Research progress of non-elastomeric toughened polymer materials

The application of polymer materials has brought about tremendous changes in the human environment. Compared with traditional materials, hydrazine polymers are inexpensive, fully functional and have many excellent properties. However, due to the limitation of its own molecular structure, many polymer materials have poor toughness and particularly poor cold resistance. Therefore, researchers have conducted a lot of research on their toughening and modification. For a long time in the past, scientific research workers have been confined to the study of polymer materials for rubber reinforcement. Elastomers tend to sacrifice the stiffness, dimensional stability, heat resistance, etc. of the material while improving the flexibility of the polymer material. In recent years, researchers have made great progress in the field of non-elastomer toughening polymer materials, especially the use of inorganic nanoparticles to toughen germanium molecular materials is the focus of research. This article expounds the aspects of resin addition, molecular system, core-shell particle increase system, liquid crystal polymer toughening system and inorganic rigid particle toughening system.

1 Thermoplastic Resin Toughening System Thermoplastic resin is a large class of materials in the ruthenium molecule, and it is also the focus of tough research by researchers on polymer materials. When a thermoplastic resin is used to toughen a polymer material, a special two-phase system is formed between the components, and an interface having a certain strength is formed between each phase or through a compatibilizer. Through the interface, you can share the load and transfer stress to increase the purpose.

The toughness of PVC is poor, and linear low density polyethylene (LLDPE) is a tough polymer of indole. When LLDPE is used to toughen PVC, the impact resistance of PVC is improved. However, due to the thermodynamic incompatibility of the two, the impact cross-section of the blend system is still brittle fracture morphology.

Zhou Qingye et al. used a graft copolymer of hydrogenated polybutadiene and methyl methacrylate as a compatibilizer for PVC and LLDPE blends. After the addition of the compatibilizer, the size of the dispersed phase LLDPE is significantly reduced and uniformized, the impact strength of the system is further increased, and the impact section is transformed from brittle fracture morphology characteristics to ductile fracture morphology characteristics. The reason is that the compatibilizer enhances the adhesion between PVC and LLDPE, so that internal forces can be better transferred between domains.

The observation by scanning electron microscopy (SEM) revealed that the blended system was in the form of a network-like structure with good compatibility between the two phases.

Raija et al. used a method in which the waste LLDPE and PVC resin were co-extruded and granulated under the action of a screw extruder to obtain an excellent blending system that was superior to PVC resin in toughness. The elongation at break of the system is an order of magnitude higher than that of PVC resin and shows a certain degree of toughness. The practical significance of this method is to solve a part of the environmental pollution problems and have a good development prospect.

PP is a crystalline polymer and produces larger spherulites. This is the main reason why PP is prone to cracks and has poor impact resistance. If the revised draft receives the date: 2003-07-22. 2002 graduate students, the research direction is molecular materials science.

Deng Qin et al. Research Progress of Nonelastic Body Toughening Polymer Materials . 73. The finer crystals of PP can improve the impact resistance. In the blending system of PP and polyethylene (PE), both are crystalline polymers, and no eutectic crystals are formed between them. Instead, they are crystallized. Moreover, PP crystals and PE crystals interact with each other. This restriction can destroy the spherulite structure of PP. The PP spherulites are divided into wafers by PE so that PP cannot generate spherulites. As the amount of PE increases, this division becomes more and more significant, and the PP crystals are further refined. The smaller size of the PP crystals improves the impact resistance.

Effects of mechanical properties of (CPE) blends. The study found that PMMA rigid particles can significantly improve the toughness of PVC/CPE blends. The compatibility and dispersibility of the two phases of the PMMA rigid particle blending system were improved, which promoted the formation and finer homogenization of the CPE network structure. When the system is impacted, the PMMA rigidly dispersed particles generate a large static pressure field around the PMMA particles, causing the brittle-ductile transition of the PMMA particles and absorbing a large amount of plastic deformation energy, improving the impact resistance of the blend system. At the same time, since PMMA itself has relatively strong strength, it has better adhesion with the substrate, and has a certain reinforcing effect on the PVC/CPE blend system. In a blend system with PVC/CPE (mass fraction) of 100:15, when the amount of PMMA is 1.5 to 4.5 Phr. The impact strength is raised from 20kj/in2 to 98kj/m2, and the tensile strength and elongation at break have also been improved.

2 Core Particle Toughening System The core-shell structural polymer is a copolymer obtained by stepwise emulsion polymerization of two or more monomers. There is a microscopic phase structure between the shell and the core of the core-shell particles. Core-shell copolymers are divided into soft core-shell and hard-core soft shells. The core-shell type particle structure used for toughening modification of polymer materials is a layer of hard plastic shell coated with a rubber core.

