How to select the hottest plastic products

2022-08-26
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How to select plastic products

select materials according to the scope of application of plastics

(1) plastic for manufacturing containers, shells, covers, and conduits

such products are generally not required to bear a large load, but they are required to have good or even excellent impact strength and hardness, good or moderate tensile strength and dimensional stability, as well as good appearance and environmental resistance, and the material price is required to be moderate. Special consideration shall be given to other special performance requirements. If it is made of metal, it is generally made of steel plate, section steel, cast aluminum or punching aluminum, light alloy or die-casting metal. These materials have high strength and stiffness. However, plastic is more suitable when the following conditions and requirements are met

a. resonance must be prevented and sound transmission must be small

b. certain elastic deformation is required to prevent dents caused by accidental collision

c. the mechanism of macro-control and market regulation of product shape is complex, and it is difficult to produce with metal processing technology

d. products do not want post-processing

e. the products are required to be electrically insulated (or partially insulated) and insulated as a whole, or colored as a whole, or transparent and translucent

f. it is required to be corrosion-resistant, moisture-resistant and rust free

considering the above characteristics, the more suitable materials are shown in the table (to be supplemented). Sometimes, a material cannot meet the requirements, and it often needs to be compounded with plastic and other materials. For example, it needs to control creep or flexural deformation or is particularly wear-resistant and time-consuming. Metal inserts with threads can be embedded in plastic parts. If the structural shell is required to withstand collision and rough use, composite plates of metal and plastic or composite plastics on the metal surface can be considered

(2) plastics for low friction applications

materials required for such applications need to have low friction coefficient, low friction coefficient even without lubrication, good wear resistance, and moderate to good shape stability, heat resistance and corrosion resistance. In the past, copper antimony tin alloy, bronze, cast iron, pre lubricated wood, graphite, etc. were used. However, plastic is more suitable when the following conditions and requirements are met

a. corrosion or abrasion

b. during processing, the lubricant will pollute the product

c. components must work at a temperature higher or lower than the applicable temperature of ordinary lubricants

d. no maintenance operation is required

e. complex lubrication system can be avoided by using plastic

f. when weight reduction is urgently required

g. electrical insulation is required

h. it is required to reduce the sound and noise

i. it is required to minimize scratches and nicks

j. the system will extrude ordinary lubricants under high load and low speed operation

k. when the slip viscosity is not appropriate

according to the above requirements, the suitable plastic as the antifriction part of the bearing is shown in the table (to be supplemented). However, when the working temperature exceeds 260 ℃ for a long time, or there is a large radial load and thrust load, or continuous high-speed operation is required, and the deflection of the shaft is required to be very small for a long time, or the wear of the shaft is required to precede the wear of the bearing, other materials should be considered. Sometimes (especially in the following cases), the combination of plastic and other materials can be considered, such as: A. heat needs to be dissipated as soon as possible, B. minimal creep is required; c. Plastic alone can't bear too much load, and so on

(3) materials used as heavy stress mechanical parts (such as gears, cams, racks, couplings, rollers, etc.)

such applications require high mechanical strength of materials, especially high bending, tensile and impact strength, good fatigue resistance and stability at elevated temperature, good machinability, dimensional stability, and molding precision tolerance products. In the past, cast iron, steel, brass, etc. were used, but when the following situations and requirements were met, it was more appropriate to consider using plastic

a. urgent weight reduction

b. there is much sand and dust in the use environment, with abrasion and corrosion

c. minimize sound or vibration

d. hope to have comprehensive efficiency

according to the above requirements, the more suitable plastics are shown in the table (to be supplemented). However, if it is required to bear heavy load, high working temperature, and the urgent need to reduce material costs. Other materials should be considered. If high impact resistance, bending resistance and low cost are required, structural composites composed of plastic and other materials (such as metal) can be considered

