APPLICATION INFORMATION
ADDITIVE SOLUTIONS FOR RECYCLING APPLICATIONS

TP-A 8

02

Additive solutions for recycling applications

Contents
03 A new life for recyclates
04 BYK’s contribution to efficient recycling of thermoplastics
06 Restabilization of recycled thermoplastics
09 Recyclates from the automotive industry
12 Recyclates from the packaging industry
16 Fiber-reinforced plastics with recyclates
18 Reduction of VOC and odors

03

A new life for recyclates
Thermoplastic materials are in high demand due totheir versatility and are used in a wide range ofindustries and applications worldwide, from automotive
and electronic products to construction, film, andpackaging industries.
When these products reach their end of use, anincreasing proportion of them do not end up in
landfills or incinerators, but find their way back via
recycling to be used again.

For additional information on
additives and technical topics,
please contact us:
Thermoplastics.BYK@altana.com

Note
To ensure the best appearance
and full functionality, please
open in Adobe Acrobat.

PET bottle recycling is a notable example in recent
decades of achieving a very high return rate with asimultaneous high-quality material stream. Ideally, thisresults in beverage bottles made of 100 % recycled PET.
Environmental and economic interests, regulatory
requirements from policy, and public opinion are
driving increased interest across industries in recycling
plastics and improving sustainability across the board.
Subtrends such as source reduction, lightweight
applications, biodegradable materials, and lesshazardous chemicals are expected to create a greener
economy around the recycling market.

Suggested additives for therecycling of thermoplastics
can be found in the brochure
TP-G 2: Recycling ofthermoplastics

04

Additive solutions for recycling applications

BYK’s contribution to efficient recycling of thermoplastics
The requirement to use ever greater quantities of recycled
polymers in final formulations and the almost unlimited
number of different polymer combinations­, fillers, and otheringredients face the industry with a large number ofchallenges.

Overcoming these challenges requires a whole toolbox anda multi-level approach to achieve the desired properties:

Toolbox to overcome recycling challenges

BYK additives toensure quality andfunctionality

Compounding andprocessing ofrecycled materials

Modernpolymerization
technologies
Recycled
material orcompoundInnovative
recyclingmachines

Intelligent
product
designG. 01

05

Additive solutions for recycling applications / BYK’s contribution to efficient recycling of thermoplastics

Twin-screw
extruderBYK is a leading global supplier of specialty chemicals. The
company’s innovative additives and differentiated solutions
optimize product and material properties a­ s well as
production and application processes. The recycling ofthermoplastics is also supported by the use of BYK additives.

Laboratorybuilding(Ø 25 mm,
LD 40)

BYK continuously develops new additives and works
together with customers to find new solutions for current
and future challenges. Our modern and professionallyequipped laboratories make it possible to try out and test
the effectiveness in realistic applications.

Cast-film
line

Injection
molding

Burning
chamber

Materialtestinglaboratory

06

Additive solutions for recycling applications

Restabilization of recycled thermoplastics
At the beginning of the first cycle of use, thermoplastics
are equipped with a variety of raw materials and additives
to prepare them for their intended use. These include, forexample, UV stabilizers or additives to increase mechanicaland thermal properties. As the finished parts are used andDuring reprocessing in the course of recycling, effects
previously desired through raw material mixtures may
interfere so strongly that reuse is not possible. A typicalchallenge, for example, is the originally complementary
combination of different plastics, such as occurs in multilayer films. The polymers can only be separated again withgreat difficulty, often not at all. As a mixture – a polymer
blend – they are virtually unusable without compatibilization.
In addition, impurities, pigment residues, or filler load,
which is now too high or incorrect for further use, canreduce the performance further. The compounds processed
directly from the recyclate in this way are often only suitable
for the manufacture of low-cost and low-quality products.

age, the components lose their effectiveness and are
depleted. At the end of use, there are various options:a. Storage at landfill
b. Incineration for energy production
c. Recycling for reuse of the polymers/polymer blends

Recycling cycle

1

Polymer
FillerAdditive
Compatibilizer

Purification
Sorting

3Compounding

Rejects2

Post-industrial
recycling

Post-consumer
recycling

Recycling

Processing

EnergyIncineration
4

End of use

Application

Landfill

G. 02

The use of BYK additives creates added value throughout
the whole recycling value chain. The granulated, non-dusting
delivery form of BYK products ensures safe handling anddosing 1 . In addition, the improvement in processability
enables process optimization­, lower lead times 2 , and areduction in rejects 3 , while the quality of the component
can be significantly increased by reducing odor andincreasing strength 4 .

