Choose the Right Moulding Plastic for Injection Molded Products

plastic injection molding, product development

In product structure design, the choice of plastic material has a very important impact on the product. Due to the wide variety of plastic materials, there are different requirements for the selection of different types of products. For the design of plastic products, it is necessary to fully consider the occasions where the products are used and the working environment, such as meeting temperature requirements, light transmittance, and fire rating requirements. This article describes the main injection moulding materials and the selection of suitable plastic materials according to design requirements.
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What Is Injection Moulding Plastic?

The moulding plastic is a kind of polymer (polymer), also known as macromolecule or macromolecule, also commonly known as plastic or resin. It can be plasticized and formed under certain conditions, and the product can keep the shape of the material in the end.

Classification of Moulding Plastics

General plastic raw materials: ABS PP PVC ADPOLY AS (SAN) CA CAB EAA EVA GPPS HDPE HIPS LDPE LLDPE MBS MS MVLDPE (metallocene).

Engineering plastic raw materials: COC K(Q) glue LCP PA/ABS PA46 PA6 PA6/66 PA612 PA66 PBT PC PC/ABS PC/PBT PC/PET PEEK PEI PET PETG PMMA POM PPA PPE PPO PPS.

Thermoplastic elastomer raw materials: CPE POE SBR SBS SEBS SIS TPE TPEE TPO TPR TPSIV TPU TPV TPX.
Thermoplastic material is what we commonly use as PP/ABS/PC material. In contrast to thermoset materials, it is repeatedly fusible. Except for the raw material before the first melting, the subsequent melting is called the recycled material, and in some places, it is also called the nozzle material. The term nozzle material, as the name suggests, is the part of the nozzle that is cut off after the product comes out. Melting these and some unqualified products together and taking them for re-molding can achieve the purpose of reducing the cost of injection molding.

Thermosetting plastic raw materials: EP PU bakelite powder electric jade powder.
Thermosetting materials refer to materials that are fusible before molding, but become infusible after molding and curing. Typical representatives are epoxy resin EP, phenolic resin PF, etc. PF, also known as bakelite, is mainly used in high temperature environments, such as bakeware handles.

The Most Commonly Used Moulding Plastic PP\ABS\PC

PP

Plastic raw material PP, chemical name: polypropylene, is a copolymer of propylene and ethylene. The density is small, the appearance of the raw material is transparent and light, non-toxic and tasteless, and the strength and elasticity are very high.

PP performance characteristics:

  • Polypropylene is another excellent resin variety developed after nylon. It is a linear polymer with high density, no side chain and high crystallinity, and has excellent comprehensive properties.
  • White, translucent and waxy when unpigmented, lighter than polyethylene. The transparency is also better than that of polyethylene, and it is harder than polyethylene.
  • The material properties have low density, strength, stiffness, hardness and heat resistance are better than low-pressure polyethylene, which can be used at about 100 degrees. It has good electrical properties and high-frequency insulation, which is not affected by humidity, but becomes brittle at low temperature and does not It is resistant to mold and easy to age. It is suitable for making general mechanical parts, corrosion-resistant parts and insulating parts.

PP main application scope: Auto parts, office supplies, injection molding supplies, electrical enclosures, transformer insulation materials etc.
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ABS

The plastic raw material ABS is synthesized from three chemical monomers of acrylonitrile, butadiene and styrene, also known as ABS resin, so it has the common properties of these three substances.

ABS performance characteristics:

  • ABS plastic has good impact strength and surface hardness within a certain temperature range, good dimensional stability, certain chemical resistance and good electrical insulation.
  • It is opaque, generally light ivory color, and can be made into any other color products with high gloss by coloring. The surface of the electroplating grade can be decorated by electroplating and vacuum coating.
  • General-purpose ABS is impermeable to water, burns slowly, softens when burning, the flame is yellow, has black smoke, and finally burns, has a special smell, but does not melt and drip, and can be processed by injection, extrusion and vacuum molding methods.

The main application scope of ABS: Auto industry parts, office equipment housings, air conditioner housings, telephone housings, typewriter keyboards, etc.
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PC

PC plastic raw material is commonly known as polycarbonate, its English name is Polycarbonate, referred to as PC. It is a general term for a type of polymer compound containing carbonate structure in the molecular chain and various materials based on it.

PC performance characteristics:

  • PC plastic raw material It is a new type of thermoplastic with a transparency of 90% and is known as a transparent metal.
  • It is rigid and tough, with high impact strength, high dimensional stability and a wide range of operating temperatures, good electrical insulation properties, heat resistance and non-toxicity. It can be extruded through injection and PC plastic materials. out of shape.
  • The thermal performance of PC plastic is excellent, it can be used for a long time between -100°C and 130°C, and the embrittlement temperature is below -100°C.

