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30. Relationship between the micromorphology and mechanical properties of semicrystalline polypropylene

Author

Zhong, Zhaoping and Bevis, M. J.

Subjects
668.4, Injection moulding
Abstract

The objective of this research project was to carry out the investigation of the relationship between processing conditions, micromorphology and mechanical properties of isotactic polypropylene homopolymer using conventional and shear controlled orientation injection moulding (SCORIM) techniques by systematically changing carefully controlled processing conditions, mould geometry and compound additives. Both SCORIM and conventional techniques were employed for iPP injection moulding using three moulds of different shapes by varying the processing conditions, including nozzle temperature, mould temperature, injection speed, hold pressure and oscillating patterns of pistons. The results obtained were compared so as to indicate the differences in microstructure and physical properties resulting from the two moulding techniques. A range of analytical methods were employed. Optical transmitted light microscopy was used to reveal the skin-core morphology and preferentially oriented fibrous textures. Transmitted Electron Microscopy represented the enlargement of the fibrous alignment. Micro hardness analysed the hardness and isotropy characteristics by measuring the diagonal lengths of the indentations. Mechanical testing determined Young's modulus, the strength and toughness of the mouldings. X-ray diffraction exhibited the distribution of the cc, 6 and 7 crystalline phases of the iPP mouldings. The WAXS Debye patterns confirmed the existence of the preferred orientation through the thickness of the moulding. Differential Scanning Calorimetry analysed the thermal behaviour from the endothermal and exothermal curves. In the initial stage of the study, the polypropylene was moulded in the form of a standard tensile bar on a conventional Sandretto injection machine in order to obtain the basic characteristics of the polypropylene study material, which could then be used to compare with those properties to be gained using the SCORIM technique. A ring mould was then used in a Negri Bossi twin injection machine to investigate improvements in uniformity of micromorphology and dimensional reproducibility of mouldings made possible by four live-feed injection moulding. Later, a study was carried out on injection moulding of polypropylene by varying processing conditions, including three hold pressures, two mould temperatures and two nozzle temperatures for both conventional and SCORIM injection processes by using a rectangular bar mould in a Demag injection moulding machine. In the finial stage, the study explores the influences of composition, in essence a limited range of nucleating agents, and processing methods, and aspects of the micromorphology, dimensional control and the mechanical properties of polypropylene. Polypropylene, as a sernicrystalline polymer, represents a class of materials in which mechanical properties are strongly influenced by processing conditions and micromorphology.

Published
1996

42. Comparison of Laminoplasty vs. Laminectomy for Cervical Spondylotic Myelopathy: A Systematic Review and Meta-Analysis

Author

Zhao, Huaguo, Ren, Rong, Ma, Weihu, Xu, Song, Peng, Linrui, Zhong, Zhaoping, and Zheng, Yan

Subjects
meta-analysis, systematic review, RD1-811, laminoplasty, Surgery, laminectomy, cervical myelopathy
Abstract

ObjectivesLaminoplasty (LP) and laminectomy (LC) with or without fusion are recommended as treatment procedures for cervical spondylotic myelopathy (CSM). The purpose of this study is to conduct a meta-analysis to analyze the results of CSM patients undergoing LP or LC surgery.MethodsWe systematically and comprehensively searched Web of Science, Cochrane Library, PubMed, EMBASE, OVID, VIP database, Google Scholar, Chinese Bio-medicine Literature database, and China Scientific Journal Full-text database to July 2021 for randomized controlled trials (RCTs) and observational case series that compared LP and LC in patients with CSM. The main endpoints were the surgical process, radiographic outcomes, clinical outcomes, and surgical complications.ResultsA total of 19 were included the inclusion criteria in this meta-analysis (n = 4,348 patients). There was no significant difference in range of motion (ROM), sagittal vertical axis (SVA), Japanese Orthopedic Association (JOA), Cobb angle, visual analog scale (VAS), cervical curvature index (CCI), Nurick score, Neck Dysfunction Index (NDI), and complications. LP was found to be superior than LC in terms of complications of C5 radiculopathy and surperficial infection.ConclusionOur results indicate that LP can achieve better results in C5 radiculopathy and superficial infection in surgical treatment of CSM compared with LC. Further high-quality research is warranted to further verify our findings.Systematic Review RegistrationPRISMA: CRD42018107070.

Published
2022
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49. An innovative alcohol-solution combustion-calcination process for the fabrication of NiFe2O4 nanorods and their adsorption characteristics of methyl blue in aqueous solution

Author

Liu Ruijiang, Fahua Zhu, Qi Xu, Jianming Xue, Zhong Zhaoping, and Yueyang Xu

Subjects
Materials science, Fabrication, Aqueous solution, Polymers and Plastics, Methyl blue, Metals and Alloys, Alcohol, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, law.invention, Biomaterials, chemistry.chemical_compound, Adsorption, chemistry, Chemical engineering, law, Scientific method, Calcination, Nanorod
Abstract

Magnetic nickel ferrite (NiFe2O4) nanorods were prepared via an innovative alcohol-solution combustion-calcination technique and evaluated for removing methyl blue (MB), which may greatly benefit for dye-polluted water treatment. The magnetic nanorods were characterized by TEM, EDS, XRD, VSM, SAED, FTIR, XPS and BET, the results showed that the NiFe2O4 sample has high magnetic saturation (Ms) and soft superparamagnetic behavior, and these properties accounted for their facile separation from the aqueous solution when an external magnetic field was applied. To understand the adsorption mechanism, adsorption experiments were performed using adsorption kinetics and adsorption isotherms. The Temkin model and the pseudo-second-order kinetic model best described the adsorption characteristics of MB onto NiFe2O4 nanorods. The effect of pH on the adsorption process was investigated, when pH was 3–7, the maximum adsorption capacity was reached, which was about 62 mg·g−1. The recycling efficiency was also estimated, after 10 runs of regeneration, it remained 70.1% initial adsorption capacity, indicating the adsorbent could be efficiently reused for the adsorption of MB.

Published
2021
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