Microcellular PETs with high expansion ratio produced by supercritical CO 2 moulding compression foaming process and their mechanical properties

PLA is a bio-based biodegradable plastic, which has excellent biocompatibility and biodegradability. Because the mechanical properties of microcellular foaming material is similar to petroleum-based plastics (PS), PLA foams have been considered as ideal alternative materials. However, PLA has several inherent drawbacks such as low melt strength and slow crystallization kinetics, which severely inhibit the PLA foaming process to produce high-density forms and uniform cell morphology. By adding a chain extender or nanoparticles, and blending with other biological materials, these ways could effectively enhance the expansion ratio and the cell density of PLA and improve the mechanical properties of PLA foams. The most current investigations on microcellular foaming of PLA were reviewed in the article, and outlook of PLA foams was raised.

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Regulating Effect of Cement Accelerator on High Content Solid-Wastes Autoclaved Aerated Concrete (HCS-AAC) Slurry Performance and Subsequent Influence

Materials ◽

10.3390/ma14040799 ◽

2021 ◽

Vol 14 (4) ◽

pp. 799

Author(s):

Dingkun Xie ◽

Lixiong Cai ◽

Jie Wang

Keyword(s):

Mechanical Properties ◽

Mechanical Property ◽

Solid Wastes ◽

Hydration Products ◽

Promoting Effect ◽

Adverse Side Effects ◽

Foaming Process ◽

Carbide Slag ◽

Negative Effect ◽

Aerated Concrete

Adverse side-effects occurred in slurry foaming and thickening process when carbide slag was substituted for quicklime in HCS-AAC. Cement accelerators were introduced to modify the slurry foaming and coagulating process during pre-curing. Meanwhile, the affiliated effects on the physical-mechanical properties and hydration products were discussed to evaluate the applicability and influence of the cement accelerator. The hydration products were characterized by mineralogical (XRD) and thermal analysis (DSC-TG). The results indicated that substituting carbide slag for quicklime retarded slurry foaming and curing progress; meanwhile, the induced mechanical property declination had a negative effect on the generation of C–S–H (I) and tobermorite. Na2SO4 and Na2O·2.0SiO2 can effectively accelerate the slurry foaming rate, but the promoting effect on slurry thickening was inconspicuous. The compressive strength of HCS-AAC obviously declined with increasing cement coagulant content, which was mainly ascribed to the decrease in bulk density caused by the accelerating effect on the slurry foaming process. Dosing Na2SO4 under 0.4% has little effect on the generation of strength contributing to hydration products while the addition of Na2O·2.0SiO2 can accelerate the generation and crystallization of C–S–H, which contributed to the high activity gelatinous SiO2 generated from the reaction between Na2O·2.0SiO2 and Ca(OH)2.

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FOAMING AND MOISTURE CROSSLINKING OF VINYL TRIETHOXY SILANE GRAFTED ETHYLENE–PROPYLENE–DIENE TERPOLYMER

Rubber Chemistry and Technology ◽

10.5254/rct.21.78953 ◽

2022 ◽

Author(s):

Zhengwei Lin ◽

Qinghong Zhang ◽

Gongliang Wang ◽

Jie Mao ◽

Martin Hoch ◽

...

Keyword(s):

