Research progress of non-elastomeric toughened polymer materials

Advances in modern plastics processing applications Research advances in non-elastomeric toughened polymer materials Deng Qin Fu Dongsheng 2 Zhang Kangshang 2 (1 Northwestern Polytechnical University, Xi’an, 710072) (2 Institute of Aerospace, Fourth Institute of Mineral Research, Xi’an, 710025) ) Polymer toughening systems and inorganic rigid particle toughening systems are outlined separately. In this paper, the research progress of non-elastomer toughened polymer materials in recent years is reviewed.

For a long time in the past, tough researches on polymer materials have been limited to rubber-based elastomers. Elastomers tend to sacrifice the rigidity, dimensional stability, heat resistance, etc. of the material while improving the toughness of the polymer material. In recent years, researchers have made great progress in the field of non-elastomer tough polymer materials. In particular, the use of inorganic nanoparticle tough polymer materials is the focus of recent research. The following are elaborated from the aspects of plastic tough polymer system, core-shell particle tough system, liquid crystal polymer tough system and inorganic rigid particle tough system.

1 Thermoplastic Toughening System Thermoplastic resins are a large class of polymers, and they are also the focus of tough research on polymer materials. When a thermoplastic resin is used as a tough 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 can play a role in stress transmission. When subjected to external forces, it induces plastic deformation of the thermoplastic plastic, absorbs stress, and avoids damage to the material, thereby achieving the purpose of toughness.

The toughness of PVC is poor, and linear low density polyethylene (LLDPE) is a high toughness polymer. When LLDPE tough PVC was used, the impact properties of PVC were improved, but due to the thermodynamic incompatibility of the two, the impact cross-section of the blend system was 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 a compatibilizer, the size of the dispersed phase LLDPE was significantly reduced and homogenized. The impact strength is further improved, and the impact fracture is transformed from brittle fracture morphology to ductile fracture morphology. The reason is that the compatibilizer enhances the adhesion between PVC and L-Like so that the internal domains can transfer internal stress better. It was observed by SEM that the blend system was in a network structure and the compatibility between the two phases was good. Raja et al. used co-extruded pelletized LLDPE products and PVC resin under the action of a screw extruder to obtain a tougher blend system than PVC resin. The elongation at break of the system was higher than that of Raja et al. The PVC tree month has been enhanced by an order of magnitude and shows some resilience. The practical significance of this method lies in solving a part of the "white pollution" problem and has a very good prospect for development.

PP is a crystalline polymer, and the resulting spherulites are large, which is the main reason why PP is prone to cracks and has low impact properties. If the crystals of PP can be made finer, impact properties can be improved. In PP and PE blends, both PP and PE are crystalline polymers, and they do not form eutectic crystals. Instead, they form crystals. The PP crystal and the PE crystal interact with each other. This restriction can destroy the spherulite structure of the PP. The PP spherulites are divided into wafers by the PE, so that the PP cannot generate spherulites. With the large amount of PE, the division becomes more difficult. The more obvious, the PP crystals are further refined. The smaller size of the PP crystals improves the impact properties.

Zhou Zhengya and others used the mechanical blending method to add polyethylene 5000S to the block copolymer polypropylene J640C (a low ethylene content block copolymer) for blending, and obtained the blending through a twin screw extruder to obtain a blend. Product. The performance test results of the product show that the addition of polyethylene has a significant effect on the improvement of the impact toughness of the material. When the polyethylene content is 8% to 14%, the impact properties of the material are born, and the material science is specialized.

Deng Qin et al. Non-elastomer toughened polymer materials have progressed to the best. From the product of the polarizing microscope photo analysis, with the addition of the 5000S content, the extinction phenomenon of polypropylene J640C spherulite shape gradually disappears, and the gaps between crystal phases gradually decrease, which proves that the spherulites are indeed refined.