07Additive solutions for recycling applications / Restabilization of recycled thermoplastics

BYK offers a variety of products to restabilize the recycledplastics and improve the mechanical properties. Improved
mechanical strength and long-term thermal stability while
maintaining rheological properties increase the recyclate­‘spotential uses. Thus, the end products can also be used inhigh-quality applications.

Applications

Use of restabilized recyclates
Value
RESTABILIZED RECYCLATES• Multiple use• Thin or thick layer• Long term

Outdoor furniture
Automotive parts
Water tanks

l

bi

ta

s
Re

n

io

t
iza

Composters

Pallets

RECYCLATES• Single use• Thick layer• Short term
QualityG. 03•	Polyolefin blends with different
compositions, e.g. bottle fractions
or multi-layer films•	Polypropylene contaminated withother polymers•	Polypropylene exposed to aggressive
substances, as in battery-housing
recyclates•	Mixed plastics from household andindustrial waste•	Polyolefins exposed to long-term
UV radiation for use in outdoor
applications, e.g. grids, barrels,
pallets, and garden furniture

08

Additive solutions for recycling applications / Restabilization of recycled thermoplastics

Restabilization of recycled thermoplastics – practical examples

A typical blend resulting from bottle recycling, for example,
is a mixture of HDPE (bottle) and PP (lid). Pure HDPE
exhibits good resistance to embrittlement during heat aging.
The stability is s­ ignificantly reduced by blending with PP,
even at a low blend ratio (­HDPE/PP 95/5). By using
RECYCLOBYK, the time to embrittlement of the blend canbe increased almost six times (G. 04).

Embrittlement of HDPE/PP blends (aging at 120 °C)
3500

Hours until embrittlement

Embrittlement of HDPE/PP blends(e.g. bottle fractions)

3000
2500
2000
1500
1000
500
0
HPDE/PP 95/5

HDPE

HPPE/PP 95/5
+ 0.2 % RECYCLOBYK 4371

G. 04

Recycled HDPE (rHDPE) becomes brittle as it ages. Since, forexample, garden furniture is exposed to different weather
conditions, the use of rHDPE outdoors is only possible to alimited extent. After approx. 3000 hours of artificial
weathering, the impact strength is only 80 % of the initialvalue. RECYCLOBYK enables the rHDPE to be used in thisarea as well. Even after 8000 hours, the impact strength isstill over 80 % of the initial value (G. 05).

Remaining relative impact strength ofrHDPE during artificial weathering

Remaining impact
strength (%)

Aging of recycled HDPE
(e.g. garden furniture)

Artificial weathering:• Xenon lamp
• 60 % relative humidity• Water spray

120
100
80
60
40
20
0
0

2000

4000

6000

8000
Time (h)rHDPE  rHDPE + 0.2 % RECYCLOBYK 4372

G. 05

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Additive solutions for recycling applications

Recyclates from the automotive industry
In the automotive industry in particular, plastic components
have now replaced many original materials. Components
made of plastics are lighter and can be shaped to meet
design requirements. In Europe, however, the automotive
industry is obliged to manufacture an increasing proportionof these plastics from recycled materials.
Bumpers are a typical example for this. The PP used ismodified with EPDM in regard of impact strength, and fillers
are added to achieve the desired price and strength level.

The recyclate may contain solid impurities such as paintresidues. BYK products neutralize the negative effect ofthese impurities and thus increase the impact strength.
Even 0.2 % paint residues in the recyclate cause asignificant drop in impact strength during aging. Afterabout 1500 hours, an impact strength around 15 % of theoriginal value can be measured. RECYCLOBYK products leadto a compatibilization of the paint impurities and a
restabilization, so that after 1500 hours, 90 % of theoriginal impact strength is still present (G. 06).

Impact strength (kJ/m2)

Impact strength of recyclate contaminated with paint residues (aging at 135 °C)
600
500
400
300
200
100
0
0

500

1000

1500

2000

2500
Time (h)Contaminated recyclate  + 0.7 % RECYCLOBYK 4373  + 1.2 % RECYCLOBYK 4373

G. 06

10

Additive solutions for recycling applications / Recyclates from the automotive industry

Another special application example is the recycling of usedbattery housings. Through a take-back system, batteries
from automobiles are c­ ollected by manufacturers or contract
companies with a very high return rate and recycled there.
Even in electric vehicles, 12 V batteries continue to be usedin addition to the high-voltage battery for the drive, as themain battery is disconnected from the vehicle network whenswitched off.

