2023, 37 (6):
1-9;
Abstract (
317 )
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68
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To improve the surface wettability of extruded polystyrene foams （XPSF） and introduce functional groups that can strengthen the reactions with mortar， polyurethane acrylate （PUA） with a micron thickness was coated on the XPSF surface using a UV-curing technology. The effect of tripropylene glycol diacrylate （TPGDA） on the performance of PUA coating and the bonding performance between the modified XPSF and mortar were investigated by using viscometry， Fourier-transformation infrared spectroscopy， static contact angle meter， and universal testing machine. The results indicated that the viscosity of PUA coating decreased along with a change in the micromorphology of the coating with an increase in the TPGDA content. The static contact angle of XPSF decreased from 90.78 ° to 55.00 °， which facilitated the spreading and wetting of mortar. The tensile strength of the XPSF/mortar composites increased at first and then decreased with increasing the TPGDA content. The composites obtained tensile strength of 0.213 MPa at a TPGDA content of 60 wt%. This result is 4.26 times higher than that of the blank sample. Their water?resistant tensile strength was further increased to 0.230 MPa after immersion in water and then drying for 7 days.
2023, 37 (6):
10-15;
Abstract (
340 )
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62
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Poly（hydroxyalkanoate） （PHA）/tea plant fiber （TPF） composites were prepared by using glycidyl methacrylate （GMA）-modified TPF and PHA as raw materials through solution casting， and their mechanical properties， chemical structure， thermal stability， and microscopic morphology were characterized using an intelligent tensile testing machine， Fourier-transformation infrared spectrometer， thermogravimetric analyzer， and scanning electron microscope. The effects of TPF and GMA contents on the properties of the composites and their action mechanisms were investigated. The results indicated that the composites exhibited an increase at first and then a decrease in tensile strength and elongation at break with an increase in the TPF content. The composites obtained optimal performance at a TPF content of 15 wt%， resulting in an increase in tensile strength by 28.87 % and in elongation at break by 52.31 % compared to pure PHA. The compatibility between the GMA-modified TPF and PHA was improved， leading to an enhancement in the mechanical properties and thermal stability of the composites. The composites showed an increase at first and then a decrease in tensile strength and elongation at break with an increase in the GMA content. The composites obtained optimal performance at a GMA content of 3 wt%， resulting in an increase in tensile strength by 66.03 % and elongation at break by 45.01 % compared to the counterpart without GMA.
2023, 37 (6):
16-20;
Abstract (
427 )
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51
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The method for determining the content of maleic anhydride （MAH） in MAH-grafted polypropylene was studied through neutralization titration. The influence factors such as the quantity of refined sample， the addition amount of xylene， dissolution temperature， dissolution time， and titration temperature were analyzed， and an optimized experimental method was obtained. The experimental results indicated that the optimal detection results were achieved when the quantity of the refined sample was 0.500 0 g， the amount of xylene was 100 mL， the dissolution temperature was 110 ℃， the dissolution time was 5 h， and the titration temperature was 110 ℃. Under this condition， a grafting rate of 1 wt% was determined with the smallest data fluctuation at a standard deviation of parallel experiments of 0.83 %， indicating the most stable determination.
2023, 37 (6):
21-30;
Abstract (
330 )
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47
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Flame retardant rigid polyurethane foam （PUF） was prepared by a one?step method using black phosphorus/expanded graphite compound as a complex flame retardant， polyether polyol and isocyanate as raw materials， dibutyltin dilaurate as a catalyst， deionized water as a foaming agent. The physical， mechanical， and thermal properties of the resultant PUF samples were investigated through analyzing their apparent density， compression strength， and thermogravimetric behavior， and their flame?retardant performance was evaluated by limiting oxygen index （LOI）. The results indicated that the addition of a small amount of black phosphorus could improve the LOI value of PUF significantly. When the content of black phosphorus was 1 wt%， the sample “PUF?BP5” obtained an LOI 20.4 vol%， which was 30 % higher than that of pure PUF. The LOI of the sample “PUF?EG?BP5” reached 24.7 vol% at a graphite content of 7 wt% and a black?phosphorus content of 1 wt%. Such a result is higher than that of pure PUF by 60 %.