(4) plastics and heat-resistant plastics used as chemical equipment

such applications require materials to be resistant to chemical corrosion and moisture absorption, and some also require high and low temperature resistance, with general to good mechanical strength. In the past, stainless steel, titanium, niobium and other precious metals were used. However, when encountering the following situations and requirements, it is more suitable to consider using plastic

a. special requirements for corrosion resistance, while stainless steel can not meet the requirements

b. both corrosion and wear resistance are required

c. it is urgent to reduce costs or prolong the service life of chemical equipment

d. it is required to reduce maintenance and facilitate maintenance

e. it is required to be heat insulated, heat insulated and resistant to instantaneous high temperature or ablation (for the convenience of material selection, heat-resistant plastics can also be divided into another category)

according to the above requirements, more suitable plastics are shown in the table (to be supplemented). In addition, unsaturated polyester FRP is also used for large hand pasted products; Phenolic or modified phenolic plastics are used for products that are resistant to high temperature, ablation, or heat and require high strength. However, if the required mechanical strength is not high, the working temperature exceeds 290 ℃ for a long time, and the dimensional stability is required under the condition of wide range of high and low temperature changes, new composite materials or other materials should be considered. If the working conditions require high strength and excellent corrosion resistance, or extreme corrosion resistance at elevated temperature, or the metal needs to be protected from damage by slow ablation of plastic at high temperature, composite materials composed of plastics and other materials (such as graphite, heat-resistant resin and filler, or composite materials composed of asbestos, carbon fiber, Si02 fiber, etc.) can be considered

(5) plastics used as electrical structural parts

such applications require materials to have excellent electrical insulation at low to medium frequencies, high strength and impact resistance, good fatigue resistance and heat resistance, and good dimensional stability at elevated temperatures. In the past, ceramics, glass or mica were used, but when the following situations and requirements were met, it was more appropriate to consider using plastics

a. there is impact load

b. pressing for weight reduction

c. the dimensional accuracy requirements are relatively strict, and the processing of inorganic insulating materials such as ceramics and glass cannot meet the requirements

d. it is required to manufacture products or parts with complex conductor insulator combinations (such as printed circuits, collector assemblies, potting or sealing inserts, etc.)

according to the above requirements, the more suitable plastics are shown in the table (to be supplemented). In addition, polyester (PETP, pbtp), fluoroplastics, polyphenylene oxide, polysulfone, polyimide, polyamide imide Phenol ether resin (Xylok new phenol ether resin. Poly (p-xylene) is also a good insulating material. As a general insulating material, polyethylene, polypropylene, polystyrene and polyvinyl chloride can also be used to manufacture general wire and cable insulation. Polycarbonate is used for transparent parts requiring high impact strength; casting epoxy or molding plastic can encapsulate electronic and electrical components. It is suitable for occasions requiring maximum resistance to the environment. Combined electrical components The combination of silicone rubber and epoxy can be used to obtain better performance; Molded epoxy is used for parts requiring dimensional stability in a wide temperature range; Melamine formaldehyde plastic is used for parts requiring greater hardness; Silicone polymers are used in high temperature resistant occasions; Amino plastics are used in occasions requiring low prices; Phenolic laminates are used for punching and die punching parts, etc. However, if the working temperature is very high or the compression load is very high, other materials should be considered

(6) transparent or colored translucent materials such as plastics used as transparent parts, transparent plates and models require good light transmittance, good to excellent secondary formability and molding processability, non fragile (impact resistant), and pesticide resistant light stabilizers, which can avoid premature aging and decomposition of greenhouse film, generally to good tensile strength. In the past, glass was mostly used, but it has some shortcomings, especially it can not meet the following requirements:

a. the products are required to be impact resistant, vibration resistant and not easy to break

b. it is required to have certain bendability

c. it is required to have higher specific strength to ensure that the extrusion volume is in linear relationship with the rotating speed of the gear pump

d. the material must be naturally translucent and should not be translucent through surface treatment

e. it is required to be easy to form products with complex shapes; Wait

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