Flow analysis of the weld line formation during injection mold filling of thermoplastics

Nguyen‐Chung, Tham

doi:10.1007/s00397-003-0339-2

Cited by 39 publications

(33 citation statements)

References 14 publications

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“…The defects like poor strength weld line are definitely needed to be understood completely. According to the current study results, The low mechanical properties in weld lines are considered to be caused by several factors such as poor intermolecular entanglement across the weld line, molecular orientation induced by fountain flow, and the stress concentration effect of surface V-notch and so on (Nguyen-Chung 2004;Diaranieh et al 1996;Nguyen-Chung et al 1998;Piotter et al 2002).…”

Section: Introductionmentioning

confidence: 92%

Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP)

Xie

Ziegmann

2009

Microsyst Technol

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As a hot fabrication technology for micro scale parts, micro injection molding is receiving increasing market attention. Improving mechanical properties of micro parts should be an important issue in the micro injection molding process. The relation between weld line strength in micro injection molding parts and processing parameters is investigated. A visual mold with variotherm unit is designed and constructed, in which the micro tensile specimen with weld line are prepared. Polypropylene (PP) is used as the research material in this study, and six processing parameters were chosen as investigating factors, which were melt temperature, mold temperature, injection pressure, packing pressure, ejection temperature and injection speed. In order to achieve optimized processing parameters and their order of significance, Taguchi experiment method was applied in this presented study. The prediction formulation of the strength of micro weld line was built up by multiple regression analysis based on Chebyshev orthogonal polynomial. The results showed the influencing significance order of parameters from strong to week separately are mold temperature, melt temperature, injection speed, ejection temperature, packing pressure and injection pressure. And the tolerance of micro weld line prediction formulation was found to be lower than 21% through confirmation experiments.

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Section: Introductionmentioning

confidence: 92%

Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP)

Xie

Ziegmann

2009

Microsyst Technol

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“…Besides, the raw polymeric materials may possess local heterogeneities of micrometer size, for example, catalyst residues, which act as a barrier in the polymer melt thus separating the melt and forming the weld line as the separated melts meet. The existence of weld line dramatically reduces the bulk strength of polymeric goods due to the weak bonding at the interface of the weld line and the localized stress concentration around the V‐notch defect . Therefore, many studies relevant to the weld line in conventional injection molding have been conducted to unravel the molecular mechanism of weld line formation, the morphology of the weld line, and its effect on the mechanical properties .…”

Section: Introductionmentioning

confidence: 99%

Predicting the location of weld line in microinjection‐molded polyethylene via molecular orientation distribution

Liao

Zhao

Yang

et al. 2019

J Polym Sci B Polym Phys

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The microstructure and molecular orientation distribution over both the length and the thickness of microinjection‐molded linear low‐density polyethylene with a weld line were characterized as a function of processing parameters using small‐angle X‐ray scattering and wide‐angle X‐ray diffraction techniques. The weld line was introduced via recombination of two separated melt streams with an angle of 180° to each other in injection molding. The lamellar structure was found to be related to the mold temperature strongly but the injection velocity and the melt temperature slightly. Furthermore, the distributions of molecular orientation at different molding conditions and different positions in the cross section of molded samples were derived from Hermans equation. The degree of orientation of polymeric chains and the thickness of oriented layers decrease considerably with an increase of both mold temperature and melt temperature, which could be explained by the stress relaxation of sheared chains and the reduced melt viscosity, respectively. The level of molecular orientation was found to be lowest in the weld line when varying injection velocity, mold temperature, and melt temperature, thus providing an effective means to identify the position of weld line induced by flow obstacles during injection‐molding process. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1705–1715

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“…Weld line is one of them which usually results in reduced mechanical property and uneven surface quality. As for normal injection molded weld line, many research works have been well done in aspects of the correlation between processing parameters/ mold design/material properties and weld line strength (Nguyen-Chung 2004;Diaranieh et al 1996;NguyenChung et al 1998;Piotter et al 2002). Nevertheless, the investigation on improving of micro injection molded weld line strength is rarely presented.…”

Section: Introductionmentioning

confidence: 96%

Reinforcement of micro injection molded weld line strength with ultrasonic oscillation

2009

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Weld lines are the unfavorable defect not only in normal injection molding process but in micro injection molding process. In this study, polypropylene (PP) was chosen as the processing material and a micro dog-bone tensile test sample was selected as the objective part. The micro tensile part was prepared by the double gate injection mold. An ultrasonic generator was integrated in this mold in order to investigate the effect of ultrasonic oscillation on the micro injection molded weld line strength. The experiments were carried out for studying how the ultrasonic output power and the oscillation inducing time affect the weld line strength. Three output power levels (400, 600 and 800 W) and two inducing mode (Mode 1. the oscillation is induced from injecting moment to ejection moment; Mode 2. the oscillation is induced from injecting moment to packing procedure finishing) were set. The results show that ultrasonic oscillation has obvious influence on the weld line strength; Mode 2 always has better performance than Mode 1 for reinforcing the weld line strength; and when output power is 400 W the weld line strength is the highest. The mechanism of ultrasonic oscillation affecting the micro injection molded weld line was also analyzed by AFM (atomic force microscope) and polarized microscope.

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Flow analysis of the weld line formation during injection mold filling of thermoplastics

Cited by 39 publications

References 14 publications

Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP)

Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP)

Predicting the location of weld line in microinjection‐molded polyethylene via molecular orientation distribution

Reinforcement of micro injection molded weld line strength with ultrasonic oscillation

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