scholarly journals Evaluation of Electron Induced Crosslinking of Masticated Natural Rubber at Different Temperatures

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1279
Author(s):  
Huang ◽  
Gohs ◽  
Müller ◽  
Zschech ◽  
Wießner
Keyword(s):  
Natural Rubber ◽  
Elevated Temperatures ◽  
Sol Gel ◽  
Complex Viscosity ◽  
Chain Scission ◽  
Nitrogen Atmosphere ◽  
Size Exclusion ◽  
Reactive Blending ◽  
Exclusion Chromatography ◽  
Branched Chains

In this work, natural rubber (NR) was masticated using an internal mixer to fit the requirements of reactive blending with polylactide and characterized by size exclusion chromatography (SEC), Fourier-transform infrared (FT-IR) spectroscopy and dynamic rheology measurements. Subsequently, the effect of elevated temperatures (25 °C, 80 °C, and 170 °C) on the electron beam (EB) induced crosslinking and degradation of masticated natural rubber (mNR) in a nitrogen atmosphere without adding crosslinking agents has been investigated. The sol gel investigation showed that the gel dose of mNR slightly increased with increasing irradiation temperature, which is also confirmed by the swelling test. The chain scission to crosslinking ratio (Gs/Gx) was found to be less than 1 for irradiated mNR at 25 °C and 80 °C, suggesting a dominating crosslinking behavior of mNR. However, a significant increase of Gs/Gx ratio (~1.12) was observed for mNR irradiated at 170 °C due to the enhanced thermal degradation behavior at high temperature. A remarkably improved elasticity (higher complex viscosity, higher storage modulus, and longer relaxation time) for EB modified mNR was demonstrated by dynamic rheological analysis. Particularly, the samples modified at higher temperatures represented more pronounced elasticity behavior which resulted from the higher number of branches and/or the longer branched chains.

scholarly journals Process-Related Changes in Polyetherimide Joined by Friction-Based Injection Clinching Joining (F-ICJ)

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1027
Author(s):  
André B. Abibe ◽  
Marilia Sônego ◽  
Leonardo B. Canto ◽  
Jorge F. dos Santos ◽  
Sergio T. Amancio-Filho
Keyword(s):  
Mechanical Strength ◽  
Physical Aging ◽  
Mechanical Performance ◽  
Base Material ◽  
Chain Scission ◽  
Size Exclusion ◽  
Lap Shear ◽  
Local Strength ◽  
Exclusion Chromatography ◽  
Static Mechanical

This work presents a comprehensive study on the effects of the Friction-based Injection Clinching Joining (F-ICJ) process on the microstructure and local properties of the stake head. The manuscript evaluates the consequences on the quasi-static mechanical performance of hybrid joints of amorphous polyetherimide (PEI) with aluminium AA6082. Through an overlay of microhardness map on a cross-polarized transmitted-light optical microscopy (CP-TLOM) image, two lower-strength microstructural zones in the PEI stake head were observed: a plastically-deformed zone (PDZ) and a thermo-mechanically-affected zone (PTMAZ). When compared to the base material, PDZ and PTMAZ have a reduction of 12%–16% and 8%–12%, respectively, in local mechanical properties. The reduced local strength was associated with distinct volumes of loosely packed PEI chains with unsteady chain conformation and thus larger free volume in the affected regions. The mechanical strength reduction is reversible through physical aging by thermal annealing the joints, which additionally shows that process-induced thermomechanical degradation of PEI by chain scission, as evidenced by size exclusion chromatography (SEC) analysis, does not appear to affect local mechanical strength. An evaluation of typical loading regimes of staked joints in lap shear (average ultimate force of 1419 ± 43 N) and cross tensile (average ultimate force of 430 ± 44 N) testing indicates that the process-induced changes of PEI do not compromise the global mechanical performance of such a structure. These findings provide a better understanding of the relationships between processing, microstructure, and properties for further F-ICJ process optimization.

