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2020, Volume 34 Issue 2 Publication date: 26 February 2020 Previous Issue Next Issue

Preparation and Performance of Phase-change Microcapsules Based on Palmitic Acid Core and Silica Shell

2020, 34 (2): 1-8; DOI: 10.19491/j.issn.1001-9278.2020.02.001

Abstract ( 539 ) PDF (10027 KB)( 95 )

The phase-change microcapsules based on the palmitic acid (PA) core and silica shell were synthesized by an emulsion templating method through interfacial polycondensation, and the effect of core/shell mass ratio on the morpho-logy, microstructure, thermal energy-storage properties, thermal stability and thermal cycling performance of the resulting microcapsules were investigated extensively. The results indicated that the phase-change microcapsules exhibited a more perfect core-shell structure and a smoother surface with an improvement of the core/shell mass ratio, and the optimum core/shell mass ratio was determined as 60/40, at which the microcapsules achieved the highest thermal energy-storage capability of 98.78 %. The encapsulation of silica shell not only effectively prevents the PA core from leaking and flowing away during the phase-change process but also improves the thermal stability and shape/form stability of the phase-change microcapsules. Moreover, the phase-change microcapsules exhibited good phase-transition reversibility and durability, and therefore they could be applied for thermal energy-storage and thermal management in various industrial and civil areas.

Influence of Annealing Heat Treatment on Solid-state Tensile Strengthening Effect of iPP Sheets

2020, 34 (2): 9-15; DOI: 10.19491/j.issn.1001-9278.2020.02.002

Abstract ( 436 ) PDF (3249 KB)( 198 )

The crystal transformation process of isotactic polypropylene (iPP) sheet during the annealing solid?state stretching process was studied. The crystalline characteristics of the resulting iPP sheet were detected by X-ray diffraction and then the relative content of β-form crystals was calculated quantitatively. Furthermore, two-dimensional small-angle X-ray scattering (2D-SAXS) was adopted to monitor the α-β crystalline transformation process. In addition, the melting properties of iPP sheet were characterized by differential scanning calorimetry. The results indicated that the iPP sheet underwent a crystal transformation during the stretching process, resulting in the presence of a diffraction peak at 16.1 ° for the (300) reflection of the β-form cylindrites, and the oriented cylindrical structure could be observed from the 2D-SAXS patterns. A relatively high content of β-form crystals was produced under the stretching condition at 110 °C, and the highest content reached 6.75 %. The mechanical results showed that the notched impact toughness of iPP sheet was improved significantly, whereas the tensile strength increased slightly. In addition, it was found that the cylindrical structure was not damaged when the solid-state stretched iPP was annealed below 110 °C. However, after the annealing temperature exceeded 110 °C, the cylindrical structure was destroyed and the spherulite structure was formed again.

Synthesis of Novel Hyperbranched Polyphosphoramide Intumescent Flame Retardant and Its Synergistic Effect on Flame Retardancy of Polypropylene with Ammonium Polyphosphate

2020, 34 (2): 16-22; DOI: 10.19491/j.issn.1001-9278.2020.02.003

Abstract ( 549 ) PDF (3446 KB)( 193 )

A novel intumescent flame retardant, hyperbranched polyphosphoramide (HBPPA), was synthesized by using phosphorus oxychloride and diaminodiphenylmethane as raw materials and triethylamine both as a catalyst and as an acid-binding agent, and its chemical structure and thermal stability were characterized. A series of flame?retardant polypropylene (PP)-based composites were prepared by melt blending with HBPPA and ammonium polyphosphate (APP), and their flame-retardant performance, thermal stability, char morphology and pyrolysis properties were analyzed. The results indicated the composite containing 30 wt% HBPPA and APP at the mass ratio of 2∶1 presented the highest limiting oxygen index of 28.2 % and achieved a UL 94 V-0 classification in the vertical burning test. Such good flame-retardant performance may ascribed to a synergistic effect between HBPPA and APP, which facilitates to form a compact and continuous char layer to inhibit the impact of degraded gaseous and also to act as a physical barrier to hinder the exchange of external oxygen and internal flammable volatile gases and the heat transmission.

