The development of plastics modification technology has not only greatly improved the performance of materials, but has also been given new properties, further expanded its application areas, and significantly increased the value of industrial applications of plastics, and has a very important position in the production practice. At present, there are four commonly used plastic modification methods: blending modification technology, filling modification and fiber reinforcement technology, chemical modification technology and surface modification technology, etc., and the development status of these plastic modification technologies has been simplified. Introduction.
1 Introduction
With the development of science and technology, artificial synthetic materials have been widely used and have penetrated into various fields of human production and life. Together with iron and steel, cement, and wood, they have become the four basic materials for modern industry and occupy an important position in the national economy. The rapid development of the plastics industry has brought two practical and important issues: the recycling of waste plastics and the modification of plastics.
By the year 2000, the total output of plastics in the world has exceeded 110 million tons, and the annual growth rate of about 8% has continued to increase. Since the reform and opening up, the consumption of plastics in China has maintained a double-digit growth rate. By 2005 China's plastic products It reached 21,985,500 tons [1]. The wide application of plastic products has facilitated people's production and life, and has also brought about the "white pollution" problem that has attracted the attention of the whole society.
The extensive application of plastics puts forward higher requirements on the properties of materials. A single polymer material can no longer meet the needs of production and life, and the material must be modified. The so-called plastic modification refers to the physical, chemical or physical/chemical methods to meet the production and living needs of plastics, or to reduce the production cost, or to improve the performance of materials, or to be given new functions [2 ].
2. Overview of research on plastic modification
There are many methods for modifying plastics, which can be divided into blend modification, filling and fiber-reinforced modification, chemical modification, and surface modification [3].
2.1 Blend Modification
Blend modification is the simplest and direct method for plastics modification. It mainly refers to the process of adding one or more other polymers or modifiers to the matrix polymer to prepare a macroscopic homogeneous material, usually including physics. Blending, chemical blending and physical/chemical blending in three cases. In a sense, the chemical structure of polymer macromolecular chains has not undergone drastic changes, mainly due to changes in system composition and microstructure.
Blending plastics with different properties can greatly improve the properties of polymers. Toughening modification of plastics is widely used in production practice and is one of the most successful examples of blend modification. Wu Chi-Fei et al [4-6] recycled PET bottles as the main raw materials, while drawing on the advantages of low-temperature solid-phase processing and reactive extrusion, the use of co-rotating twin-screw extruder for PET/PC/SEBS system for blend extrusion The use of 4,4'-diphenylmethane diisocyanate (MDI) as a chain extender for chain extension and compatibilization, to prepare a simply supported beam with a notched impact strength >65 kJ/m2, and with good strength and toughness Polymer alloys. Guimariäes et al. [7] studied the mechanical and thermal properties of HDPE/POE blends. The results show that HDPE and POE have some interactions, and the tensile properties of the blends are significantly improved. When the POE amount reaches 5wt% Room temperature super tough materials are available. Feng et al [8] studied the phase structure and toughening mechanism of the PP/POE blend system. The results show that POE forms a uniform Salami structure in PP, which can effectively improve the impact strength of PP at room temperature and low temperature.
Blending technology can not only use the complementary properties of different plastics to prepare new polymer materials with good properties, but also can realize the blending of expensive plastics and relatively inexpensive plastics, without reducing or slightly reducing the performance of the former. Lower production costs.
2.2 Filling and Fiber Reinforced Modification
In the process of polymer processing and molding, in order to achieve the purpose of improving a certain performance of the plastic or reducing the production cost, in most cases, different proportions of fillers are added to the plastic. Most of these fillers are materials such as inorganic powders or fibers. In filled modification systems, the more successful examples are the application of nano calcium carbonate and montmorillonite in plastics.
The study of PVC/CaCO3 system and PVC/ACR/CaCO3 system by Hu Shengfei et al [9] showed that when the amount of nano-CaCO3 is 10wt%, the tensile strength of the material reaches the maximum, which is higher than the corresponding PVC and PVC/ACR blends. The tensile strength of the material is high; at the same time, the impact strength of the material is also significantly improved. Ren Xiancheng [10] studied the nano-CaCO3 toughening and reinforcing PP system and found that when adding a small amount of CaCO3, it mainly plays a reinforcing role, with the increase in the amount of CaCO3, the volume fraction of the flexible interfacial layer inside the composite rises. The flexible interface layer yields prior to the external force under the action of the external body, resulting in a decrease in the tensile strength of the material.
Fiber-reinforced composite materials are characterized by "light weight and high strength" and are a class of outstanding performance materials that have been widely used in national production. Commonly used fiber types include glass fiber, carbon fiber, aramid fiber, etc. Thermoplastic bases include PP, PA, PBT, PC, ABS, POM, PPS, and P.
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