Study on LDPE/EVA/SEBS Foaming Materials in Plastics Industry Han Lizhi, Li Li, Zheng Hongjuan, Zhang Aimin (State Key Laboratory of Polymer Materials Engineering, Institute of Polymer Science, Sichuan University, Chengdu 610065, China) Butylene-Styrene Copolymer (SEBS) Used in low density polyethylene (LDPE) / ethylene vinyl acetate copolymer (EVA) foaming materials. The effects of SEBS dosage and SEBS oil filling on the properties of LDPE/EVA foaming materials were discussed. The effects of blowing agent azodicarbonamide (AC), cross-linking dicumyl peroxide (DCP) and filler fine heavy calcium carbonate (CaC3) on the properties of LDPE/EVA/SEBS foaming materials were discussed. . For the sample before foaming, the SEBS phase region of the brittle section was etched away with a solvent, and the sample was observed by SEM, and it was found that SEBS was uniformly dispersed in the resin. Observation of the brittle section of the sample before foaming by SEM revealed that CaCO3 was uniformly dispersed in the resin. Observation of the cut surface of the foamed sample by SEM revealed that the cells were relatively uniform.
Butene-styrene copolymer; oil-filled amount; low-density polyethylene; ethylene-vinyl acetate copolymer; scanning electron microscope; foaming material SEBS is a hydrogenated product of thermoplastic elastomer SBS, often called hydrogenated SBS. It is characterized by good plasticity, low shrinkage, high strength and toughness, good weather resistance, good touch, good matte finish, high compression resistance, high slip resistance, high flexibility and low temperature resistance. It has the advantages of simple process, no rubber odor, easy coloring, etc. Because the aliphatic double bond is saturated, it has the characteristics of weather resistance, ultraviolet light, oxygen, ozone and heat. It can be used to mix various rubber/plastic mixing products. Or used in various thermoplastic rubber / plastic as a modified material for impact resistance, slip resistance, wear resistance, compression resistance, cold resistance.
Foam is a plastic product based on a resin with numerous microporous gases inside, also known as porous plastic. According to different foaming methods, it can be divided into physical foaming, chemical foaming, and mechanical foaming. The chemical foaming method was used to study the application of SEBS in foam plastics, and the influence of the variation of different component amounts on the properties of LDPE/EVA/SEBS foaming materials was discussed.
The world's various brands of sports shoes, in which the bottom material requirements are very light and excellent performance. EVA and its blends are easier to produce lighter midsole foaming materials than PU. At present, most of the midsole materials of various brands of sports shoes in the world are foamed materials using EVA and its blend with resin and rubber.
The LDPE/EVA foaming material has the disadvantages of slipping, puncture resistance and low temperature hardening, and needs to be modified by adding an elastomer such as NR, EPDM or the like. The addition of the elastomer also improves the viscoelasticity of the LDPE/EVA and improves the wear resistance and folding resistance of the material. Compared with other elastomers, SEBS has good heat resistance, flexibility and good solubility and blending characteristics. And SEBS oil can significantly reduce costs. Therefore, SEK can be used instead of NR, EPDM and other elastomers to blend with LDPE/EVA to produce materials with lower cost and superior performance to meet the special needs of people for material properties.
1 Experimental part 1.1 Main raw materials SEBS: YH502, Sinopec Baling Petrochemical Co., Ltd.; Low density polyethylene (LDPE): 1I2A, Beijing Yanshan Petrochemical Company; Ethylene-vinyl acetate copolymer (EVA): 7350M, Taiwan TAISOX ;fine heavy calcium carbonate (CaC3): Pd90, Guangdong Meixian Tepai Chemical Co., Ltd.; foaming agent azodicarbonamide (AC): industrial grade, Ningxia Shengsheng Chemical Group; cross-linking dicumyl peroxide (DCP): chemically pure, China Pharmaceutical Group Shanghai Chemical Reagent Company; main foaming agent zinc oxide (ZnO): analytical grade, Chengdu Kelon Chemical Reagent Factory; promotion of foaming agent zinc stearate (ZriSt): analysis Pure, Chengdu Kelon Chemical Reagent Factory.
