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Ketoprix™ Polyketone Polymers - A Unique Value Proposition for demanding applications

Published Thursday, September 1, 2016

Crystalline thermoplastic resins (i.e. PA, PPS, POM, PP) generally provide better chemical resistance than do amorphous (i.e. PC, ABS, PS, PMMA) resins and Ketoprix™ polyketone is no exception to this rule. However, crystalline resins rarely exhibit resistance to attack by a broad range of chemicals, have excellent practical toughness AND good strength properties. Typically crystalline resins either exhibit good strength values or good toughness but rarely both. For example, PBT, POM, PA, PPS, and PPA exhibit good strength and stiffness but generally do not exhibit good practical toughness (impact resistance) - particularly at low temperatures. On the other hand some PE co and ter polymers do offer good practical toughness but exhibit relatively low strength and stiffness.  In this way Ketoprix™ polyketone resins offers a unique value proposition with the combination of excellent ductility (toughness) at room and sub-ambient temperatures, and high strength values as well as excellent resistance to attack by a wide range of chemicals.

When a thermoplastic part is subjected to an impact load it will dissipate the energy in one of two ways: it will deform without breaking or it will deform and crack or shatter.  The primary material property that determines which of these outcomes occurs is whether or not the imposed strain (deformation) related to the impact event exceeds the elongation at break value for the material used to produce the part.  Said another way – the higher the elongation at break value a material exhibits the more impact resistant the material.  As can be seen in table 1 below the tensile elongation at break for unreinforced grades of Ketoprix™ polyketone resins are very high for a crystalline resin with high strength values which translates into the ability of the material to dissipate high levels of impact energy without cracking or shattering.  In other words, it’s tough!

Table 1. Tensile Elongation @ break, 23C for several crystalline resins

Resin

POM

PA66, dry

GF PPS

PVDF

Ketoprix™

Tensile Elongation @ break, 23C,%

45

25

1.2

35

>350

 

Similarly, the ability of a resin to sustain numerous impact events without cracking, or repeated loading to high strain rates such as occurs with multiple snap fit assembly-disassembly cycles without failure is reflected in the tensile elongation at yield value exhibited by the resin. Simply put the greater this value, the greater the deformation the part made from the material can survive without permanent damage.  As is shown in Table 2 below, Ketoprix™ polyketone resins excel in this regard as well.

Table 2. Tensile Elongation @ yield, 23C for several crystalline resins

Resin

POM

PA66, dry

GF PPS

PVDF

Ketoprix™

Tensile Elongation @ yield, 23C,%

10

4.5

1.2

7

~25

 

Ketoprix™ polyketone resins also retain their ductility over a wide range of temperatures as is reflected in the graph below which provides tensile stress and strain values for an unfilled grade of Ketoprix™ polyketone resin at temperatures ranging from -40 C to 100 C. As is shown there the tensile elongation at yield for this resin is greater than 10% even at -40C!  For frame of reference the tensile elongation at yield for a general purpose unreinforced polycarbonate resin –which is one of the most ductile of thermoplastic resins - is in the range of 5-7% at 23C.

 

Perhaps the most commonly overlooked fundamental indications of a materials toughness is the tensile stress-strain test.  When this test is performed an axial load is applied to a standard specimen and the resultant deflection measured. When these values are plotted the area underneath this curve is proportional to the energy absorbed by the material during the test.  Accordingly, the higher the load (strength) and elongation at yield values a resin exhibits the greater the area underneath this curve will be and therefore so is the amount of energy absorbed by the material during the test. Therefore, when a material has both higher strength and elongation at yield, as does Ketoprix™ polyketone, this is an indication that the material should be able to survive high levels of impact energy without failure.  It is important to remember when reviewing tensile-stress strain data that due to the inherent viscoelastic nature of all thermoplastics the mechanical response of the material to loading is both temperature and rate dependent so whenever possible data which is collected at the temperature your applications may be exposed to will provide the most relevant insight into how the material will behave in the conditions your part will experience.