Preparation and Performance Investigation of Novel Composite Films Based on Formic Acid Crosslinked PVA and ZIF-8

2020, 34 (2): 23-29; DOI: 10.19491/j.issn.1001-9278.2020.02.004

Abstract ( 515 ) PDF (5754 KB)( 218 )

A series of novel composite films were prepared by a solution casting method using poly(vinyl alcohol) and zeolitic imidazolate frameworks (ZIF-8) as raw materials at different mass ratios, and their properties were investigated by contact angle, swelling degree, tensile strength, transmittance and haze index, moisture permeability and FTIR. The effects of ZIF-8 content on the hydrophilicity, mechanical properties, permeability and light transmittance of the composite films were studied. The results indicated that the water resistance of the composite films increased significantly with an increase of ZIF-8 content, and their contact angle and moisture permeability increased by 20.01 % and 7.12×10-13 (g·cm)/(cm2·s·Pa), respectively. However the tensile strength and light transmittance of the composite films decreased by 71.52 MPa and 33.43 %, respectively.

Study on Modification of Diatomite with Silane Coupling Agent and Its Application for High?density Polyethylene Composites

2020, 34 (2): 30-35; DOI: 10.19491/j.issn.1001-9278.2020.02.005

Abstract ( 497 ) PDF (2118 KB)( 157 )

Diatomite was pretreated by calcination and acidification, surface-modified with three different silane coupling agents (KH550, KH590, Si69), and then used for the reinforcement of high-density polyethylene (PE-HD) through melt blending. The effects of the diatomite loading and coupling?agent type on the mechanical properties and thermal resistance of the composites were investigated. The compatibility and morphology of PE-HD composites with the KH590-modified diatomite were studied by Fourier transformation infrared spectroscopy and scanning electron microscopy. The results indicated that the KH590-modified diatomite was homogeneously dispersed in the PE?HD matrix, and the impact fracture surface exhibited a more uniform morphology due to the enhancement of the interfacial compatibility between diatomite and PE-HD. The optimum modification effect was obtained for the composites when 1 parts per hundred (phr) of KH590 and 2 phr of diatomite were incorporated. In this case, the tensile strength of the composites increased by 23.8 MPa, the impact strength increased by 122.1 kJ/m2, and the thermal decomposition increased by 10 °C.

Study on Reinforcement Modification of PPC/PBS with Hyperbranched Ethylenediamine Trazine Polymer

2020, 34 (2): 36-42; DOI: 10.19491/j.issn.1001-9278.2020.02.006

Abstract ( 432 ) PDF (4881 KB)( 220 )

Poly(propylene carbonate) (PPC)/poly(butylene succinate) (PBS)/hyperbranched ethylenediamine triazine polymer (HBETP) blends were prepared by melting blending, their thermal properties, rheological properties, mechanical properties and morphology of impact fracture surfaces were investigated by dynamic mechanical analysis, thermogravimetric analysis, tensile and impact measurements, rotational rheometer and scanning electron microscopy. The results indicated that the blends achieved the maximum in tensile strength at the HBETP content of 0.5 wt%, and, in this case, the tensile strength increased by 49.6 % from 7.56 MPa to 11.22 MPa. Moreover, the introduction of HBETP enhanced the compatibility between the PPC and PBS phases and therefore improved the tensile strength of the blends.

Performance Investigation on Polyetheretherketone Film

2020, 34 (2): 43-48; DOI: 10.19491/j.issn.1001-9278.2020.02.007

Abstract ( 692 ) PDF (3473 KB)( 201 )

A series of polyetheretherketone (PEEK) films were prepared by an extrusion casting method, and their natural characteristics, optical properties, mechanical performance were investigated by means of tensile tester, differential scanning calorimeter, UV spectrophotometer, and light transmittance & haze meter. The results indicated that the transmittance of the PEEK films decreased with an increase of the degree of crystallinity, and there was little effect of tensile rate on tensile strength and elongation at break. The yield strength increased with an increase in tensile speed significantly. Moreover, The tensile strength trend to increase as the speed of the casting roll increased. The PEEK films achieved the tensile strength of 203 MPa after biaxial stretching, and their anti-ultraviolet performance was also improved with the increase of film thickness and degree of crystallinity.