1.2 Instruments and equipment Extruder: SH type co-rotating twin-screw extruder, Nanjing Jie Ente Electromechanical Co., Ltd.; flat vulcanizing machine: HPEH63 (D) type 0.63 trillion semi-automatic pressure forming machine, Shanghai Xima Weili Rubber Machinery Co., Ltd.; universal material testing machine: 4302, American Instion; scanning electron microscope: SM-5900LV, Japan Electronics Co., Ltd.; hardness tester: LX-A Shore rubber hardness tester, Shanghai Liuling Instrument Factory.
3 performance test 1.4 process flow ingredients> twin-screw extrusion>granulation>molding foam molding>parking one> sample preparation performance test formula 1 SEBS applied to LDPE/EVA foaming material LDPE 70 parts, EVA 30 parts, other components fixed To study the effect of adding different amounts of SEBS (100 parts by oil) on the performance of LDPE/EVA foaming materials, and determine the amount of SEBS added; under this addition amount, other conditions are unchanged, change the oil content of SEBS, research charge The effect of changes in oil quantity on material properties.
2 The effect of blowing agent, cross-linking agent and CaCO3 on the properties of LDPE/EVA/SEBS foaming materials LDPE, EVA, SEBS and other additives were unchanged. The foaming agent, cross-linking agent and CaCO3 dosage were discussed respectively. /EVA/SEBS foam material properties.
2 Results and discussion 21SEBS applied to LDPE/EVA foaming material 1.1SEBS dosage affects the performance of LDPE/EVA foaming material. Resilience and weather resistance, it is as easy to process and shape as thermoplastics, and can be recycled. Moreover, it has excellent compatibility with other plastic materials, and since SEBS can adjust the hardness of the material by adding an expansion oil, a foamed product having a wide range of hardness can be obtained. Because SEBS has the characteristics of thermoplasticity, the molded product after foaming can be further shaped to obtain a finished product with complicated shape, and the foamed product can be recycled. The addition of SEBS to the LDPE/EVA foaming material can improve compression set, slip resistance and the like.
Table 1 The effect of SEBS dosage on the properties of foaming materials SEBS dosage / part density tensile strength / MPa elongation at break / % tear strength / kNcm1 hardness (HA) The effect of SEBS on the density and mechanical properties of foamed materials is shown in Table L. It can be seen from Table 1 that with the increase of the amount of SEBS, the density of the foamed material is basically unchanged, the tensile strength and hardness are all decreased, the tear strength is basically unchanged, and the elongation at break is obviously improved.
SEBS has good compatibility with LDPE and EVA, and it is easy to form a dispersed phase in the system. SEBS was added to the LDPE/EVA system, granulated by twin-screw mixing, and then quenched in liquid nitrogen after injection molding. The SEBS phase region of the brittle section was etched away with a solvent to observe the surface morphology by scanning electron microscopy (SEM). See the picture. It can be seen that the black hole area is the etched SEBS phase area, and the SEBS phase area is very uniform. There are rubber segments in the SBES molecular chain, which have good elasticity. Because they are dispersed in the LDPE/EVA system, they can reduce the force between the molecular chains and play a plasticizing role. At this time, SEBS is considered to be a polymer. Plasticizer; therefore, in the LDPE/EVA foaming system, when SEBS is added, the tensile strength of the foamed material is lowered, the tear strength is not greatly changed, and the elongation at break is increased, and the softness of the hard material is improved. Because there is a hard segment of plastic in SEBS, which is dispersed in the continuous phase of the elastomer, it acts as a physical cross-linking point. Therefore, the tensile strength is not greatly reduced, and the tear strength is basically unchanged.
2.1.2 Effect of SEBS oil filling on the performance of LDPE/EVA foaming materials Table 2 The effect of SEBS oil filling on the properties of foaming materials is to improve the LDPE/EVA foaming materials with SEBS compared with other rubbers such as EPDM. In the case of the same amount of blowing agent added, the hardness is much lower.
2.2 The effect of the amount of cross-linking agent on the properties of LDPE/EVA/SEBS foaming materials Table 4 The effect of the amount of cross-linking agent on the properties of foaming materials SEBS oil filling capacity / part density tensile strength / MPa elongation at break / % tear Strength / kNDm1 hardness (HA) crosslinker dosage / part density tensile strength / MPa elongation at break / % tear strength / kNDm1 hardness (HA) increase this effect S strengthen d to reduce the dn worth ing A peach that may act as a nucleus. It is the material foaming. The effect of Iki in the liquid nitrogen ring bookmark4 SEBS oil filling on the density and mechanical properties of foaming materials is shown in Table 2. It can be seen from Table 2 that with the increase of SEBS oil filling, the foaming material density is reduced, tensile strength, The tear strength is reduced, the elongation at break does not change much, and the hardness decreases significantly. The addition of filler oil to SEBS can reduce the force between macromolecules, increase the softness and fluidity of the mixture, and increase the elasticity of the mixture. Therefore, as the oil filling amount increases, the hardness decreases.
