As a high molecular material, aging is a common phenomenon in plastics. During the use of high molecular materials, due to the combined effects of environmental factors such as heat, oxygen, water, light, microorganisms, and chemical media, the chemical composition and structure of the high molecular materials will undergo a series of changes, and the physical properties will also deteriorate accordingly, such as hardening, stickiness, embrittlement, discoloration, and loss of strength. These changes and phenomena are called aging. General preventive measures 1. Humidity Polyesters, polyacetals, polyamides, and polysaccharide polymers can undergo hydrolysis in the presence of water under acid or alkali catalysis. In areas with serious air pollution and frequent acid rain, the use of these polymeric materials will be limited. If a waterproof film can be applied to the surface of these materials, hydrolysis aging can be reduced or even avoided. 2. Oxygen In the processing of polymers, amine antioxidants, phenolic antioxidants, sulfur-containing organic compounds, and phosphorus-containing compounds are added. They can react rapidly with peroxy radicals, causing the chain reaction to terminate prematurely. 3. Photoaging If light stabilizers are added during the processing of materials, the aging degradation of the materials can be avoided. According to the mechanism of action, these light stabilizers include light screens, UV absorbers, quenchers, and radical scavengers. Since plastic polymeric materials have so many influencing factors and corresponding measures during use, if the use is very inconvenient and the components are too many and the proportions are complex, it is recommended to use a composite antioxidant. Generally, composite antioxidants will consider comprehensive issues such as antioxidant, anti-ultraviolet, light stability, and shielding. Generally, manufacturers encounter four phenomena when solving the aging problem of plastics. What are the four phenomena? 1. Only buy expensive ones, not the right ones It is believed that expensive ones are always good. In fact, any auxiliary agent has advantages and disadvantages, advantages and disadvantages. For example, UV absorbers have different optimal absorption bands, ranging from 270-430 nm. Different types of UV absorbers are distributed, targeting the anti-ultraviolet properties of plastic products at different wavelengths. Choosing the right UV is the best choice and can achieve the best effect. 2. Only recognize foreign goods, not domestic ones It is believed that only foreign goods can solve the problem. This is not the case. The quality and reliability of imported auxiliaries are generally recognized, but if only one auxiliary agent is used, the functional defects of the auxiliary agent itself will be manifested. Some problems are solved, but not all functional problems can be solved. Of course, if all foreign goods are used, the effect should be good, but what about the cost of use? What about raw material procurement? Many troubles will be encountered. 3. Only buy general-purpose ones, not special-purpose ones Different plastics and different polymers have different internal molecular structures. Some have good oxidation resistance, some are resistant to light, and some are resistant to rainwater. Therefore, the requirements for this series of anti-aging are certainly different. How can we use the same approach to solve different problems? It is definitely wrong. Even if there is an effect, the cost of use is probably not cost-effective. 4. Only recognize UV absorption, without considering other synergy UV absorbers have excellent performance in UV light, but the function is still single. There are so many factors affecting aging, not just one UV absorber can solve it. This requires us to consider comprehensively, solve the UV light, and at the same time solve the problems of oxygen, heat, and hydrophobicity. This is the first choice. In this way, composite plastic antioxidants have emerged, better solving the comprehensive problem of plastic aging.

A reactive ultraviolet absorber, 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone (BPMA), was prepared using organic synthesis methods. Using the prepared BPMA, a pre-irradiation grafting reaction was carried out using polyvinylidene fluoride (PVDF) powder as a substrate to obtain PVDF-g-BPMA. The irradiation dose of PVDF in the pre-irradiation experiment was 15 kGy, the melt grafting reaction temperature in the rheometer was 190 °C, the reaction time was 6 min, and the speed was 50 r/min. The structure and UV absorption performance of PVDF-g-BPMA were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and UV-Vis spectroscopy. The results show that BPMA was successfully grafted onto PVDF, with a grafting rate of 7.04%. The crystallinity of PVDF decreased after grafting, but the crystal type did not change. Compared with ungrafted PVDF, the UV transmittance of PVDF-g-BPMA film in the wavelength range of 280-340 nm was reduced to below 0.27%, showing excellent UV absorption performance. Compared with the PVDF/BPMA composite film, its UV absorption performance did not change significantly after ethanol extraction for 