Effect of Thiourea-intercalated Kaolin on Flame-retardant and Mechanical Properties of PP

2020, 34 (2): 49-53; DOI: 10.19491/j.issn.1001-9278.2020.02.008

Abstract ( 421 ) PDF (2713 KB)( 165 )

The thiourea-intercalated kaolinite (TU-Kaol) was prepared by a three-step reaction and then was incorporated into polypropylene (PP) to prepare the flame-retardant compounds by melt blending. The flammable characteristics and mechanical properties were evaluated by limiting oxygen index, cone calorimetry and universal test machine. The results indicated that the peak heat release rate of the composite containing 1.5 wt% of TU-Kaol decreased significantly from 1 474 kW/m2 to 1 100 kW/m2 compared to pure PP, whereas their tensile strength increased from 35.3 MPa to 39.8 MPa.

Numerical Simulation of Water-assisted Injection Molding under Different Water Injection Nozzle Diameters

2020, 34 (2): 54-60; DOI: 10.19491/j.issn.1001-9278.2020.02.009

Abstract ( 567 ) PDF (1463 KB)( 150 )

The structure of water injection nozzle was designed by a 3D drawing software to meet the experimental requirements. A visualization investigation was performed for the fluid-assisted injection molding of three-dimensional bending pipe with a 120 °~150 ° chamber by the overflow method using a fluid mechanics software. The diameter of water injection nozzle, the delay time of water injection, water injection pressure and melt temperature varied for this investigation, and the influence of these four parameters on the water penetration behavior inside the pipe was analyzed. The results indicated that the internal penetration length of the pipe increased significantly when the diameter of water injection nozzle was set to 7 mm, which also resulted in a thinner residual wall thickness. Owing to the influence from the structure of water injection nozzle, the water injection delay time was 1s, the water injection pressure was 8 MPa, and the melt temperature was 230 °C. The water penetration length increased by 400 % but the residual wall thickness decreased by 20 %. The maximum penetration length of 298 mm was achieved at the water injection delay time of 1 s, the water injection pressure of 10 MPa and the melt temperature of 230 °C. There was a more great influence from the water injection nozzle for the experimental groups with melt temperatures of 210 ℃ and 230 ℃ at the water injection delay time of 1 s, the water injection pressure of 8 MPa and the melt temperature of 250 °C. The hollow rate of the pipes could be improved effectively and their wall thickness could become thinner by shortening the water injection delay time and improving the water injection pressure and melt temperature. However, the influence of water injection nozzle on water-assisted injection molding could be ignored, because any small changes in its structure could greatly change the internal cavity of the molded parts and effectively improved the efficiency of water penetration behavior.

Defect Analysis of Polyethylene Oil Tanks

2020, 34 (2): 61-66; DOI: 10.19491/j.issn.1001-9278.2020.02.010

Abstract ( 364 ) PDF (4819 KB)( 159 )

This paper focuses on the causes of defects in the polyethylene oil tanks made by an imported polyethylene (PE) material through rotational molding. The transverse and longitudinal sections of the tanks and their internal and external morphologies and diameter distribution of pores were analyzed by SEM, stereoscopic microscopy and micro CT instrument. The results indicated that there were a large number of pores inside the tanks but few of them on the external surface contacting the mold. Moreover, there were also some pores found on the other sides, and most of the pores were distributed in the sub-outer layer, where the penetrating holes were found with a depth more than 1.9 mm and an overall porosity of 2.4 %. The gel content in each layer of the transverse section was higher than 60 wt%. A comprehensive investigation showed that the presence of abundant pores inside the defective tanks was due to the premature cross-linking of PE during the rotational molding process, which resulted in an increase of viscosity of the system. As a result, the bubbles were not expelled out of the tanks, thus leading to the porous defect. Some suggestions for the prevention of porous defect were finally proposed in this work.