2.2 The effect of blowing agent, cross-linking agent and CaC3 on the properties of LDPE/EVA/SEBS foaming material 2.1 The effect of foaming agent dosage on the properties of LDPE/EVA/SEBS foaming material Table 3 The amount of blowing agent used for foaming material Effect of performance foaming agent dosage / part density tensile strength / MPa elongation at break / % tear strength / kNDm1 hardness (HA) AC gas generation is large, the price is cheap, the decomposition product is non-toxic, odorless, non-polluting, suitable It is a widely used chemical foaming agent for atmospheric pressure and pressure foaming of PE, EVA, PP, PVC, ABS resin, and the like. Low density is an important performance requirement for foamed materials. The effect of the amount of foaming agent on the density and mechanical properties of the foamed material is shown in Table 3. It can be seen from Table 3 that with the increase of the amount of foaming agent, the density of the foamed material is significantly reduced, tensile strength, tear strength and elongation at break. Both rate and hardness showed a downward trend.
The foaming agent decomposes to generate a gas, and the gas expands to increase the volume of the foam and lower the density. Under other conditions, the effect of the amount of cross-linking agent on the density and mechanical properties of the foamed material is shown in Table 4. As can be seen from Table 4, as the amount of cross-linking agent increases, the density of the foamed material increases. The tensile strength and the tear strength increase, the elongation at break decreases, and the hardness slightly increases.
The decomposition of the cross-linking agent causes a network structure to be formed between the resin molecular chains, so that the foam body is more compact and the density is increased. As the number of crosslinkers increases, this effect is enhanced and the density increases. Due to the formation of such a network structure between the resin molecular chains, the foam body is made more compact, so that the tensile strength and the tear strength of the material increase, especially the tear strength increases obviously. Of course, the network structure also limits the molecular chain. The relative motion between them makes the material appear stiffer, causing the elongation at break of the material to decrease and the hardness to rise slightly.
Effect of 23CaC3 dosage on properties of LDPE/EVA/SEBS foaming materials Table 5 Effect of CaC3 dosage on properties of foaming materials/Part density Tensile strength/MPa elongation at break/% tear strength/kNDm1 hardness (HA) CaC3 dosage The effects of foaming material density and mechanical properties are shown in Table 5. It can be seen from Table 5 that as the amount of CaC3 increases, the density of the foamed material increases, the tensile strength increases slightly, the tear strength increases, and the elongation at break decreases. There was no significant change in hardness. The tensile strength is slightly increased and the tear strength is increased. This is because when CaC3 is filled, a small amount of CaC3 particles can be dispersed into the pores between the cells to reinforce. Moreover, CaC3 was quenched in the process of foaming, and the surface morphology was observed by scanning electron microscopy (SEM) to observe the dispersion of CaC3. As can be seen from the figure, C£3 (white dots in the figure) is scattered evenly. This has a very good effect on the uniformity of the cells after foaming.
After the material was foamed, the surface morphology was observed by SEM to observe the cell structure of the material, and the cell pores were relatively uniform with respect to the density (0.1231 g/cm3).
3 Conclusions The results are even. In the LDPE/EVA foaming system, the tensile strength of the foamed material decreases with the addition of SEBS, and the tear strength does not change greatly, while the elongation at break increases and the hardness decreases. The addition of SEBS to the LDPE/EVA foaming system will result in a softer material.
The addition of filler oil to SEBS can reduce the force between macromolecules, increase the softness and fluidity of the mixture, and increase the elasticity of the mixture. Therefore, as the oil filling amount increases, the hardness decreases.
Compared with other rubbers such as EPDM, the LDPE/EVA foamed material is modified with SEBS, and the hardness is much lower in the case of the same amount of the foaming agent.
As the amount of the crosslinking agent increases, the density of the foamed material increases, the tensile strength and the tear strength increase, the elongation at break decreases, and the hardness slightly increases.
With the increase of the amount of CaC3, the density of the foamed material increased, the tensile strength increased slightly, the tear strength increased, the elongation at break decreased, and the hardness did not change significantly.
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