{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T19:17:38Z","timestamp":1787944658225,"version":"build-2784847793"},"reference-count":19,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T00:00:00Z","timestamp":1787875200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Guangdong Provincial Key Project for Breakthroughs in Advanced Chemical Materials","award":["KJ0220252001"],"award-info":[{"award-number":["KJ0220252001"]}]},{"name":"Guangxi Major Science and Technology Project","award":["AA23062063"],"award-info":[{"award-number":["AA23062063"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>Glass-fiber-reinforced polypropylene (GF\/PP) composite foams combine reinforcement with weight reduction, but how GF content governs the competition between cell refinement and foam expansion under fixed-cavity molding remains unclear. GF\/PP composite foams containing 0\u201315 wt.% GF and a fixed 5 wt.% PP-g-MAH were prepared by fixed-cavity MuCell injection molding. Gas-free melt rheology, crystallization, cellular morphology, density, and mechanical properties were evaluated. Increasing GF content raised the apparent viscosity and shifted crystallization toward higher temperatures. The cell density increased from 6.12 \u00d7 104 to 1.56 \u00d7 107 cells cm\u22123, whereas the average cell diameter decreased from 264.5 to 27.1 \u03bcm. However, the expansion ratio peaked at 1.27 for GF9 and then decreased to 1.12 for GF15, showing that continuous cell refinement did not produce a monotonic improvement in foam expansion. These trends suggest competing effects of GF on cellular development: at low-to-intermediate contents, GF interfaces may favor heterogeneous nucleation, while increased melt resistance may suppress excessive cell growth and coalescence; at higher contents, fiber crowding, reduced interfiber spacing, geometric confinement, and interfacial heterogeneity may increasingly restrict cell growth and foam expansion. Although the absolute tensile and flexural properties increased with GF content, the density-normalized properties and impact strength varied nonmonotonically. GF9 exhibited the highest measured mean specific tensile, flexural, and impact strengths, together with a mean impact strength of 24.4 kJ\u00b7m\u22122, which was 32.6% higher than that of GF0. Thus, cell refinement alone does not ensure improved lightweight efficiency; an intermediate GF content provides the most favorable balance among cellular refinement, foam expansion, and fiber reinforcement.<\/jats:p>","DOI":"10.3390\/polym18172089","type":"journal-article","created":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T18:33:52Z","timestamp":1787942032000},"page":"2089","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Effects of Glass Fiber Content on the Cellular Morphology and Mechanical Properties of Microcellular Injection-Molded Polypropylene Composite Foams"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-5255-5753","authenticated-orcid":false,"given":"He","family":"Zhang","sequence":"first","affiliation":[{"name":"State Key Laboratory of Light Superalloys, Wuhan University of Technology, Wuhan 430070, China"},{"name":"Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China"},{"name":"Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan University of Technology, Wuhan 430070, China"},{"name":"Hubei Research Center for New Energy & Intelligent Connected Vehicle, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9496-4243","authenticated-orcid":false,"given":"Wei","family":"Guo","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Light Superalloys, Wuhan University of Technology, Wuhan 430070, China"},{"name":"Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China"},{"name":"Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan University of Technology, Wuhan 430070, China"},{"name":"Hubei Research Center for New Energy & Intelligent Connected Vehicle, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"110994","DOI":"10.1016\/j.matdes.2022.110994","article-title":"Advanced Lightweight Materials for Automobiles: A Review","volume":"221","author":"Zhang","year":"2022","journal-title":"Mater. Des."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1001","DOI":"10.1016\/j.jer.2024.02.017","article-title":"Advances of Composite Materials in Automobile Applications\u2014A Review","volume":"13","author":"Khan","year":"2025","journal-title":"J. Eng. Res."