As we all know, the pure resin properties of some polymers are not very good, most of them cannot be used directly, and need to be modified to meet the needs of products. What are the properties of modified plastics that we often talk about changed? What performance can be changed, density, transparency, hardness, processability, strength or toughness?
1. Density of modified plastics
The density of modified plastics is divided into two types, one is to reduce the density of the plastic, and the other is to increase the density of the plastic, depending on the choice of the end application. Here are the main ways to reduce the density of plastics.
Reducing the density of plastics: According to the high school formula M=ρV, that is to say, when the density of the material is reduced, the quality of the original product will also decrease on the premise that the volume of the original product remains unchanged. It is commonly used in the lightweight of automobiles and other terminals. Common methods to reduce the density of plastics include adding lightweight fillers or resins, but the reduction in density is small; the other is foaming technology, which has a wide range of weight reduction, but it is a little difficult.
2. Transparency of modified plastics
Regarding the transparency of plastics, the relationship between the lens and transparency is generally used. The transparency of plastics is related to the crystallinity of the product. By controlling the different morphological structures of the product, its transparency can be improved.
To measure the transparency of a material, there are many performance indicators that need to be considered. Commonly used indicators are: light transmittance, haze, refractive index, birefringence, dispersion and so on. A good transparency material requires excellent and balanced performance indicators above.
3. Hardness and flexibility of modified plastics
(1) Hardness
Changing the hardness of plastics is divided into surface hardness and overall hardness. Generally, hard additives are added to plastics, generally rigid inorganic fillers.
(2) flexibility
Generally, plasticizers are added to change the flexibility of plastics. The main function of plasticizers is to improve the processability of resins, that is, to reduce processing temperature and improve processing fluidity. But it can also impart flexibility to the product when added to the related resin. Resins suitable for plasticizers to improve flexibility include: PVC, PVDC, CPE, SBS, PA, ABS, PVA, chlorinated polyethers and so on.
4. Processing properties of modified plastics
Improving the processing performance of plastics is generally manifested in: increasing the thermal decomposition temperature of the resin; reducing the melting temperature of the resin; improving the processing fluidity of the resin; improving the melt characteristics of the resin.
5. Strength of modified plastics
The reinforcement of plastics is generally by adding reinforcing fillers and fibers. Most conventional fillers are added directly to the resin, causing a reduction in the tensile strength of the plastic. However, some special fillers added directly will not only not cause the decrease of tensile strength, but will increase the tensile strength to a certain extent. We call such fillers as reinforcing fillers. The reinforcement and modification of the reinforcing filler is far less than that of the reinforcing fiber, and can only be used in some occasions where the strength requirements are not too high. The plastic fiber reinforcement method is the most common and effective reinforcement method.
6. The toughness of modified plastics
The toughening of plastics is generally by blending elastomer materials to enhance the toughness of plastics. Commonly used elastomer toughening materials are: high impact resins, such as CPE, MBS, EVA, modified petroleum resin (MPR), etc.; high impact rubbers, such as ethylene propylene rubber (EPR), ethylene propylene diene monomer(EPDM) , nitrile butadiene rubber (NBR), styrene butadiene rubber, natural rubber, butadiene rubber, neoprene, etc.
7. Thermal properties of modified plastics
The thermal properties of modified plastics that affect the use of plastic products are mainly heat-resistant temperature and low-temperature resistance. The heat resistance temperature can be mainly expressed by heat distortion temperature, Martin heat resistance temperature and Vicat softening point; and low temperature resistance can generally be expressed by embrittlement temperature.
Among all fillers, in addition to organic fillers, most inorganic mineral fillers can significantly increase the heat resistance temperature of plastics. Commonly used heat-resistant fillers are: calcium carbonate, talc, wollastonite, mica, calcined clay, bauxite, asbestos and so on.
In addition, the effect of plastic reinforcement to change the heat resistance is better than that of filling, mainly because the heat resistance temperature of most fibers is very high, and the melting point is mostly more than 1500 degrees Celsius. Commonly used heat-resistant fibers are: asbestos fibers, glass fibers, carbon fibers, whiskers, polyamide fibers, acrylic fibers and so on.
8. Flame retardant properties of modified plastics
Most plastics are flammable, and their flame retardant properties are not very good, so flame retardants are added to some formulas. Generally, flame retardants can increase the ignition point of plastics or inhibit the spread of flames.
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