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Microcellular injection molding process for producing lightweight thermoplastic polyurethane with customizable properties

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Frontiers of Mechanical Engineering 2018年第1期13卷 96-106页

作者： Thomas ELLINGHAM Hrishikesh KHARBAS Mihai MANITIU Guenter SCHOLZ lih-sheng turng Department of Mechanical Engineering University of Wisconsin-Madison Madison WI 53706 USA Wisconsin Institute for Discovery University of Wiseonsin-MadisonMadison WI 53715 USA BASF Corporation Wyandotte MI 48192 USA

A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying local densities, microstructures, and mechanical properties in the same microcellular injection molded part. Two stages of cavity expansion through sequential core retractions and a third expansion in a separate mold at an elevated temperature were carried out. The densities varied from 0.25 to 0.42 g/cm3 （77% to 62% weight reduction）. The mechanical properties varied as well Cyclic com- pressive strengths and hysteresis loss ratios, together with the microstructures, were characterized and reported.

关键词： thermoplastic polyurethane microcellularinjection molding cavity expansion compressive strength,hysteresis loss ratio

A biomimetic basementmembrane consisted of hybrid aligned nanofibers andmicrofibers with immobilized collagen IV and laminin for rapid endothelialization

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Bio-Design and Manufacturing 2021年第2期4卷 171-189页

作者： Chenglong Yu Guoping Guan Stefanie Glas Lu Wang Zhutong Li lih-sheng turng Key Laboratory of Textile Industry for Biomedical Textile Materials and Technology College of TextilesDonghua University2999 North Renmin RoadSongjiang DistrictShanghai 201620China Engineering Research Center of Technical Textiles of Ministry of Education College of TextilesDonghua UniversityShanghai 201620China Wisconsin Institute for Discovery University of Wisconsin-Madison330 North Orchard StreetMadisonWI 53715USA Department of Mechanical Engineering University of Wisconsin-Madison1513 University AveMadisonWI 53706USA

Rapid formation of a continuous endothelial cell(EC)monolayer with healthy endothelium function on the luminal surface of vascular implants is imperative to improve the longtime patency of small-diameter vascular *** the present study,we combined the contact guidance effects of aligned nanofibers,which enhance EC adhesion and proliferation because of its similar fiber scale with native vascular basement membranes,and aligned microfibers,which could induce EC elongation effectively and allow ECs *** was followed by successive immobilization of collagen IV and laminin to fabricate a biomimetic basement membrane(BBM)with structural and compositional *** hemolysis assay and platelet adhesion results showed that the BBM exhibited excellent ***,the adhered human umbilical vein endothelial cells(HUVECs)onto theBBMaligned along the orientation of the microfibers with an elongated morphology,and the data demonstrated that the BBM showed favorable effects on EC attachment,proliferation,and *** oriented EC monolayer formed on the BBM exhibited improved antithrombotic capability as indicated by higher production of nitric oxide and prostacyclin(PGI2).Furthermore,fluorescence images indicated that HUVECs could infiltrate into the BBM,implying theBBM’s ability to enhance transmural ***,theBBMpossessed the properties to regulate ECbehaviors and allow transmural ingrowth,demonstrating the potential to be applied as the luminal surface of small-diameter vascular implants for rapid endothelialization.

关键词： Biomimetic basement membranes Aligned electrospun fibers Surface modification Endothelialization Anti-thrombogenicity Transmural ingrowth

Improving Polylactide Toughness by Plasticizing with Low Molecular Weight Polylactide-Poly(Butylene Succinate)Copolymer

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Journal of Renewable Materials 2021年第7期9卷 1267-1281页

作者： Yottha Srithep Onpreeya Veang-in Dutchanee Pholharn lih-sheng turng John Morris Manufacturing and Materials Research Unit Department of Manufacturing EngineeringFaculty of EngineeringMahasarakham UniversityMahasarakham44150Thailand Department of Chemistry Faculty of Science and TechnologyRajabhat Maha Sarakham UniversityMahasarakham44000Thailand Polymer Engineering Center Department of Mechanical EngineeringUniversity of Wisconsin-MadisonMadison53705USA King Mongkut Institute of Technology Ladkrabang Bangkok10520Thailand

A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent *** copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to *** copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)*** melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA ***,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure ***,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS ***,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.