High Efficiency ◽

Low Cost ◽

Side Reaction ◽

High Energy ◽

Expansion Ratio ◽

Ethylene Propylene ◽

Foaming Process ◽

The Matrix ◽

High Energy Absorption ◽

Ethylene Propylene Diene Terpolymer

ABSTRACT Moisture crosslinking of polyolefins has attracted increasing attention because of its high efficiency, low cost, and easy processing. However, the crucial shortcoming of moisture crosslinking is that the side reaction of peroxide scorch (precrosslinking) simultaneously occurs in silane grafting. It has been recognized that making peroxide precrosslinking useful is an effective way to broaden the application of moisture crosslinking. A novel foaming process combined with moisture crosslinking is proposed. The matrix of ethylene–propylene–diene terpolymer grafted with silane vinyl triethoxysilane (EPDM-g-VTES) was prepared by melt grafting, with dicumyl peroxide as initiator. Foaming was then carried out with azodicarbonamide (AC) as the blowing agent by making use of precrosslinking. Subsequently, the EPDM-g-VTES foams were immersed in a water bath to achieve moisture crosslinking with dibutyl tin dilaurate as the catalyst. The results showed that VTES was grafted onto EPDM and the EPDM-g-VTES foams were successfully crosslinked by moisture. The EPDM-g-VTES compounds with AC obtained great cells by compression molding with the help of precrosslinking. The mechanical property of the EPDM-g-VTES foam was improved by moisture crosslinking. The moisture-cured foam with 4 wt% AC had an expansion ratio of about three times, which could bear large deformation and showed a high energy-absorption effect.

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Bitumen Foaming Optimisation Process on the Basis of Rheological Properties

Materials ◽

10.3390/ma11101854 ◽

2018 ◽

Vol 11 (10) ◽

pp. 1854 ◽

Cited By ~ 9

Author(s):

Marek Iwański ◽

Grzegorz Mazurek ◽

Przemysław Buczyński

Keyword(s):

Half Life ◽

Expansion Ratio ◽

Fractional Factorial ◽

Effective Control ◽

Maximum Expansion ◽

Foaming Process ◽

Original Apparatus ◽

Foam Properties ◽

Foamed Bitumen ◽

Intended Use

This article discusses the results of bitumen foam properties optimisation with respect to three factors: air pressure, bitumen temperature and amount of water. The test materials were unmodified bitumen 50/70 and bitumen 50/70 modified with 2.5% synthetic wax. The experiment was designed according to the 3(3−1) fractional factorial design. The distribution of parameters of bitumen foam were measured with the authors’ original apparatus using a laser beam. This measurement method increased the accuracy of maximum expansion ratio (ER) and half-life (HL) estimation. Based on HL and ER results, it was found that the foaming process increased bitumen stiffness due to the dynamic ageing of the bitumen. The experimental design allows more effective control over the properties of foamed bitumen with respect to its intended use. The presence of synthetic wax extended the half-life of the bitumen foam.

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Effect of Expansion Ratio and Wall Thickness on Large-Diameter Solid Expandable Tubular after Expansion

Journal of Pressure Vessel Technology ◽

10.1115/1.4050220 ◽

2021 ◽

Author(s):

Changshuai Shi ◽

Kailin Chen ◽

Xiaohua Zhu ◽

Feilong Cheng ◽

Yuekui Qi ◽

...

Keyword(s):

Mechanical Properties ◽

Internal Pressure ◽

Wall Thickness ◽

Performance Test ◽

Large Diameter ◽

Expansion Ratio ◽

Fe Model ◽

Laboratory Test Results ◽

Low Efficiency ◽

Pressure Resistance

Abstract The large-diameter solid expandable tubular with a smaller wall thickness faces the risk of internal pressure burst and external squeeze collapse in repairing damaged casing well. The internal pressure and external squeezing resistance calculation of the tubes using the analytical method require many expansion experiments and post-expansion tensile experiments, resulting in high costs and low efficiency. This paper gives a set of laboratory expansion and post-expansion performance test, which is based on the laboratory experiment and mechanical properties of material expansion. Two materials are studied: 316L and 20G. Then it analyses the error and causes of the error in the traditional analytical algorithm. Besides, it establishes an accurate finite element (FE) model to study the quantitative influence of expansion ratio and wall thickness on the burst strengths and collapse strengths of the tube. The results show that the toughness and hardening ratio of 316L is better than 20G at the same expansion ratio. The numerical simulation results of the model can effectively simulate the expansion process and the mechanical properties of SET in good agreement with the laboratory test results. The expansion ratio and wall thickness affect the mechanical properties after expansion. Thus the quantitative laws of the expansion driving force, internal pressure resistance, and external squeezing resistance under different variables are summarized. To ensure the integrity of the reinforced wellbore, the expansion ratio should not exceed 12.7%. In the current study lays a theoretical basis and technical support for optimizing SET and preventing downhole accidents.

