You want your new car’s gleaming interior to appear like new for as long as possible.

After all, you paid handsomely for it. So you do your best to avoid knocks and gouges

in daily use. So there’s no hiding your disappointment when, six months later, the

interior panels, consoles, and gearstick cover, appear scuffed and old.

Designers of these nylon or polycarbonate products can’t rely on hardcoating or

painting the exposed surface to avoid this marring. It’s simply too difficult and expensive.

Here’s test data on a new additive that improves surface durability of engineering thermoplastics at very low loadings, and may even improve mechanical properties.

No Hard Coating Needed

Now There’s an Additive That Improves Scratch/Mar Resistance in Molded & Extruded Parts

Processors and their customers in

automotive, electronics, and consumer-products

are looking for a way to protect plastics

against scratching and marring in storage,

transportation, and use—without the high

cost of painting or hard coating. A new additive

may be the answer.

42 DECEMBER 2016Plastics Technology PTonline.com

ADDITIVES

Automotive OEMs are not the only ones concerned with scratch

and mar performance. Many molders and extruders of thermo-

plastics in consumer products, electronics,

and interior furnish-

ings also demand

better performing resins that resist abuse and

retain their surface quality as long as possible.

Molders of such products are frustrated by the

high rate of scuffing appearing on their nylon

parts sometime between the injection molding

machine and their end-use customer. Some have

turned to a new and cost-effective approach.

TenasiTech (U.S. office in Marblehead,

Mass., tenasitech.com) has developed a new additive called

Solid-TT that when compounded into resins—usually at only 1% by

weight of the host polymer—provides significant improvements in

scratch and mar resistance without the expense of painting or hard

coating. Molded parts and extruded sheets made with

this additive can withstand rougher handling without

surface marring (see Starting Up, Jan. ’16). Here are

further technical details on this new technology.

SURFACE-TREATED CLAYSDevelopment of this additive began in the research

laboratories of The University of Queensland in

Australia. The research yielded patented organoclays

with a new type of surface treatment. The unique

organic treatment helps maximise the disassociation

of the clays when compounded into thermoplastics.

The additive is not intended to replace hard

coating. Companies that have already gone through

the expense and time required to establish a hard-

coating line are unlikely to change. But the vast

majority of plastic products in any given resin market

will never have the benefit of a high-performance

coating or painting. Not only is hard coating too

expensive for many end-uses, molded parts with

curved surfaces are notoriously difficult to hard

coat efficiently. Furthermore, extruded sheeting is

commonly thermoformed, which involves stretching

the sheet. This can mean that hard coating is not an

option, given the potential for damage to the coating.

Solid-TT is a true polymer reinforcement, not simply a lubri-

cant or other migrating additive. So there are no issues with surface

rub-off or long-term durability. Products made with the new additive

can withstand routine cleaning and maintain glossy surfaces.

The additive is compounded into resins using standard twin-

screw extrusion. The resins can then be molded or extruded as

normal. Molders say that cycle time is not increased, and only a

slight increase in injection pressure is required.

Solid-TT additive has shown significantly improved protection

against scratch or mar damage across a range of nylons of varying

viscosity and also with acrylics. The additive does not degrade the

polymers or cause significant discoloration.

Importantly, impact and drop resistance is

not impaired by the inclusion of the additive in

thermoplastics. This has been a major drawback

to previous attempts to create performance

additives for surface hardness. The additive also

does not affect the modulus of nylon 6.

When Solid-TT was added to an extrusion-

grade nylon 6, mechanical properties were

significantly better than those of the same

nylon without it. For example, there was a 41% gain in strain-at-

break for Nycoa 1637 nylon 6 with 1% Solid-TT, compared with the

nylon compounded without it. A 34% gain in toughness and 14%

gain in tensile strength were also recorded (see Fig. 2).

Thermoplastics incorporating Solid-TT have undergone

1000 hr accelerated UV aging. The plastic did not show any

additional deterioration when compared to the neat resin.

The vast majority of plastic products

in any given resin market will never

have the benefit of a high performance coating or painting.

By Richard MarshallTenasiTech

QUESTIONS ABOUT ADDITIVES?

Visit the Additives Zone.

A special surface-treated organoclay retains surface gloss of nylons and acrylic without affecting UV or chemical resistance, toughness, or modulus. It also shows promising results in polycarbonate, PET, and PVC/acrylic.

@plastechmag 43Plastics Technology

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Furthermore, the additive maintained the excellent pencil-

hardness performance after UV exposure.

Chemical resistance of the plastic is also unaffected, which is

logical given the low addition rate of this performance additive.

SCRATCH & MAR TEST PERFORMANCEScratch and mar behavior can be incredibly complex, and there is

no universally agreed-upon single test to measure performance.

Among a wide array of tests, pencil hardness is a simple, shorthand

method that can communicate across dif-

ferent polymers and is globally understood.

Other tests, such as Erichsen Scratch (ISO

4586-2) and Taber Linear Scratch (ISO

1518:2001) are commonly used for scratch

testing. For mar resistance, friction and

wiping tests such as Crockmaster are

commonly used.