关键词： Polylactide poly(butylene succinate) low molecular weight copolymer biodegradability plasticizer

Experiment and simulation of foaming injection molding of polypropylene/nano-calcium carbonate composites by supercritical carbon dioxide

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Chinese Journal of Chemical Engineering 2016年第1期24卷 180-189页

作者： Zhenhao Xi Jie Chen Tao Liu Ling Zhao lih-sheng turng State Key Laboratory of Chemical Engineering East China University of Science and Technology Department of Mechanical Engineering University of Wisconsin–Madison

Microcellular injection molding of neat isotactic polypropylene(iPP) and isotactic polypropylene/nano-calcium carbonate composites(i PP/nano-CaCO_3) was performed using supercritical carbon dioxide as the physical blowing agent. The influences of filler content and operating conditions on microstructure morphology of i PP and i PP/nano-CaCO_3 microcellular samples were studied systematically. The results showed the bubble size of the microcellular samples could be effectively decreased while the cell density increased for i PP/nano-CaCO_3 composites, especially at high CO_2 concentration and back pressure, low mold temperature and injection speed, and high filler content. Then Moldex 3D was applied to simulate the microcellular injection molding process, with the application of the measured ScCO_2 solubility and diffusion data for i PP and i PP/nano-Ca CO_3 composites respectively. For neat i PP, the simulated bubble size and density distribution in the center section of tensile bars showed a good agreement with the experimental values. However, for i PP/nano-CaCO_3 composites, the correction factor for nucleation activation energy F and the pre-exponential factor of nucleation rate f_0 were obtained by nonlinear regression on the experimental bubble size and density distribution. The parameters F and f_0 can be used to predict the microcellular injection molding process for i PP/nano-CaCO_3 composites by Moldex 3D.

关键词： Microcellular injection molding Isotactic polypropylene/nano-calcium carbonate Cell morphology Nucleation activation energy Numerical simulation

Fabrication of shish-kebab-structured carbon nanotube/poly(ε-caprolactone) composite nanofibers for potential tissue engineering applications

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Rare Metals 2019年第1期38卷 64-72页

作者： Tong Wu Xin Chen Jin Sha Yi-Yan Peng Yu-Lu Ma Lin-sheng Xie lih-sheng turng Engineering Center of Efficient Green Process Equipment and Energy Conservation Ministry of Education East China University of Science and Technology School of Mechanical and Power Engineering East China University of Science and Technology Wisconsin Institute for Discovery University of Wisconsin-Madison

The electrospinning process was applied to fabricate the nanofibers of biodegradable poly(ε-caprolactone)(PCL) in which different contents of multiwalled carbon nanotubes(MWCNTs) were embedded. Afterward,the electrospun nanofibers were successfully decorated with shish-kebab structure via a self-induced crystallization technique. The topographical features and the mechanical properties of the composite scaffolds were characterized,and the biocompatibility of the material was assessed by using human osteogenic sarcoma osteoblasts(MG-63 cells). The carbon nanotube(CNT) concentration is found to affect the fiber diameter and mechanical properties of electrospun nanofibers and the periodic distance of the shish-kebab architecture. Cellular attachment and proliferation assays reveal that 0.5 wt% CNT-embedded PCL scaffold shows enhanced biocompatibility with MG-63 cells than their counterparts made of neat PCL, and the collagen-like nanotopology provided by the shish-kebab structure further facilitates the cell adhesion and proliferation. The superior interactions between cells and scaffolds demonstrate that the shish-kebab-structured CNTs/PCL nanofibers may be promising candidate for tissue engineering scaffold application.

关键词： Carbon nanotubes Poly(ε-caprolactone) Electrospinning Shish-kebab structure Tissue engineering

Fabrication of scaffolds in tissue engineering： A review

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Frontiers of Mechanical Engineering 2018年第1期13卷 107-119页

作者： Peng ZHAO Haibing GU Haoyang MI Chengchen RAO Jianzhong FU lih-sheng turng State Key Laboratory of Fluid Power arid Mechatronic Systems Zhejiang University Hangzhou 310027 China Key Laboratory of 3DPrinting Process and Equipment of Zhejiang Province ZhejiangUniversity Hangzhou 310027 China Wisconsin Institute for Discovery University of Wisconsin-MadisonMadison WI 53715 USA

Tissue engineering （TE） is an integrated discipline that involves engineering and natural science in the development of biological materials to replace, repair, and improve the function of diseased or missing tissues. Traditional medical and surgical treatments have been reported to have side effects on patients caused by organ necrosis and tissue loss. However, engineered tissues and organs provide a new way to cure specific diseases. Scaffold fabrication is an important step in the TE process. This paper summarizes and reviews the widely used scaffold fabrication methods, including conventional methods, electrospinning, three-dimensional printing, and a combination of molding techniques. Furthermore, the differences among the properties of tissues, such as pore size and distribution, porosity, structure, and mechanical properties, are elucidated and critically reviewed. Some studies that combine two or more methods are also reviewed. Finally, this paper provides some guidance and suggestions for the future of scaffold fabrication.