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Effect of rare earth nucleating agent on supercritical CO2 foaming behavior of block copolymerized polypropylene

Cellular Polymers ◽

10.1177/02624893211053678 ◽

2021 ◽

pp. 026248932110536

Author(s):

Yun Zhang ◽

Yadong He ◽

Chunling Xin ◽

Yanbin Su

Keyword(s):

Rare Earth ◽

Saturation Temperature ◽

Nucleating Agent ◽

Expansion Ratio ◽

Good Effect ◽

Cell Diameter ◽

Average Cell ◽

Foaming Process ◽

Foaming Temperature ◽

Crystal Content

The rare earth nucleating agent was used to modify block copolymerized polypropylene (PPB) in foaming process. The results show that the crystallization of PPB and the melting temperature of β-crystal increased gradually with increased β-crystal nucleating agent content. The total crystallinity decreased with amount of addition increasing, and the relative content of β-crystal increased first and then decreased. When β-crystal nucleating agent content was 0.4 wt%, the relative β-crystal content reached the maximum value of 95.27%, and the final crystal grain refinement significantly. The addition of rare earth β-crystal nucleating agent has a good effect on improving the uniformity of foam cells. Under the same content of β-crystal nucleating agent and pressure, the average cell diameter and expansion ratio increased with the saturation temperature increasing. After the foaming temperature reaches 155°C, the expansion ratio began to decrease, which was also consistent with the changed trend of relative β-crystal content. At the same content of temperature and relative β-crystal, as the foaming pressure increased, the cell diameter decreased gradually, and the expansion ratio increased first, and then decreased.

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Study on Integrated Properties of PP Composites Filled with Rice Husks Powder

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.217-218.347 ◽

2011 ◽

Vol 217-218 ◽

pp. 347-352 ◽

Cited By ~ 5

Author(s):

Chun Xia He ◽

Jun Jun Liu ◽

Pan Fang Xue ◽

Hong Yan Gu

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Flexural Strength ◽

Water Absorption ◽

Volume Expansion ◽

Flexural Modulus ◽

Expansion Ratio ◽

Rice Husks ◽

Elongation Ratio ◽

Pp Composites

The influence of the rice husks powder (RHP) content and its particle size distribution on the composite’s tensile strength, fracturing elongation ratio, flexural strength and flexural elastic modulus has been investigated. Respective water absorption and thermal properties of PP composites incorporated with different proportion of RHP have also been analyzed. The microstructure of fractured surfaces was further observed in scanning electron microscopy (SEM). The results showed that the composites with RHP of 245 μm have higher mechanical properties. The tensile strength and fracturing elongation ratio decrease with the increase of RHP content, and reach peak values in 30% RHP content. Water absorption and volume expansion ratio of the composite increase with the increasing of RHP content. Flexural strength and flexural modulus decrease after water absorption. When PHR content is low, the RHP particles are well distributed and the interface of RHP and PP is smooth. When PHR content is higher, the RHP particles tend to agglomerate, leading to poorer interface and lower mechanical properties, the composite failed with brittle fracture.

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Enhancement by Metallic Tube Filling of the Mechanical Properties of Electromagnetic Wave Absorbent Polymethacrylimide Foam

Polymers ◽

10.3390/polym11020372 ◽

2019 ◽

Vol 11 (2) ◽

pp. 372 ◽

Cited By ~ 7

Author(s):

Leilei Yan ◽

Wei Jiang ◽

Chun Zhang ◽

Yunwei Zhang ◽

Zhiheng He ◽

...

Keyword(s):