48 h, indicating that the pre-irradiation grafting of BPMA onto PVDF effectively prevented the migration of the UV absorber in PVDF. Polyvinylidene fluoride (PVDF) is a high molecular material widely used in automobiles, energy, aerospace, electronics, and chemical industries. It has excellent processability, fatigue resistance, weather resistance, stain resistance, chemical resistance, and excellent electrical and optical properties. Currently, there are many studies on the modification of PVDF, but there are no relevant reports on improving its UV absorption performance. When high molecular materials are used outdoors, they are easily excited by ultraviolet light in sunlight, causing a series of photochemical reactions, leading to molecular structure damage and performance degradation, and finally losing their usability. UV absorbers can effectively prevent or delay the occurrence of such phenomena and prolong the service life of the material. Therefore, improving the UV absorption performance of PVDF is of great significance. The modification methods for PVDF mainly include solution treatment, grafting treatment, blending treatment, and gas treatment. Benzophenone-type UV absorbers are widely used light shielding agents, and many varieties have been commercialized. Its mechanism of action is mainly through intermolecular hydrogen bonding. When the molecule is irradiated with ultraviolet light, it absorbs energy, resonance occurs, and the hydrogen bond is broken. Then, the ultraviolet light energy is converted into lower vibrational energy and released. Small molecule UV absorbers are easily affected by the external environment and migrate during application. Therefore, it is necessary to graft the UV absorber to the polymer or prepare a polymer-type UV absorber. Compared with other methods, the pre-irradiation grafting method can generate free radicals on the molecular chain, further initiating the grafting reaction of the reactive small molecule UV absorber. After the reaction, it has a high grafting rate; it is easy to operate, the experimental conditions are easy to control, it has little environmental pollution, and it can be mass-produced. At the same time, no initiator is needed in the reaction, and a relatively pure grafted polymer can be obtained except for the homopolymer of the monomer. The monomer is not directly irradiated, which can reduce the homopolymerization reaction of the monomer. Referring to the literature, 2,4-dihydroxybenzophenone (UV-O) and glycidyl methacrylate (GMA) were used as raw materials to prepare a polymerizable benzophenone-type UV absorber—2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone (BPMA). The 60Co-γ-ray pre-irradiated PVDF and BPMA were subjected to a melt grafting reaction in a micro-mixing rheometer to prepare PVDF-g-BPMA. There are currently no relevant literature reports on this type of research. The experimental test results show that PVDF grafted with BPMA has excellent UV absorption performance, which is conducive to increasing the application of PVDF as a protective layer material. At the same time, an experimental method is discussed that can effectively prevent the migration of UV absorbers in addition to preparing macromolecular UV absorbers. This has certain guiding significance for applications in other materials. PVDF: Solef 6010, Solvay Specialty Polymers; UV-O, GMA: analytical grade, Aladdin Reagent Company; sodium hydroxide (NaOH), anhydrous magnesium sulfate (MgSO4), concentrated sulfuric acid, anhydrous ethanol, ethyl acetate, toluene: analytical grade, Beijing Chemical Factory; petroleum ether: analytical grade, Tianjin Fuyu Fine Chemical Co., Ltd.; dimethylacetamide (DMAc): analytical grade, Xilong Chemical Co., Ltd.; silica gel: 200-300 mesh, refined type, Qingdao Marine Chemical Factory. 2. Main instruments and equipment Fourier transform infrared (FTIR) spectrometer: Bruker Vertex 70, Bruker, Germany; Thermogravimetric (TG) analyzer: TGA 7, Perkin-Elmer, USA; Differential scanning calorimeter (DSC): STARe System, Mettler Toledo, Switzerland; Nuclear magnetic resonance (NMR) spectrometer: Bruker AV 400, Bruker, Germany; Wide-angle X-ray diffraction (WAXD) instrument: D8 Advance, Bruker, Germany; UV-Vis spectrophotometer: UV 3600, Shimadzu, Japan; Ion chromatograph (IC): ICS-1000, Dionex, USA; Micro-mixing rheometer: Minilab CTW5, Thermo Fisher, Germany. 3. Synthesis of BPMA Referring to the method in the literature, UV-O (8.56 g, 40 mmol) and GMA (6.24 g, 44 mmol) were added to a 250 mL three-necked round-bottom flask. After being protected with nitrogen, the mixture was stirred evenly at room temperature, and NaOH (0.124 g, 3.1 mmol) was added as a catalyst. The temperature was set to 80 °C, and the mixture was heated and stirred under reflux for 7 h. After the temperature dropped to room temperature, toluene was added to dissolve the mixture. After washing with 1% dilute sulfuric acid to remove NaOH, MgSO4 was added and stirred for 20 h. The mixture was filtered to remove MgSO4, and the filtrate was rotary evaporated to obtain a viscous liquid. The target product was separated by silica gel column chromatography. The eluent was ethyl acetate and petroleum ether