When to Use thermoplastic compounds？

Plastics Compounding 101: Comparing Thermoplastic Materials

What are Thermoplastics?

In plastics, there are two general, but broad categories of polymers, thermoplastics and thermosets. A thermoplastic is a plastic polymer that is moldable at elevated temperatures and solidifies upon cooling. Thermoplastic materials can be heated to their melting point, cooled, and reheated again without significant degradation. Due to their properties, thermoplastic resins can be molded into a variety of shapes and structures, making the plastic materials applicable to many industries.

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The simplest way to differentiate thermoplastics and thermosets is to understand that thermoplastics can be melted and reused again and again, while thermosets cannot. Another way to explain this is by thinking of a cake. After all of the ingredients are mixed, and it is exposed to heat, the final result of this is a cake, but you cannot return it to cake batter by melting it down. In the same analogy, the thermoplastic material is like chocolate, as it can be melted and cooled, then re-melted and used again. 

Is Thermoplastic Material Recyclable?

Yes, thermoplastic resin is recyclable! Thermoplastics liquefy, allowing them to be easily injection molded and recycled afterward, and because they are inherently recyclable, they align well with sustainability initiatives. Thermoplastics, once recycled, can be reformulated, and since there are such a variety of applications with a range of performance requirements, there are plenty of outlets for the recycled-content. This provides an excellent material choice for companies who have sustainability initiatives based on reusing their own scrap for future molding or for programs with their own recycled products. In contrast, thermosets, such as fiberglass, cannot be re-melted, and therefore cannot be recycled.

Different Types of Thermoplastic Material

Thermoplastic material has several different types, but in this blog, we will focus on the most common engineering-grade thermoplastic resin including, polycarbonate (PC) acrylonitrile butadiene styrene (ABS), polycarbonate-ABS (PC/ABS) and other PC alloys. 

PC

Polycarbonate is a high-performance, durable (stronger than glass), material that is thermoformed with strong electrical properties. Easily molded, PC is a fairly high-temperature amorphous resin that inherently has transparent properties and good impact strength. Due to its transparency, it is colorable and easily recyclable. With the right technology, PC material can be alloyed with fiberglass, ABS, PBT, or PET compounds.

Applications: Polycarbonate thermoplastic applications include – automotive components, electronics such as CDs, DVDs and cell phones, lightweight eyeglass lenses, shatterproof windows, face shields and safety glasses. PC is also used for many electrical applications, including circuit breakers, electrical housing, lighting applications, in addition to appliances such as food mixers, refrigerators and washing machines. 

ABS

Acrylonitrile butadiene styrene is a thermoplastic resin that is made from three different monomers: acrylonitrile, butadiene and styrene. It is one of the most affordable opaque plastics, resistant to strong impacts and corrosive chemicals. ABS has strong heat resistance, is impact resistant and is also recyclable. It is easy to mold into large parts, cost-effective and is also relatively harmless since the plastic material does not have any known toxic carcinogens in it.

Applications: ABS thermoplastic is used in applications where the price versus properties of PC are lower. Some applications including auto parts, appliances, business machines such as copiers and paper shredders, consumer goods, medical equipment, pipe fittings and even toys such as LEGO pieces. 

PC/ABS

Polycarbonate/Acrylonitrile Butadiene Styrene combines two engineering materials, which is a non-homogenous resin mixture, and is specified when ABS properties are not enough value for the application. PC and ABS form one versatile compounded resin. PC/ABS process with the ease of ABS but has more toughness, similar to PC. The combined alloy of the two materials provides cost benefits, excellent physical properties, and scratch resistance. It also features a key advantage over PC, as it has low-temperature impact resistance.  

Applications: PC/ABS is a commonly used thermoplastic in electronics such as keyboards, computer and cases, housings, safety applications such as helmets and in the medical and industrial markets.

Specialty Polymers

The term Specialty Polymer doesn’t refer to one specific polymer-type, but the needs met by the material. Star Plastics employs the thermoplastics above to create custom formulated compounds to fit all of our customers’ needs—no matter how complex. Whether the need is a simple compound with a broad range of properties, or if the application requires exact specifications with specialty additives or performance and testing requirements, the Star team is highly experienced and knowledgeable to create it. 

These specialty polymer product offerings include UL-recognized Flame Retardant plastic materials and our Star PC-Siloxane Cold Temperature Impact products, which is part of the StarPrime line. As a complement to our thermoplastic material offerings, we also offer pre-consumer and post-consumer plastic compounds within our specialty UL-recognized ReStart line. No matter what unique challenge you may have, we have the capability to formulate specifically to your application performance or testing needs.

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Material Selection – The Correct Evaluation Questions to Ask 

As laid out above, there are several different thermoplastic materials to choose from, and there is also a lot of cross-over in the applications that they can be used for. With the versatility of these materials, how do you select the correct thermoplastic resin for your application?

It starts by asking the right questions. At Star, we have laid out some common questions that we find to be the most valuable in helping our customers find the perfect material match. These questions include:

• Defining the function
  • What is the function?
  • How much exposure will it have? Is the part to be used indoor or outdoor? Will it be exposed long-term outdoor?
  • Is there part-performance related stress involved in the application?
  • Are there any automotive, FDA, or NSF requirements?
  • Any regulatory needs, such as UL requirements for flammability, RoHS, or REACH?