Mechanical Properties ◽

Electromagnetic Wave ◽

Energy Absorption ◽

Structural Integrity ◽

Compressive Loading ◽

Metallic Tube ◽

Foaming Process ◽

Novel Structure ◽

Load Carrying ◽

Tube Filling

By the addition of a carbon-based electromagnetic absorbing agent during the foaming process, a novel electromagnetic absorbent polymethacrylimide (PMI) foam was obtained. The proposed foam exhibits excellent electromagnetic wave-absorbing properties, with absorptivity exceeding 85% at a large frequency range of 4.9–18 GHz. However, its poor mechanical properties would limit its application in load-carrying structures. In the present study, a novel enhancement approach is proposed by inserting metallic tubes into pre-perforated holes of PMI foam blocks. The mechanical properties of the tube-enhanced PMI foams were studied experimentally under compressive loading conditions. The elastic modulus, compressive strength, energy absorption per unit volume, and energy absorption per unit mass were increased by 127.9%, 133.8%, 54.2%, and 46.4%, respectively, by the metallic tube filling, and the density increased only by 5.3%. The failure mechanism of the foams was also explored. We found that the weaker interfaces between the foam and the electromagnetic absorbing agent induced crack initiation and subsequent collapses, which destroyed the structural integrity. The excellent mechanical and electromagnetic absorbing properties make the novel structure much more competitive in electromagnetic wave stealth applications, while acting simultaneously as load-carrying structures.

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Effect of Plasticizer (DOP) on Cell Structure and Mechanical Properties of Extrusion-Foamed PVC Sheet

Materials Science Forum ◽

10.4028/www.scientific.net/msf.815.601 ◽

2015 ◽

Vol 815 ◽

pp. 601-606 ◽

Cited By ~ 1

Author(s):

Ming Yi Wang ◽

Nan Qiao Zhou ◽

Jun Hu

Keyword(s):

Mechanical Properties ◽

Cell Structure ◽

Dioctyl Phthalate ◽

Bubble Coalescence ◽

Low Density ◽

Foaming Agent ◽

Elongation At Break ◽

Foaming Process ◽

Continuous Extrusion ◽

Scanning Electron

Using supercritical CO2 as the foaming agent, rigid polyvinyl chloride (R-PVC) foam sheets were prepared in a continuous extrusion foaming system. The effects of dioctyl phthalate (DOP) on the rheological properties of PVC were investigated using a Brabender torque rheometer while other basic formula remained unchanged. The influences of DOP content on microstructure, mechanical properties and density of PVC micro foamed sheet were investigated with scanning electron microscopy (SEM). The results showed that the addition of DOP resulted in increased flexibility and the elongation at break of the foamed PVC sheet, while the mechanical properties of foamed PVC sheet decreased with the increase of DOP content, implying that excessive addition of DOP will cause gas escape and bubble coalescence in the foaming process. Low density PVC foam sheets with fine cell morphology were obtained when 2 phr DOP was added in PVCformula.

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Effects of compatilizers on the cellular structures, interfacial morphologies and mechanical properties of PP foam composites

e-Polymers ◽

10.1515/epoly.2011.11.1.822 ◽

2011 ◽

Vol 11 (1) ◽

Cited By ~ 2

Author(s):

Ji-Nian Yang ◽

Zi-Quan Li ◽

Jin-Song Liu

Keyword(s):

Mechanical Properties ◽

Maleic Anhydride ◽

Cell Size ◽

Cellular Structures ◽

Cell Size Distribution ◽

Foaming Process ◽

Short Glass Fiber ◽

Elastomeric Particles ◽

The Impact ◽

Short Glass

AbstractThe short glass fiber (SGF)/polypropylene (PP) and ethylene-1-octene copolymer (POE)/SGF/PP foam composites were prepared by extrusion and subsequent post-foaming process in designed dies. The compatilizers, maleic anhydride grafted PP (PP-g-MAH) and maleic anhydride grafted POE (POE-g- MAH), were employed to improve the performance of the foam composites, respectively, and their influences on the cellular structures, interfacial morphologies and mechanical properties of PP foam composites were investigated. It was found that the compatilizers resulted in modified PP foam composites characterized by uniform cell size distribution, reduced cell size and increased cell density except POE/SGF/PP with POE-g-MAH. The obvious enhanced SGF-matrix interfacial bonding was observed from the SEM examination, and POE-g-MAH also facilitated the compatibility between elastomeric particles and matrix. Testing results indicated that, by the introduction of PP-g-MAH or POE-g-MAH, the mechanical properties of PP foam composites were significantly improved, and it seemed that the PP-g-MAH was more effective in strengthening the flexural and compressive strength while POE-g-MAH greatly increased the impact toughness.

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