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3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems
http://www.pumpsandsystems.com/pumps/march-2015-customized-compounding-boosts-resilience-harsh-conditions 1/3
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Written by: Dr. Joel Bell & Will Taber (RTP Company)
Published: March 26, 2015
Pump manufacturers have a long, successful history of working with metals
and are familiar with the beneficial properties they deliver in a variety of
pumping applications. Similarly, the pump industry has been using
thermoplastics in pump designs for several decades because of their low
cost, light weight, superior chemical resistance, manufacturability and other
valuable—and profitable—advantages.
While unmodified thermoplastic resins have many inherent benefits, they
also pose many limitations for pump applications if used in an unmodified form. Chief among these
limitations are strength, impact, wear resistance and flame-retardant properties that can often fall short of
those same properties in metals.
Despite these setbacks, manufacturers have a broad range of options for enhancing the properties of
unmodified resins. Compounders can add combinations of reinforcing fibers, fillers and additives to a
carefully selected base resin to create a high-performance compound with a host of distinct properties
instilled into a single material. Many manufacturers are frequently surprised at the diversity of properties
that can be readily built into a compound—including flame retardancy, impact resistance, strength, wear
and friction resistance, conductivity, temperature resistance, chemical resistance, corrosion resistance and
colorability—to deliver the exact performance criteria that they have specified.
Developing the Right FormulationThe job of the compounder is to first understand the pump application and its challenges and then consider
the wide variety of base resins, reinforcing fibers, fillers and additives in its portfolio to develop the optimum
formulation. Experienced compounders can begin with lower cost base resins such as polypropylene for
less demanding applications, higher-temperature resins such as polyphenylene sulfide (PPS) and
polyetheretherketone (PEEK) for more demanding thermal and wear requirements, or fluoropolymers such
as polyvinylidene fluoride (PVDF) and ethylene tetrafluoroethylene (ETFE) for extreme chemical
resistance.
From this base resin, the compounder works to create the composite using a combination of reinforcing
fibers, fillers and additives such as long glass fiber to increase mechanical properties or the internal
lubricant polytetrafluoroethylene (PTFE) for reduced wear and friction. Other options include aramid fibers,
graphite or ceramic powders for improved wear resistance, halogenated or non-halogenated flame-
retardant additives, conductive carbon fiber, and pigments and dyes for custom color options.
Depending on the challenges presented by the application, some of these formulations may be created
from scratch with no base resin in mind, while others may begin with previously developed resin/additive
combinations.
During the development stage, manufacturers often continually request additional properties. For example,
they may begin by requesting that strength be added to the compound. Later, they may ask for a flame
retardant and finish off by requesting that the compound be made the company's corporate color. An
experienced compounder is often able to accommodate these requests, but compounding technology
requires balance and compromise of ingredients and properties. Sometimes, when one performance
criteria is added, issues may arise with others. For example, imparting conductive properties may result in
reduction of overall strength or impact resistance for which the formulation must compensate. A skilled
compounder understands how different constituents of the formulation interact, as well as their advantages
Reinforcing additives combined with a carefully selected base resincan create a high-performance compound for any application.
Customized Compounding Boosts Resiliencein Harsh Conditions
Pump Ed 101
Pump Repair
HI Pump FAQs
3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems
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Info for editorial submissions
Info to keep your pumps running smoothly
Tags: March 2015 Harsh Conditions compounding thermoplastic additives
compound strength ATEX RTP Company Joel Bell Will Taber
and limitations.
Maximizing Compound Strength
Compounders use a variety of reinforcing fibers, including short glass fiber, carbon fiber and very longglass fiber, to achieve maximum strength and other specific properties. The manner in which these fibersare introduced into the melt stream and the sizing chemistry used on the fiber are key considerations whenstriving to maximize material strength.
As an example, a manufacturer was looking to convert components of a fluid-handling pump that moveswaste products at up to 155 gallons per minute (gpm) from metal to a thermoplastic. Polypropylene wasconsidered because its weight savings were projected at 20 to 50 percent and the manufacturing processwas relatively quick and easy. Because of the inherent properties of polypropylene, the manufacturerachieved excellent chemical resistance but was unable to obtain the required level of tensile strength.