The polymers used for the housings (in this case PP) are
exposed to aggressive substances during their time of use,
meaning the recyclates obtained may still contain acid andmetal residues despite cleaning. Direct reuse would
significantly accelerate the aging of the plastic. For thisreason, the use of special additives, such as RECYCLOBYK
products, is necessary for restabilization.

The results show that theuse of a standard stabilizer
package improves aging
properties, but even at 1 %,it only performs about thesame as 0.2 % RECYCLOBYK.

Impact strength of recyclate contaminated with acid and metal residues(aging at 135 °C)

Notched impact strength (kJ/m2)

For testing, specimens are subjected to accelerated artificial
heat aging conditions at 135 °C or 155 °C and the time toembrittlement is measured. Without additives, theaccelerated heat aging lifetime in the example shown is lessthan 250 hours for the unstabilized compound. By using
0.2–1.0 % RECYCLOBYK, this time can be extended tomore than 2000 hours, significantly exceeding a standard
stabilizer package (1250 hours) (G. 07).

12
10
8
6
4
2
0
0

500

1000

1500

2000
Time (h)Contaminated recyclate+ 0.2 % Standard stabilizer package+ 0.2 % RECYCLOBYK 4371

+ 0.5 % RECYCLOBYK 4371

+ 1.0 % Standard stabilizer package

G. 07

11

Additive solutions for recycling applications / Recyclates from the automotive industry

The improved performance is evident in terms of elongation,
tensile strength, and modulus, as well as Charpy impact
strength.

Additives compared to the non-stabilized zero sample (= 100 %) before aging
Hours at
135 °C

Control

250

Standard stabilizer package

RECYCLOBYK 4371

0.2 %

0.5 %

1.0 %

0.2 %

0.5 %

1.0 %

0

101

108

111

105

110

114

500

0

89

100

108

99

109

108

1000

0

0

96

107

92

109

110

1250

0

0

46

89

89

105

107

1500

0

0

0

0

5

105

105

2000

0

0

0

0

0

99

102

Standard stabilizer package: B-2

The results show the combined relative performance interms of elongation, tensile strength, and tensile modulus,
as well as Charpy impact strength compared to the nonstabilized control sample (= 100 %). The use of a standard
stabilizer package i­mproves the aging properties­,
but even at 1 %, it only achieves around the same
performance as 0.2 % RECYCLOBYK.

T. 01

12

Additive solutions for recycling applications

Recyclates from the packaging industry
A polymer rarely directly fulfills the complete required
property profile. Since the strengths and weaknesses of thedifferent polymers are very different, the properties are often
combined. The combination can be in the form of a blend(e.g. PC/ABS or HIPS), or by joining the unmixed polymers, asin the case of a multi-layer film or a hard-soft composite.
Although these polymer combinations are extremely
beneficial in their initial use, they lead to s­ ignificant
challenges when recycled.

LLDPE and polyamide in multi-layer films
A particularly challenging area of application is the recyclingof multi-layer films. These typically combine the uniqueproperties of different polymers to achieve the required
performance. The main focus is on extending the shelf lifeof food products by providing a good barrier against oxygenand moisture. One polymer combination commonly used forthis purpose is polyamide and LLDPE. The good barrier
properties and the high strength of a polyamide complement
the advantages of LLDPE, such as high impact and puncture
resistance.

The separation of the two polymer layers is c­ urrently notpossible during reprocessing on an i­ndustrial scale, since theless dominant phase (PA in this case) forms large polymer
spheres in the LLDPE matrix during regranulation due to thedifferent surface energies. This deteriorates the opticalproperties (especially t­ ransparency) of the material. The
insufficient compatibility of the two polymers also leads to
low mechanical resistances, especially in terms of elongationand impact strength. Compatibilization by using a highly
functionalized SCONA modifier makes it possible to makethe non-polar LLDPE compatible with the polar PA.

13

Additive solutions for recycling applications / Recyclates from the packaging industry

Compatibilization with SCONA
In situ formation of the amphiphilic compatibilizer
SCONA modifier*

Polyamide

Poor dispersion:
Low interfacial adhesion = poor mechanical properties

PI

PI

Good dispersion:
High impact strength

Non-polar component

Non-polar matrix
PI

Polar impurity

Acid/anhydride group  

PI

Amine group  PI

SCONA modifier  Polar component

Polyamide* Simplified reaction scheme with the amine end group, however the internal amide groups may also take part in the reaction.

G. 08

14

Additive solutions for recycling applications / Recyclates from the packaging industry

Mechanical and optical properties of PA/LLDPE blends

Notched impact strength (kJ/m2)

2 µm

80
70
60
50
40
30
20
10
2 µm

0
PA/LLDPE 30/70

Notched impact strength (kJ/m2)

With SCONA modifier
With a highly functionalized SCONA
modifier for excellent compatibility andimproved mechanical and optical properties.