2023, 37 (6):
31-36;
Abstract (
293 )
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50
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A type of composite foams was fabricated by using low-density polyethylene （PE-LD） and high-density polyethylene （PE-HD） as matrix resins， calcium sulfate whisk （CSW） as a reinforcing agent， and azodicarbonamide as a foaming agent. The effect of CSW content on the melt flow rate， thermal properties， foaming behavior， mechanical properties， thermal conductivity， and thermal stability of the PE-LD/PE-HD/CSW blends were investigated. The results indicated that the introduction of CSW reduced the melt flow rate of the blends but improved their thermal stability. Compared to pure PE-LD/PE-HD complex foam， the PE-LD/PE-HD/CSW complex foams obtained better comprehensive properties at a CSW content of 8 wt%. Under such a CSW loading， the complex foams achieved an increase in tensile strength by 21.3 %， in compression strength by 17.8 %， in compression modulus by 31.3 %， in hardness by 10.9 %， and in tear strength by 16.4 %， but a decrease in thermal conductivity by 15.5 %.
2023, 37 (6):
37-42;
Abstract (
334 )
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63
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An artificial accelerated UV aging experiment and a thermal aging test at 50 ℃ were carried out on a drip tap. The changes in oxidation induction time （OIT）， melting temperature （Tm）， tensile strength （σm）， tensile fracture strain （εm）， melt flow rate （MFR）， and carbon black content （c） before and after aging were investigated. The changes of flow uniformity， burst pressure， water pressure resistance， drawing resistance， and sediment blockage resistance hydraulics after thermal aging at 50 ℃ as well as their accordance with national standards were also studied. The results indicated that the variation range of performance indexes of the drip tape after the accelerated UV aging was significantly greater than that after the thermal aging at 50 ℃， especially fir OIT. After aging for 624 h， the OIT obtained from artificial accelerated UV aging was 4.25 times the decrement rate of that from the thermal aging at 50 ℃. The σm， εm， c， Tm and MFR from the artificial accelerated UV aging are 1.24， 1.17， 1.11， 1.02 and 1.01 times as decrement rates of those from the thermal aging at 50 ℃， respectively. The changes in the retention rates of OIT， σm， εm and c of the drip tape were very significant after the accelerated UV aging. After thermal aging at 50 ℃， the change in the OIT retention rate was greater than that of other indexes. The hydraulic performance was less influenced by the thermal aging at 50 ℃， which could meet the requirement of the national standard for the 624 h aging. As for the OIT of no more than 5 minutes in the national standard， the retention rate of σm reaches a failure level at 21 %. Therefore， the OIT of drip tapes should not be less than 1.05 min to avoid the invalidation of practical use.
2023, 37 (6):
43-49;
Abstract (
574 )
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42
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Hydrogenated styrene isoprene styrene （SEPS）/polypropylene （PP） masterbatch was prepared through melt blending and underwater wire drawing. The resultant SEPS/PP bead foams with a uniform cell structure were then prepared through autoclave foaming with CO2 as a foaming agent. The effect of foaming process on the cell size， foaming ratio， bulk density， and cell density of the bead foams were investigated. The crystallization behavior of SEPS/PP masterbatch and the change of cell size during foaming was studied by differential scanning calorimetry and scanning electron microscopy. The results indicated that the bead foams obtained a cell size of 61~190 μm， an expansion ratio of 3~10， and a cell density of 7.9×105~3.9×107 cells/cm3. This type of SEPS/PP bead foams could be prepared at a foaming temperature of 116~124 ℃ and a saturation time of 0~60 min with a saturation pressure of 2.5~4.0 MPa. The effect of steam chest pressure on the mechanical properties and cyclic compression of the SEPS/PP foam boards with different densities were investigated by selecting the SEPS/PP foam boards with expansion ratios of 5， 7， and 10 through steam chest molding. The results indicated that the foam boards exhibited the highest tensile strength of 715 kPa and the largest elongation at break of 63 % when prepared at an expansion ratio of 10. A highest recovery rate of up to 88 % was achieved for the foam boards at a foam ratio of 7. This foaming material exhibited great application potential to replace the thermoplastic polyurethane （TPU） and ethylene vinyl acetate （EVA） foaming materials.
2023, 37 (6):
50-58;
Abstract (
230 )
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55
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In this work， the mechanical properties of in?situ fibrous foam materials with different porosity were measured， and the ABAQUS UMAT subroutine was used to model the obtained mechanical properties based on continuum mechanics. The stress response of the sandwich?structural foam was analyzed under three different loads of tension， compression and bending， and the simulation results were compared with the experimental ones. The results indicated that the error between the experimental and simulation data was less than 10 %， and the deviation was small. This demonstrated that the constitutive model used in this study could well reflect the mechanical properties of in?situ fibrous foam materials.