NATURAL RUBBER/CARBON NANOTUBE NANOCOMPOSITES PREPARED BY ULTRASONICALLY AIDED EXTRUSION

2013 ◽  
Vol 86 (1) ◽  
pp. 109-131 ◽  
Author(s):  
Jaesun Choi ◽  
Avraam I. Isayev
Keyword(s):  
Carbon Nanotube ◽  
Power Consumption ◽  
Natural Rubber ◽  
Ultrasonic Treatment ◽  
Complex Viscosity ◽  
Chain Scission ◽  
Optical Microscope ◽  
Dispersion Analysis ◽  
Multiwalled Carbon ◽  
Link Density

ABSTRACT Natural rubber/multiwalled carbon nanotube (MWCNT) nanocomposites at loadings from 2 to 25 phr were prepared by ultrasonically aided extrusion at ultrasonic amplitudes up to 7.5 μm. Die pressure significantly decreased with an increase of ultrasonic amplitude, especially at higher loadings. Power consumption increased with ultrasonic amplitude and was almost insensitive to loadings until an amplitude of 5.0 μm. However, lower values of power consumption were observed at an amplitude of 7.5 μm for loadings of 10 and 15 phr. At these loadings, complex viscosity, storage, and loss moduli of compounds and vulcanizates were unaffected by ultrasonic treatment, whereas at other loadings, these properties were reduced with ultrasonic amplitude, indicating chain scission. Bound rubber in compounds decreased with treatment. The induction time during vulcanization was unaffected by ultrasonic treatment but decreased with loading, with the largest decrease observed at the lowest loading. The maximum torque in curing, cross-link density, and gel fraction of vulcanizates at loadings of 2, 3.5, 5, 7.5, and 25 phr decreased with ultrasonic amplitude, with the largest decrease observed at loading of 25 phr at an amplitude of 7.5 μm. The modulus at 100% and 300% and tensile strength of vulcanizates at loadings up to 15 phr were unaffected by the ultrasonic treatment, but these properties significantly decreased at a loading of 25 phr at an amplitude of 7.5 μm. Atomic force microscope studies of vulcanizates at a loading of 3.5 phr showed a deagglomeration at an amplitude of 7.5 μm, although dispersion analysis from an optical microscope at loadings of 3.5 and 7.5 phr did not show an improvement of dispersion by ultrasonic treatment. Optical microscope and AFM studies of vulcanizates at a loading of 25 phr indicated that ultrasonic treatment at an amplitude of 7.5 μm significantly improved dispersion of MWCNT. Such a behavior led to a strong Payne effect and an increase in hardness of vulcanizates.

Use of Sol-Gel Analysis to Estimate Chain Scission during Vulcanization. II. Peroxide Vulcanization of Synthetic cis-Polyisoprene

1965 ◽  
Vol 38 (2) ◽  
pp. 367-369
Author(s):  
G. M. Bristow
Keyword(s):  
Natural Rubber ◽  
Sol Gel ◽  
Chain Scission ◽  
A Value

Abstract Sol-gel analysis indicates that in the vulcanization of synthetic cis-polyisoprene by cumyl peroxide there are only 2–3 sites of scission per 100 crosslinked isoprene units, a value closely comparable with that observed for natural rubber.

Characterization of natural rubber using size-exclusion chromatography with online multi-angle light scattering

2008 ◽  
Vol 1213 (2) ◽  
pp. 181-188 ◽  
Author(s):  
Chandy Kim ◽  
Marie-Hélène Morel ◽  
Jérôme Sainte Beuve ◽  
Stéphane Guilbert ◽  
André Collet ◽  
...  
Keyword(s):  
Light Scattering ◽  
Natural Rubber ◽  
Size Exclusion Chromatography ◽  
Size Exclusion ◽  
Exclusion Chromatography

Monitoring the grafting of epoxidized natural rubber by size-exclusion chromatography coupled to FTIR spectroscopy

2003 ◽  
Vol 88 (10) ◽  
pp. 2539-2549 ◽  
Author(s):  
Andr� J. P. Van Zyl ◽  
Sven M. Graef ◽  
Ronald D. Sanderson ◽  
Bert Klumperman ◽  
Harald Pasch
Keyword(s):  
Natural Rubber ◽  
Ftir Spectroscopy ◽  
Size Exclusion Chromatography ◽  
Size Exclusion ◽  
Epoxidized Natural Rubber ◽  
Exclusion Chromatography