Yan Yanqin et al. studied that ultra-high molecular weight polyethylene has a very high relative molecular mass, excellent tensile strength and elongation at break, and UHMWPE can improve the toughness and strength of the blends by UHMWPE. UHMWPE The tensile strength of the copolymerized PP toughened system containing ethylene chains showed a peak at the PP/UHMWPE (mass ratio) of 100/10, and its impact strength also increased to some extent.

Yang Wenjun et al. studied the effect of rigid polymer (PMMA, SAN, etc.) on the mechanical properties of PVC/CPE blends based on the concept of non-elastoplastic tough plastics. In the study, it was found that PMMA rigid particles can significantly improve the toughness of the PVC/CPE blend system, and the compatibility and dispersibility of the two phases of the PMMA rigid particle blend system are improved, which promotes the formation and subtlety of the CPE network structure. Homogenization. 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 PMMA particles and absorbing a large amount of plastic deformation energy, which improves the impact performance of the blend system. At the same time, PMMA itself has higher strength and better adhesion to the substrate, which has a certain strong effect on the PVC/CPE blend system. In the blend system with a mass ratio of PVC/CPE of 100/15, when the amount of PMMA was 1.5 to 4.5 parts, the impact strength was increased from 20 kJ/m2 to 98 kj/m2, and the tensile strength and elongation at break also increased.

2 Core-shell particle growth system The core-shell structure of the polymer is 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 the tough modification of the polymer material is a hard plastic shell coated with a rubber core.

Li Youming first prepared a micro-cross-linked poly(butyl acrylate) (PBA) seed emulsion by emulsion polymerization, and then introduced a poly(methyl methacrylate) shell on the seed to obtain core-shell particles. When the epoxy resin is toughened by the particles, since the solubility parameter of the polymethyl methacrylate is similar to the solubility parameter of the epoxy resin, 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 the epoxy resin, while the micro-crosslinked PBA of the core was in the form of particles in the epoxy matrix. Dynamic mechanical analysis was performed in dynamic mechanics. In the high temperature region of the spectrum, no glass transition peaks corresponding to PMMA can be found, and only the glass transition peak corresponding to the epoxy resin, which also proves the compatibility of epoxy resin and PMMA. The notched impact strength of the modified system was significantly improved, and the fracture surface was characterized by the brittle fracture of the epoxy resin into a ductile fracture.

Wang Xiaodong et al. studied the toughness of nylon 6 with PBA/PMMA core-shell particles. To add 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. The addition of DGEBA can significantly increase the torque of the modified system, effectively improving its toughness. From the electron micrographs, it can be seen that the core-shell particles are well dispersed in the modified system. Utilizing nylon-reactive group-amide groups, acrylic resins and their copolymers can be used to achieve the reaction volume. DR Paul and others used the "shell-shell" type MBS polymer and ABS polymer respectively blended with nylon 6, and the impact strength of the tough system obtained with styrene-maleic anhydride copolymer (SMA) as a compatibilizer. The surface of the inorganic filler was pretreated by the solution method, and the interfacial adhesion between kaolin particles with kaolin as the core and the interfacial modifier coating as the shell was obtained. On the other hand, the interfacial adhesion was added through the soft ether bond and the interface. Under the deformation capacity.When the amount of filler is 30%, the impact value of the material is as high as 480J/m2, which is 12 times that of the untreated material.Continue to add the filler to 50%, the impact strength of the material does not decrease significantly.

3 liquid crystal polymer toughening system liquid crystal polymer is a class of molecules containing mesogenic units of high molecular compounds, can be divided into lyotropic liquid crystal and thermotropic liquid crystal.

The tough mechanism of thermotropic liquid crystal (TLCP) is mainly the mechanism of crack nail anchorage. The TLCP, as the second phase (similar to the rigid body), has a certain toughness and a high elongation at break. Therefore, only a small amount of TLCP can be used to tough polymer materials, while improving its modulus and heat resistance. The use of TLCP tough polymer materials not only improves its toughness, but also ensures that it does not reduce the other mechanical properties and heat resistance of the polymer material.