PA/LLDPE 30/70
Inhomogeneous material with poor
compatibility, poor optical properties,
and low mechanical resistance.

80
70
60
50
40
30
20
10
0
+ 3 % SCONA TSPOE 1002 GBLL
G. 09

The use of the modifier leads to better bonding of thepolyamide to the polyolefin phase and thus to finer
distribution. This improves the mechanical and opticalproperties. The best possible distribution is achieved byusing a twin-screw extruder.

15

Additive solutions for recycling applications / Recyclates from the packaging industry

Improving strength in PET strapping

PET strapping
Recycled PET can be available in different quality grades.
High-quality rPET can be used to produce beverage bottles
from 100 % rPET, whereas lower grades are used forstrapping.

Not modified

With SCONA modifier
Very lowstrength

Stretching

Very high strength

Very high strength

PET strapping is stretched up to five times in the direction offlow during manufacture. This results in the required tensile
strength, but causes poor tear resistance along the PET
molecules aligned in parallel by the stretching. The strapping
is susceptible to splicing. SCONA modifiers can create thenecessary chemical bonds between the single PET molecule
chains to prevent further tearing.

High
strength

Stretching

G. 10

30
25
20
15

2500

Notched impact strength (kJ/m2)

35

Flexural strength (MPa)MVR, 270 °C, 2.16 kg (cm3, 10 min)The use of SCONA modifiers has an influence on MVR (melt volume rate), flexural strength, and notched impact strength.

2000

1500

1000

10

70
60
50
40
30
20

500
5

10
0

0
PET

+ 6%
SCONA TSPOE
1002 GBLL+ 10 %SCONA TSPOE
1002 GBLL+ 18 %SCONA TSPOE
1002 GBLL

0
PET

+ 6%
SCONA TSPOE
1002 GBLL+ 10 %SCONA TSPOE
1002 GBLL+ 18 %SCONA TSPOE
1002 GBLL

PET

+ 6%
SCONA TSPOE
1002 GBLL+ 10 %SCONA TSPOE
1002 GBLL+ 18 %SCONA TSPOE
1002 GBLL

G. 11

16

Additive solutions for recycling applications

Fiber-reinforced plastics with recyclates
Various fibers can be used to improve the properties ofrecycled materials. This can be done for price reasons, butalso for environmental protection aspects or to enhance
properties. Basically, there are two different types ofrecyclates:
On the one hand, fibers can be used in thermoplastic
recyclates, such as in wood fiber-reinforced plastics (WPC)
based on recycled polyolefin blends. On the other hand,recycled carbon fibers from secondary sources (rCF) can
also be used in PP (PP-rCF), which is gaining popularity
especially in the automotive industry.

Normally, recyclates are not of uniform quality, andmixtures of PE and PP are frequently found. The
incompatibility of PE and PP, combined with polymer
degradation­, degraded processing aids, and consumed lightand heat stabilizers make it challenging to achieve goodresults with conventional coupling agents t­o improvemechanical properties in WPC applications.
By using BYK products, good properties of wood fiberreinforced recyclates can be achieved even at low input
quantities, e.g. due to a very high degree of grafting (G. 12).

Flexural strength (MPa)

Mechanical properties of recyclates (PE/PP)
reinforced with wood fibers (50 %)
80
70
60
50
40
30
20
10
0
Control

1 %  2 %Industry standard

1%
SCONA TPPP 8112 GA

1%
SCONA TPPP 9212 GA

1%
SCONA TSPP 10213 GB
G. 12

17

Additive solutions for recycling applications / Fiber-reinforced plastics with recyclates

Waste and components from the automotive sector
containing carbon fibers can be recycled, and the recycled
carbon fibers obtained from this can be u
­ sed inthermoplastics w­ ith only a slight cost difference compared
to glass fibers.­Unlike glass fibers, however, such recycled
carbon fibers do not have a sizing that allows better
compatibility with polyolefins such as polypropylene.
Nevertheless, in order to achieve good adhesion between
the matrix and fiber, a coupling agent with a high degreeof functionalization is required. BYK products are ideallysuited for this purpose.

