Cellular and Microcellular Materials最新文献

Effect of Talc on the Cell-Population Density of Extruded Polypropylene Foams 滑石粉对挤出聚丙烯泡沫塑料胞群密度的影响

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1410

L. K. Cheung, Chul B. Park

引用次数: 1

Extrusion of Low-Density Microcellular HIPS Foams Using CO2 CO2挤压低密度微孔HIPS泡沫

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1407

A. Behravesh, Chul B. Park, R. D. Venter

{"title":"Extrusion of Low-Density Microcellular HIPS Foams Using CO2","authors":"A. Behravesh, Chul B. Park, R. D. Venter","doi":"10.1115/imece1996-1407","DOIUrl":"https://doi.org/10.1115/imece1996-1407","url":null,"abstract":"\u0000 A continuous extrusion process for the manufacture of low-density microcellular polymer is presented. Microcellular polymers are foamed plastics characterized by a cell density greater than 109 cells/cm3 and a fully grown cell size on the order of 10 μm. The basic approach to the production of microcellular structures is to continuously form a polymer/gas solution, nucleate a large number of bubbles using rapid pressure drop, shape a nucleated polymer/gas solution under pressure, and induce a volume expansion to a desired expansion ratio. Successful completion of these steps in extrusion will enable the manufacture of microcellular foamed plastics with a high cell-population density.\u0000 Previous research on the continuous processing of microcellular polymers has focused on control of microcell nucleation in extrusion. This paper presents an effective means for the control of cell growth to achieve a desired expansion ratio with CO2 as a blowing agent in microcellular foam processing. Also, a strategy to prevent the deterioration of the cell-population density via cell coalescence during expansion is presented. The promotion of a desired volume expansion ratio and the prevention of the cell coalescence in microcellular foam processing were experimentally verified. By tailoring the extrusion processing parameters, microcellular HIPS foams with a cell density of 1010 cells/cm3 and a controlled expansion ratio in the range of 1.5 to 23 were obtained.","PeriodicalId":190692,"journal":{"name":"Cellular and Microcellular Materials","volume":"59 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121015137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

Effect of Cell Morphology on the Properties of Microcellular Foamed PVC/Wood-Fiber Composites 细胞形态对微孔发泡PVC/木纤维复合材料性能的影响

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1403

L. Matuana, Chul B. Park, J. Balatinecz

{"title":"Effect of Cell Morphology on the Properties of Microcellular Foamed PVC/Wood-Fiber Composites","authors":"L. Matuana, Chul B. Park, J. Balatinecz","doi":"10.1115/imece1996-1403","DOIUrl":"https://doi.org/10.1115/imece1996-1403","url":null,"abstract":"\u0000 Wood-fiber composites make use of cellulose fibers as a reinforcing filler in the polymer matrix and are known to have a lower material cost and a higher stiffness compared to neat polymers. However, the lower material cost and enhanced stiffness of wood-fiber composites are achieved at the expense of other properties such as the ductility and the impact strength. Since microcellular plastics exhibit a higher relative impact strength, higher relative toughness, and increased relative fatigue life compared to unfoamed plastics, microcellular foaming of wood-fiber composites will improve the mechanical properties of the composites and therefore increase the usefulness of the materials. In this paper, microcellular foamed PVC/wood-fiber composites with unique cell morphology and material composition are characterized. Microcellular structures are produced in PVC/wood-fiber composites by first saturating the composite samples with CO2 under high pressure followed by rapidly decreasing the solubility of gas in the samples. The void fraction of the microcellular foamed PVC/wood-fiber composites is controlled by tailoring the composition of materials and the foaming process parameters. The results indicate that tensile and impact properties of microcellular foamed PVC/wood-fiber composites are most sensitive to changes in the cell morphology and the surface modification of fibers.","PeriodicalId":190692,"journal":{"name":"Cellular and Microcellular Materials","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127163785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Cell Nucleation in Solid-State Polycarbonate-CO2 Foams: Evidence of a Triaxial Tensile Failure Mechanism 固态聚碳酸酯- co2泡沫中的细胞成核:三轴拉伸破坏机制的证据

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1406

M. Holl, Vipin Kumar, J. Garbini, W. R. Murray

{"title":"Cell Nucleation in Solid-State Polycarbonate-CO2 Foams: Evidence of a Triaxial Tensile Failure Mechanism","authors":"M. Holl, Vipin Kumar, J. Garbini, W. R. Murray","doi":"10.1115/imece1996-1406","DOIUrl":"https://doi.org/10.1115/imece1996-1406","url":null,"abstract":"\u0000 The mechanism for nucleation phenomenon in solid state microcellular foams is identified as a solid state failure process. This process originates at internal flaws within the gas-polymer matrix where it is induced by the presence of a state of hydrostatic tensile stress within the polymer matrix. The hydrostatic tensile stress is caused by the presence of the saturating gas within the polymer. The nucleation phenomenon is thermally activated at the effective glass transition temperature of the gas-polymer mixture. At this critical temperature, the hydrostatic tensile stress within the gas-polymer mixture is sufficient to cause the polymer matrix to fail, thereby creating a foam cell nucleus.\u0000 In general, the nucleation sites are observed to be flat, approximately circular, fracture sites. After the appearance of the initial fracture, gas diffuses from the gas-polymer matrix into the fracture. The fracture seam inflates during the growth process where growth begins with the appearance of a disk shaped fracture and concludes with an approximately spherical cell. The results and conclusions presented here are distinct from previous attempts to address the nucleation phenomena in solid state microcellular plastics, and suggest a new avenue to explain the cell nucleation phenomena observed in this process.","PeriodicalId":190692,"journal":{"name":"Cellular and Microcellular Materials","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114746813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Stress-Strain Relationships of Open-Cell Foams 开孔泡沫的应力-应变关系