Zhang Baolong et al. synthesized a side chain polymer liquid crystal to tough epoxy resin. When the compound is tough epoxy resin, the flexible main chain of the liquid crystal polymer can make up for the brittleness of the epoxy matrix and the phase of the side chains. The toughening of the PBA/PMMA core-shell particles into the epoxy matrix system into the rigid unit ensures that the modulus of the modified system does not decrease, and modern plastics processing applications increase the overall mechanical properties of the system. During the study, it was also found that the impact properties of the system were large with large amounts of side-chain polymer liquid crystals, and the maximum impact properties were obtained when the amount was 20% to 30% (molar fraction). Through SEM observation and analysis, the impact fractured epoxy resin was in a continuous phase, and the liquid crystal was dispersed in the resin matrix in the form of particles. When impacted, 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 liquid epoxy 4,4 diglycidyl ether diphenyl hydrazide (PHBHQ) tough E-51 epoxy resin containing aryl ester. The melting point was the same as that of the liquid crystal phase, and the reaction activity was low. The mixed aromatic amine is a curing agent, when the amount of PHBHQ used is 50% (mass content), the impact strength of the cured resin is 40. The impact performance without PHWFlQ is increased by 31.72 kj/m2, and the glass transition temperature is also certain. Raising 110. The copolyarylates of p-hydroxybenzoic acid and 2,6-hydroxybenzoic acid introduced by the company were blended at 350*C through a screw extruder to obtain a PEEK/TLCP blended toughening system. It was found that when the TLCP content was 2.5%, the elongation at break of the blend system was 18% longer than that of the pure PEEK. Simultaneously with the addition of TLCP, the impact strength of the blend system was also increased.

When the content of TLCP is greater than 10%, the impact strength is significantly increased. When the content of TLCP is 90%, the impact strength of the blend is 1 032 J/m2, which is almost twice that of pure TLCP. The blend system was observed by scanning electron microscopy. It was found that the blend system was a skin-core structure. When the TLCP content was less than 10%, the TLCP was dispersed in the core layer in the form of small ellipsoids.

When the TLCP content was higher than 25%, TLCP expanded fibers with an average diameter of 10 Um were observed in the core layer, and fibers with a diameter of less than 8 Um were observed in the cortex. This fiber structure greatly improves the overall performance of the blend system. When the TLCP content is higher than 50%, the morphology changes greatly. The blend system reversed and PEEK dispersed in the TLCP matrix as a dispersed phase.

4 inorganic rigid particle toughening system has been used as a polymer material filler for a period of time to reduce product costs. The introduction of large particles of rigid particles acts as a source of stress concentration in the material, reducing the toughness of the resin matrix. It was found that when the particle size of a rigid particle is smaller than a certain value, its volume is reduced, the specific surface area is large, and the contact area with the resin matrix is ​​also large, and it can function as a tough polymer material.

Wu Wei et al. studied the properties of plastics with different physical properties and chemical activity mainly depends on two factors, one is the average particle size of inorganic particles; the other is the surface activity of inorganic particles. Comparison of the toughness effects of lighter C-CO3, common active CaC3, ultrafine activated CaC3, and CaC3 particles treated with a titanate coupling agent on the system revealed that when the CaC3 particle size is large, the impact of the blending system The strength decreases with the increase of the dosage; the surface treated CaC3 particles blended modified system has better impact performance than the untreated CaC3 modified system; after the grain size refinement, the impact strength of the system plus the maximum of the CaC3 particles increases. For example, when the amount of ultrafine activated CaC3 is 10 parts, the impact strength of the system is from 15kj/m2 to 27kj/m2. Wu Qiqi and other macromolecule carboxylated carboxylated styrene-butadiene latex are used to activate CaC3 particles to improve the matrix resin. The interface between the adhesion, so as to achieve the role of stress transmission. The study found that after adding 10 parts of modified particles, the impact strength of the system was from 4.2kJ/m2 to 7. 7kJ/m2. At the same time, 10 parts of CPE were added to the blend system, and the impact strength of the blend system was rapidly increased to 20.7kJ/m2. The reason for this is that CPE acts as a coupling agent in this system and can increase the compatibility between the two phases. At the same time, CPE can impart certain toughness to the matrix material so that it can undergo brittle-ductile transformation when subjected to impact. To achieve the purpose of toughness, the synergistic effect among the three components in the system makes the blend system have good comprehensive mechanical properties.

