best-in-test non-phthalate plasticizers for pvc plastisols

Best-in-test non-phthalate plasticizers for PVC plastisols

PEHO-234, PETV article.indd 1 2017-04-12 14:22

In search of the best-of-the-best non-phthalate

The technical issue for flexible PVC formulations is getting the balance of properties right as plasticizers play an essential role in defining the final mechanical properties of PVC and its lifetime performance. The aim is to develop formulations that harvest the best properties and minimize or eliminate the negatives. For example, Low Molecular Weight (LMW) plasticizers tend to be more compatible with PVC, are softer, and gel or are absorbed more easily, but they are poor on vo-latility, which creates permanence, safety, and sustainability concerns. Yet High Molecular Weight (HMW) plasticizers are less volatile, have lower migration and promote a longer life but are less soft and slower to gel.

Traditionally there has been this trade-off in properties, so this article explores how the best non-phthalate plasticizers perform under test and if they can achieve the right balance in all the critical assessment areas.

Can non-phthalates live up to their promise?

Non-phthalate plasticizers can contribute to a better mechanical and chemical performance, as well as processing efficiency, safety, and sustainability. The tests were conducted using the three leading non-phthalate plasticizers –

• PETV (Pentaerythritol tetravalerate) – marketed as Pevalen™ by Perstorp

• DINCH® (Di-isononyl cyclohexane dicarboxylate) – marketed by BASF

• DOTP (Di-octyl terephthalate)* * DOTP is a terephthalate, and some consider it to be a non-phthalate thinking phthalate safety only applies to iso- and ortho- phthalates.

Best-in-test non-phthalate plasticizers for PVC plastisols

Using phthalate-free or non-phthalate plasticizers with PVC no longer has to do with overcoming the safety concerns surrounding phthalates. The new generation of general-purpose phthalate-free plasticizers is technically superior in several key areas compared to the traditional phthalate plasti-cizers. This article explores the best-of-the-best of them and why serious consideration should be given to using them in a much wider range of flexible PVC applications including coated textiles.

A plastisol start formulation was used to test 6 key areas that are highly relevant to the plastisol PVC outcome, processing and application requirements. All three non-phthalates performed well as expected, but some exceptional results were achieved.

A. MagnussonTechnical Market Development Manager PlasticizersPerstorp

*Recommended stabilizer;Baerostab 711-1 X RF, Lankrostab LZB 864Naftosafe P XX 30152 OBS +Naftolube HRP 83683Reagens CLX 759-9-SF

Ingredients Phr

PVC K-70 100

Plasticizer 50

ESBO 2-5

Stabilizer* 2-3,5


1. Hardness

Hardness is actually to do with softness, as the degree of softness is clearly paramount in flexible PVC, such as coated textiles, and in formulating a specified softness for each PVC application area. Significantly, the softer, the better the plasticizing efficiency becomes, as you need less plasticizer to achieve an equivalent result, which in turn reduces the amount of raw material consumed. This can have an impor-tant bearing on reducing costs, as the ratio of plasticizer to PVC can be 50:50 in formulations. Less consumption of raw materials is also good for the environmental profile.

Test ResultsIn the Hardness test all three non-phthalates performed very well, and indeed yielded a better plasticizing efficiency and softer material than in similar phthalate benchmark tests. In overall terms the lower the score, the more efficient and soft the material is. In fact, PETV was more than 15% softer than DINCH® and 10% softer than DOTP. PETV’s extraordinary softness makes it technically superior, on this measure, to all leading non-phthalate and phthalate plasticizers.

6 Critical Test Areas The following test results highlight the technical performance of each of the three leading general-purpose non-phthalates in the critical areas. To make the comparisons easier to interpret at the end of each result section there is a star rating system from 1 to 5 stars; 5 stars being outstanding and 1 star being poor. This comparison takes into account not just the leading non-phthalates but the leading phthalates too.

