The performance of recycled plastic blending modification technology will be more excellent
Recycled plastics have become an effective social resource, and recycled plastic components are often blended by two or more different materials, which can be used to produce a variety of plastic products. Modification of plastics is another simple and effective method to obtain new properties of resins besides polymerization.
The modified synthetic material is not only simple in process, low in cost, but also has excellent performance, thus expanding the application field of synthetic resin. The blending modification technology is a scientific and practical new technology to achieve high performance, multi-function and refinement of recycled plastics.
PVC has many excellent properties and is widely used, but there are also obvious shortcomings, such as low softening point, poor heat resistance, cold resistance, easy decomposition, poor thermal stability, etc. In order to improve its shortcomings, some modified varieties of polyvinyl chloride have appeared.
1. Blending modification of recycled PVC
1).PVC/CPE blend modification
Polyvinyl chloride and polyethylene are a large amount of general plastics, occupy a large proportion of waste plastics, and recycling waste plastics are often difficult to sort. CPE is the product of chlorination of polyethylene. CPE with a chlorine content of 25% to 40% has the properties of elastomers. CPE can play the role of compatibilizer between PVC and polyethylene, can improve the performance of the blend, and is of great significance for the recycling of PVC and polyethylene recycled plastics.
In addition, CPE can also be added to PVC hard products, mainly to play the role of toughening modification. CPE with 36% chlorine content is usually used as toughening modifier for PVC.
2).PVC/MBS blend modification
MBS is a graft blend formed by grafting methyl methacrylate (MMA) and styrene (ST) onto polybutadiene (PB) or butadiene gum (SBR) macromolecular chains.
MBS resin has good compatibility with PVC, can significantly improve the impact strength of PVC, but also improve the processing performance of PVC, PVC/MBS blend has good transparency, therefore, MBS is widely used in hard PVC toughening modification, especially in transparent products.
3).PVC/EVA blend modification
EVA is a random copolymer of ethylene and vinyl acetate. PVC is blended with EVA, EVA can be used for toughening and modifying hard PVC, and can also be used for soft PVC. Rigid PVC/EVA blends can be used in the production of sheets and profiles, as well as in the production of low-foaming products.
The use of EVA for soft PVC can significantly improve the cold resistance of PVC, and the embrittlement temperature of this PVC/EVA blend can reach -70℃. In addition, the soft PVC/EVA blend also has a good feel. Soft PVC/EVA blends can be used to produce cold-resistant films, sheets, artificial leather, etc., and can also be used to produce foamed products.
4).PVC/ABS blend modification
ABS is acrylonitrile butadiene styrene copolymer, which has the characteristics of high impact performance, easy molding, good hand feeling and easy electroplating. PVC is blended with ABS, which can synthesize the advantages of the two, and become a new material with wide use in electrical shell, electrical components, automobile instrument panel, textile equipment, luggage and so on.
ABS can be used as a toughening modifier for rigid polyvinyl chloride, and the processing fluidity is also significantly improved. Due to the moderate degree of compatibility between PVC and ABS, compatibles such as CPE and SAN should be added when blending. The impact strength of ABS/PVC blending system can be significantly improved by adding compatibilizer CPE into the blending system. In addition, because ABS contains unsaturated double bonds, its thermal stability and antioxidant properties are low, so in addition to adding heat stabilizer, antioxidant should also be added in the formula.
The blending of ABS and PVC can also significantly improve the flame retardancy of ABS. This feature makes ABS/PVC blends suitable for the manufacture of electrical housings and components, which can avoid the shortcomings of performance degradation and additive precipitation caused by the addition of small molecule flame retardants. In the PVC/ABS blend system, an appropriate amount of plasticizer can also be added to become a semi-hard product, which can be used to manufacture automotive dashboards.
5).PVC/TPU blending modification
After blending and modifying PVC with thermoplastic polyurethane, it becomes a new thermoplastic elastomer, also known as polyurethane rubber. Polyurethane has excellent physical and chemical properties and excellent biocompatibility. By blending TPU with PVC and replacing DOP with TPU to make soft PVC medical products, the migration of liquid plasticizer can be avoided. In the PVC/TPU blending system, reinforcing agents can be added to improve the mechanical properties. Among all kinds of reinforcing agents, the reinforcing effect of white carbon black (silica) is better. Polyvinyl chloride heat stabilizer can be selected calcium stearate. TPU can also be used in PVC hard products, as a toughening agent for PVC, to prepare PVC/TPU blend toughening material.
2. Blending of different varieties of PVC
The blending modification of PVC includes not only the blending of PVC with other polymers, but also the blending of different varieties of PVC.
High degree polyvinyl chloride is blended with ordinary polyvinyl chloride. High degree of polymerization polyvinyl chloride resin (HPVC) refers to polyvinyl chloride resin with a polymerization degree greater than 2000. HPVC can be used to manufacture PVC thermoplastic elastomers. However, due to the high degree of polymerization, the processing and molding of HPVC are difficult. The processing fluidity of HPVC can be improved by blending HPVC with ordinary polyvinyl chloride.
For ordinary PVC, HPVC can be regarded as a modifier that can improve the performance of ordinary PVC. The plasticizer capacity of HPVC is higher than that of ordinary polyvinyl chloride, and more plasticizers can be added to the HPVC/PVC blend system to improve the cold resistance and elasticity of the product. Here HPVC plays a similar role to nitrile butadiene rubber. For example, adding more than 20 pieces of HPVC to the soft polyvinyl chloride film makes the product elastic and has good low softness and softness.