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Mohammadi, H., Ahmad, Z., Mazlan, S.A., Faizal Johari, M.A., Siebert, G., Petr\u016f, M., and Rahimian Koloor, S.S. (2023). Lightweight Glass Fiber\u2013Reinforced Polymer Composite for Automotive Bumper Applications: A Review. Polymers, 15.","DOI":"10.3390\/polym15010193"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1084","DOI":"10.3390\/ma5061084","article-title":"Glass Fiber Reinforced Polypropylene Mechanical Properties Enhancement by Adhesion Improvement","volume":"5","author":"Etcheverry","year":"2012","journal-title":"Materials"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Ding, Y., Hassan, M.H., Bakker, O., Hinduja, S., and B\u00e1rtolo, P. (2021). A Review on Microcellular Injection Moulding. Materials, 14.","DOI":"10.3390\/ma14154209"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"100694","DOI":"10.1016\/j.coche.2021.100694","article-title":"Microcellular Injection Molding of Polymers: A Review of Process Know-How, Emerging Technologies, and Future Directions","volume":"33","author":"Jiang","year":"2021","journal-title":"Curr. Opin. Chem. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"646","DOI":"10.1177\/0021955X20912207","article-title":"Advances in Microcellular Injection Moulding","volume":"56","author":"Llewelyn","year":"2020","journal-title":"J. Cell. Plast."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"485","DOI":"10.1002\/pen.760270702","article-title":"The Nucleation of Microcellular Thermoplastic Foam with Additives: Part I: Theoretical Considerations","volume":"27","author":"Colton","year":"1987","journal-title":"Polym. Eng. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1070","DOI":"10.1002\/pen.20786","article-title":"Cell Structure and Dynamic Properties of Injection Molded Polypropylene Foams","volume":"47","author":"Guo","year":"2007","journal-title":"Polym. Eng. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"489","DOI":"10.1177\/0021955X14528931","article-title":"Microcellular Injection Molding of Polypropylene and Glass Fiber Composites with Supercritical Nitrogen","volume":"50","author":"Xi","year":"2014","journal-title":"J. Cell. Plast."},{"key":"ref_11","first-page":"1","article-title":"Microcellular GF\/PP Composites: Morphological, Mechanical and Fracture Characterization","volume":"104","author":"Maspoch","year":"2018","journal-title":"Compos. Part A Appl. Sci. Manuf."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"752","DOI":"10.1016\/j.jmrt.2025.12.175","article-title":"Morphology, Mechanical Properties, and Environmental Impact of Long Glass Fiber\u2013Reinforced Polypropylene Foams","volume":"40","author":"Hain","year":"2026","journal-title":"J. Mater. Res. Technol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2920","DOI":"10.1016\/j.jmrt.2021.08.052","article-title":"Lightweight and Strong Glass Fiber Reinforced Polypropylene Composite Foams Achieved by Mold-Opening Microcellular Injection Molding","volume":"14","author":"Yang","year":"2021","journal-title":"J. Mater. Res. Technol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"4747","DOI":"10.1016\/0032-3861(93)90712-J","article-title":"Heterogeneous Nucleation of Short Glass Fibre\u2013Polypropylene Composites","volume":"34","author":"Iroh","year":"1993","journal-title":"Polymer"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Wang, Y., Cheng, L., Cui, X., and Guo, W. (2019). Crystallization Behavior and Properties of Glass Fiber Reinforced Polypropylene Composites. Polymers, 11.","DOI":"10.3390\/polym11071198"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Pretschuh, C., Mihalic, M., Sponner, C., Lummerstorfer, T., Steurer, A., and Unterweger, C. (2025). Physical Foam Injection Molding of Cellulose Fiber Reinforced Polypropylene by Using CO2: Parameter Variation and Comparison to Chemical Foam Injection Molding. J. Compos. Sci., 9.","DOI":"10.3390\/jcs9010050"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Simon, S.A., Hain, J., Sracic, M.W., Tewani, H.R., Prabhakar, P., and Osswald, T.A. (2022). Mechanical Response of Fiber\u2013Filled Automotive Body Panels Manufactured with the Ku-Fizz\u2122 Microcellular Injection Molding Process. Polymers, 14.","DOI":"10.3390\/polym14224916"},{"key":"ref_18","first-page":"202","article-title":"Effective Elastic Modulus of Foamed Long Glass Fiber Reinforced Polypropylene: Experiment and Computation","volume":"235","author":"Cai","year":"2021","journal-title":"Proc. Inst. Mech. Eng. Part L J. Mater. Des. Appl."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Szewczykowski, P., Sykutera, D., Czy\u017cewski, P., Cieszko, M., Szczepa\u0144ski, Z., and Nowinka, B. (2023). Structure Analysis and Its Correlation with Mechanical Properties of Microcellular Polyamide Composites Reinforced with Glass Fibers. Materials, 16.","DOI":"10.3390\/ma16237501"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/17\/2089\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T18:39:23Z","timestamp":1787942363000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/17\/2089"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,28]]},"references-count":19,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["polym18172089"],"URL":"https:\/\/doi.org\/10.3390\/polym18172089","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,28]]}}}