DINCH®

DOTP

PETV

2. Volatility

Low volatility is key to reducing weight loss, and minimizing migration. It also helps to ensure that PVC maintains its stability, shape, and form over its useful life. Plasticizer reten-tion is key to PVC’s lifetime performance since plasticizers add or control many of the positive properties. Generally, the higher the molecular weight, the less volatile and the less risk of migration or extraction from either material contact or solvents like water. The molecular weights of the three leading non-phthalates tested were:

PETV Mw: 472 g/molDINCH® Mw: 425 g/molDOTP Mw: 391 g/mol

Test ResultsVolatility is measured as weight loss over a period of 7 days at 100°C. In this test PETV again is shown to have the lowest volatility with 17,5% loss in weight compared to DOTP 22,5% and DINCH® 26%.

DINCH®

DOTP

PETV

Hardness Shore A Volatility

Loss of plasticizers

Wei

ght

Loss

, %

PETV PETVDOTP DOTPDINCH® DINCH®

72

70

68

66

64

62

60

58

30

25

20

15

10

5

0


3. Fogging

Related to volatility, fogging is the residue that forms or collects on glass surfaces, as in automotive interiors. PVC materials and foils release volatile substances often through exposure to heat or high interior temperatures. Reducing fogging ensures good driver visibility, which can be impor-tant when the sun is low or at night time.

Test ResultsThe fogging test measures the reflectometric value on a glass plate after exposure of automotive foil to heat. It can also me-asure weight loss too, which is shown in the graph. The test clearly shows that PETV is significantly better in achieving both a lower weight loss and higher reflectometric value.

DINCH®

DOTP

PETV

4. Viscosity

Initial low viscosity is important in processing PVC to enable it to flow more consistently in the manufacturing process. If there is a time delay between preparations and processing, it is important that low viscosity is maintained, for example in plastisols where the difference between the preparation phase and processing can be several days. This ensures no unnecessary production costs are incurred or time lost.

Test ResultsIn the test, DINCH® scored an outstanding result with PETV close behind both with initial viscosity and then when tested over time. This means they are well adapted to preparing a plastisol and processing over several days, as they maintain their low viscosity during that time.

DINCH®

DOTP

PETV

ViscosityAs a function of shear and time

FoggingAutomotive Foil

TOTM PETV DINCH® DOTP

2 h 24 h 1 w0,1 1 10 100 0,1 1 10 100 0,1 1 10 100

DOTP

DINCH®

PETV

6

5

4

3

2

1

0

90

80

70

60

50

40

30

20

10

0

3

2,5

2

1,5

1

0,5

0

Refle

ctom

etric

, %

Gra

vim

etric

, mg


DINCH®

DOTP

PETV

5. Gelation & absorption

Gelation and fusion are important in facilitating a high manufacturing volume. Speed in moving from a liquid to solid plastic saves on processing time increasing both pro-ductivity and volume. The degree of fusion is often expressed as strain, which is a function of time and processing tempe-rature. Absorption speed is also important in maintaining formulation, processing and extrusion efficiency in S-PVC (Suspension polymerization).

Test ResultsThe rheology graph (Fig 1), which measures moving from liquid to a gelatinous and fused state clearly shows PETV is faster and achieves this at a lower temperature. This means PETV consumes less energy and is more suited to high

Fig 2

Fig 1

Fig 3

RheologyGelation and fusion as function of temperature

ProcessingAbsorption time in S-PVC

Degree of gelationStrain as a function of time and processing temperature

Temperature, °C

25 75 125 175

PETV

DOTP

DINCH®

1000000

100000

10000

1000

100

10

1

14:24

12:00

09:36

07:12

04:48

02:24

00:00

Time (min) Temperature (C°) Plasticizer Strain (%)

2 160PETV

DINCH®10070

5 160PETV

DINCH®300100

3.5 180PETV

DINCH®415295

2 200PETV

DINCH®470280

160 160PETV

DINCH®400430

volume manufacturing. The strain test (Fig 2) highlights the degree of fusion or gelation over time. The higher the strain value, the faster you can process and increase productivity. PETV achieved 100% strain at 160°C after just 2 minutes, compared to DINCH® 70%. The absorption graph (Fig 3) shows the time it takes for each non-phthalate plasticizer to be absorbed into the S-PVC with PETV coming out a clear winner. Again this is important for processing and productivity.

