Effect of Nucleating Agents on Crystallization and Melting Behavior and Mechanical Properties of Nucleated Syndiotactic Poly(propylene)

Abstract

Summary: The effects of various nucleating agents [e.g. 1,3:2,4‐dibenzylidene sorbitol (DBS), 1,3:2,4‐di‐p‐methyldibenzilidene sorbitol (MDBS), 1,3:2,4‐di‐m,p‐methylbenzylidene sorbitol (DMDBS), kaolin, talcum, marl, titanium dioxide (TiO2) and silica (SiO2)] on non‐isothermal melt crystallization and the subsequent melting behavior and mechanical properties of nucleated syndiotactic poly(propylene) (sPP) in comparison with those of the neat sample were investigated. Analysis of the non‐isothermal melt‐crystallization exotherms revealed that the ability of these fillers to nucleate sPP could be ranked from the best to the worst as follows: DBS > talcum > MDBS > kaolin > SiO2 > DMDBS > marl > TiO2. The subsequent melting endotherms for most of the sPP compounds exhibited double melting peaks, while that for the marl‐filled sPP exhibited triple melting peaks. Wide‐angle X‐ray diffraction analysis showed that addition of these fillers did not affect the crystal modification of the sPP matrix. Mechanical property measurements revealed that both the tensile strength and the percentage of elongation at yield for the sPP compounds investigated were not much different from those of the neat sPP. After natural weathering for 1 month, the tensile strength at yield for the sPP compounds investigated increased, at the expense of the percentage of elongation at yield, but, after natural weathering for 3 months, both the tensile strength and the percentage of elongation at yield were found to decrease.Effects of various organic and inorganic nucleating agents on non‐isothermal melt‐crystallization of syndiotactic poly(propylene) (recorded at a cooling rate of 10 °C · min−1).magnified imageEffects of various organic and inorganic nucleating agents on non‐isothermal melt‐crystallization of syndiotactic poly(propylene) (recorded at a cooling rate of 10 °C · min−1).

The TiO2–Clay-LDPE Nanocomposite Packaging Films: Investigation on the Structure and Physicomechanical Properties

“…The peaks were clearly visible which may correspond to the orthorhombic phase in LDPE [27] . However, the intensity of the peaks possibly diminished due to the disturbing effects of TiO 2 nanoparticles on LDPE crystal formation.…”

“…Generally, it was found that the presence of the TiO 2 nanoparticles did not alter LDPE crystallinity. Supaphol et al showed that the addition of fillers such as TiO 2 , SiO 2 and kaolin did not affect the crystal modification of the syndiotactic polypropylene matrix [27] . According to Wang et al, in observations on the degree of crystallinity in PE=silicate nanocomposites, the amount of filler was more effective than the filler type on the crystallinity of PE=silicate nanocomposites [28] .…”

Nucleator-Enhanced Molecular Orientation and Crystallization in Melt-Spun Monofilaments of Syndiotactic Polypropylene

“…Figure 1 presents the non-isothermal melt-crystallization traces for nucleated and pure sPP, respectively. As expected, DBS showed an apparent nucleation ability towards sPP when a slow crystallization rate was used and enhanced the crystallization temperature by about 6 • C. Different from other inorganic nucleators, [22,23] such as talc, carbon nanotubes, etc., a small amount of organic DBS can be dissolved in the polymer melt to form a homogenous liquid at elevated temperature. Upon cooling, DBS nucleator crystallizes prior to sPP and forms large aspect ratio nanofibrils that provide active nucleation sites to induce the crystallization of sPP.…”

“…[13,16,17] In commercial processing, on the other hand, incorporation of some amount of inorganic or organic nucleator in sPP is effective to accelerate its crystallization rate. [22,23] In particular, dibenzylidene sorbitol (DBS) and its derivative 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) show significant heterogeneous nucleation effects towards sPP, manifested by dramatic increasing of the crystallization temperature during cooling from the melt. [22] As demonstrated in the studies on other DBS or DMDBS nucleated polymers, for instance iPP, the dissolved DBS or DMDBS in the polymer melt, upon cooling, can self-organize into high aspect ratio nanofibrils that act as nucleation sites to induce polymer crystallization.…”

“…[22,23] In particular, dibenzylidene sorbitol (DBS) and its derivative 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) show significant heterogeneous nucleation effects towards sPP, manifested by dramatic increasing of the crystallization temperature during cooling from the melt. [22] As demonstrated in the studies on other DBS or DMDBS nucleated polymers, for instance iPP, the dissolved DBS or DMDBS in the polymer melt, upon cooling, can self-organize into high aspect ratio nanofibrils that act as nucleation sites to induce polymer crystallization. [24][25][26] More importantly, these phase-separated nanofibrils can be easily aligned in the iPP melt under flow and subsequently template the oriented growth of crystals.…”