• Identifying the physical properties
  • Physical properties as melt flow and Izod requirement, UV, RoHS/REACH, GF, etc.
• Looking at the structure of the part
  • Are there issues with the current resin being used?
  • What is the thickness/thinness of the walls?
  • Where is the gate located?
• Temperature
  • What processing temperatures are currently being used to run machines?
• Pricing
  • There is always a cost-benefit analysis.

Asking the right questions helps to save time and money, as it leads you to the perfect thermoplastic resin faster. Have a more complex need? Star Plastics also sources and supplies specialty thermoplastic polymers. Whatever your needs are, our friendly team is on hand to get your project started.

How Star Plastics can help

When you need thermoplastic resin, you can trust Star Plastics to deliver, every time. To date, Star has over a 99% on-time delivery rate for . With 32 years in business and three locations in North America and Asia, including shipping to Mexico and Europe, we deliver faster than market lead-times. Specializing in custom polymer compounding services, we offer alloys, polycarbonates, ABS, PC/ABS, ASA, HIPS, PC/PBT, polycarbonate alloys, commodity resins, and much more in any color needed.

A Basic Introduction to Formulating Thermoplastic Compounds.

In order to achieve the right aesthetics and mechanical performance for any plastic article it’s important to design the most cost- effective formula.
The first task is to choose the most suitable polymer for the application. The properties of Thermoplastics can be very diverse, and pricing can vary tremendously, especially for some of the more exotic high-performance polymers.

Thermoplastics can generally be classified into three groups, Commodity grades, Engineering grades and High-Performance grades.

Commodity grades- Are thermoplastics made in vast quantities for applications where exceptional mechanical properties are not generally required. E.g., Milk bottles, Food Packaging, Carrier bags, Household products etc. Costs for these types of polymers are generally cheaper when compared to engineering plastics and high-performance grades.

Polyethylene, Polypropylene, PVC, Polyethylene Terephthalate(PET) and Polystyrene are some good examples of commodity grades.

Engineering grades- The mechanical properties of these types of thermoplastics are generally superior to commodity grades. Certain grades can handle heat and stress well, when in use, and because of their high mechanical strength can often be used as metal replacements. The Automotive, Aerospace, Building Construction and Electronics industries all benefit from the use of these types of polymers.

Acrylonitrile Butadiene Styrene (ABS), Polycarbonate, Polyamides (Nylon) are some of the more common engineering grades.

High-Performance grades- Thermoplastics that fall into this group have a variety of exceptional properties. Their ability to withstand high temperatures, chemical attack and their excellent mechanical strength make them ideal candidates for use within the Aerospace, Automotive and Electronics industries. Some good examples of high- performance grades are Poly Ether Ketone (PEEK), Polysulfone (PSU), and Polyphenylene Sulfide (PPS)

When the polymer with the most suitable properties has been selected for the end article, further modifications can be made during a compounding process. This often involves the addition of colourants and or additives and fillers to achieve the desired look and finished product properties.

When it comes to colouring thermoplastics compounds, care must be taken to ensure the colourants selected for the formula, are compatible with the chosen polymer, and that their properties such as heat stability, light and weather fastness are all at the desired level to suit the end application.

Performance enhancing additives can also be compounded into the polymer of choice to further enhance their outdoor UV performance, Antistatic properties, Conductivity, Surface Frictional properties, Antimicrobial, Flame Retardancy, Heat Stability, etc.

Fillers are often added to thermoplastic compounds to drastically modify the mechanical/performance properties or aesthetics required for the end article. The most commonly used fillers are; Magnesium Silicate (Talc) Calcium Carbonate (Chalk) Mica, Glass fiber or beads, Aluminum Trihydrate, Magnesium Hydroxide, these last two fillers are specifically used to improve flame retardancy. The other fillers are mainly used to improve stiffness, mechanical strength, surface hardness, or change visual appearance.

Fully formulated compounds tend to be used for applications where the technical properties are paramount. They just need to be processed as supplied under the recommended processing conditions. Flame retardant compounds, Talc/Chalk/Glass filled compound and Conductive compounds are some of the most common grades supplied to the end converters.

There is another process whereby natural thermoplastic polymers can be modified and that’s by using a masterbatch. A masterbatch is a concentration of colourants, additives or a combination of both that’s added into the natural polymer during processing at a specified addition rate. Whilst this method is often cheaper than the fully compounded route, the end converter must ensure that he uses the recommended addition rate, and that their equipment is fully capable of achieving a homogenous mix. Failure to achieve this can lead to mechanical failures and inconsistencies in the colour appearance.

Polymer chemists, Plastic engineers and experienced Colour Chemists should always be consulted when designing plastic applications in order for the right solution to be reached.

Author: 

Pravin S Mistry - Global CEO of PREA Ltd and International Polymer Consultancy - Plastics, Composites, Rubber, Adhesives, Polyurethane... focuses globally on:

• Mergers & Acquisitions, buying selling companies
• Recruitment- Full time and Interim
• Interim CEO / MD
• Polymer Consultancy
   

He personally has worked for over 40 years in the industry - UK, USA, Mainland Europe, Asia... in the polymer other manufacturing industries as Divisional Managing Director and CEO for multinational companies. Early career roles include Operations Director, Technical Director, Technical Quality Manager , Chemical Engineer, Laboratory Technician.