Prospects for the future development of filled modified plastics
Adding inorganic mineral powder such as calcium carbonate to the matrix resin plays a three-fold role of increasing, improving performance and increasing function, and is called filling modification of plastic. In the case where the use performance is satisfied, the more powder used, the greater the effect of cost reduction. From the perspective of reducing the amount of synthetic resin used in petroleum-based raw materials, the contribution to society is greater. As China's economic development enters the "new normal" and changes in economic growth patterns, the industry has put forward more new requirements for filling modified plastics. Overall, lightweight, functional and ecological are the future direction of the industry.
Lightweight
Since the density of the inorganic mineral powder is higher than the density of the polymer resin (a difference of 2-3 times), the density of the filled plastic material is also significantly increased by the addition of the powder. The material per unit weight is smaller than the pure resin. Therefore, when the price is calculated based on the number, length and area, the loss due to the reduction of these factors is often greater than the use of cheap powder filler. Benefits. In addition, weight gain also brings about problems such as increased transportation costs and labor intensity. However, relevant research has found that through the innovation of raw and auxiliary materials and process equipment, the “weight gain problem†can be solved to a certain extent.
Stretching process
After the polypropylene (PP) flat yarn is uniaxially stretched by nearly six times, the calcium carbonate powder particles are dispersed in the void formed by the pulling of the PP macromolecule, so that the length of the flat yarn of the same weight is not obvious. The change, therefore, the problem of weight gain of high-power uniaxially stretched articles is not obvious.
The blow molded plastic film is subjected to biaxial stretching during processing, and the stretching ratio varies depending on the raw materials, but is generally 2 to 3 times. Therefore, the density of the blown film is much smaller than that of an injection molded plastic material to which the same amount of powder is added.
The test results also show that even if it is injection molding, if the injection pressure and holding time can be mastered, the material density of the injection molding products can reach 3-4% change in the same formulation and processing equipment.
Microporous structure
The molecules of polyethylene (PE) are crosslinked to form a sufficiently strong cell wall, and the gas is sealed to form a microporous plastic, so that the density of the plastic material is reduced in the presence of the crosslinking agent.
Both polyvinyl chloride (PVC) and polystyrene (PS) are capable of forming a cell wall of sufficient strength, so that a foaming process does not require the use of a crosslinking agent.
Microfoaming
A foamed PE plastic can be obtained by using a crosslinking agent, but the odor is large and the crosslinked plastic is not suitable for recycling. Invented by Wuhan Linghui Polymer Materials Co., Ltd., without using any cross-linking agent, the density of HDPE sheets with 30% heavy calcium is reduced by more than 10% compared with the same proportion of comparative sheets. Among the products of HDPE sheet, it is a major breakthrough in lightweight technology.
Lightweight filler
After the microporous calcium silicate is made into a masterbatch, it is added to the HDPE resin in the same proportion as the calcium carbonate masterbatch to make a sheet. The density of the product is obviously different, and the density of the microporous calcium silicate micro-material filled HDPE is differently added. There were more than 10% declines, and there was no significant difference in performance.
Whisker calcium carbonate
According to the experience of using whisker calcium carbonate in rubber materials, Zhao Xuehua has treated the specially prepared whisker calcium carbonate and mixed it with the base plastic. It has been found that it can be filled without affecting the performance of the plastic material. The density of plastics has decreased. At the same time, the nano-scale micropores also help to undergo elastic deformation under external force, absorb impact energy, and help the filled plastic to maintain good impact resistance. Taking Φ110mm PVC double-wall corrugated pipe as an example, in the original formula, the specially treated whisker calcium carbonate is used instead of the equivalent amount of chlorinated polyethylene (CPE) impact modifier, and the properties of the extruded pipe are shown in Table 1. .
The test results show that the performance of the pipe is still good after replacing the CPE impact modifier with the specially treated whisker calcium carbonate; the material density of the pipe wall of the CPE is replaced compared with the material density of the pipe wall of the original formula. Decrease, about 0.5~1%; in addition, in order to achieve the same meter weight of different formula pipes, the three pipes replaced by CPE need to be accelerated when forming, which means the time required to produce the same weight of pipe Reduced, production efficiency is improved.
Functionalization and ecologicalization
Functionalization means that the polymer material has properties that are not possessed by adding fillers and corresponding auxiliaries, such as flame retardancy, antistatic property, magnetic properties, barrier properties, etc.; ecologicalization means maintaining during filling plastic processing. Environmental protection, energy saving, and consumption reduction. These two trends are now becoming more and more obvious in the field of filled modified plastics.
Slow release and heat preservation of microporous calcium silicate
The important function of functional agricultural greenhouse film is no dripping and heat preservation. The dripping agent currently produced in China can be dripped in the agricultural film, but the time is shorter than the life of the film. The main reason is that the used dripping agent has poor compatibility with PE molecules, and migrates from the film center. It is necessary to exert a droplet on the surface of the membrane, but the migration is too fast and the consumption is fast, so that the action of the droplets cannot be synchronized with the service life of the membrane.
Microporous calcium silicate dense micropores can adsorb dripping agent, delay the migration time to the surface of the film, achieve sustained release, and prolong the time of action of the dripping agent.
Related tests have shown that the presence of talc powder in the agricultural film with talc powder, the better the infrared barrier property of the film at night, the weaker the ability of heat to radiate through the film through infrared radiation, so the heat is retained in the plastic greenhouse. . Microporous calcium silicate has a similar infrared blocking effect as talc powder in the form of a slow release agent for dripping agent, and becomes a heat insulating agent for agricultural greenhouse film, and its heat preservation effect is better than talc powder.
Microporous calcium silicate high adsorption environmentally friendly masterbatch
The microporous calcium silicate dense, nano-scale microporous structure can be used to make an environmentally friendly masterbatch that adsorbs odor or harmful gases. The related research results show that the calcium silicate masterbatch has obvious adsorption effect on formaldehyde, and the adsorption amount reaches 2.7% in 24 hours, while the calcium carbonate masterbatch and barium sulfate masterbatch do not have the ability to adsorb formaldehyde.
In addition, when the SY320-720 type 2mm thick plastic sheet is produced using the microporous calcium silicate masterbatch, the extrusion die is used when the calcium carbonate masterbatch is used in the extrusion molding of HDPE: masterbatch = 60:40 ratio. There is smoke and taste, and when it is replaced by microporous calcium silicate, the smoke and odor at the die disappear, and the surface gloss of the plate is good, and the coloring performance is more excellent.
At this time, not only the density of the sheet decreased from 1.28 g/cm3 to 1.12%, but also the mechanical properties were better, achieving a triple modification effect of weight reduction, functionalization, and ecologicalization.
High-efficiency energy-saving effect of powder surface activation equipment
The surface of inorganic mineral powders such as calcium carbonate and talc may be changed from hydrophilic to lipophilic by organic treatment. The most commonly used activation equipment for many years is the high-speed mixer, but the high-speed and large-load rotation of the blade consumes a high amount of electric energy, and it is intermittent operation. When the material is fed and discharged, even when the additive is added midway, the dust is raised. The operating environment is very bad.
For this reason, equipment manufacturers have upgraded high-speed mixers, added dust removal facilities, and changed the masterbatch processing technology. The dust problem was basically solved. Some enterprises have successfully processed continuous processing equipment to solve the problem of intermittent operation of high-mixing machines, but the energy consumption of powder processing has not fundamentally changed, especially the activation degree is not guaranteed.
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