2023, 37 (6):
59-65;
Abstract (
359 )
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57
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Taking an intelligent sweeper clamshell as an example， the Moldex3d mold flow analysis software was used to optimize the injection molding of thin-walled complex parts. A two-gate mode was recommended for the better glue feeding method through comparing the two-gate and four?gate glue feeding methods. Based on the orthogonal experimental analysis， the optimal injection molding process combination was determined to be a packing time of 7 s， a packing pressure of 50 %， a melt temperature of 220 °C， and a mold temperature of 50 °C. Meanwhile， the main and secondary factors affecting the warping deformation of the parts were determined as the packing pressure， melt temperature， packing time， and mold temperature. Through optimizing the packing pressure curve to obtain the optimal injection molding process， the warpage deformation of the parts was reduced by 44.8% from 2.482 mm to 1.369 mm.
2023, 37 (6):
66-73;
Abstract (
323 )
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57
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A type of toughened epoxy resin with good heat resistance， high strength and long application period was prepared for pultrusion by using bisphenol-A and bisphenol-F epoxy resins as raw materials and methylhexahydrophthalic anhydride as curing agent， and its curing reaction and dynamic mechanical properties were studied through non-isothermal scanning calorimetry and dynamic mechanical analysis （DMA）. The mean activation energy of the curing reaction was calculated to be 71.715 kJ/mol by using the Kissinger′s， Ozawa′s， and Flynn-Wall-Ozawa′s methods. The optimal reaction mechanism of the curing process was obtained through the fitting with several mechanism functions. The kinetic parameters， m， n， and lnA， were determined to be 0.46， 1.17， and 0.626， respectively， by using the Sestak-Berggren autocatalytic reaction model. The theoretical curves were in good agreement with the experimental data. The calculated theoretical curves were in good agreement with the experimental data. The CHILE （Tg） model established through DMA could well predict the relationship between the resin modulus and temperature under different curing degrees. This provides effective theoretical guidance and evidence for the determination of pultrusion process and quality control of composite materials.
2023, 37 (6):
74-82;
Abstract (
279 )
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47
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To investigate the tensile properties of PE-HD， PU and EPDM， axial tensile tests were conducted to obtain their stress-strain curves at different strain rates. The results indicated that PE-HD exhibited favorable ductility with large plastic deformation during the tests， whereas PU presented an elastic nature. On the other hand， EPDM as a type of viscoelastic material showed an evident time-dependency of deformation recovery performance. The yield strength and tensile modulus of PE-HD increased significantly with an increase in strain rate but its strain at yield strength decreased. PE-HD obtained an increase in yield strength by 23.4 % and in tensile modulus by 40.4 % when the strain rate increased from 0.01 s-1 to 1.0 s-1. The tensile modulus and elongation at break of PU were significantly influenced by strain rate； however， there was little influence of strain rate on its tensile strength. Compared to the tensile modulus and elongation at break obtained at a strain rate of 0.01 s-1， PU exhibited an increase in tensile modulus by 39.1 % but a decrease in elongation at break by 55.2 % at a strain rate of 1.0 s-1. With increasing the strain rate， the tensile strength and tensile modulus of EPDM increased but its elongation at break decreased. When the strain rate increased from 0.01 s-1 to 1.0 s-1， the tensile strength and tensile modulus of EPDM increased by 19.9 % and 16.5 %， respectively.
2023, 37 (6):
83-90;
Abstract (
313 )
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50
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In this work， an orthogonal experiment of 4 factors and 3 levels was carried out to determine the optimal process conditions for powder electrostatic spraying process of polyoxymethylene （POM） powders as a spraying voltage of 60 kV， a powder supply air pressure of 0.2 MPa， a curing temperature of 170 oC， and a curing time of 20 min. The coatings were then modified using polytetrafluoroethylene （PTFE） and molybdenum disulfide （MoS2） to improve their wear resistance. The resultant composite coatings were characterized by testing their thickness， hardness， adhesion， impact strength， chemical solvent resistance， microstructure， and frictional wear. The results indicated that all of coating samples had good appearance and chemical solvent resistance， their thickness was distributed in the range of 100~140 μm， their Shore hardness was above 63， and their impact performance reached at least 36 kg·cm. However， the composite coatings could all reach an adhesion of grade 2 or above except for the coating containing 0.7 wt% MoS2 powers. The composite coatings looked dense and compact without any holes and defects， and the two types of wear?resistant fillers were evenly dispersed in the coatings. When 5 wt% PTFE and 0.7 wt% MoS2 were incorporated into the POM powders， the friction coefficient of the composite coating decreased to 0.223 and 0.245， respectively， and their wear amounts decreased to 1.4 mg and 1 mg， respectively. This suggests a significant improvement in the friction and wear performance of the POM?matrix composite coatings.
