Morphology evolution and crystalline structure of controlled‐rheology polypropylene in micro‐injection molding

Abstract

In this paper, the microstructural evolution of controlled-rheology polypropylene (CRPP) with different melt viscoelasticities was investigated by polarized optical microscopy, scanning electronic microscopy, differential scanning calorimeter, and wide-angle X-ray diffraction. It is found that a typical "skin-core" structure formed in CRPP microparts and the thickness of oriented layer of CRPP microparts decreases notably with the addition of peroxide. The thickness of oriented layer and the distribution of different layers strongly depend on the melt flow properties and the corresponding relaxation time (λ). Furthermore, the mechanisms of the suppressed formation of oriented layers during the micro-injection molding process are discussed mainly from the viewpoint of rheology and thermodynamics. It is revealed that the shear-induced orientation is one of the key factors for the formation of oriented molecular structure (row nuclei). The final thickness of the oriented layer is the result of the competition between the orientation behavior and the disorientation behavior.

Improved processability and performance of biomedical devices with poly(lactic acid)/poly(ethylene glycol) blends

“…Compared with traditional injection‐molding technology, microinjection molding has the advantages of a low cost and high production efficiency . As a result, innovative processing technology has been widely used in the production of biological probes, biological instruments, and so on . We adopted acrylonitrile butadiene styrene (ABS) to blend with PLA, used microinjection molding to produce tensile samples, and found that the addition of ABS could actively alter the samples' rheological properties .…”

Crystallization and Microstructure Evolution of Microinjection Molded Isotactic Polypropylene with the Assistance of Poly(Ethylene Terephthalate)

“…Microinjection molding (µIM) has been widely adopted to prepare microcomponents, which features very high shearing and cooling effects during the mold cavity filling process [4,6,7]. Relative to the microparts made with metals, polymeric microparts can be produced at a large scale at relatively low cost per part [8].…”

The Influence of Talc Addition on the Performance of Polypropylene Membranes Formed by TIPS Method

“…However, in the majority of cases, the studied membranes were formed under laboratory conditions. Therefore, certain phenomena taking place during the membranes production on the industrial scale, such as the row arrangement of polymer chains resulting in the formation of linear structure of the membrane matrix, can affect the polymer mechanical properties [46]. The possibilities of preventing the polymer degradation and methods for improvement of the mechanical properties of PP membranes by introducing fillers into the dope solution, are presented in this paper.…”