关键词： tissue engineering scaffolds electrospinning,3D printing molding techniques conventional methods

Fabrication of Highly Porous Interconnected Three-dimensional Scaffolds with Micro-channels

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Chinese Journal of Polymer Science 2014年第7期32卷 864-870页

作者： Zhi-xiang Cui Hai-bin Zhao Yi-yan Peng Yottha Srithep lih-sheng turng 申长雨 Fujian University of Technology Shandong University University of Wisconsin-Madison Zhengzhou University

A novel highly porous 3-D poly（e-caprolactone）（PCL） scaffold with micro-channels was fabricated by injection molding and diluent acetic acids leaching technologies. In this study, the chitosan fiber was employed to form the microchannel in PCL matrix. The morphology, porosity and mechanical properties of the scaffolds were studied and calculated. It was found that the larger the content of chitosan fiber is, the higher the porosity would be, due to the volumetric expansion of chitosan fiber in PCL matrix during it being leached. In addition, the less the content of chitosan fiber is, the higher the compressive modulus would be.

关键词： Injection molding Micro-channel Chitosan fiber Poly(ε-caprolactone) scaffold.

The Degradation Rate of Polyanhydride (Poly(sebacic acid), diacetoxy terminated, PSADT)

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Journal of Wuhan University of Technology(Materials Science) 2013年第4期28卷 793-797页

作者：崔志香 PENG Yiyan LI Ke PENG Jun ZHAO Haibin turng lih-sheng SHEN Changyu School of Materials Science and Engineering Fujian University of Technology Polymer Engineering Center University of Wisconsin-Madison National Engineering Research Center of Novel Technology South China University of Technology School of Materials Science and Engineering Zhengzhou University

The in vitro degradation rate of polyanhydride （poly（sebacic acid）, diacetoxy terminated）, also known as PSADT, was investigated. PSADT tablets with a circular cross-section were formed using a compression molding device, and then immersed into phosphate buffer saline （PBS） for in vitro degradation experiments. The mechanisms of degradation and the degradation rate were characterized by the change in molecular weight and reduction in specimen mass. In addition, the effects of processing temperature and the geometry of the formed PSADT tablets on the rate of degradation were studied. The surface morphology at different degradation times was observed by scanning electron microscopy （SEM）. The experimental results showed that PSADT exhibited sur^hce erosion due to the fact that near zero-order degradation kinetics was observed during its degradation process. Moreover, it is found that the geometry of tablets played an important role on the rate of degradation, while the processing temperature had no significant effect on the PSADT degradation rate.

关键词： degradation rate polyanhydride biodegradable polymer surface erosion compression molding

化学物理联合微孔发泡成型制备聚己内酯多孔材料

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化工学报 2014年第6期65卷 2386-2392页

作者：王小峰蒋晶侯建华王市伟李倩 turng lih-sheng 申长雨微纳成型技术国际联合研究中心微成型技术河南省重点实验室河南郑州450001 郑州大学橡塑模具国家工程研究中心河南郑州450002 The Wisconsin Institute for Discovery UW-Madison

将超临界气体发泡技术与化学发泡技术联合用于制备多孔材料。采用碳酸氢钠作为化学发泡剂,将聚己内酯与碳酸氢钠挤出共混之后,使用传统注射成型和微注射成型,进行了发泡实验对比。结果表明,物理化学联合发泡用于制备多孔材料具有可行性... 详细信息

将超临界气体发泡技术与化学发泡技术联合用于制备多孔材料。采用碳酸氢钠作为化学发泡剂,将聚己内酯与碳酸氢钠挤出共混之后,使用传统注射成型和微注射成型,进行了发泡实验对比。结果表明,物理化学联合发泡用于制备多孔材料具有可行性,化学发泡剂的加入不仅改善了整体发泡效果,还能够作为气泡成核剂促进物理发泡的质量。对于所得结构在一定程度上表现的泡孔相互连通性进行了讨论,同时对泡孔壁面上出现的"网"状结构进行了分析。气泡在成核生长过程中,对于泡孔壁产生多方向拉伸的作用,相邻气泡共同作用于公共壁面,最终导致壁面部分形成"网"状结构。

关键词：聚己内酯超临界流体二氧化碳碳酸氢钠发泡成核多孔状结构