Influence of processing conditions on the weld line in doubly injection‐molded glassy polycarbonate and polystyrene: Microindentation hardness study

Boyanova, M.; Calleja, F. J. Baltá; Fakirov, S.; Kuehnert, Ines; Mennig, G.

doi:10.1002/adv.20028

Cited by 10 publications

(12 citation statements)

References 11 publications

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“…In a more recent work we extended the above studies on the same two glassy polymers (PC and PS) processed using a two‐component injection‐molding system 10. Specifically, the influence of processing temperature on the H‐value across the weld line, arising when the two opposite flow fronts meet, coherently filling the cavity of the mold, was examined.…”

Section: Introductionmentioning

confidence: 97%

“…Specifically, the influence of processing temperature on the H‐value across the weld line, arising when the two opposite flow fronts meet, coherently filling the cavity of the mold, was examined. It was found10 that the broadening of the weld line (expressed in the microhardness changes across the line z = 0) depends primarily on opportunities for mutual chain diffusion from the two polymer fronts coming from opposite sides. Such a case is very close to the well‐studied phenomenon of physical healing,11, 12 in which the mutual interdiffusion is determined by chain flexibility and diffusion conditions (temperature, molecular weight, etc.).…”

Section: Introductionmentioning

confidence: 99%

“…Such a case is very close to the well‐studied phenomenon of physical healing,11, 12 in which the mutual interdiffusion is determined by chain flexibility and diffusion conditions (temperature, molecular weight, etc.). Furthermore, it was shown10 that the main factors affecting the quality of the welding at the line z = 0 are the glass‐transition temperature ( T g ) of the polymer under investigation and the processing conditions: melt temperature, mold temperature, injection speed, and others.…”

Section: Introductionmentioning

confidence: 99%

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Effect of an obstacle during processing on the weld line of injection‐molded glassy polystyrene: Microhardness study

Nguyen‐Chung¹,

Mennig²,

Boyanova³

et al. 2004

J of Applied Polymer Sci

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ABSTRACT:The microhardness (H) technique is used to characterize the quality of the weld line in injection-molded glassy polystyrene by means of a cylindrical obstacle. In particular, the effect of the indentation location (closer or further from the obstacle edge parallel to the injection direction and across the weld line), both on the surface and in the bulk, was examined. Only for surface measurements close to the obstacle (up to 10 mm) a well-pronounced decrease in H (ϳ30%), followed by a sharp increase in a narrow distance (0.20 -0.25 mm), was observed. For the bulk measurements on the same location a slight decrease in H was detected. Additional H measurements made up to 60 mm from the obstacle for both cases showed that the weld line remains undetectable. The results obtained reveal that the presence of a cylindrical obstacle causes the formation of a weld line on and near the surface only at distances not exceeding the obstacle diameter. At larger distances, because of the effective mutual interdiffusion of polymer chains, the two parallel fronts coming from the two sides of the obstacle developed a homogeneous material without any weld line according to the microhardness test.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of an obstacle during processing on the weld line of injection‐molded glassy polystyrene: Microhardness study

Nguyen‐Chung¹,

Mennig²,

Boyanova³

et al. 2004

J of Applied Polymer Sci

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“…The latter has enabled to establish the relationships between the process variables and product characteristics [11,12]. At macroscale, some interesting findings, in this direction, have been reported, substantiating the validity of the microindentation technique for the assessment of the microhardness variation along the weld line of the macrosized PS and PC parts [13][14][15]. The same concept was applied to the assessment of welded joints in several polymers and metals [16][17][18].…”

Section: Introductionmentioning

confidence: 81%

Mechanical testing of micromolded plastic parts by nanoindentation

Zhiltsova

Daga

Frontini

et al. 2017

Polymer Engineering & Sci

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Weld lines occur when two melt streams are combined. They may result in purely cosmetic imperfections, but also may represent part failure if placed in an area on the plastic highly subjected to stress during service. Qualitative assessment of these structural and cosmetics defects is usually accomplished by conventional mechanical characterization, destructive by nature, such as tensile testing or dynamic mechanical analysis (DMA). Nanoindentation offers the possibility for quick quasi‐nondestructive in situ testing, allowing for monitoring the changes that occur in the surface layer of a plastic micropart. In this study, a methodology for the assessment of the superficial properties: hardness (H) and reduced Young's modulus (Er) of micromolded parts was developed. The microparts, molded from Polyoxymethylene with two different sets of processing conditions were tested throughout the entire length and in the vicinity of the welding line. The observed hardness (H) and reduced Young's modulus (Er) suggest that there is a steady increase in both values along the weld line from the adjoining flow front point at the inner side of the micropart towards the outer edge. In addition, H and Er were found out to vary consistently with the alterations induced by the processing conditions. POLYM. ENG. SCI., 58:609–614, 2018. © 2017 Society of Plastics Engineers

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“…Weld line is an unfavorable disadvantage for both of them. Many research works have been done for weld line in conventional injection molding (Chang and Faison 1999;Koster 1999;Boyanova et al 2005;Cho et al 1997;Kim et al 1997;Klein et al 2000), also some work are carried out for micro injection molding weld line (Xie and Ziegmann 2008a, b). In these research works, it is investigated very well how the processing parameters influence the weld line strength both for macro and for micro injection molding.…”

Section: Introductionmentioning

confidence: 98%

Effect of micro tensile sample’s cross section shape on the strength of weld line in micro injection molding process

et al. 2009

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As a suitable mass and cost efficiency fabrication method, micro injection molding is doing a very good performance in micro plastic parts production. The mold design is an important part affecting micro parts properties. In this study, a micro injection mold with multi cavities of micro tensile bar is used. These micro cavities are fabricated by a micro milling process in different cross section shapes (semicircle R = 0.5 mm, equilateral triangle D = 0.3 mm, and trapezoid D = 0.336 mm t = 0.2 mm bottom angle = 95°). With an Arburg Ò 320C injection molding machine, micro tensile test sample are prepared in different processing parameters so that a correlation between the cross section shapes with micro weld line strength in different conditions could be investigated by tensile test. Final results show that when the cross section shape is different, their corresponding weld line strength is also different. Equilateral triangle cross section is leading to strongest weld line, and then followed by trapezoid, semi-circle is the last. By analysis of these tensile test results, the quantitative factor a is defined as the ratio of perimeter to area of cross section shape, and higher a value is corresponding stronger weld line. After weld line strength comparison in different processing conditions, the results show that higher injection pressure induced to lower weld line strength whatever the cross section shape is. By higher mold and melt temperature, equilateral triangle cross section gives improved weld line strength. But mold and melt temperature affect weld line strength negative for other cross section shapes.

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Influence of processing conditions on the weld line in doubly injection‐molded glassy polycarbonate and polystyrene: Microindentation hardness study

Cited by 10 publications

References 11 publications

Effect of an obstacle during processing on the weld line of injection‐molded glassy polystyrene: Microhardness study

Effect of an obstacle during processing on the weld line of injection‐molded glassy polystyrene: Microhardness study

Mechanical testing of micromolded plastic parts by nanoindentation

Effect of micro tensile sample’s cross section shape on the strength of weld line in micro injection molding process

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