An Optimization Design Method for Buried Polyethylene Winded Wall Pipe Based on NSGA-Ⅱ

2020, 34 (2): 67-73; DOI: 10.19491/j.issn.1001-9278.2020.02.011

Abstract ( 470 ) PDF (3681 KB)( 166 )

In this work, an optimization method for the design of the complex cross section of winding wall tube was proposed to obtain the optimal allocation of stiffness, structural size and pipe weight of the diameter section ring. Taking the performance requirement and optimal economic benefit in engineering design as an optimization objective and the requirements for manufacturability and structural dimension rationality as the constrained conditions, the design of the buried polyethylene winded wall pipe was optimized on the basis of the NSGA-Ⅱ. With this methodology, the optimal section type and size of pipeline could be achieved under the conditions that the nominal diameter, material modulus and ring stiffness of the pipeline were determined. This method was testified to meet the requirement for the selection and optimization design of winding structure wall pipe with s complex cross section in engineering design and also could provide some references for the optimization design of other pipelines.

Effect of Intercalated Hydrotalcite-like Compounds with Different Interlayer Ions on Thermal Stability of PVC

2020, 34 (2): 74-78; DOI: 10.19491/j.issn.1001-9278.2020.02.012

Abstract ( 461 ) PDF (1299 KB)( 161 )

A series of hydrotalcite-like compounds were synthesized, and these compounds had different interlayer ions and various intercalations with different valence inorganic acid radicals and different chain-length organic acid radicals. The effect of the hydrotalcite-like compounds on the thermal stability of PVC were investigated by means of thermal aging oven method, Congo red method and torque rheometer. The results indicated that the thermal stability of PVC was improved by incorporating the rare-earth elements and increasing the quantity of ions in the interlay of the compounds. For the hydrotalcite-like compounds with different valence inorganic acid radicals and organic acid radicals, the compounds intercalated with bivalent acid radicals exhibited the best thermal stability. Moreover, the thermal stability showed an increasing trend at first and then tended to decrease with an increase of the carbon-chain length of organic acids in the hydrotalcite-like intercalation.

Migration of Hydroxylic Acids in Food Contact Materials

2020, 34 (2): 79-84; DOI: 10.19491/j.issn.1001-9278.2020.02.013

Abstract ( 337 ) PDF (1171 KB)( 161 )

The migration of three types of hydroxylic acids (terephthalic acid, isophthalic acid and maleic acid) in plastic food contact materials was determined simultaneously by a HPLC internal standard method. The chromatographic conditions were optimized in terms of the mobile phase, mobile phase gradient and ultraviolet wavelength, and the detection limit, quantitative limit, recovery rate and relative standard deviation were calculated. Furthermore, the migration amounts of terephthalic acid, phthalic acid and maleic acid from the samples were measured under the optimized chromatographic conditions. The results indicated that the test data exhibited a good linear relationship in the concentration range of 1~20 mg/L with a correlation coefficient of R>0.999, a recovery rate of 98.3 %~109.7 % and a relative standard deviation of 0.14 %~3.75 %. This method has a high accuracy and precision and also shows high analysis efficiency by presenting a test time within 11 min. Under the general test conditions, the migration amounts of terephthalic acid, isophthalic acid, and maleic acid in the samples were found to meet the requirements of the safety limitation of food contact materials. However, the safety evaluation should be further conducted under the misuse conditions.