The use of inorganic nanoparticles to modify PVC is a new technology developed in recent years. Nanoparticles have unique surface effects, volume effects, and quantum effects. The use of nano-scale CaC3 particles to modify PVC can achieve strong, tough dual effects. Hu Shengfei et al. used nano-CaC3 particles to modify the PVC, and compared the toughness and strong effects of nano-sized CaC3 and micro-sized CaC3 particles on the PVC matrix. When the dosage of CaC3 nanoparticles is 10%, the impact strength of the system is increased by 3 times compared with PVC matrix resin. At this time, the maximum tensile strength of the system is 58MPa, which is 11MPa higher than that of the matrix. While the micron-sized CaC3 particles are tough, the impact is The performance has a lower degree of improvement, but its tensile strength has not changed significantly. The degree of dispersion of inorganic nanoparticles has a great influence on the properties of the blend system. After many nano-particles are dispersed in the system, it is difficult to produce the phenomenon of particle agglomeration, and the stress concentration of the system is easily caused. At the same time, when the system is subjected to external forces, the agglomerated particles are likely to slip with each other and the system performance is deteriorated. From the SEM photographs of tensile and impact fracture of the sample, it can be seen that the uniformly dispersed nano-particles are distributed in a matrix, and there is no obvious gap between the particles and the matrix interface, and there is a certain web-like yield of the matrix in the impact direction. When the amount of nano-particles is large, the aggregates are aggregated in the impact fracture, and the adhesion to the matrix is ​​poor.

Ren Xiancheng et al. prepared the PP/nano-CaC3 system by the melt blending process on the surface-pretreated nano-CaC3 and found nano-C-sningHouse. Deng Qin et al. Research progress of non-elastomeric toughened polymer materials The amount of CO3 used is less than 10% to increase the notched impact strength of PP by 3 to 4 times. At the same time, it is also found that the phenomenon of brittle-ductile transition occurs obviously when the nano-CaC3 is tough, and the better the toughness of the PP matrix used, the lower the critical amount of PP is. After analyzing the crystal form by DSC, it is believed that nano-CaC3 has a greater induction effect on the crystallization process of PP. Increasing the content of 0-crystal can change the toughness of PP matrix.

Chen Zhonghua et al. prepared modified PP/modified bentonite blended system by modified blended bentonite. The analysis showed that when the bentonite content was 2%, the notched impact strength of the material was nearly 3 times higher than that of pure PP. Tensile strength increased by about 10%. Zheng Yaping used Si2 nanoparticles for a large number of modified epoxy resin systems. Through the use of dispersants, uniform mixing of nanoparticles and epoxy resin is achieved, and the problem that nanoparticles are easily agglomerated due to too small particle size is solved. The results show that the presence of hydroxyl groups on the surface of Si2 particles in the Si2/EP composite system has strong intermolecular forces at the interface and therefore has good compatibility. Through TEM observation and analysis, the nanoparticles were dispersed in the modified system, and the epoxy resin was continuous phase. The nanoparticles are more uniformly dispersed in the resin matrix in the form of a second aggregate. Because of the good bonding performance between the two, they can absorb the impact energy when impacted, so as to achieve the purpose of toughness.

5 Conclusion The tough modification of polymer materials has become an important means of engineering. The idea of ​​non-elastomeric tough polymer materials has opened up a new field of study on toughening modification of polymer materials. In recent years, foreign developed thermoplastic rubber products, such as PE, PVC, PP, etc., have been used in the process of blending pellets to recycle polymer materials. This has effectively solved part of the environmental pollution problems, and the blending group has achieved tremendous results. With the continuous deepening of research on polymer toughness by scientific researchers, polymer materials will have more excellent overall performance and will be more widely used in daily life.