Tim

e, m

inut

es

PETV DOTP DINCH®


6. Aging & visual appearance

PVC products, in many outdoor applications, need to be able to weather the climate without early degradation and continue to look good throughout their useful life. Changes in temperature, UV, rain and damp all play their part in affecting the PVC materials around us. PVC for coated textiles, such as marquees, and soft-top automobile roofs need to perform well over a long period and maintain their looks.

Test ResultsThe QUV graph shows the results of an accelerated weathe-ring test that includes exposing PVC to sun, rain, and dew. Remarkably PETV was unaffected in the QUV environment even after some 2,000 hours of simulated testing. Both the other non-phthalates, DOTP and DINCH®, showed marked and progressive effects of degradation and aging. DINP the phthalate benchmark was also tested with slightly worse results over the 2,000 hours. Tests on visual appearance relating to transparency and legibility of writing show that PETV yields PVC films of higher clarity.

It is clear from the summary results of the tests that PETV is a clear winner in the battle for the best-of-the-best non-phthalates. It is rated outstanding in softness, aging and gelation plus it scored very well on volatility. Perhaps even more impressive is that PETV is superior to all leading non-phthalates in 3 out of the 6 critical areas and is generally on a par in the other 3 areas.

DINCH®

DOTP

PETV

Summary

Test summary Hardness Volatility Viscosity Fogging Gel & Fusion Aging & Visual Overall

PETV 5 4 4 4 5 5 27

DINCH® 3 3 5 2 3 3 19

DOTP 4 3 3 2 4 3 19

QUV Index

Yello

w in

dex,

Yi

80

70

60

50

40

30

20

10

0

0 h 500 h 1000 h 1500 h

DINP

DINCH®

DOTP

PETV

+

*

******* **

++

+

+

++

+


The nirvana for plasticizers is achieving a unique balance of hardness and volatility to arrive at an unbeatable combination of low volatility with high plasticizing efficiency. This means you use less plasticizer to produce softer, more stable and more durable PVC, which in turn reduces issues of fogging and migration of the plasticizer out of the PVC. It also contributes to a more sustainable profile because the PVC’s performance or useful life is maintained over a longer time.

PETV, which is marketed as Pevalen™ by Perstorp, actual-ly achieves the unique balance of hardness and volatility. In fact, it yielded outstanding softness not just compared to the leading non-phthalates, but to the leading phthala-tes too. In the volatility test PETV also displayed very low volatility and with this unique combination should make it a preferred choice in coated textiles and other flexible PVC applications. Simply put plastisols love PETV, as on a molecular level they are instantly attracted to each other.

PETV’s aliphatic structure with its polyol ester and matching polarity with plastisol molecules make this perhaps the most compatible plasticizer – non-phthalate or phthalate – for plastisol formulations and processing. The degree of compatibility is very important in achieving superior softness and plasticizing efficiency, and this power of attraction is key to low volatility, in other words, the closer the match the less volatile the formulation and PVC is over time.

Two other areas of outstanding performance were in PETV’s ease of processing and the slowing of the aging process in PVC products. PETV showed exceptional performance in ease of integration with PVC both in gelation and fusion tests, which can make a significant contribution to increasing productivity and saving valuable time. It also showed world leading performance in permanence. The QUV test results highlight that PVC using PETV will easily survive what the weather can throw at it and retain its visual appearance much longer than its non-phthalate competitors. These two areas also underline that plastisols and PETV are very compatible, and bond closely.

You could say PVC and PETV is a match made in heaven!

PETV achieves the perfect balance of hardness & volatility

For more information about PETV marketed as PevalenTM by Perstorp contact Anders Magnusson on +46 435 37848 or email [email protected]

Hardness and volatility

Har

dnes

s, S

hore

A

Weight Loss, %

72

71

70

69

68

67

66

65

64

63

6215 20 25 30

PETV

DOTP

DINCH®x

x


best-in-test non-phthalate plasticizers for pvc plastisols

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