Recycling of EPDM rubber

Blends of EPDM rubber / Thermoplastics


Jinxia Li

Luleå University of Technology, Luleå, Sweden
Master Thesis, Continuation Courses
Advanced material Science and Engineering
Department of Applied Physics and Mechanical Engineering
Division of Polymer Engineering

http://epubl.ltu.se/1653-0187/2008/106/LTU-PB-EX-08106-SE.pdf

PREFACE


This thesis was carried out at the Division of Polymer Engineering at Luleå University of Technology during the period from February 2008 to October 2008.

First of all, I would like to give my special thanks to my supervisor Dr. Lennart Wallström, for his academic instructions and all the support during this thesis.

I also thank Mr. Johnny Grahn, Lars Frisk and Roberts Joffe for their technical support and instructions.
I also would like to thank all my colleagues at the Polymer Division for all the help they gave me.

This thesis is part of AMASE Master Program, which is financed by European Commission and is gratefully acknowledged.

Finally, I wish to express my gratitude to my family for all their support and encouragement.

ABSTRACT

Blends containing recycled EPDM rubber and thermoplastics, EMA and LDPE were studied. Two compatibilization methods, reactive and non-reactive, were evaluated. Ethyleneoctene copolymer (EXACT 0210) was used as non-reactive compatibilizer. Phenolic resins (SP1045 & HRJ10518) were reactive agents. There existed an optimal composition ofcompatibilizers which were 25wt% in the case of reactive and non-reactive agents added to 15wt%EMA and 55-60wt% EPDM rubber. EXACT-compatibilized blends gave high elongation at break while phenolic resin-compatibilized mixtures gave high stiffness in comparison with the chosen reference material.

Comparison in compatibilizing capabilities HRJ-10518 and SP-1045 was carried out. The former one had better capabilities than the latter at high compatibilizer content. Talcum was used as anti-agglomeration agent but failed to work properly. Pressing pressure could be minimized without any adverse effect. Nonvulcanized rubber was used to enhance tear strength but its effect was small by assuming that there exists degradation of the interfacial surface at high temperature. SEM analysis revealed  homogeneous microstructure in both kinds of compatibilization. EXACT 0210-compatibilized blends showed more plastic deformation of the matrix than reactive blends.

Stable connection etween phases was also observed. Tensile strength of the LDPE based blends were a little lower than that of EMA based blends and the hardness was a little higher. Compared to EMA based blends, the elongation at break was much lower while the young’s modulus was much higher with LDPE based blends. Compression set of both LDPE and EMA based blends was high compared to the reference materials.

Keywords:
Recycled EPDM rubber, unvulcanized rubber, LDPE, EMA, reactive compatibilization, nonreactive compatibilization, ethylene octene copolymer, phenolic resins, tensile properties, tearstrength, microstructure, pressing pressure

LIST OF TABLES AND FIGURES
Figure 1.1: Chemical structure of EPDM
Figure 1.2: Image of recycled EPDM rubber under microscopy
Figure 1.3: Various copolymer grades visible at the boundary layer of two polymers
Figure 1.4: Effect of polar compatibilizer type and compatibilizer loading on Charpy notched impact strength (kJ/m2) of PP/ midsole compounds
Figure 1.5: Effect of nonpolar compatibilizer type and compatibilizer loading on Charpy notched impact strength (kJ/m2) of PP/scrap dust compounds
Figure 1.6:Reactive groups commonly encountered in reactive compatibilization
Figure 1.7: Tensile strength of thermoplastic vulcanizates of 60/40 NR/HDPE blends with various types of blend compatibilizers
Figure 1.8: Elongation of thermoplastic vulcanizates of 60/40 NR/HDPE blends with various types of blend compatibilizers
Figure 3.1: Standard dumbbell die C for tensile strength test (ASTM-D412-06a
Figure 3.2: Standard die T for tear strength test (ASTM-D 624-91)
Figure 4.1: Comparison of tear strength between different non-reactive compatibilizer
Figure 4.2: Tensile strength of recycled EPDM rubber/EMA blends compatibilized by EXACT
Figure 4.3: Elongation at break of recycled EPDM rubber/EMA blends compatibilized by EXACT
Figure 4.4: Young’s Modulus of recycled EPDM rubber/EMA blends compatibilized by EXACT
Figure 4.5: Tear strength of recycled EPDM rubber/EMA blends compatibilized by EXACT
Figure 4.6: Hardness of recycled EPDM rubber/EMA blends compatibilized by EXACT
Figure 4.7 : Stress-elongation relationship of recycled EPDM rubber/EMA blends compatibilized by EXACT
Figure 4.8: Effect of talcum on the mechanical properties of 70wt% EPDM rubber + 15wt%EXACT+ 15wt% EMA
Figure 4.9: Molecular structure of reactive agents
Figure 4.10: Tensile strength of recycled EPDM rubber/EMA blends compatibilized by reactive agent
Figure 4.11: Elongation at break of recycled EPDM rubber/EMA blends compatibilized by reactive agent
Figure 4.12: Tear strength of recycled EPDM rubber/EMA blends
compatibilized by reactive agent
Figure 4.13: Young’s Modulus of recycled EPDM rubber/EMA blends compatibilized by reactive agentFigure 4.14: Hardness of recycled EPDM rubber/EMA blends compatibilized by reactive agent
Figure 4.15: Mechanical properties of recycled tired rubber/EMA blends compatibilized by reactive agents
Figure 4.16: Comparison of mechanical properties of recycled EPDM rubber / EMA blends
Figure 4.17: Effect of pressure on the mechanical properties of recycled EPDM rubber/EMA blends
Figure 4.18: Effect of unvulcanized rubber and blending temperature on tear trength of recycled EPDM rubber/EMA blends
Figure 4.19: DSC analysis of unvulcanized rubber, scanning rate 10 0C/min
Figure 4.20: SEM images of recycled EPDM rubber/EMA blends
Figure 4.21: Phase connection of recycled EPDM rubber/EMA blends
Figure 4.22:Mechanical properties of the blends: EMA/EPDM/EXACT and LDPE/EPDM/EXACT
Figure 4.23: Mechanical properties of the blends: EMA/EPDM/DRM and LDPE/EPDM/HRJ
Figure 4.24: Mechanical properties of the blends: EMA/EPDM and LDPE/EPDM ( the blends with HRJ contain 4wt% additives)
Figure 4.25: Comparison of compression set under different temperature: A 55 0C B Room temperature 23 0C
Table 1: Compounding formulation used to prepare rubber/thermoplastics blends
Table 2: Mixing schedule (descending order) 21

ABBREVIATION

EMA Copolymer of ethylene and methyl acrylate
EPDM Ethylene Propylene Diene
PE Polyethylene
PP Polypropylene
POE Poly Olefin Elastomer
EVA Ethylene Vinyl Acetate
PVC Polyvinyl chloride
SBR Styrene Butadiene Rubber
SRP Synthetic rubber powder
TPE Thermo Plastic Elastomer
EXACT EXACT 0210, Ethylene based Octene Plastomer
HRJ Phenolic resion with active hydroxymethyl (methylol) groups (HRJ-10518)
SP Dimethylol phenolic resin or octylphenol-formaldehyde resin (SP-1045)

References

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