Plastic Injection Molding : Choosing the best resin material for your project
Due to their versatility, strength and light weight characteristics, plastics are taking a larger role in the transportation, medical,construction industries and our daily life. For the mould designers, the plastic material of the part is closely relate to the type of mould steel we should use, the runner system, cooling system and ejection plan.
Here are five requirements to keep in mind when choosing your resin:
- The final part appearance including surface texture and transparency or color requirements.
- The part strength, flexibility or rigidity
- The chemical or environmental (the wind, rain, cold or heat) resistance
- Regulatory requirements that need to be met including FDA, RoHS, REACH and NSF
- The life expectancy of the part
A plastics primer – thermoset vs. thermoplastic
Plastics fall into two basic categories, thermoset plastics, and thermoplastics. To help you remember the difference, think of thermosets just as the term implies, they are “set” during processing. When these plastics are heated, it creates a chemical reaction that “sets” the part into a permanent form. The chemical reaction is not reversible, so parts made with thermosets can’t be re-melted or reshaped. These materials can be a recycling challenge unless a bio-based polymer is used.
Thermoplastics are heated then cooled in a mold to form a part. Once the parts are cooled, they revert to their original state and can be re-melted and cooled again. For this reason, thermoplastics are easier to reuse and recycle. They comprise the majority of the manufactured polymer resins on the market today and are used in the injection molding process.
In a word, Once the thermoset plastic is shaped, it can not be soften again. On the other words, it is unrecyclable. Thermoplastic can be remelted and reused for several times.
Fine tuning the resin selection
Thermoplastics are categorized by family and type. They fall into three main categories; commodity resins,engineering resins, and specialty or high-performance resins. The high-performance resins also come with a higher cost. That is why commodity plastic resins are often used for many everyday applications. Commodity resins are easy to process and are inexpensive. They are often found in standard mass produced items like packaging.Engineering resins are more expensive but offer better strength and resistance to chemicals and environmental exposure.
Within each of these families, some resins have different morphology. Morphology describes the arrangement of molecules in a resin and fall into two categories, amorphous and semi-crystalline. Amorphous resins have the following characteristics: they shrink less when cooled, offer better transparency, work well for tight-tolerance applications, tend to be brittle and lack chemical resistance. Semi-crystalline resins have the following characteristics: tend to be opaque, offer excellent abrasion and chemical resistance, are less brittle and have higher shrinkage rates.
The final selection
Choosing the right material for a project is one of the most important factors in creating perfect plastic parts.The advances in polymer science have contributed to the development of a large selection of resins from which to choose. It is important to work with an injection molder that has experience with a variety of resins and applications including resins that are compliant with FDA, RoHS, REACH and NSF.
Over the years, OK industry has developed strategic relationships with the best resin suppliers in the country.you can consult with us to determine the best material for a particular project. Any questions,please feel free to contact with us:firstname.lastname@example.org or click okmolding.com
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