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Effect of gel time of 3D sand printing binder system on quality of sand mold/core

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China Foundry 2021年第6期18卷 581-586页

作者： Yan Wang Rui-long Yu Shao-kui Yin Rui Tan Yan-chun Lou Shenyang Research Institute of Foundry Co. Ltd.Shenyang 110022China State Key Laboratory of Light Alloy Casting Technology for High-end Equipment Shenyang 110022China

Two important factors affecting the performance of sand mold/core generated by 3D printing(3DP)are strength and dimensional accuracy,which are not only closely related to the reactivity of furan resin and the phase transition of silica sand,but also the curing agent system of furan *** paper studies the influence of gel time on the strength and dimensional accuracy of a 3DP sand mold/core,taking the furan resin system as an example and using a sand specimen generated by a 3DP inkjet molding *** experiment demonstrates that the gel time of 3 to 6 min for the sand mixture suits 3DP core-making most under the experimental ***,it should be noted that under the same resin condition,the strength of a no-bake sand mold/core is higher than that of a 3DP sand mold/*** dimensional accuracy of the sand mold/core does not change significantly when the gel time is less than 15 *** the activity of binder and developing ultra-strong acid with low corrosion shall be an effective way to improve the quality of the mold/core by 3D printing.

关键词： 3D sand printing gel time sand strength dimensional accuracy

Mechanical properties of anti-seepage grouting materials for heavy metal contaminated soil

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Transactions of Nonferrous Metals Society of China 2014年第10期24卷 3316-3323页

作者：杨宇友王建强豆海军中国地质大学(北京)工程技术学院北京100083 云南地质工程勘察设计研究院昆明650041

Cement-based composite grouting materials were used to construct grouting cutoff wall for heavy metal contaminated soil in non-ferrous metal mining areas. Cement, fly ash, and slag as principal ingredients were mixed with water glass in different ways to produce three composite grouting materials. In order to investigate the effect of water glass mixing ratio, Baume degree, fly ash and slag contents on the mechanical properties of the composite grouting materials, particularly their gel time and compressive strength, the beaker-to-beaker method of gel time test and unconfined compressive strength test were conducted. In addition, the phase composition and microstructure of the composite grouting materials were analyzed by the X-ray diffraction（XRD） and scanning electron microscope（SEM） techniques. The test results show that their gel time increases when water glass mixing ratio and Baume degree increase. The gel time increases dramatically when fly ash is added, but decreases slightly if fly ash is partly replaced by slag. When the mixing ratio of water glass is below 20%, their compressive strength increases with the increases of the ratio; when the ratio is above 20%, it significantly decreases. The compressive strength also tends to increase as Baume degree increases, and improves if fly ash and slag are added.

关键词： heavy metal contaminated soil composite grouting material gel time compressive strength microstructure

Using fracture grouting to lift structures in clayey sand

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第11期11卷 879-886页

作者： James C. NI Wen-chieh CHENG Department of Civil Engineering National Taipei University of Technology College of Engineering National Taipei University of Technology

An inclined seven-story reinforced concrete building was leveled by a fracture grouting technique with quick-setting grout on a differential thickness of a clayey sand layer. The permeability and strength of clayey sand were controlled by clay content, although sand was the primary component of the foundation soil. The elevations of the building columns at basement level were closely monitored to record both the heaved volume of mat foundation after grouting and the settled volume during pore pressure dissipation. During the stabilizing stage of grouting, the foundation soil was densified by the repetitive fracturing process, which resulted in the lateral movement of the foundation soil. When the grout is less able to push soil laterally than upwards, the building starts to lift, the so-called lifting stage of grouting. The grouting efficiency is influenced by soil type, soil stress history, and foundation pressure. A final grouting efficiency of 27% and a linear relationship between grout use and percentage of eleva-tion were obtained when this building was successfully and permanently leveled.

关键词： Fracture grouting gel time Mat foundation Grouting efficiency Clayey sand

Shear Strength and Morphological Study of Polyurethane- OMMT Clay Nanocomposite Adhesive Derived from Vegetable Oil-Based Constituents

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Journal of Renewable Materials 2018年第1期6卷 117-125页

作者： Swarnalata Sahoo Hemjyoti Kalita Smita Mohanty Sanjay Kumar Nayak Central Institute of Plastic Engineering and Technology ChennaiTamil Nadu 600032India Laboratory for Advanced Research in Polymeric Materials(LARPM) CIPETBhubaneswar 751024 India and ChennaiTamil Nadu 600032India

In the current work,we have synthesized vegetable oil-based polyurethane-OMMT clay nanocomposite(PUNC)adhesive with the incorporation of different wt%of organically modified nanoclay(1 to 5 wt%)into the biobased polyurethane(PU)matrix through in-situ polymerization process via ultrasonication *** the initial stage,PU adhesive was prepared using polyol and partially biobased aliphatic isocyanate,wherein polyol was derived from the transesterified castor oil using ethylene *** formation of PU and PUNC adhesive was confirmed using Fourier transform infrared(FTIR)spectroscopy *** tensile strength of PU with different wt%of nanoclay was determined and the analysis showed that the loading of 3 wt%of nanoclay within the PU matrix showed better performance as compared to the ***,shear strength of PU and PUNC(3 wt%nanoclay)adhesives were determined using lap shear test,in which PUNC adhesive showed higher adhesive strength at 70°***,the dispersibility of OMMT nanoclay within the PU matrix along with exfoliation and amorphous structure was confirmed through wide angle X-ray diffractometer(WAXD)and transmission electron microscopy(TEM)*** phase separation structure was analyzed using dynamic mechanical analysis(DMA).The analysis revealed that with the addition of organically modified nanoclay in the PU matrix,the glass transition temperature(Tg)of the damping curve was shifted towards higher temperature.

关键词： Biobased raw material composite material green strength gel time DMA

Experimental Study on Viscosity Characteristics of Expanding Polymer Grout

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Journal of Wuhan University of Technology(Materials Science) 2021年第2期36卷 297-302页

作者： HAO Meimei LI Xiaolong WANG Xinling ZHONG Yanhui ZHANG Bei WANG Fuming ZHANG Yulong School of Water Conservancy Engineering Zhengzhou UniversityZhengzhou 450001China School of Civil Engineering Zhengzhou UniversityZhengzhou 450001China

The viscosity evolution for different temperatures was studied experimentally.A time-varying viscosity model was derived and the influence of the initial temperature on gel time was *** experimental results show that the viscosity of polymer grout increases exponentially with *** can be divided into two *** gelation,the viscosity variable quantity is very *** the gel point,there is a sudden increase in *** initial viscosity and gel time decrease with the increasing initial temperature within a certain range,The study contributes to deepening understanding of the rheological properties of polymer grout,which can provide some references for polymer grouting construction.

关键词： polymer grout viscosity initial temperature gel time

Curing Process of Phenol Formaldehyde Resin for Plywood under Vacuum Conditions

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Journal of Renewable Materials 2023年第9期11卷 3447-3461页

作者： Guobing Xiong Lu Hong Zehui Ju Xiaoning Lu Juwan Jin College of Furnishings and Industrial Design Nanjing Forestry UniversityNanjing210037China School of Forestry&Landscape Architecture Anhui Agricultural UniversityHefei230036China College of Materials Science and Engineering Nanjing Forestry UniversityNanjing210037China

The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric *** changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as *** was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made *** spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in *** was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF *** different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed *** addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF *** results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.

关键词： Phenol formaldehyde resin vacuum gel time FTIR plywood bonding strength