Reinforcing and toughening isotactic polypropylene through shear-induced crystallization and β-nucleating agent induced crystallization

Wang, Guang-Long; Hou, Sen; Cao, Junhui; Ding, Peng; Shen, Junfang

doi:10.1007/s10965-018-1632-1

Cited by 6 publications

(3 citation statements)

References 42 publications

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“…As mentioned before, the mechanical properties of thermoplastic polymers significantly depend on the microstructure parameters, such as the type of spherulites and the degree of crystallinity. Like any transformation phase, crystallization abides by the laws of thermodynamics [17,18]. The size of crystals depends on the control of thermal heat processing.…”

Section: Introductionmentioning

confidence: 99%

Non-isothermal crystallization kinetics and its effect on the mechanical properties of homopolymer isotactic polypropylene

et al. 2021

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The non-isothermal crystallization of the isotactic Polypropylene (iPP) was studied using differential scanning calorimetry and polarizing optical microscopy. Jeziorny's model and Ozawa's theoretical approaches were applied to study the nonisothermal kinetics of the iPP. Jeziorny's approach proved to be the most relevant model to the present material. Simultaneously, the activation energy was calculated with Kissinger's method and Vyazovkin's iso-conversional approach. Indeed, the latter provides an activation energy varying between 100 and 176 kJ/mol. Furthermore, the WAXD scans indicated the presence of a single crystalline form in the used material. To study the effect of the microstructure on the mechanical properties of the iPP, multiscale tensile tests were carried out for different film microstructures. At macroscopic scale, the increase in the diameter of spherulites, inevitably accompanied by a rise in the crystallinity rate, induces the growth of rigidity, brittleness, and elastic limit. Moreover, the results of the in-situ micro-tensile tests present the evolution of spherulites during loading.

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Section: Introductionmentioning

confidence: 99%

Non-isothermal crystallization kinetics and its effect on the mechanical properties of homopolymer isotactic polypropylene

et al. 2021

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“…For crystalline polymers, the PVT relationship diagram is even more complicated because of phase changes (Figure 1a) [15]. Controlling the extent of molded part shrinkage in crystalline polymers is particularly difficult because the processing conditions also affect the degree of crystallinity (DOC) [16][17][18][19], which plays a significant role in determining part shrinkage. To avoid the ambiguity of DOCinduced uncertainties for shrinkage or PVT behavior (Figure 1b), the solidification process during crystallization is often monitored [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Prediction of Part Shrinkage for Injection Molded Crystalline Polymer via Cavity Pressure and Melt Temperature Monitoring

Chen,

Tsai,

Hsieh

et al. 2023

Applied Sciences

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During an injection molding process, different parts of the molded material are subjected to various thermal–mechanical stresses, such as variable pressures, temperatures, and shear stresses. These variations form different pressure–temperature paths on the pressure–volume–temperature diagram. If these paths cannot converge at a specific target volume value during ejection, it often leads to different levels of shrinkage and associated warping, which pose a significant challenge for molders during mold trials and part quality control. The situation is particularly complicated when molding crystalline polymers because the degree of crystallinity depends on the processing conditions and may vary across different locations. In this study, we propose an innovative and practical approach to improving part shrinkage when molding crystalline polymers. For the first time, we utilized melt temperature profile monitoring rather than the previous mold temperature measurement to detect the crystallization process and determine the time taken to complete the crystallization at different melt and mold temperatures. In addition, we used response surface methodology to build a crystallization time prediction model. The feasibility of the prediction model was verified by determining the warpage of parts molded at various cooling times. Based on this model, we varied the packing pressure, packing time, and melt temperatures to determine the correlation with part shrinkage. Through regression analysis, the time-averaged solidification pressure values can accurately control part shrinkage. Two prediction models provide reasonable accuracy and efficiency for part shrinkage control, as demonstrated by subsequent verification experiments.

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“…The capability of DCHT to induce either β-or αphase formation, depending on the respective thermal history, has been studied extensively by Varga and Menyhárd [21] and limits its industrial applicability. Despite this problem, DCHT has been used in several other studies, both before [22,23] and after [24][25][26][27][28][29][30][31] the discoveries of Varga and Menyhárd, including studies of processing effects [32]. Quite recently, combined effects of DCHT nucleation and glass fiber (GF) reinforcement have been studied [33], finding a better performance than in combination of GF and α-nucleation [34].…”

Section: Introductionmentioning

confidence: 99%

β-Nucleation of isotactic polypropylene: Chain structure effects on the effectiveness of two different nucleating agents

Wang¹,

Gahleitner²,

Gloger³

et al. 2020

Express Polym. Lett.

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Of all crystal modifications of isotactic polypropylene (iPP), the β-phase has received particular attention in both academia and industry because of the toughness increase resulting from its formation. Several novel nucleating agents have been presented and studied in recent years, most prominently the 'lanthanum complex' WBG. The majority of these studies are based only on one type of iPP, mostly an iPP homopolymer, despite the fact that chain irregularities are known to affect β-phase formation negatively. In the present study, several different iPP homo-and copolymers based on Ziegler-Natta and single-site catalysts differing mostly in chain defect concentration were used to evaluate the sensitivity of a 'reference' nucleating agent, quinacridonequinone, as well as WBG to chain structure effects. The results in terms of crystal structure, as well as mechanics, indicate a much greater sensitivity of WBG, resulting in a massively reduced β-phase formation for SSC-iPP hompolymers and ZN-iPP random copolymers with ethylene. An increase of γ-phase content in nucleation of the polymers with least regular chain structure hints at some duality for WBG as also observed for other β-nucleating agents before.

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Reinforcing and toughening isotactic polypropylene through shear-induced crystallization and β-nucleating agent induced crystallization

Cited by 6 publications

References 42 publications

Non-isothermal crystallization kinetics and its effect on the mechanical properties of homopolymer isotactic polypropylene

Non-isothermal crystallization kinetics and its effect on the mechanical properties of homopolymer isotactic polypropylene

Prediction of Part Shrinkage for Injection Molded Crystalline Polymer via Cavity Pressure and Melt Temperature Monitoring

β-Nucleation of isotactic polypropylene: Chain structure effects on the effectiveness of two different nucleating agents

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