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1405

B. A. Todd, S. L. Smith, Tera S. Bunn

引用次数: 1

Study of Foam Sheet Formation: Part III — Effects of Foam Thickness and Cell Density 泡沫板形成的研究:第三部分-泡沫厚度和细胞密度的影响

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1409

S. -. Lee, N. Ramesh

{"title":"Study of Foam Sheet Formation: Part III — Effects of Foam Thickness and Cell Density","authors":"S. -. Lee, N. Ramesh","doi":"10.1115/imece1996-1409","DOIUrl":"https://doi.org/10.1115/imece1996-1409","url":null,"abstract":"\u0000 The existing cell growth model in the literature has been modified to include the gas loss effects due to surface evaporation experienced in a high surface to volume ratio of this foam sheet formation. As it exits from the high pressure die, nucleation occurs due to sudden pressure drop and then the sheet experiences natural cooling, expansion due to gas diffusion and gas loss from its surface. Rheological experiments were performed to supply simulation parameters for the modeling using the Haake rheometer. Both HCFC-22 and -142b were studied with low density polyethylene (LDPE) in generating the rheological data. They were also used to make foams to generate experimental data discussed in this paper using a 70 mm counter-rotating twin screw extruder. The theoretical and experimental results are compared in terms of foam density and foaming efficiency. Foaming efficiency is defined as the actual expansion over maximum possible theoretical expansion dictated by the ideal gas law for a particular blowing agent. The agreement is good when the foam expansion is under ten times and the deviation increases when the foam expands further, in which bubble-bubble interaction effects become significant.","PeriodicalId":190692,"journal":{"name":"Cellular and Microcellular Materials","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115121848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Net-Shape Forming of Sintered Microcellular Foam Parts 烧结微孔泡沫件的净形成形

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1408

Karl A. Seeler, S. A. Billington, B. D. Drake, Vipin Kumar

{"title":"Net-Shape Forming of Sintered Microcellular Foam Parts","authors":"Karl A. Seeler, S. A. Billington, B. D. Drake, Vipin Kumar","doi":"10.1115/imece1996-1408","DOIUrl":"https://doi.org/10.1115/imece1996-1408","url":null,"abstract":"\u0000 The time required to saturate a polymer with gas increases with the square of the diffusion length. This has effectively limited the application of the batch process of producing microcellular foam to thin parts. Saturating powdered polymer rather than solid polymer and then sintering the particles to create a net-shape microcellular part is an alternative technique. The advantage of sintering microcellular parts from saturated polymer powder is the great reduction in the diffusion length reduces saturation time from days to minutes. Saturation time is decoupled from part thickness.\u0000 A prototype has been designed and tested in which saturated polymer powder is blown into a mold under the pressure of the saturating gas. The absorbed gas plasticizes the polymer. The powder is compressed into a solid preform to remove macroscopic voids, increase the diffusion distance to slow gas desorption, and to increase thermal conductivity. The preform is then heated, the mold expanded, and microcellular part formed to net shape in a closed mold. Preliminary tests with polycarbonate, amorphous polyethylene terephtalate (PET-G), and cellulose acetate have been successful.","PeriodicalId":190692,"journal":{"name":"Cellular and Microcellular Materials","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134548358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

The Effect of Cell Size on the Tensile Behavior of Microcellular Polycarbonate 微孔聚碳酸酯微孔尺寸对拉伸性能的影响

Cellular and Microcellular Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-1404

Vipin Kumar, J. E. Weller

{"title":"The Effect of Cell Size on the Tensile Behavior of Microcellular Polycarbonate","authors":"Vipin Kumar, J. E. Weller","doi":"10.1115/imece1996-1404","DOIUrl":"https://doi.org/10.1115/imece1996-1404","url":null,"abstract":"\u0000 Previously, processing conditions were presented that produce polycarbonate (PC) foams with the same density and significantly different average cell size (Kumar and Weller, 1994a). It was shown that the average cell size could be varied by an order of magnitude in different foams while maintaining the same foam density. The ability to produce foams with controlled density and cell size opened the possibility for a systematic evaluation of the effect of cell size on the mechanical properties of cellular materials.\u0000 A set of experiments was performed to determine if cell size (or equivalently processing conditions) had an affects the tensile behavior of microcellular polycarbonate. A series of tensile tests was performed on polycarbonate foams where the cell size was varied from approximately 2 μm to 37 μm, while the relative density was held nearly constant at 0.56. It was determined that the tensile behavior of microcellular PC is not affected by the average cell size for the range of microstructures produced in this study. The stiffness, strength and toughness showed no definitive trends with cell size. Consequently, the only microstructural variable that determines the tensile properties is the bulk foam density.","PeriodicalId":190692,"journal":{"name":"Cellular and Microcellular Materials","volume":"128 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123610868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7