No method for guarding against scratch

and mar damage will qualify according to

every scratch test. This is true even for some

hard-coating methods. The Solid-TT additive

will not provide protection against more

aggressive, gouging-type scratching. Tests

such as Taber Abrasion can be very aggres-

sive, and differentiating between polymers

containing Solid-TT can be very difficult.

It is common that the ultimate scratch or mar qualification

happens in the field. Processors or their OEM customers may have

their standard lab test as well as a required period of time that the

product must survive without exces-

sive surface damage in normal use.

Sometimes a field test is as simple

as abuse with a pair of car keys, or a

fingernail. In other cases customers

subject their end product, such as a

ski or a bottle, to a “use life” typical

for its end market.

In tests, nylon 6 with Solid-TT

improved scratch resistance by 71%,

and transparent, cycloaliphatic

nylon 12 with the additive exhibited

improved scratch resistance of 55%,

according to the turntable-type

Erichsen Scratch Test (see Fig. 1).

Mar resistance is different than

scratch resistance. It is a change

to the surface such as color, gloss,

or haze caused by friction or

rubbing, but without significant

loss of material from the surface.

Rubbing tests are a good way to measure this: In so-called

Crockmaster tests, a mechanical finger drags a standardized

textile against the plastic surface, using a consistent force, for

a predetermined number of cycles. To mimic normal use of an

automobile interior this testing can require up to 40,000 cycles

of cloth wiping. For mobile consumer devices, the number of

cycles can be 5000 to 10,000 using a textile to match clothing.

In either case, a visual assessment is made of the plastic with

and without the additive.

Solid-TT has been shown to significantly reduce the marring

when these tests have been performed on nylons and acrylics.

Similar results are expected for polycarbonates and other polymers.

There is a wide variety of tests, but Solid-TT has shown good performance in pencil hardness, Erichsen scratch, and Crockmaster mar tests.

43.5

32.5

21.5

10.5

0

Nylon 6 with Solid-TT improved scratch resistance by 71%, and transparent, cycloaliphatic nylon 12 exhibited improved scratch gains of 55%, according to the Erichsen Scratch Test.

Improved Scratch Resistance for Nylon 6 and 12

Erichsen Scratch (N) (Modified ISO 4586-2)

Nylon 6 Nylon 6 and Solid-TT

Nylon 12 and Solid-TT

Nylon 12

1.41.2

10.80.60.40.2

0

FIG 1

44 DECEMBER 2016Plastics Technology PTonline.com

ADDITIVES

BEYOND NYLONScratch performance for polycarbonates with Solid-TT has shown

pencil hardness of “H”, versus “2B” without the additive. This

opens significant potential for PC molded products and sheeting

where hard coating remains too expensive an option.

In external tests, PMMA formulated with Solid-TT showed

damage at “7H” pencil hardness, vs. “4H” without the additive.

What’s more, PET and PVC/PMMA alloys have shown very

promising improvements in anti-scratch performance with the

additive, though this work remains in development.

PVC/PMMA alloys are excellent options for sheeting in

airplane interiors, such as bulkhead partitions. They are very

tough and chemically resistant. But, like many polymers, they are

subject to scratch damage. Hard coating of PVC/PMMA sheet isn’t

an affordable option, and is unsuitable because the sheet will be

thermoformed to the final product shape.

TenasiTech has measured the scratch resistance of the PVC/

PMMA alloy sheet and seen a tripling of the force required to leave

a permanent scratch, as per the Erichsen Scratch test (Fig. 3)

When Solid-TT was added to an extrusion grade nylon 6, mechanical properties were significantly better when compared with the same nylon, which had also been compounded.

FIG 2

FIG 3

Property Boosts in Nylon 6 With Solid-TT

Nylon 6 Nylon 6 with Solid-TT (at 1% weight)

Tensile Strength

(MPa)

Toughness (MPa)

Strain (%)

400350300250200150100500

1.81.61.41.2

10.80.60.40.2

0

Improved Scratch Resistance of PVC/PMMA sheet with Solid-TT

PVC/PMMA alloys have shown very promising improvements in anti-scratch performance with the addition of Solid-TT.

ABOUT THE AUTHOR: Richard Marshall is CEO of TenasiTech Pty Ltd, headquartered in Australia. He has 22 years of experience with technology startups, venture funds, and top multinationals. He was coauthor of a book chapter on the commercialisation of nanomaterials for industrial applications, published in 2013. He has an MBA from Oxford University, with Engineering and Science undergraduate degrees from the Queensland University of Technology. Contact: (518) 572-8572; richard@tenasitech.com, tenasitech.com.

Solid-TT additive has little or no effect on molding and extrusion of nylon or acrylic compounds.

PVC/PMMA with Solid-TT (at 1%)

Erichsen Scratch (N) Modified ISO 4586-2

14% gain

34% gain

41% gain

PVC/PMMA

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