There are also a number of standardized impact tests utilized in the thermoplastics industry as a means to quantify a resins’ toughness/impact resistance.  Some of the more common are:

*Izod Impact (Notched & Un-Notched)

*Charpy Impact (Notched & Un-Notched)

*Instrumented Impact

*Tensile Impact

Perhaps the most commonly referenced test method among these is Notched Izod Impact resistance. In this test a standardized rectangular bar with a specific notch cut in the center of the sample is clamped on one end in a vise and impacted on the side of the bar opposite this notch with a weighted pendulum. The amount of energy required to fracture the bar is reflected in the distance the pendulum travels beyond the clamp where the sample is mounted.  As can be seen in table 3 below Ketoprix™ polyketone excels in this regard not only at room temperature but in sub ambient temperatures as well when compared to some other crystalline resins.

Table 3. Notched Izod Impact at 23C & -40C for several crystalline resins

Resin

POM

PA66, dry

GF PPS

PVDF

Ketoprix™ EK63

Notched Izod Impact,  J/m,23C

64

53

91

160

240

Notched Izod Impact, j/m, -40C

43

27

N/A

N/A

50

 

While it is common to find crystalline resins which offer good strength these resins are typically not very tough (ductile or impact resistant) and those crystalline resins which do offer good impact resistance typically do not offer good strength values.  As noted previously it is this combination of properties which makes Ketoprix™ polyketone resins a unique value proposition since it does afford high strength and good impact resistance as shown in Table 4 below.

Table 4. Tensile strength, elongation and Notched Izod Impact values for two grades of Ketoprix™ 

Property

Ketoprix™  EK33

Ketoprix™  EK63

Melt Flow Rate, g/10min

60

6

Tensile Strength, yield, 23C, psi

8700

9400

Tensile Elongation, yield, 23C, %

20

25

Tensile Elongation, break, 23C, %

>250

>350

Notched Izod Impact, 23C, j/m

107

240

 

Ketoprix™ polyketones exhibit another unique and valuable trait as well. As is the case with many crystalline resins they readily accept reinforcement; however, unlike what usually happens when glass fiber is added to a resin glass reinforced Ketoprix™ polyketone resins retain their good practical toughness. As a result glass reinforced grades of Ketoprix™ polyketone resins exhibit not only very high strength properties but excellent impact resistance as well. For example EKT33G3P Ketoprix™ polyketone exhibits a tensile strength of approximately 22,500 psi with a Notched Izod Impact value of approximately 2.4 ft-lb/in (128 j/m) at 23C in the dry as molded state.

Owing largely to their di-polar and semi-crystalline morphology Ketoprix™ polyketone resins exhibit excellent resistance to attack by a broad range of chemicals including:

  • Aromatic & aliphatic hydrocarbons
  • Ketones, esters & ethers
  • Inorganic Salt Solutions
  • Weak Acids & bases

There are in fact few known solvents for Ketoprix™ polyketone resins.  The structure of the resin also confers excellent permeation resistance to aliphatic and aromatic hydrocarbons. As a result the material is widely used in hydrocarbon barrier applications resins.

In addition to resistance to attack by a broad range of chemicals the carbon-carbon backbone of the resin ensures that it exhibits good hydrolytic stability with only limited affinity for moisture.  This inherent hydrolytic stability and chemical resistance is reflected in the data in table 5 below. The table provide tensile strength at yield values for Ketoprix™ EK63 polyketone resin after 25 days exposure to various aqueous environments for 25 days as compared to type 6,6 polyamide (nylon).

Table 5. Hydrolytic stability data for Polyketone & Polyamide 6,6

 

Some examples of applications where Ketoprix™ polyketone resins present an excellent value proposition as a result of this unique combination of properties are under the hood automotive connectors, fuse boxes, gears for appliances and printers, pumps & valves in the chemical processing and agricultural industries, plumbing and conveying applications as well as fuel lines, radiator end tank caps and oil/gas pipelines. 

 


To summarize, if your application requires good strength and practical toughness while being resistant to attack by a broad range of chemicals along with hydrolytic stability, Ketoprix™ polyketone resins offer an excellent value proposition.

Want to know more about Ketoprix™ polyketone resins? Have an application with which you need some assistance?   Please visit our website at www.esprixtech.com for product information or contact Mr. Dang Le at dle@esprixtech.com or +281-969-8763.