Direct relationship between crystalline structure and part deformation of polypropylene copolymer parts fabricated by material extrusion additive manufacturing

Ju, Weilong; Gao, Xia; Su, Yunlan; Luo, Faliang; Wang, Dujin

doi:10.1002/pol.20230365

Cited by 2 publications

(1 citation statement)

References 64 publications

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“…Shrinkage and warpage are main reasons for poor dimensional accuracy of polymer parts. Shrinkage refers to a significant deviation of the actual dimension from the designed dimension, induced by thermal gradient, nonuniform crystallinity, chain orientation, and so on 50,51 . Whereas, warpage represents a distortion of the shape of final parts, caused by an anisotropic or nonuniform volumetric shrinkage with accumulation of internal stresses 36 .…”

Section: Resultsmentioning

confidence: 99%

Reducing part deformation of isotactic polypropylene specimens fabricated with powder bed fusion technique through controlling crystallization behaviors

Gao,

Guo,

Zhang

et al. 2024

Journal of Polymer Science

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Serious shrinkage and warpage are obstacles to the development of ideal isotactic polypropylene (iPP) materials for polymer‐based powder bed fusion (PBF) technique. In this work, the variations of the dimensional accuracy of the PBF‐printed iPP parts were investigated with various printing parameter and nucleating agent. The iPP parts printed at a scanning speed of 700 mm/s exhibit smaller extents of shrinkage and curling than those at lower speeds, due to a lower degree of crystallinity. Interestingly, iPP blended with the α‐ or β‐nucleating agent demonstrates more serious part deformation with respect to neat iPP. Especially, α‐nucleating agent tends to trigger the most severe curling under the investigated printing parameters. Based on X‐ray diffraction and differential scanning calorimetry (DSC) results, both neat iPP and α‐iPP parts crystallize into α‐crystal, while β‐iPP parts display the coexistence of β‐ and α‐crystals. And, the difference of the crystallinity is less than 3% in three specimens. This suggests that both crystallinity and crystalline structure are not the main reasons for the shrinkage and warpage in this case. Instead, the severe part deformation of the α‐iPP parts is assigned to the narrower sintering window as well as the higher onset crystallization temperature of α‐iPP, which hinder relaxation of residual stresses. This work provides insights into the part deformation mechanism for PBF‐processed polymer materials.

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Section: Resultsmentioning

confidence: 99%

Reducing part deformation of isotactic polypropylene specimens fabricated with powder bed fusion technique through controlling crystallization behaviors

Gao,

Guo,

Zhang

et al. 2024

Journal of Polymer Science

Self Cite

View full text Add to dashboard Cite

show abstract

Development of isotactic polypropylene‐based 3D printing materials with good dimensional accuracy and excellent impact properties

Shen,

Gao,

Luo

2024

Journal of Polymer Science

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The main challenge of fused deposition modeling (FDM) is the limited variety of commercially available semicrystalline polymer materials. Isotactic polypropylene (iPP), with a fast crystallization rate and high crystallinity, tends to undergo extensive volumetric shrinkage during the FDM process, further inducing severe deformation and poor dimensional accuracy in 3D‐printed parts. This study aims to develop desirable iPP‐based materials for the FDM technique through physically blending iPP and thermoplastic polyester elastomer (TPEE). TPEE retards the nonisothermal crystallization ability of iPP, as indicated by the significant decrease in crystallinity (Xc) from 47.7% for neat iPP to 28.5% for the iPP blend at a weight ratio of 30/70. The suppressed crystallization behavior accounts for a drastic decrease in the warpage degree of the 3D‐printed parts. The greater the content of TPEE is, the lower warpage the 3D‐printed parts have. Additionally, the presence of TPEE slightly influences the shear viscosity of iPP. As a result, iPP blends exhibit excellent extrudability during a typical FDM process. TPEE also enhances the impact strength of 3D‐printed parts by 168% compared to that of injection‐molded iPP. Taken together, the iPP blends developed in this work are promising FDM feedstock materials with good dimensional accuracy and excellent impact strength.

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Direct relationship between crystalline structure and part deformation of polypropylene copolymer parts fabricated by material extrusion additive manufacturing

Cited by 2 publications

References 64 publications

Reducing part deformation of isotactic polypropylene specimens fabricated with powder bed fusion technique through controlling crystallization behaviors

Reducing part deformation of isotactic polypropylene specimens fabricated with powder bed fusion technique through controlling crystallization behaviors

Development of isotactic polypropylene‐based 3D printing materials with good dimensional accuracy and excellent impact properties

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