The main application scope of PC: Commonly used in transparent lenses, medical equipment, stationery, coffee pot appearance, watch case, etc.
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More Molding Plastic Materials PA/POM/PMMA/PBT

PA

PA is commonly known as nylon. High mechanical strength, good toughness, high heat resistance, and small friction coefficient lead to excellent friction resistance. In addition, it has better insulating properties. The disadvantage is that the water absorption is very large, and the dimensional stability and electrical insulation performance will be affected after water absorption. It is often used to make gears, rollers and other parts with frequent friction. At present, there are few parts that use PA alone, and glass fiber is often added to cooperate with them. The commonly used ones are PA6 and PA66. Mainly used in cables, pipes, gears, mechanical parts, etc.

POM

Because of its excellent mechanical properties, POM is very close to metal, so it is commonly known as “Saigang” or “Super Steel”. It is also one of the wear-resistant materials, which is quite similar to PA. In addition, POM has good dimensional stability, high stiffness and strength, and good electrical insulation and is not very affected by temperature and humidity, which is just the opposite of PA. Mainly used for machining and welding.

PMMA

Commonly known as “plexiglass” or “acrylic”. It has super transparency, mechanical strength and insulation, and has strong aging resistance. That is, the hardness of the surface is relatively low, which makes it easy to scratch. Mainly used for decorative parts with high load capacity.

PBT

High mechanical strength, good fatigue resistance and dimensional stability, and strong aging resistance. Excellent electrical properties and low water absorption make it possible to maintain good electrical properties in a certain humidity environment. The disadvantage is that it is brittle and easy to crack. In addition, its heat resistance is high, and the heat resistance will be further enhanced after adding 30GF, and it is often used to make parts in contact with heating elements.

Moulding Plastic Selection for Injection Products

Injection molding raw materials not only need to meet the use requirements of injection molded parts but even the design of the mold is dominated by the inherent properties of the raw materials. For example, when designing the mold, the fluidity, molding shrinkage, and operating temperature of the plastic melt must be considered.

General principles of raw material selection

  • Learn more about the working environment of plastic parts. Any plastic part has its working environment, and these environmental conditions are critical to the selection of raw materials for plastic parts. It is necessary to find out how high and low temperature the plastic part has to withstand, whether the working place is indoor or outdoor, what force is to be subjected to when working, what medium is affected when working, voltage, frequency and temperature in the electrical environment, etc. . Then according to the environmental conditions that the plastic parts may encounter, find the raw material varieties that meet the environmental conditions.
  • The processing technology is good. Different varieties of raw materials, different processing technology, like PA and PSF of engineering plastics, in terms of technology, PA is much better than PSF.
  • Low price. In the case of meeting the requirements of use, the one with the lowest price should be selected. For example, when the working environment is 150°C, PSF can be used to meet the requirements, instead of PPSU with better performance and higher price.

Precautions when selecting raw materials

  • The linear expansion coefficient of plastic is generally larger than that of metal, and some are easy to absorb water, so the size changes greatly. In the mold design, the gap and tolerance must be considered according to the selected plastic variety.
  • Various plastics have a certain range of use strength and allowable media, which should be considered when selecting.
  • Some plastics, such as PC, PS, etc., have a stress cracking phenomenon. During design and injection, stress should be minimized, and stress concentration should be avoided during design.
  • The thermal conductivity of plastics is generally low, and this must be fully considered when selecting and designing cooling systems.
  • Some plastics have a tendency to creep and post-shrinkage, or deformation, and should be fully paid attention to when selecting and designing.

Custom Moulding Plastic Products

Sungmould is mainly engaged in injection molding processing, plastic product development and mold making. We have a series of modern production and processing equipment such as injection moulding, plastic mold building, and assembly. Our company provides customers with OEM services from product design, mold building, plastic injection moulding, etc.

Plastic materials such as ABS/PP/PC/PE/PMMA/POM can be injected.
Color matching can be made according to customer needs.
The range of products that can be produced: housing accessories for household appliances, engineering products, daily necessities, plastic parts for vehicles, plastic parts for sports equipment, plastic products for medical and restaurant use, plastic toys, etc.
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If you have plans for a new custom plastic product, contact us for a free quote and project evaluation:

  • Please provide 3D drawings (STP, STEP, IGS format), if you have samples, please send them to us.
  • The exact size/weight/material of the product, specific process requirements, and surface requirements (surface requirements include: textured surface/ordinary glossy surface/high glossy surface/oil injection/screen printing, etc.).
  • The amount of products (monthly output and total output) in order to determine the mold structure and material.
About Sungmould

About Sungmould

Sungmould is a plastic product manufacturer with rich experience in injection molding. According to the different product development requirements, we flexibly adjust the manufacturing process to achieve high quality, high efficiency and more economical.

We offer a variety of manufacturing services: Rapid Prototyping, Tool Making, Injection Molding, Product Design and Development, CNC Machining and Metal Stamping. You can choose from a variety of plastics, silicone rubber, or metal for your product. Regardless of mass production or small batch customization, sungmould has always been committed to providing assured, efficient and more economical one-stop processing services for your projects.

Contact us for a free quote and project review.

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