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Foam plastic is a new type of material. It uses plastic as its basic component, and it has light weight, low thermal conductivity, good heat insulation performance, ability to absorb impact loads, and high specific strength. Due to these properties, it has been widely used in many fields, especially in the fields of packaging, construction, daily life, and high-tech. Foam plastics have occupied an irreplaceable position.
Although foam has many valuable properties, its absolute strength is lower than that of non-foamed plastics. In order to increase the strength of foams, there have been many enhanced foams in recent decades. Variety, such as adding reinforcing agents, reinforcing fillers, changing the structure of the foam and so on.
In recent years, the potential advantages of natural plant fibers as reinforcing materials have attracted more and more attention. It is rich in resources and low in price; its density is lower than that of all inorganic fibers, and its modulus and tensile strength are similar to those of inorganic fibers; in the processing of plant fiber composites, the energy consumption is reduced, and the loss of processing equipment is small, which is beneficial to Energy conservation; and its most prominent advantage is its biodegradability and reproducibility, which is unmatched by any other reinforcing material. Since the 1980s, people have begun research on thermoplastic/plant fiber composites.
This area is particularly active in India, Japan, Europe and the United States. Scholars among them did a lot of research on polypropylene and wood fiber composites, and some scholars used different plant fibers to reinforce thermoplastics (PE, PP, etc.), and the effect was also very obvious. The main ingredient of paper is cellulose fibers. Using waste paper powder to fill thermoplastics not only reduces costs, but also protects the environment due to the degradability of the fibers. At present, there are few materials used to fill thermoplastic materials with waste paper powder on the market, and it has not been reported that blending the two materials into foamed materials.
In this paper, polyethylene resin and waste paper as the main raw materials, adding foaming agent, cross-linking agent, etc., foaming a foaming material prepared by molding method, studied the material formula, the material can be developed according to different density, Its use.
1 Experimental Part 1.1 Raw Materials General Plant; waste paper (chemical pulp paper), crushed by a grinder; foaming agent, azo compound, Suzhou Auxiliary Plant; crosslinker, peroxide, Suihua Chemical Factory; Tribasic lead sulfate (three salts), Jixi Chemical No. 2 Plant; titanate coupling agent, chemical plant of Nanjing University.
1.2 Main Instruments and Equipment Type 160, Tianjin Electrical Machinery Factory; Flat vulcanizing machine, Type XLB-D350x350x2, Shanghai No. 1 Rubber Machinery Factory; High-speed heating mixer, GRH-10-n type, Liaoning Fuxin Heat Source Equipment Factory; Machine, CP-25 type, Shanghai Chemical Machinery Plant; -W type, Chengde Experimental Machine Factory, Hebei; Electronic universal testing machine, CSS-2200, China Jiji Institute of Applied Technology; Shore A hardness meter, LX-A type , Shanghai Liuzhong Measuring Instrument Experimental Factory; Electronic Balance, FA2004, Shanghai Precision Scientific Instrument Co., Ltd.
1.3 Preparation of Samples 1.3.1 Preparation of PE/Waste Paper Powder (Untreated) Composite Foamed Material Samples A certain amount of PE was added to a double-roll mill. After the entire melt was melted, the quantitative proportions were added in batches. Paper powder is mixed evenly, and then foaming agent and trisalt are added. Finally, a cross-linking agent is added, thin-passed several times, mixed uniformly, and then sheeted. The material is cut into the shape of the mold, and then the appropriate amount of the material is stacked and added to the preheated mold, placed on the plate vulcanizing machine, after a certain temperature and pressure for a certain period of time, the pressure relief quickly, so that the melt Material expansion pops up.
1.3.2 Polyethylene/waste paper powder (treated with coupling agent) Preparation of Composite Foam Material Samples Waste paper powder with a certain amount of stearic acid is added to a 40X: high-mixer, and then added after 2 minutes. The coupling agent was discharged after 8 minutes of mixing. The processed paper powder is then mixed with polyethylene and tested in the same way as in 1.3.1.1.4 Performance Test 1.4.1 Tensile Strength Test 6344-86. The shape of the punched sample was dumbbell-shaped, 115 mm long, and the width of the parallel portion was 6 mm. The thickness of the test sample was tested with a hardness of 1.12 Shore A hardness 527-83. Specimen size: all sides are 50mm, thickness is greater than 6mm. 1.4.3 Apparent density test 6344-66 standard test, sample shape: a 50mm square side.
