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Combination of plasma treatment and sol-gel chemistry for enhanced rubber / fibre

adherence

Kristina Klinkhammer, Esther Rohleder, Maike Rabe, Eberhard Janssen

Aachen-Dresden-Denkendorf Deutsches Fachkolloquium Textil 28.-29.03.2017, Aachen

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Content

textile reinforcement material properties application standard functionalisation

aim of the project plasma technology sol-gel technology results summary

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Textile Reinforcement

textile reinforcement • are embedded in a second material, e.g. rubber • increase stability and durability of a product • many different application

Cam-, V-belts

tyres

conveyor belts hose

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Reinforced plastic - material

textile material: • polyester • polyamide 6.6 (nylon) • p-aramide • other

materials for embedding matrix:

• natural rubber • synthetic rubber ( e.g. VP, SBR) • plastics (e.g. PU, PVC, PE)

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Reinforced plastic - properties

• textile reinforcement are embedded in (rubber) matrix to enhance

product properties

• rubber properties differ from textile properties, e.g.

• surface morphology

• flexibility

• E modulus

• low reactivity and low polarity of textile fibres

need for chemical functionalisation for better adherence

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Reinforced plastic - properties

material E modulus (N/mm²) polyethylen-terephthalat (PET)

2800-3000

PA6 3000 / 1000 PA66 3100 / 1100 aramide 59000-100000 natural rubber 50 SBR 10 PU 20-220 PVC 3000 PE 720-1100

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Reinforced plastic - functionalisation

standard for water based systems: RFL (resorcinol–formaldehyde–latex) preparation: 1. reaction between resorcinol and formaldehyde RF resin (binds to

fibre) 2. introduction of latex (rubber-like, bonds to rubber by co-

vulcanization) 3. dipping of fibres in RFL 4. heat treatment (drying 130-170 °C, curing 190-240 °C)

RF resin

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RFL - problems

formaldehyde:

great interest to substitute RFL dip

reclassified from class 2 to class 1B (carcinogenic) US and EU

impact on regulations currently discussed evaluating endocrine disruptive properties

done in 2016 (in CoRAP) impact on future regulations open

resorcinol:

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Research project - aims

• adhesion improvement between textile reinforcement and rubber matrix

• substitution of RFL dip • use of more environmental friendly chemicals • combination of plasma and sol-gel-chemistry

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Surface functionalisation - plasma technology

Plasma (fourth state of matter) • nature: thunderbolt, solar wind • artificial: by electrical discharge • ionised gas • neutral and electrical charged species (electrons,

ions, neutral particles)

ww

w.w

ikip

edia

.de

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Plasma technology – types of plasma

atmospheric pressure plasma: • pressure: approx. 1 bar • energy: electric discharge • Corona / DBD 5 – 100 kHz • DBD (dielectric barrier discharge) • rel. high temperature • high process gas consumption

low pressure plasma: • pressure: 0.5 mbar • energy: RF-Generator • homogenous reactions • low temperature • low process gas consumption • closed circuit: toxic gases possible

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Surface functionalisation – sol-gel technology

originally: wet-chemical process for surface functionalisation

SiR

RO OROR

SiR

RO OHOR

H2OH+ / OH-

+

SiR

RO OHOR

SiR

OH OROR

SiR

O OHOR

SiR

ROOR

+- H2O

1. hydrolysis:

2. condensation:

XR’-Si-(OR)3 with X = functional group R’ = alkyl or aryl, R = mainly CH3 or CH2CH3 OR crosslinking and film formation X special functions of the film

precursors:

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sol application via padding, drying and polymerisation

drying : evaporation of the solvent (water, ethanol) increase of sol concentration condensation of particles and film formation (polymerisation)

fibre fibre fibre

Sol-gel-technology - film formation

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aqueous dispersion of silane (mix)

application

conventional dryer (oven)

plasma

a)

b)

Experimental

• material: polyester fibres for embedding in rubber • silanes with different functionalities: alky, amino, vinyl, mercapto,

glycidoxy, … • drying and condensation (polymerisation): oven or plasma

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Analytics

• hydrophilicity (droplet test)

• functional groups (KMnO4)

• elemental composition (EDX)

• surface morphology (REM)

• adhesion (peel test)

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Results: hydophilicity / hydrophobicity

droplet test: absorption time of water droplet

hydrophilic: short absorption time

plasma decreases absorption time

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Detection of functional groups: KMnO4

violett solution becomes clear by reaction with double bonds and other functional groups

00,5

11,5

22,5

3

350 450 550 650

Adso

rban

ce

wave lengths (nm)

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Results: REM / EDX

Si localised around fibres and in interspaces

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Results: REM / EDX

coating with 10% vinylsilane

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Results: REM / EDX

coating with 4% vinylsilane

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Results: peeltest samples

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Results: adhesion

name functionalisation treatment adhesion force (N/25mm)

raw PES

none none 106

raw PES

RFL (standard) oven 185

MG33 glycidoxy silane oven 118 MG34 glycidoxy silane plasma 182 MG127 amino silane plasma 189

plasma treatment of functionalised fibres results in higher adhesion than

oven heating

variation of chemical concentration / variation results in high adhesion

force

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Summary

• polyester fibres were functionalised with silanes and treated with

plasma or in the oven

• plasma treatment shows clear advantages in comparison to oven

treatment

• the finishing is located around the fibres and in interspaces

• high adhesion forces comparable to RFL dip are achieved

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Acknowledgment Acknowledgment

Many thanks to the colleagues and students of FTB at Niederrhein

University of Applied Science: Noman Mughal, Alexandra Glogowski and

Anne Hartmann

Thanks to German Federal Ministry of Education and

Research (BMBF) for financial support (grant no.

03X0129B).

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Dr. Kristina Klinkhammer, phone: +49 (0)2161-186 6042 Dr. Esther Rohleder, phone: +49 (0)2161-186 6008 Prof. Dr. Maike Rabe, phone: +49 (0)2161-186 6110 Prof. Dr. Eberhard Janssen, phone: +49 (0)2161-186 6042 Niederrhein University of Applied Sciences Research Institute for Textile and Clothing (FTB) Richard-Wagner-Str. 97 41065 Mönchengladbach Germany

Contact