Study of Micro-Injection Moulding: Factors Affecting the Content of the β-phase in Isotactic Polypropylene with β-nucleating Agent

Abstract

The special processing conditions of micro-injection moulding will affect the micro-structure of polymer microparts processed by micro-injection moulding. In this article, two-dimensional wideangle X-ray diffraction (2D-WAXD) and differential scanning calorimetry (DSC) were used to study the influence of nucleating agent concentration, mould temperature and injection pressure on content of the b-phase in isotactic polypropylene (iPP) with b-nucleating agent in micro-injection moulding. It was found that the high shear stress during micro-injection moulding could induce the formation of b-phase crystals in pure iPP, but which could restrain the formation of b-phase crystals in iPP with b-nucleating agent. The b-crystal content in micro-injection moulded samples decreased continuously with increasing the mould temperature from 130 C to 160 C. Besides, the shear stress that could restrain the nucleating efficiency of b-nucleating agent in b-nucleated iPP increased with the rise of the injection pressure and resulted in the decrease of b-phase crystals in the sample.

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

“…. It can be seen that the positions of the diffraction peaks for CRPP microparts are similar, in which the following crystallographic planes for the monoclinic α ‐crystal were analyzed: (110), (040), (130), (111), and (−131), corresponding to the diffraction angles 2 θ = 14.1°, 16.9°, 18.5°, 21.4°, and 21.8°, respectively . A diffraction peak at 2 θ = 16.1° indicates that the β ‐form crystals existed in CRPP micropart.…”

“…6. It can be seen that the positions of the diffraction peaks for CRPP microparts are similar, in which the following crystallographic planes for the monoclinic α-crystal were analyzed: (110), (040), [34] A diffraction peak at 2θ = 16.1°indicates that the β-form crystals existed in CRPP micropart. Note that the intensity of the peak (2θ = 16.1°) becomes weaker with the addition of DCP.…”

Effect of in situ poly(ethylene terephthalate) (PET) microfibrils on the morphological structure and crystallization behavior of isotactic polypropylene (iPP) under an intensive shear rate

“…found that a wide distribution of shish‐kebab structure and higher orientation degree existed in microparts. It can be seen that the researches on microparts are mostly focused on neat polymers while investigations of microparts on the polymer blends or composites are rather rare. But it is significantly important to make microparts with multi‐functions and high performances.…”

Microinjection molding of polyamide 6/carbon nanotube composites

“…17 However, other works report that high CNT concentrations, mainly with functionalized CNT (f-CNT) with a stronger compatibility with PA6, 18,19 hinder the mobility of PA6 chains, delay the crystal growth and thus lead to the decrease of crystallinity relative to neat PA6. [20][21][22][23] Limited literature is found concerning the crystalline characteristics of mP of neat polymers [24][25][26][27] and polymer/CNT nanocomposites. 22,23 Only recently, Abassi et al 28 reported the effect of the processing method on the crystallinity of nanocomposites and concluded that compression, mIM, and mIMcompression do not dramatically influence the crystallinity.…”