2 Results Discussion 2.1 The impact of various components and pressure on the performance of the composite foaming material 2.1.1 Impact of the use of foaming agent on the performance of the composite foaming material When the amount of fixed cross-linking agent and the amount of PE and paper powder When changing the amount of foaming agent, the properties were measured as shown in Table 1. Table 1. Foaming agent used for the composite foaming material shadow S performance foaming agent amount / hardness (Shao A) tensile strength / MPa Elongation at break/% Note: The amount of cross-linking agent is 0.9 parts; foaming agent: three salts = As seen from Table 1, with the increase in the amount of foaming agent, the density of the composite foam, the hardness of the Shore A and Tensile strength decreased, but elongation at break showed an upward trend. This shows that when there is a large amount of blowing agent, there are many nucleation sites, and the amount of gas generated per unit volume is large, so the density decreases. When the air volume is large, the size of the foam body also increases, so the foam body wall is thin, the force that can withstand can be reduced, so the tensile strength, Shore A hardness is reduced. Due to the presence of the bubble structure, the larger the bubble size, the stronger the deformation ability, the better the ductility of the material, and the greater the elongation at break.
2.1.2 The effect of the amount of cross-linking agent on the properties of the material The amount of fixed foaming agent and the ratio of resin to paper powder, change the amount of cross-linking agent, and measured the performance as shown in Table 2. Table 2 Cross-linking agent used to set the PE /Influence of waste paper composite foaming materials Amount of crosslinker/parts hardness (Shao A) Tensile Strength/MPa Elongation at break/% Note: The amount of foaming agent is 3 parts; foaming agent: three salts = The purpose of adding a cross-linking agent to a foamed plastic is generally two types. One is to improve the molding ability of the plastic, and the other is to improve a certain use performance. It can be seen from Table 2 that under the condition of a certain amount of foaming agent, the amount of the cross-linking agent is increased, the density, the Shore A hardness, and the tensile strength of the composite foamed material increase, but the elongation at break tends to decrease. . However, when the amount of cross-linking agent reaches a certain amount, the performance changes are slowed down. This is due to the resistance of the melt with viscoelasticity when the bubble expands. When the degree of cross-linking increases, this resistance increases, and the number of cells changes with the increase in the amount of cross-linking agent. More and smaller in size, so the density increases. After the cross-linking, the mechanical properties have been improved due to the continuous formation of the melt into a network structure. In addition, as the cross-linking agent increases, when the gelation rate reaches a certain value, the cross-linking degree will hardly change with the change of the cross-linking agent amount, so when the cross-linking agent is increased to a certain amount, the properties tend to be gentle. The trend.
2.1.3 Effect of Molding Pressure on the Properties of Composite Foams The expansion of gases is not only affected by viscoelasticity but also by external pressure, which also affects the performance of foamed materials. Since the gas generated by the decomposition of the blowing agent is mainly N2, the relative molecular mass is small, and it is easy to diffuse in the melt, and the melting of the gas in the melt generally rises with the increase of the external pressure, so it is controlled. In the process conditions, the molding pressure should not be too high. If it is too crucible, the gas will easily escape on the surface of the melt and the air bubbles will collapse and break. This is because when the pressure inside and outside the melt is unbalanced, it will cause the gas in the bubble to diffuse into the melt. If the diffusion rate is too fast, once the elasticity of the solution is insufficient to support the expanding load, the bubble will collapse or even burst. During the experiment, it was found that the foaming pressure of the compounded material was much lower than that of pure PE. When the pressure value is 10 MPa or more, pure PE foaming will result in uniform and dense foamed products. Under the same conditions, the PE/waste paper composite foaming phenomenon is that the internal bubbles are connected in series to form a large bubble, and the gas passes through. The surface of the melt escaping outwards results in the collapse of the bubble due to the imbalance of internal and external pressures. The moulding pressure of PE/waste paper composite foaming should not exceed 5 MPa. 2.2 The effect of coupling agent on the properties of composite foaming materials The main component of waste paper is cellulose fibres. The polarity of fibres due to the presence of hydroxyl and carbon oxygen bonds is very high. Strong, and PE is non-polar, so the compatibility between them is poor, the interface force is very small.
In the blending process, the matrix resin melt must be able to infiltrate the fiber well, but due to the poor compatibility of the two, it is difficult to form a combination of physical or chemical bonds, the interface layer is thin, the interfacial tension is large, and thus the material is affected In order to improve the compatibility of paper powder and matrix resin, the mechanical properties of the powder were increased by using a coupling agent to improve the mechanical properties of the material. The test results are shown in Table 3. It can be seen from Table 3 that the coupling is added. After the agent, all the properties of the material have been greatly improved.
Table 3 Effect of Coupling Agent on Material Properties Performance Material Foaming Agent: 5 parts Cross-linking agent: 0.6 parts Foaming agent: 7 parts Cross-linking agent: 1.2 parts Add titanate Blank plus titanate Blank Hardness (Shao A ) Tensile strength AlPa elongation at break /% Note: foaming agent: three salt = 6:1. 3 Conclusion In the formulation of polyethylene / waste paper composite foaming, the amount of foaming agent has the greatest impact, cross-linking The effect of dosage was the next (the ratio of PE to waste paper powder was 70:30).
The pressure of PE/waste paper composite foaming is much lower than that of pure PE foam.
After adding the coupling agent, the properties of the material have been greatly improved.
Also, as the content of waste paper powder increases, the properties of the material also increase.
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