Agricultural film production should mainly pay attention to the selection of basic resin, formulation screening and control of product processing quality.
1 Choose a base resin with good performance:
The types of resins commonly used in functional agricultural films are LDPE, LLDPE and EVa. When used in agricultural films, they are subject to the following principles without exception:
1.1 In this variety, the resin has a high molecular weight and a narrow molecular weight distribution.
Many of the superior properties of polymers are derived from their large molecular weight. Certain properties (such as mechanical properties, aging resistance) increase with increasing molecular weight and eventually tend to a certain limit. It is considered that the melt viscosity of the polymer also increases with an increase in molecular weight, which causes difficulty in processing, so the molecular weight cannot be infinitely large.
The molecular weight distribution is a parameter for characterizing the degree of molecular weight dispersion, and the narrow molecular weight distribution indicates that the dispersion of the low molecular weight substance in the high polymer is small. On the other hand, a resin having a broad molecular weight distribution has a high processing fluidity, but a relatively high content of a low molecular weight substance is disadvantageous to the weather resistance of the film.
1.2 The number of branches, double bonds, and initial carbonyl content of the resin is as low as possible.
The number of branches indicates the degree of branching of the polymer chain, and the larger the value, the worse the stability of the polymer chain. Both the double bond and the carbonyl group in the resin can be regarded as a photosensitive chromophore which is aged early in the resin. The existence of these groups should be minimized.
1.3 The selected resin has a low crystallinity and a small crystallite size.
The higher the crystallinity of the semi-crystalline material, the worse the regularity of the structure, and the longer the optical path of the absorbed light, the worse the stability to light. At the same time, the high degree of crystallinity also affects the dispersion uniformity of the anti-aging assistant and the drip aid.
1.4 The oxidation induction period of the resin is longer. The oxidation induction period value is a simple and quick method to evaluate the thermal aging behavior of the resin. At least a certain amount of antioxidant should be added to the resin, the main purpose is to protect the granulation from thermal aging degradation. The thermal oxidation protection of the light stabilizer during the blown film process also needs to be considered in the formulation design.
1.5 The metal ion content or the residual amount of the catalyst in the resin is preferably low.
The metal ions in the resin, such as Fe, Ti, al, etc., may be residual catalysts or foreign contamination. The high Fe ion content has a negative influence on the aging resistance of the resin, and it is desirable that the metal ions are not detected or the lower the better at the time of detection.
1.6 resin has good processability:
The indicators for characterizing workability include melting point, rheology, melt tension, film forming property, degree of plasticization, etc., and resins which are relatively easy to process and have balanced mechanical properties should be selected. When the mechanical properties, aging resistance and processability of the resin are inconsistent, it can be solved by formula adjustment and adding a small amount of processing aid such as fluoroelastomer to ensure the excellent performance of the product.
2 formula screening
The design of the product formula first requires clear requirements for use, such as the environment in which the site is used, the climate characteristics, the shed type, the type of crop, the variety and frequency of pesticide application.
A large amount of experimental verification work is required for the selection of various functional additives in the formulation. There are a few feelings for the reference of the industry:
2.1 Light stabilizers must use high-performance polymer hindered amines. And a single variety is not as good as a combination. The compounding effect of the radical scavenger and the quencher or ultraviolet absorber is obvious.
2.2 Antioxidant acts to protect the light stabilizer from thermal degradation or consumption during processing. The combination of the hindered phenol primary antioxidant and the phosphite auxiliary antioxidant is better than the single application, and the auxiliary antioxidant ratio should be higher than the primary antioxidant. Because of its reaction with hydroperoxide, the product has a synergistic effect of continuing catalytic decomposition of hydrogen peroxidation [2].
In order to resist the poor back-plate effect of the light stabilizer at high temperatures, it is a good choice to properly add an antioxidant containing a metal chelate.
2.3 For areas where halogen-containing pesticides or sulfur-containing fumigants are frequently applied, nickel salts or new light stabilizers may be considered as the main light stabilizer.
2.4 dripping agent is one of the indispensable additives in greenhouses and greenhouses in winter and spring. The flow drip must control the acid value, otherwise the reaction of the residual acid with a highly basic light stabilizer will reduce the activity of the light stabilizer.
At the same time, the carbonyl group (carboxyl group and ester group) in the dripping agent adversely affects the weather resistance, which is a problem that cannot be ignored in designing a drip-type agricultural film.
2.5 With the trend of thinning trend of agricultural film, special attention should be paid to the content of photothermal stabilizer in the unit area (volume) of agricultural film.
3 Control of processing quality
The monitoring of the processing should be strictly controlled.
3.1 Generally, the auxiliary agent and the carrier are used as a masterbatch, and then the base resin is uniformly stirred to ensure uniform mixing of the resin and the auxiliary agent.
3.2 Control points of process conditions:
Extruder temperature, speed, air volume, wind speed, traction speed, winding speed, inflation ratio, draft ratio, etc. should be kept stable and optimal.
3.3 Maintain film thickness uniformity:
The main control thickness limit deviation and thickness average deviation. In particular, the latter is crucial to the life of the agricultural film.
3.4 Storage and transportation links should not be ignored
Failure to pay attention to the arrangement, connection and protection at this stage will often lead to abandonment.
Compared with the traditional toilet cover, the Square Bidet Toilet Seat has been greatly upgraded in terms of appearance and function. Its appearance design is more modern, concise and grand, which can better match the modern bathroom decoration style.
In terms of function, the square Smart Toilet seat usually integrates a variety of intelligent functions. For example, it can be automatically cleaned and flushed, so that users do not need to manually clean, which improves the hygienic safety of use. At the same time, the square bidet toilet seat can also adjust the water temperature and water pressure, and adjust the temperature and intensity of flushing water according to the needs of users to achieve a more comfortable use experience. In addition, some advanced models of square smart toilet covers are also equipped with a warm air drying function, which can help users dry quickly after use to avoid being troubled by moisture.
In short, the square smart toilet seat is a high-end bathroom product that integrates a variety of intelligent functions. It not only improves the convenience and comfort of use, but also has the characteristics of being more environmentally friendly, energy-saving and hygienic.
Square Bidet Toilet Seat, Intelligent Toilet Seat, Square Toilet Seat, Square Heated Toilet Seat
Guangdong Fabia Intelligent Technology Co., Ltd , https://www.fabiaintelligent.com