Scanning acoustic microscopy investigation of weld lines in injection-molded parts manufactured from industrial thermoplastic polymer

Mohamed, Esam T. Ahmed; Zhai, Min; Schneider, Gerold A.; Kalmar, Rachel S.; Fendler, M.; Locquet, Alexandre; Citrin, D. S.; Declercq, Nico F.

doi:10.1016/j.micron.2020.102925

Cited by 8 publications

(8 citation statements)

References 29 publications

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“…8(a), a weld line with heterogeneity in the microstructure with respect to the mechanical properties and flow patterns is detectable, as was also reported in Ref. [27]. The estimated width of the weld line is ~ 500 𝜇m.…”

Section: Sam Characterizationsupporting

confidence: 81%

“…In this study, we apply polarization-resolved THz imaging to characterize the spatially dependent THz birefringence due to the anisotropy near weld lines, and verify the interpretation of the SAM results in Ref. [27]. By these means we locate injection-mold weld lines in an Acrylonitrile Butadiene Styrene (ABS) thermoplastic electrical receptacle plate in a nondestructive manner and characterize the associated THz electromagnetic, acoustomechanical, and morphological features.…”

Section: Introductionmentioning

confidence: 52%

“…The remaining frozen-in molecular orientation affects the tensile strength of the weld line as well as the THz birefringence [2]. Moreover, the variation of the mechanical density near the weld line will also influence the refractive index n, even though it is difficult to quantify the spatial dependence [27].…”

Section: Thz Characterizationmentioning

confidence: 99%

“…In our previous work presented in Ref. [27], the acoustic properties near injection-weld lines were investigated by comparing the velocity of Rayleigh surface acoustic waves (RSAW) in locations proximate to and distant from the weld lines. A discrepancy of about 100 m/s in the velocity of RSAWs between the locations was found, indicating anisotropic propagation of differently polarized ultrasonic waves.…”

Section: Introductionmentioning

confidence: 99%

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Diagnosis of injection-molded weld lines in ABS thermoplastic by polarized terahertz reflective imaging

Zhai

Mohamed²,

Locquet³

et al. 2021

NDT & E International

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Section: Sam Characterizationsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 52%

Section: Thz Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Diagnosis of injection-molded weld lines in ABS thermoplastic by polarized terahertz reflective imaging

Zhai

Mohamed²,

Locquet³

et al. 2021

NDT & E International

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“…V-notches—surface grooves circumscribing the weld-area, resulting from, for example, anisotropic shrinkage and air trapped by the convergence of melt fronts—frequently accompany weld lines [ 11 , 13 , 14 ]. In addition to their obvious effects as surface blemishes, these defects may have substantial deleterious effects on the mechanical performance of specimens: acting as stress concentrators, in addition to bisecting the highly oriented skin layer of a moulding [ 10 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

The Tensile Behaviour of Highly Filled High-Density Polyethylene Quaternary Composites: Weld-Line Effects, DIC Curiosities and Shifted Deformation Mechanisms

et al. 2021

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The interactive effects between additives and weld lines, which are frequent injection-moulding defects, were studied in high-density polyethylene (HDPE) and compared to weld-line-free reference samples. These materials were formulated around a D- and I-optimal experimental design, based on a quadratic Scheffé polynomial model, with up to 60 wt% calcium carbonate, masterbatched carbon black and a stabiliser package. Where reasonable and appropriate, the behaviours of the systems were modelled using statistical techniques, for a better understanding of the underlying trends. The characterisations were performed through the use of conventional tensile testing, digital image correlation (DIC) and scanning electron microscopy (SEM). A range of complex interactive effects were found during conventional tensile testing, with DIC used to better understand and explain these effects. SEM is used to better understand the failure mechanics of some of these systems through fractography, particularly regarding particle effects. A measure is introduced to quantify the deviation of the pre-yield deformation curve from the ideal elastic case. Novel analysis of DIC results is proposed, through the use of combined time-series plots and measures quantifying the extent and localisation of peak deformation. Through this, it could be found that strong shifts in the deformation mechanisms occur as a function of formulation and the presence/absence of weld lines. Primarily, changes are noted in the onset of continuous inter- and intralamellar slip and cavitation/fibrillation, seen through the onset of localised deformation and stress-whitening.

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Influence of injection molding parameters, melt flow rate, and reinforcing material on the weld‐line characteristics of polypropylene

Purgleitner¹,

Viljoen

Kuehnert

et al. 2023

Polymer Engineering & Sci

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In this work, the relation of injection molding parameters to the mechanical properties of various polypropylene grades is investigated to find the optimal processing parameters to minimize weld‐line effects like reduced mechanical and/or optical performance. Injection molded test specimens of five polypropylene grades with different melt flow rates were characterized for their mechanical behavior and compared with equal‐shaped specimens with a colliding weld line in the middle of the specimen. For the production of these weld‐line specimens, a special mold was used and injection molding parameters were systematically varied, tensile (ISO 527‐2) and impact (ISO 179‐1/1eU) properties were measured, and statistical analyses were performed to gain insight on the correlation between melt flow rate and weld‐line behavior. It showed that mechanical properties of specimens with weld lines can be influenced by the processing parameters, but the effect is limited. Positive correlations were found between tool temperature and tensile modulus and strength. Polypropylene grades with low melt flow indexes seem to be more susceptible to weld‐line‐induced property reductions. In a second test series similar to the pure PP investigations, glass‐fiber‐ and talc‐filled PP were used to gain insight into the weld‐line behavior of PP composites. In addition to mechanical characterization, optical and scanning electron micrographs were taken of the weld‐line areas. It was found that the reinforcing particles align along the melt flow front in the weld‐line area. As a result, the mechanical performance of weld‐line specimens is poor. Injection molding parameters were found to have only a small effect.

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Scanning acoustic microscopy investigation of weld lines in injection-molded parts manufactured from industrial thermoplastic polymer

Abstract: Graphical abstract Scanning acoustic microscopy (SAM) and Terahertz imaging analysis of weld lines in thermoplastic polymer (ABS) manufactured by injection-molding.

Cited by 8 publications

References 29 publications

Diagnosis of injection-molded weld lines in ABS thermoplastic by polarized terahertz reflective imaging

Diagnosis of injection-molded weld lines in ABS thermoplastic by polarized terahertz reflective imaging

The Tensile Behaviour of Highly Filled High-Density Polyethylene Quaternary Composites: Weld-Line Effects, DIC Curiosities and Shifted Deformation Mechanisms

Influence of injection molding parameters, melt flow rate, and reinforcing material on the weld‐line characteristics of polypropylene

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