After carefully analyzing the application, the compounder selected a 40 percent long glass fiber reinforcedpolypropylene, with a 17,500 pounds per square inch (121 megapascal) tensile strength and 5.0 foot-pounds per inch (267 joule/meter) notched izod impact strength that met all structural and impactrequirements of the application. The long glass fiber reinforcement, with its unique balance of strength andimpact properties, allowed the manufacturer to benefit from the use of a thermoplastic compound, ascenario that otherwise would have been impossible because of the inherent strength deficit of thepolypropylene alone.
Incorporating Superior Wear Resistance
Another property of enormous consequence to pump manufacturers is wear and abrasion resistance.Despite the large number of moving parts, pumps must provide a long useful life with minimal downtimewhile maintaining effective operation in corrosive, high-temperature and other inhospitable environments.
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3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems
http://www.pumpsandsystems.com/pumps/march-2015-customized-compounding-boosts-resilience-harsh-conditions?page=2 1/3
MORE PUMP INDUSTRY NEWS »
& Pumps) مضخاتت ووأأنظظمة االشررقق ااألووسطط ووشمالل أأفرريیقيیاSystems MENA) تفتتح مكتبب أألمبيیعاتت ااألووررووبيMar 24, 2015
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Written by: Dr. Joel Bell & Will Taber (RTP Company)
Published: March 26, 2015
To incorporate wear resistance, the compounder can select an additive
technology, such as PTFE, perfluoropolyether (PFPE), silicone, carbon and
aramid fibers, graphite and molybdenum disulfide. As illustrated in Figure 1,
wear resistance (per American Society for Testing and Materials D3702)
can be improved in inherently wear-resistant materials such as nylon 6/6
and acetal (POM) by incorporating PTFE alone or in combination with
PFPE.
Figure 1. Wear resistance of unmodified vs. modified materials (Graphics courtesy of RTP Company).
Another common scenario for pumps used in corrosive environments is selecting PPS—a highly chemically
resistant thermoplastic with excellent thermal stability—and building in required wear resistance with the
addition of carbon fibers used in conjunction with PTFE. This particular type of compound has been highly
successful in pump vane applications.
All fiber reinforcement, fillers and additives have some considerations, and the compounder must
understand them. For example, mating surfaces, applied loads and speeds, and operating temperatures
influence wear and friction along with the wear package used.
Compounding: A Key to ATEX SuccessATEX is a legal guideline based on two European Union directives that describe what equipment and
protective systems are allowed in an environment with a potentially explosive atmosphere. Derived from
the French title of the 94/9/EC directive Appareils destinés à être utilisés en ATmosphères Explosives,
ATEX is a concern for thousands of manufacturers worldwide. Often, it is a race to meet stringent
conductivity standards so that products can continue to be used in mines and other potentially explosive
environments. Ironically, these are many of the same environments where the light weighting, strength and
corrosion resistance provided by thermoplastic compounds have become so valuable (see Figure 2).
To maintain the use of thermoplastics in these applications, manufacturers can work with compounders to
find the appropriate conductive technology from possibilities such as carbon fibers, carbon nanotubes,
Reinforcing additives combined with a carefully selected base resincan create a high-performance compound for any application.
Customized Compounding Boosts Resiliencein Harsh Conditions
Pump Ed 101
Pump Repair
HI Pump FAQs
3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems
http://www.pumpsandsystems.com/pumps/march-2015-customized-compounding-boosts-resilience-harsh-conditions?page=2 2/3
Figure 2. Centrifugal pump impeller utilizing PPSwith carbon fiber and PTFE for maximum strength
and wear resistance
Figure 3. ATEX-compliant pump utilizing aconductive PP with glass fiber reinforcement
Author Bio:
Dr. Joel Bell is the international technology manager for RTP Company in Winona, Minnesota. He holds a
Doctor of Philosophy in materials science engineering from the University of Minnesota-Twin Cities. He
may be reached at [email protected] or 507-454-6900.
Will Taber is industrial market manager for RTP Company in Winona, Minnesota. He holds a bachelor\'92s
in plastics engineering technology from Pittsburg State University and an MBA in finance from the
University of Kansas. He may be reached at [email protected] or 507-454-6900.
Tags: March 2015 Harsh Conditions compounding thermoplastic additives
compound strength ATEX RTP Company Joel Bell Will Taber
inherently conductive polymers and carbon black.
Some of these impact the strength of
thermoplastics, so the compounder must create the
right formula to maintain all the properties required
by the application. The compounder also needs to
understand that ATEX compliance might require a
combination of several other properties, such as
flame retardancy, impact resistance and thermal
resistance—most of which are well within reach of
compounded thermoplastics.
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