Synergistic Regulation of Structure and Properties of Polypropylene Micro-injection Molded Parts via In Situ Fibrillation and Interfacial Compatibilization

HE Junwei; LIU Anqi; CAI Bozhi; JIANG Jing; LI Qian

doi:10.3969/j.issn.1674-6457.2026.09.001

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (9) : 1-11. DOI: 10.3969/j.issn.1674-6457.2026.09.001

Synergistic Regulation of Structure and Properties of Polypropylene Micro-injection Molded Parts via In Situ Fibrillation and Interfacial Compatibilization

HE Junwei^a,b, LIU Anqi^a,b, CAI Bozhi^b, JIANG Jing^a,b,*, LI Qian^b

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Abstract

The work aims to investigate the effects of microfibrillar networks and compatibilizers on the “skin- core” structure and mechanical properties of polypropylene (PP) micro-injection molded products. PP/PET microfibrillar composites were prepared via an in situ fibrillation technology combining “melt blending and high-speed hot stretching”, with polyethylene terephthalate (PET) as the fibrillated phase and maleic anhydride-grafted polypropylene (PP-g-MAH) as the interfacial compatibilizer. Subsequently, micro-injection molding was employed to fabricate products with typical “skin-core” structures. The morphology of PET microfibers, molecular chain orientation, and local mechanical properties within the micro-injection molded products were systematically characterized by scanning electron microscopy, polarized infrared spectroscopy, and nanoindentation. The synergistic effects of the compatibilizer and the microfibrillar networkon the macroscopic and microscopic mechanical properties of the products were investigated. The results demonstrated that the addition of PP-g-MAH significantly reduced the domain size of the PET dispersed phase. When the compatibilizer content was 1-2 parts by weight, a uniformly distributed PET microfibrillar network with an average diameter of approximately 400 nm was successfully constructed within the PP matrix. The synergistic effect of the microfibrillar structure and compatibilizer significantly increased the core-layer thickness fraction and enhanced the orientation degree of PP molecular chains, thereby reducing the orientation difference between the skin and core layers. Furthermore, the hardness and elastic modulus of the core layer could exceed those of the skin layer. Compared with the non-compatibilized PP/PET blend, the compatibilized microfibrillar composites exhibited increases of 33.5%, 306.3%, and 110.8% in yield strength, Young’s modulus, and tensile fracture energy, respectively. In conclusion, the combined effects of the in situ microfibrillar network and interfacial compatibilization enhance molecular orientation and modulus in the core layer of PP microinjection-molded products, providing a new processing strategy for the strengthening and toughening of high-performance PP micro-injection molded products.

Key words

polypropylene / in situ fibrillation / compatibilizer / micro-injection / “skin-core” structure / mechanical properties

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HE Junwei, LIU Anqi, CAI Bozhi, JIANG Jing, LI Qian. Synergistic Regulation of Structure and Properties of Polypropylene Micro-injection Molded Parts via In Situ Fibrillation and Interfacial Compatibilization[J]. Journal of Netshape Forming Engineering. 2026, 18(9): 1-11 https://doi.org/10.3969/j.issn.1674-6457.2026.09.001