2023, 37 (6):
91-98;
Abstract (
423 )
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53
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This paper reviewed the research progress in waste polyethylene （RPE）， waste polypropylene （RPP）， and their blends （RPE/RPP） modified asphalt in recent years. The advantages and disadvantages of these three modifiers were summarized and analyzed， and the future development trend of waste plastic modifiers was prospected.
2023, 37 (6):
99-106;
Abstract (
361 )
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54
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This paper reviewed the research status in biodegradable solid agricultural mulches， such as starch， plant fiber and lignin as raw material， according to the mechanical properties of the mulches which can meet the requirement of mechanical laying strength. The difficulties in the development of biodegradable mulching films were proposed， and the future development direction of biodegradable mulching films was prospected. The paper can provide a technical basis for the development and performance improvement of biodegradable plastic film materials.
2023, 37 (6):
107-116;
Abstract (
399 )
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61
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This paper analyzed and summarized the differences among the international standards ISO16422：2014， Chinese National Standard GB/T 41422—2022， European Standard EN 17176?2：2019， Australian/New Zealand Standard AS/NAS 4441：2017， Brazilian Standard ABNT NBR 15750：2020， and Indian Standard IS 16647：2017 in terms of their scope， terms and definitions， material， material classification， classification and selection of pipes， geometrical characteristics， and mechanical characteristics for PVC?O pipes. The differences among the North American standard system represented by the American standard ASTM F 1483?17 and the Canadian standard CSA B137.3.1：20 and the ISO standard system were also simply summarized. The application prospects of PVC?O pipes were proposed.
2023, 37 (6):
117-122;
Abstract (
498 )
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45
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According to the structural characteristics of the terminal protection sleeve of an electric power equipment， two sets of motion mechanisms were designed to implement automatic thread demolding. These two mechanisms are a screw rod nut pair driving slider to move in a straight line and a thread core edge rotating in a straight line with the slider. The teeth of the slider gear and thread demolding gear have the same numbers， and their screw rod pitch is the same as that of the thread core. The hydraulic motor can drive the driving gear to rotate， and the driving gear is engaged with the slider gear and thread demolding gear at the same time. This ensures that the slider moves synchronously with the thread demolding without any damage in the plastic part thread. The plastic part of the protective sleeve was made of 30 % glass?fiber-reinforced polybutylene terephthalate （PBT+30 % GF）. During the injection molding， the heat loss of the mold cavity and core should be fast and uniform. The cooling effect of the mold directly influenced the bending deformation of the plastic part. The axial movement of the designed spiral core was driven by the slider， which is advantageous to the design and processing of the cooling water path and the solution of the cooling problem of the threaded core. The mold flow analysis and verification were carried out for the design scheme， which shortened the development period of products and ensured the product quality.
2023, 37 (6):
123-130;
Abstract (
471 )
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50
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This paper reviewed the research progress in halogen?free flame-retardant thermoplastic polyolefin materials in recent years， and the effect of various flame retardants on the flame?retardant and mechanical properties of polyolefin materials were analyzed. These halogen?free flame retardants for thermoplastic polyolefin mainly included metal hydroxide flame retardants and intumescent flame retardants， in which phosphate intumescent flame retardants were the most widely used. Nevertheless， the new type of one?component intumescent flame retardants has become a trend in future development.
2023, 37 (6):
131-140;
Abstract (
589 )
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52
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This paper reviewed the research progress in long afterglow materials in recent years. The organic afterglow materials were developed recently through breaking through the difficulty in modulating the excited state with ultra?fast decay and they exhibited long?life emission with persistent luminescence at room temperature. The lifetime of these developed organic afterglow materials was several orders of magnitude longer than that of conventional fluorescence and phosphorescence emission. The synthetic strategies of organic afterglow materials were also discussed， which included crystal induction， heavy atom effect， hydrogen bonding， self-assembly， host?guest doping， etc. Own to the unique properties of organic afterglow materials such as long luminescence life， large Stokes shift， easy excited state transition， and environment-sensitive emission， their application prospects in various fields were further discussed.
