its good comprehensive performance and low cost. – To obtain higher mechanical properties, elastomers such as polyolefin elastomer (POE) and ethylene–propylene random copolymer (EPR) are often blended with PP. – Injection molding is one of the most popular industrial manufacturing technologies because of its advantages of mass production, repeatability, automation, and accuracy. Nowadays, large injection molded products of PP/elastomer blends are increasingly applied in automobiles, such as car bumpers, dashboards, door panels, and other interior pieces. , In addition to meeting the requirements of mechanical properties, such as toughness, strength, etc., these products are also supposed to have an aesthetically pleasing appearance.…”