Relative property profile of 4 % SCONA TSPP 10213 GB in PP
with 30 % carbon fiber compared to the industry standard andto a control sample without a coupling agent

Tensile modulus

MFR 230 °C, 2,16 kg

Tensile strength

0%
50 %
100 %
150 %
200 %
HDT A

Control  Industry standard  

SCONA TSPP 10213 GB

250 %Impact strength

G. 13

18

Additive solutions for recycling applications

Reduction of VOC and odors
When thermoplastics are recycled, the type of pre-processingcan ­have a significant impact on the quality of the final
product. In addition to affecting physical properties andresistances, processing can increase odors and volatileorganic compounds in the recycled plastics. Washing of therecyclate is very limited, as this only reaches the surface, but
VOCs (volatile organic compounds) are present throughout
the plastic and migrate back to the surface and ambient air.
A popular option is the use of vacuum degassing during

processing. Mixing the material maximizes the surface area,
and the high temperature and vacuum increase the mobilityof the VOCs, partially eliminating them. Other aids include
the use of activated carbon, zeolites, or entraining agents
such as water, CO2, or nitrogen.

Step 1
During extrusion, the active ingredient is released. Ininteraction with the temperatures in the extruder andthe shear forces, microfoam is formed in the melt, which
absorbs odor and VOC components.

This is where BYK’s products come in. The two-stage m­ odeof action can be c­ learly illustrated using the specific example
of BYK-MAX P 4200:

Step 2
During the subsequent vacuum degassing, the microfoam isremoved from the melt together with the impurities contained.

Feeding

Strong degassing is required
Vacuum degassing

Feeding zone

Melting zone

Metering zone

Vacuum degassing zone

Metering zone

Pressure

Pressure build-up during extrusion

G. 14

19

Additive solutions for recycling applications / Reduction of VOC and odors

VOC (ppm)

VOC reduction in finished parts made of PP-GF (30 %) with BYK-MAX P 4200,
measured according to VDA 277
200

Odor

150
100
50
0
Extrusion without vacuum

With vacuum, without additive

1.5 % BYK-MAX P 4200 with vacuum

G. 15

1 means no odor is perceived at all,6 smells unbearable. 2–3 means
perceptible odor, but not disturbing.
For the results shown here, the sample
was exposed to 80 °C for 2 hours.

Odor reduction with BYK-MAX P 4200 according to VDA 270 in finishedparts made of PP-GF (30 %)VDA 270
Extrusion without vacuum

4 –5

Vacuum with 50 mbar

4 –5

1.5 % BYK-MAX P 4200 and 50 mbar vacuum

2–3

How is the odor actually determined?
By smelling. Even though there are
already approaches to analyticallydetermine odor with measuring
instruments, the human perceptionof odor is still the preferred andsimplest method. A defined amountof the sample is conditioned in a glass
container and then evaluated according
to the German school grading system:

T. 02

05/2022
TP-A 8BYK-Chemie GmbH
Abelstraße 4546483 Wesel
GermanyTel +49 281 670-0
Fax +49 281 65735

ADD-MAX®, ADD-VANCE®, ANTI-TERRA®, AQUACER®, AQUAMAT®, AQUATIX®, BENTOLITE®, BYK®, BYK-AQUAGEL®, BYK®-DYNWET®, BYK-MAX®,
BYK®-SILCLEAN®, BYKANOL®, BYKCARE®, BYKETOL®, BYKJET®, BYKO2BLOCK®, BYKONITE®, BYKOPLAST®, BYKUMEN®, CARBOBYK®, CERACOL®,CERAFAK®, CERAFLOUR®, CERAMAT®, CERATIX®, CLAYTONE®, CLOISITE®, DISPERBYK®, DISPERPLAST®, FULACOLOR®, FULCAT®, GARAMITE®,GELWHITE®, HORDAMER®, LACTIMON®, LAPONITE®, MINERPOL®, NANOBYK®, OPTIBENT®, OPTIFLO®, OPTIGEL®, POLYAD®, PRIEX®, PURABYK®,
PURE THIX®, RECYCLOBLEND®, RECYCLOBYK®, RECYCLOSSORB®, RECYCLOSTAB®, RHEOBYK®, RHEOCIN®, RHEOTIX®, SCONA®, SILBYK®, TIXOGEL®
and VISCOBYK® are registered trademarks of the BYK group.

info@byk.com
www.byk.com

The information herein is based on our present knowledge and experience. The information merely describes the properties of our products but noguarantee of properties in the legal sense shall be implied. We recommend testing our products as to their suitability for your envisaged purpose prior touse. No warranties of any kind, either express or implied, including warranties of merchantability or fitness for a particular purpose, are made regarding
any products mentioned herein and data or information set forth, or that such products, data or information may be used without infringing intellectual
property rights of third parties. We reserve the right to make any changes according to technological progress or further developments.
This issue replaces all previous versions.