Li et al. first prepared the butyl acrylate (PBA) seed emulsion by an emulsion polymerization method and synthesized a nuclear emulsion under the action of an initiator, and then introduced PMMA shell on the seed to obtain core-shell particles. When the EP is toughened by the particles, since the solubility parameter of PMMA is similar to the solubility parameter of EP, the interface compatibility between the two is very good. When observed by SEM, it was found that the shell of the core-shell particles was dissolved in EP and the core PBA was in the form of a granular dispersed phase in the epoxy matrix. Okuto conducted a dynamic mechanical analysis of the PBA/PMMA core-shell particle toughening epoxy matrix system. On the dynamic mechanical map, it was found that there was no glass transition peak corresponding to PMMA in the high temperature zone, and only the glass transition peak corresponding to EP, which also proved the compatibility of EP and PMMA. The notched impact strength of the modified system is significantly improved, and the fracture morphology is transformed from brittle fracture of EP to ductile fracture.

Wang Xiaodong et al. studied the toughening effect of PBA/PMMA core-shell particles on polyamide (PA)6. In order to increase the compatibility between the two, a bisphenol A epoxy resin (DGEBA) was used as a compatibilizer. The hydroxyl groups in DGEBA can form hydrogen bonds with the carbonyl oxygen of PMMA and have good compatibility with PMMA. Addition of DGEBA can significantly increase the torque of the modified system and effectively improve its toughness. From the SEM photos, it can be seen that the core-shell particles are well dispersed in the modified system. The use of PA6 reactive groups amide groups, with acrylic and its copolymer compatibilization can achieve the purpose of the reaction compatibilization. Paul et al. use "core-shell" methyl methacrylate-butadiene-styrene terpolymer and acrylonitrile-butadiene-styrene terpolymer to blend with PA6 and benzene respectively. The tenacity of the toughened system obtained from the ethylene-maleic anhydride copolymer as a compatibilizer is nearly 10 times higher.

Yu Yuchun et al. pretreated the surface of inorganic fillers by the solution method, and obtained “core-shell” structure particles with kaolinite as the core and the interfacial modifier coating as the shell, and used it as a modified PP additive. Agent. This "core-shell" structure on the one hand enhances the interfacial adhesion between PP and inorganic kaolin particles, and on the other hand increases the deformation ability of the interface under stress through the soft ether bond. When the amount of filler is 30%, the impact strength of the material is as high as 480 J/m, which is 12 times that of the untreated material. If the filler is further increased to 50%, the impact strength of the material does not decrease significantly.

Synthetic resin and plastics 3 Liquid crystal polymer toughening system Liquid crystal polymer is a type of polymer compound containing crystalline units in the molecule. In general, lyotropic liquid crystals and thermotropic liquid crystals (TCLP) can be classified according to the physical conditions in which they form a liquid crystal state. The toughening mechanism of TCLP is mainly cracked nail anchor mechanism. TCLP as a second phase (rigid to the substrate) has a certain toughness and a high elongation at break. Therefore, only a small amount of TCLP can be used to toughen polymer materials, and increase their modulus and heat resistance. Using TCLP to toughen polymer materials can not only improve its toughness, but also ensure that other mechanical properties of polymer materials are not reduced. Heat resistance.

Toughening of EP by liquid crystals. When the compound toughens EP, the main chain of the flexible liquid crystal molecules can make up for the brittleness of the epoxy matrix, and the rigid units of the side chains ensure that the modulus of the modified system does not decrease, thereby improving the system. The comprehensive mechanical properties. The study also found that the impact resistance of the system increases with the increase of the amount of the side chain type liquid crystal polymer, and has the highest impact resistance when the molar fraction is 20% to 30%. Through SEM observation and analysis, the impact section EP showed a continuous phase, and the liquid crystal was dispersed in the resin matrix in the form of particles. When subjected to impact, the liquid crystal particles are a source of stress concentration and induce plastic deformation of the surrounding epoxy matrix to absorb energy.

Chang Peng made good use of nano-CaC03 particles to modify the PVC, and compared the toughening and strengthening effect of nano-sized (C:03 and CaC03 particles on the PVC matrix. When the nano-CaC03 particles were used as a 10% child, The impact strength of the system is 3 times higher than that of the PVC matrix resin.At this time, the maximum tensile strength of the system is 58MPa, which improves the tensile strength of the particle toughening system. However, there is no obvious change.The degree of dispersion of inorganic nanoparticles has a great influence on the performance of the blend system.After increasing the number of nano-particles, it is difficult to disperse in the system, it is easy to produce the phenomenon of particle agglomeration, and it is easy to cause stress concentration of the system; When the external force acts, the agglomerated particles are liable to slip with each other and the performance of the system is degraded.From the SEM photographs of the tensile and impact sections of the specimen, it can be seen that the uniformly dispersed nanoparticles are distributed in a matrix, the particles and the matrix. There are no obvious gaps between the interfaces, and there is a certain net-like yield in the impact direction of the matrix, and when the amount of nano-particles increases, it will show a lump-like aggregation state in the impact section. Poor adhesion.

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