with a volume ratio of 1:3. The separated yellow crystals were dried in a vacuum oven at 50 °C for 48 h to obtain 8.45 g of pure BPMA with a yield of 59%. Figure 1 shows the synthesis route of BPMA. 4. Pre-irradiation grafting PVDF was placed in a bag and sealed. The bag was placed in a cobalt source and irradiated with 60Co-γ rays with a dose rate of 15 kGy. After irradiation, it was stored at low temperature for later use. 4.8 g of pre-irradiated PVDF and 1.2 g of BPMA were placed in a micro-mixing rheometer for reaction. The temperature was 190 °C, the speed was 50 r/min, and the time was 6 min. The crude product after the reaction was dissolved in DMAc, and then precipitated with anhydrous ethanol, centrifuged, and repeated three times. Then, the unreacted BPMA was extracted in a Soxhlet extractor with anhydrous ethanol. The extracted product was dried in a vacuum oven at 70 °C for 48 h for characterization. 5. Performance testing and structural characterization 1H-NMR test: 5 mg of BPMA and 10 mg of PVDF-g-BPMA were taken and analyzed using an NMR instrument, with deuterated dimethylsulfoxide as the solvent. TG analysis: air atmosphere, heating rate 10 °C/min, temperature range 30-800 °C. FTIR test: PVDF and PVDF-g-BPMA solutions were coated to form films with a thickness of 40 μm for testing. The test wavenumber range was 500-4000 cm-1, the resolution was 2 cm-1, and the mode was total reflection. DSC test: 6 mg of the sample was placed in an alumina sample pan, and the PVDF before and after grafting was tested in a nitrogen atmosphere using a secondary heating method at a heating and cooling rate of 10 °C/min. IC test: The F element content of PVDF before and after grafting was tested. WAXD test: PVDF and PVDF-g-BPMA solutions were coated to form films for testing. Cu target, test angle 10-50°. UV absorption performance characterization: The prepared PVDF and PVDF-g-BPMA films (40 μm) were subjected to UV-Vis transmittance testing. The scanning interval was 1 nm, and the scanning range was 200-800 nm. Migration resistance test: The prepared PVDF/BPMA composite film and PVDF-g-BPMA film (thickness 40 μm) were extracted with ethanol as the solvent for 48 h, and then the UV absorption performance was tested.

For temperatures below 300 degrees, thermal decomposition of general UV agents does not need to be considered. Although there will be some degree of thermal loss (TGA) at high temperatures, UV agents with relatively small TGA and suitable effects can be selected during use, or the dosage can be increased to avoid insufficient amount after volatilization. Main feeding is sufficient; for those with low melting points, side feeding or masterbatch can be selected. The light stabilizer 770 shows good effects in the PA6/glass fiber system.

Photosensitizer, also known as sensitizer. In photochemical reactions, there is a class of molecules that only absorb photons and transfer energy to molecules that cannot absorb photons, promoting their chemical reactions, while they themselves do not participate in the chemical reaction and return to their original state. These molecules are called photosensitizers. Ultraviolet absorbers. Since sunlight contains a large amount of ultraviolet light harmful to colored objects, with a wavelength of about 290-460 nanometers, this harmful ultraviolet light, through chemical redox reactions, causes the color molecules to decompose and fade. Using ultraviolet absorbers to effectively prevent or weaken the damage to the color of the protected object. Preventing the damage of harmful ultraviolet light to the color. Ultraviolet absorbers can be classified into the following categories according to their chemical structure: salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines. Conditions for the action of photosensitizers (1) It can be activated by light irradiation first; (2) There is sufficient concentration in the system, and it can absorb sufficient photons; (3) It must be able to transfer its energy to the reactants. Photosensitizers are generally aromatic ketones and benzoate ethers: such as benzophenone, dimethoxybenzophenone, etc.

Water-based UV absorbers are white to light yellow powders, made through exquisite processes. They have the following characteristics: Good water solubility, forming a light yellow, highly transparent liquid when dissolved in water; Improve the stability of various substances in aqueous systems; Extremely high absorption efficiency, absorption wavelength at 290-390nm; Good light and heat stability, not easily perishable, long service life; Extremely low usage concentration, extremely high absorption performance; Powder packaging, convenient transportation; Non-toxic, non-teratogenic side effects, harmless and environmentally friendly Water-based UV absorbers are a water-soluble, neutral, broad-spectrum UV absorber suitable for absorbing UV wavelengths of 290-390nm. Mainly used in water-based coating systems, water-soluble chemical sunscreens, sunscreens, lotions, shampoos, shower gels, oilfield water-based drilling fluids, oilfield water-based lubricants, and various other organic aqueous systems. It can effectively prevent various harms caused by ultraviolet rays.