Design of Conformal Cooling Channel of Injection Mold of Instrument Cover Based on 3D Printing

2020, 34 (2): 85-89; DOI: 10.19491/j.issn.1001-9278.2020.02.014

Abstract ( 538 ) PDF (3176 KB)( 193 )

Taking a typical instrument cover as the research object, a conformal cooling channel was design by the Moldflow software, and then an intensive investigation was conducted to compare the cooling effectiveness between the conformal cooling channel designed by this work and traditional cooling channel so as to evaluate the advantages for practical use of the conformal cooling channel. This work provided a theoretical guide for the design of the conformal cooling channel and also supplied an optimum design of mold cooling system for the product in actual production. The results indicated that, compared to traditional cooling channel, the scheme of conformal cooling channel exhibited an increase in cooling efficiency by over 31.6 %, and the uniformity of product surface temperature increased by over 44.6 %.

Design of Mold with Five Linkage Slider Mechanism for Bracket of B-Mode Ultrasound Scanner

2020, 34 (2): 90-95; DOI: 10.19491/j.issn.1001-9278.2020.02.015

Abstract ( 373 ) PDF (2815 KB)( 144 )

The choice of parting mode determines the difficulty of design in mold mechanisms such as the demolding mechanism and overall structure of the mold during the injection-molding process of a plastic part. Through combining with the shape characteristics of the plastic part for the bracket of B-mode ultrasound scanner, the design of the overall structure and demolding mechanism of the plastic part were simplified by choosing the parting surface of the plastic part reasonably. Aiming at the complexity of demolding process in the plastic part, a five?slider linkage mechanism was designed, in which the demolding of the inner wall with five buckles and the inner wall of concave part of the inner wall were implemented at first, then the demolding of the outer wall with two inclined guide-pillar slider mechanisms and core-pulling demolding of the side hole at the side end were performed, and finally the demolding of the plastic parts was completed by pushing the tube out. To meet the requirement for the action of the demolding mechanism, a three-plate mold holder was chosen. The first opening of the mold holder drove the core pulling action of the five-slider linkage mechanism, and the second opening drove the core pulling action of the side slider mechanism driven by the inclined guide pillar at the outer wall and side end. In the design of five-slider linkage mechanism, a central T?groove driving block was used to drive the intermediate transition slider, so that five forming sliders could be driven by dovetail groove connection to pull in core-pulling motion. Such a design artfully solved the problems in the inadequacy of design space for multi-core-pulling mechanism in the local area of plastic parts and ensured the reliability of automotive production for the injection molded plastic parts.

Research Progress in Laser Processing of PEEK

2020, 34 (2): 96-102; DOI: 10.19491/j.issn.1001-9278.2020.02.016

Abstract ( 537 ) PDF (4630 KB)( 320 )

This paper reviewed the applications and research progress of laser processing technology including laser additive manufacturing, laser transmission scanning welding and laser etching techniques in the PEEK manufacturing area. Furthermore, the principles and advantages of laser processing technology as well as some current problems in laser processing were discussed by comparing with the traditional processing technologies. The application prospect of laser processing technology was depicted.

Research Progress in Novel Composite Dielectrics Based on Polymers and Thermally Conductive Fillers

2020, 34 (2): 103-109; DOI: 10.19491/j.issn.1001-9278.2020.02.017

Abstract ( 371 ) PDF (12324 KB)( 108 )

This paper reviewed the latest research progress in novel composite dielectrics based on polymers and thermally conductive fillers and analyzed the effects of several novel inorganic nanoparticles and their content, surface modification and processing methods on the thermal conductivity and dielectric properties of the composite dielectrics. These nanoparticles include nanosized diamond, carbide silicone, ferroelectric ceramics and other inorganic functional particles. Moreover, the paper also introduced some types of organic molecular crystals which could improve the thermal conductivity of polymers by constructing a continuous way for phonons. The continuous thermal conduction pathways for phonon transfer could be constructed in the matrix by use of novel inorganic particles and organic molecular crystals, thus leading to the suppression of interfacial thermal resistance and the improvement of thermal conductivity. Compared to the thermally conductive particles used commonly, the novel thermally conductive particles not only can improve the thermal conductivity but also can enhance other physical properties such as magnetism, excellent dielectric properties and energy storage of the composites.