References

[1] CZEPIEL M, BAŃKOSZ M, SOBCZAK-KUPIEC A. Advanced Injection Molding Methods: Review[J]. Materials, 2023, 16(17): 5802.
[2] WANG L X, JIANG L, LI S, et al.Influence of Scale Effect and Injection Speed on Morphology and Structure of the Microinjection Molded Isotactic Polypropylene Parts[J]. Polymers for Advanced Technologies, 2020, 31(7): 1463-1473.
[3] SUN J W, LI Q, JIANG Y F, et al.Lightweight and High Impact Toughness PP/PET/POE Composite Foams Fabricated by in Situ Nanofibrillation and Microcellular Injection Molding[J]. Polymers, 2023, 15(1): 227.
[4] PARENTEAU T, AUSIAS G, GROHENS Y, et al.Structure, Mechanical Properties and Modelling of Polypropylene for Different Degrees of Crystallinity[J]. Polymer, 2012, 53(25): 5873-5884.
[5] OVSIK M, FUCIKOVA K, MANAS L, et al.Influence of Polymer Flow on Polypropylene Morphology, Micro-Mechanical, and Tribological Properties of Injected Part[J]. Lubricants, 2024, 12(6): 202.
[6] 李爽, 王利霞, 李倩, 等. 微注塑聚丙烯制品的形态结构[J]. 高分子材料科学与工程, 2013, 29(5): 74-78.
LI S, WANG L X, LI Q, et al.Morphology of Micro Injection Molded Polypropylene Parts[J]. Polymer Materials Science & Engineering, 2013, 29(5): 74-78.
[7] WANG K, WANG S S, WU F, et al.A New Strategy for Preparation of Long-Chain Branched Polypropylene via Reactive Extrusion with Supercritical CO₂ Designed for an Improved Foaming Approach[J]. Journal of Materials Science, 2016, 51(5): 2705-2715.
[8] HOSSAIN M T, SHAHID M A, MAHMUD N, et al.Research and Application of Polypropylene: A Review[J]. Discover Nano, 2024, 19(1): 2.
[9] ELBAKYAN L, ZAPOROTSKOVA I.Polypropylene Modified with Carbon Nanomaterials: Structure, Properties and Application (a Review)[J]. Polymers, 2025, 17(4): 517.
[10] JIANG J, YANG L, JIA C Y, et al.Lightweight and High Mechanical Properties of in Situ Poly(ethylene terephthalate) Reinforced Polypropylene Composite Foams by Chemical Foam Injection Molding[J]. Industrial & Engineering Chemistry Research, 2023, 62(49): 21498-21508.
[11] JIANG J, JIA C Y, YANG S Y, et al.Unveiling Lightweight and High Impact Tough Polypropylene Foams through Compatibilized in Situ Fibrillation Integrated Chemical Foam Injection Molding[J]. Frontiers of Chemical Science and Engineering, 2025, 19(6): 54.
[12] HEJAZI E S, MASOOMI M.Investigation the Effect of Processing Condition and Dispersed Phase Content on Rheology-Morphology Relationship in Polypropylene/Polyethylene Terephthalate Microfibrillar Composite[J]. Polymers for Advanced Technologies, 2023, 34(3): 855-875.
[13] GASSNER C, VONGSVIVUT J, RYU M, et al.Bridging Spectroscopy and Advanced Molecular Orientation Analysis with New 4+Angle Polarization Toolbox in Quasar[J]. Computers in Biology and Medicine, 2025, 196: 110573.
[14] BOERIO F J, BAHL S K, MCGRAW G E.Vibrational Analysis of Polyethylene Terephthalate and Its Deuterated Derivatives[J]. Journal of Polymer Science: Polymer Physics Edition, 1976, 14(6): 1029-1046.
[15] JAKES J E, O’DELL J, STONE D S. Viscoelastic Moduli and Path-Dependent Hardness across Four Decades of Timescale in Semicrystalline Polymers from Berkovich Nanoindentation[J]. JOM, 2024, 76(6): 2956-2969.
[16] OLIVER W C, PHARR G M.An Improved Technique for Determining Hardness and Elastic Modulus Using Load and Displacement Sensing Indentation Experiments[J]. Journal of Materials Research, 1992, 7(6): 1564-1583.
[17] 王玉, 孙文杰, 马玉录, 等. 增容作用对PP/PA6原位微纤复合材料形貌及性能的影响[J]. 中国塑料, 2021, 35(5): 1-5.
WANG Y, SUN W J, MA Y L, et al.Effect of Compatibilizer on Morphology and Performance of PP/PA6 Microfibrillar Composites[J]. China Plastics, 2021, 35(5): 1-5.
[18] KUZMANOVIĆ M, DELVA L, CARDON L, et al.The Effect of Injection Molding Temperature on the Morphology and Mechanical Properties of PP/PET Blends and Microfibrillar Composites[J]. Polymers, 2016, 8(10): 355.
[19] JIANG Y F, JIANG J, YANG L, et al.In Situ Nanofibrillar Polypropylene-Based Composite Microcellular Foams with Enhanced Mechanical and Flame-Retardant Performances[J]. Polymers, 2023, 15(6): 1497.
[20] KHARGHANIAN M, PERCHICOT R, IRUSTA S, et al.Manufacture and Rheological Behavior of all Recycled PET/PP Microfibrillar Blends[J]. Polymer Engineering & Science, 2023, 63(6): 1702-1715.
[21] ZHAO C X, MARK L H, ALSHRAH M, et al.Challenge in Manufacturing Nanofibril Composites with Low Matrix Viscosity: Effects of Matrix Viscosity and Fibril Content[J]. European Polymer Journal, 2019, 121: 109310.
[22] 郑谏齐. 等规聚丙烯微注塑制品结晶形态与制品收缩的研究[D]. 郑州: 郑州大学, 2012.
ZHENG J Q.Study on Crystalline Morphology and Shrinkage of Isotactic Polypropylene Micro-Injection Molded Parts[D]. Zhengzhou: Zhengzhou University, 2012.
[23] JIANG J, WANG S W, HOU J H, et al.Effect of Injection Velocity on the Structure and Mechanical Properties of Micro Injection Molded Polycarbonate/Poly(ethylene terephthalate) Blends[J]. Materials & Design, 2018, 141: 132-141.
[24] SOLTANI I, MARK L H, JALALI A, et al.Optimization of Manufacturing Process for Nanofibrillated Spunbond Composite Products[J]. Journal of Manufacturing Pro- cesses, 2024, 120: 680-693.
[25] FUCIKOVA K, OVSIK M, CESNEK A, et al.Influence of Injection Molding Parameters and Distance from Gate on the Mechanical Properties of Injection-Molded Polypropylene[J]. Polymers, 2025, 17(8): 1012.
[26] YANG Y H, XU M X, LUO Z, et al.Long-Chain- Branched Polypropylene with an Ester Group as an Effective Compatibilizer to Improve the Performance of PP/PET Blends[J]. ACS Applied Polymer Materials, 2024, 6(23): 14580-14589.