Effect of weld-line on tensile properties for thermoplastic glass filled material

Jadhav, Ganesh; Gaval, Vivek; Divekar, Mahesh

doi:10.1177/08927057221124480

Cited by 5 publications

(10 citation statements)

References 18 publications

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“…Equation ( 10) further used to introduce weld-line strength as a function of reptation time under isothermal conditions by Kausch and Tirrell 38 and validated molecular dynamics and experimental work. The weld-line strength factor is defined in Equation (11).…”

Section: Theoretical Methodsmentioning

confidence: 99%

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Weld‐lines and its strength evaluation in injection molded parts: A review

Jadhav,

Gaval,

Solanke

et al. 2023

Polymer Engineering & Sci

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Injection molding manufacturing is immensely popular nowadays because of its excellent manufacturability for complex designs produced from a wide range of different engineering plastic materials. Weld‐line is a defect that arises in injection molding when two or more flow fronts collide. The weld‐lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms of weld‐line, etc. The presence of a weld‐line weakens components locally due to insufficient intermolecular diffusion, v‐notch formation, fiber anisotropy, insufficient process conditions, and so on. When a component is under load, crack propagation usually begins with a weak weld‐line area. Therefore, the designer should anticipate the presence of weld‐lines and their strength to avoid failure of components during operation. In this article, the review of published research work on weld‐line formation during injection molding has been summarized. The review focuses on the phenomenon of weld‐line formation, the type of weld‐lines, and the importance of weld‐line evaluations. The theoretical, experimental, and computational approaches to analyzing weld‐line and its strength are covered in detail. At last, methods for reducing weld‐lines and increasing the strength of weld‐line area have been discussed. This review also gathers data on weld‐line strength with respect to different materials.Highlights Details of weld‐line formation and its types. Importance of weld‐line evaluation. Methods of weld‐line strength evaluation. Methods of reduction of the number of weld‐line and its effect. Summary of weld‐line strength for different material.

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Section: Theoretical Methodsmentioning

confidence: 99%

“…Weld-line, also known as the knit line, is a flaw that occurs in injection molding when two or more polymetric melt-fronts are meeting each other. 1,10,11 When the rounded flow fronts of the melt streams come into contact with each other, they flatten, and fuse as shown in Figure 1. Stretching of the very viscous flow fronts is required in this operation.…”

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confidence: 99%

Weld‐lines and its strength evaluation in injection molded parts: A review

Jadhav,

Gaval,

Solanke

et al. 2023

Polymer Engineering & Sci

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“…Such particles have a high influence on weld-line effects, as they are much bigger than the polymer molecules and do not merge when colliding in a melt front, and orientate almost parallel to the weld line. [14,25,29,30] Therefore, the aim of this work was to investigate the influence of injection molding processing parameters on the mechanical properties of specimens, with and without weld lines, of reinforced and unreinforced polypropylene. The results from the five different polypropylene grades were related to their melt flow indexes to find a connection between weld-line effects and melt flow indexes.…”

Section: Introductionmentioning

confidence: 99%

“…Such particles have a high influence on weld‐line effects, as they are much bigger than the polymer molecules and do not merge when colliding in a melt front, and orientate almost parallel to the weld line. [ 14,25,29,30 ]…”

Section: Introductionmentioning

confidence: 99%

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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“…Weng et al, 7 carried out a series of injection molding experiments and constructed a simulation model to evaluate the filling quality of micropillars by varying packing pressure and melt temperature and concluded that the filling quality of microstructures of the micropillars can be improved with increasing melt temperature and packing pressure. Jadhav et al 11 conducted an experimental investigation to find the effect of weld-line and weld-line angle on tensile properties for thermoplastic glass-filled material and found a 49% strength reduction in weld-line specimens compared with those without weld-line specimens. Gao et al 12 developed a new simulation method based on healing theory and the interdiffusion model for the prediction of product strength considering weld-line and fiber orientation and concluded that their approach is effective as far as design aspects are concerned.…”

Section: Introductionmentioning

confidence: 99%

Effect of packing pressure on stagnation weld-line strength for thermoplastic semicrystalline glass fiber reinforced material

Jadhav

Gaval

Divekar³

et al. 2022

Journal of Thermoplastic Composite Materials

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Weld-Line in an injection molded part develops when two or more melt fronts are converged together. The weld-line is unavoidable when the design is complex where two melt flow fronts are mating each other head-to-head, this mating area is mechanically weak compared to other portions of the modeled part. The decrease in strength in the weld-line area can be attributed to several factors like molecular diffusion, fiber orientation effect, unoptimized process conditions, surface tension effect, internal residual stresses, etc. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. This has been examined with experimental testing and scanning electron micrographs of the fractured surface on the weld-line and without weld-line specimens. The special injection mold is designed and fabricated to produce plaques having stagnation weld-line. The plaques are prepared out of 30% glass-filled Polyamide 6 material. The four sets of plaques are produced by changing the magnitude of packing pressure equal to 60% of filling pressure, with increment of 20% up to 120% of filling pressure. The tensile test specimens are machined on these plaques for two different angular orientations and testing is conducted as per ISO 527-2. The results demonstrated that, without weld-line specimens, the tensile modulus, stress at break marginally increases with an increase in packing pressure, and strain at break decreases with an increase in packing pressure. However, for specimens with stagnation weld-lines, both the tensile modulus and stress at break are observed to be 42% of without weld-lines samples for minimum packing pressure. The results obtained are evident from stress-strain graphs and scanning electron micrographs.

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Effect of weld-line on tensile properties for thermoplastic glass filled material

Cited by 5 publications

References 18 publications

Weld‐lines and its strength evaluation in injection molded parts: A review

Weld‐lines and its strength evaluation in injection molded parts: A review

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

Effect of packing pressure on stagnation weld-line strength for thermoplastic semicrystalline glass fiber reinforced material

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