Prediction of Morphology Distribution within Injection Molded Parts Obtained with Fast Cavity Heating Cycles: Effect of Packing Pressure

Speranza, Vito; Liparoti, Sara; Pantani, Roberto

doi:10.1002/mame.202200436

Cited by 6 publications

(3 citation statements)

References 26 publications

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“…A fas temperature increase/decrease rate will be assured by the heater design, with the purpos of guaranteeing efficient cooling at the packing end. Injection molding tests were per formed on polypropylene (iPP)to explore the heating power's effect on molecular orien tation [20,21]. Results were examined on the basis of the numerical simulations of the pro cess.…”

Section: Methodsmentioning

confidence: 99%

Rapid Heating of Mold: Effect of Uneven Filling Temperature on Part Morphology and Molecular Orientation

Liparoti¹,

Sofia²,

Pantani³

2023

Processes

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Mold temperature is the key parameter in determining the morphology of molded parts. Uneven temperature distribution could induce significant effects on part performances. In such cases, uneven temperature is induced to analyze the morphology developed in the molded specimens. The technology used for controlling mold temperature during the process is crucial to maintain the short processing time. This paper proposed a strategy for controlling mold temperature during the process, avoiding a significant increase in processing time. A thin electrical heater is designed and adapted below the cavity surface, allowing for the increase of the cavity surface temperature soon after the mold closure, and the fast decrease of the mold temperature soon after the filling. The effect of several heating powers and heating durations on the molecular orientation was analyzed and exploited considering the temperature and flow field realized during the process.

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Section: Methodsmentioning

confidence: 99%

Rapid Heating of Mold: Effect of Uneven Filling Temperature on Part Morphology and Molecular Orientation

Liparoti¹,

Sofia²,

Pantani³

2023

Processes

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“…The position at d = 0.474 shows the highest temperature according to both a reduction of the flow strength and the presence of viscous dissipation. It could be expected that the degree of orientation of polymeric chains and the thickness of oriented layers decrease considerably with mold temperature increases, which is induced by the stress relaxation of sheared chains and the reduced melt viscosity [29,30].…”

Section: µIm Simulationsmentioning

confidence: 99%

Analysis of Weld Lines in Micro-Injection Molding

Liparoti,

De Piano,

Salomone

et al. 2023

Materials

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Micro-injection molding (µIM) is a widespread process for the production of plastic parts with at least one dimension, or feature, in the microscale (conventionally below 500 µm). Despite injection molding being recognized as a robust process for obtaining parts with high geometry accuracy, one last occurrence remains a challenge in micro-injection molding, especially when junctions are present on the parts: the so-called weld lines. As weld lines are crucial in determining mechanical part performances, it is mandatory to clarify weld line position and characteristics, especially at the industrial scale during mold design, to limit failure causes. Many works deal with weld lines and their dependence on processing parameters for conventional injection molding, but only a few works focus on the weld line in µIM. This work examines the influence of mold temperature on the weld line position and strength by both experimental and simulation approaches in µIM. At mold temperatures below 100 °C, only short shots were obtained in the chosen cavity. At increased mold temperatures, weld lines show up to a 40% decrease in the whole length, and the overall tensile modulus doubles. This finding can be attributed to the reduction of the orientation at the weld line location favored by high mold temperatures. Moldflow simulations consistently reproduce the main features of the process, weld line position and length. The discrepancy between experimental and simulated results was attributed to the fact that crystallization in flow conditions was not accounted for in the model.

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“…The model for describing crystallization evolution is given in a previous paper [ 20 , 21 , 22 , 23 ]. It is briefly reported in the Supplementary Material .…”

Section: The Crystallization Modelmentioning

confidence: 99%

Modeling and Analysis of Morphology of Injection Molding Polypropylene Parts Induced by In-Mold Annealing

et al. 2022

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It is generally recognized that high-temperature treatments, namely annealing, influence the microstructure and the morphology, which, in turn, determine the mechanical properties of polymeric parts. Therefore, annealing can be adopted to control the mechanical performance of the molded parts. This work aims to assess the effect of annealing on the morphology developed in isotactic polypropylene (iPP) injection-molded parts. In particular, a two-step annealing is adopted: the polymer is injected in a mold at a high temperature (413 or 433 K), which is kept for 5 min (first annealing step); afterward, the mold temperature is cooled down at 403 K and held at that temperature for a time compatible with the crystallization half-time at that temperature (second annealing step). The characterization of morphology is carried out by optical and electronic scanning microscopy. The temperature of the first annealing step does not influence the thickness of the fibrillar skin layer; however, such a layer is thinner than that found in the molded parts obtained without any annealing steps. The second annealing step does not influence the thickness of the fibrillar skin layer. The dimension of spherulites found in the core is strongly influenced by both annealing steps: the spherulite dimensions enlarge by the effect of annealing steps. A model that considers spherulite and fibril evolutions is adopted to describe the effect of molding conditions on the final morphology distribution along the part thickness. The model, which adopts as input the thermo-mechanical histories calculated by commercial software for injection molding simulation, consistently predicts the main effects of the molding conditions on the morphology distributions.

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Prediction of Morphology Distribution within Injection Molded Parts Obtained with Fast Cavity Heating Cycles: Effect of Packing Pressure

Cited by 6 publications

References 26 publications

Rapid Heating of Mold: Effect of Uneven Filling Temperature on Part Morphology and Molecular Orientation

Rapid Heating of Mold: Effect of Uneven Filling Temperature on Part Morphology and Molecular Orientation

Analysis of Weld Lines in Micro-Injection Molding

Modeling and Analysis of Morphology of Injection Molding Polypropylene Parts Induced by In-Mold Annealing

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