Sol-Gel Analysis to Estimate Chain Scission during Cure. I. Peroxide Vulcanization of Natural Rubber

1964 ◽  
Vol 37 (4) ◽  
pp. 904-909
Author(s):  
G. M. Bristow
Keyword(s):  
Natural Rubber ◽  
Sol Gel ◽  
Chain Scission ◽  
Dicumyl Peroxide ◽  
Degree Of Cure

Abstract Sol-gel analysis, that is, the measurement of the fraction of rubber remaining unconnected to the network as a function of the degree of cure, has been used to estimate the extent of chain scission in the vulcanization of natural rubber with dicumyl peroxide at 130° C. For peroxide concentrations in the range 1–5 per cent and masticated rubbers of Mn=0.84−2.67×105 there are only 1–3 sites of scission per 100 crosslinked isoprene units.

UNRAVELING THE MYSTERY OF NATURAL RUBBER BIOSYNTHESIS. PART II: COMPOSITION AND GROWTH OF IN VITRO NATURAL RUBBER USING HIGH-RESOLUTION SIZE EXCLUSION CHROMATOGRAPHY

2014 ◽  
Vol 87 (3) ◽  
pp. 451-458 ◽  
Author(s):  
Cheng Ching K. Chiang ◽  
Balaka Barkakaty ◽  
Judit E. Puskas ◽  
Wenshuang Xie ◽  
Katrina Cornish ◽  
...  
Keyword(s):  
High Resolution ◽  
Natural Rubber ◽  
Size Exclusion Chromatography ◽  
Rubber Tree ◽  
Size Exclusion ◽  
Common Source ◽  
Rubber Biosynthesis ◽  
Flight Mass Spectrometry ◽  
Exclusion Chromatography

ABSTRACT The superior properties of natural rubber (cis-1,4-polyisoprene [NR]) are a function of its structure and composition, properties that still remain a mystery and that are irreplaceable by any synthetic rubber. NR from guayule (Parthenium argentatum) has been gaining special interest for its hypoallergenic properties while maintaining superior mechanical properties that are commonly associated with the Brazilian rubber tree (Hevea brasiliensis), the most common source of NR. Techniques exist to isolate washed rubber particles (WRPs) that contain enzymatically active rubber transferase, to study NR biosynthesis, and previous work on the in vitro NR growth in Hevea has demonstrated the presence of around 50 wt% of a low molecular weight ([MW], Mn <10 000 g/mol) fraction. Structural and compositional analyses of this low MW fraction in Hevea are challenging due to the high protein content. We discuss the analysis and composition of guayule latex and WRPs using high-resolution Size Exclusion Chromatography. We also discuss the composition of the soluble fraction of inactive guayule latex using matrix-assisted laser desorption ionization/time of flight mass spectrometry.

UNRAVELING THE MYSTERY OF NATURAL RUBBER BIOSYNTHESIS. PART I: INVESTIGATION OF THE COMPOSITION AND GROWTH OF IN VITRO NATURAL RUBBER USING HIGH RESOLUTION SIZE EXCLUSION CHROMATOGRAPHY

2011 ◽  
Vol 84 (2) ◽  
pp. 166-177 ◽  
Author(s):  
Chengching K. Chiang ◽  
Wenshuang Xie ◽  
Colleen McMahan ◽  
Judit E. Puskas
Keyword(s):  
High Resolution ◽  
Natural Rubber ◽  
Size Exclusion Chromatography ◽  
Weight Fraction ◽  
Size Exclusion ◽  
Gravimetric Analysis ◽  
In Vitro Synthesis ◽  
Rubber Biosynthesis ◽  
Exclusion Chromatography

Abstract Monitoring the growth of in vitro natural rubber was accomplished by high resolution size exclusion chromatography, SEC. Washed rubber particles isolated from H. brasiliensis latex, containing the rubber transferase enzyme, were used to catalyze the polymerization of synthetic isopentenyl pyrophosphate monomer in the presence of farnesyl pyrophosphate initiator. The high-resolution SEC was able to detect the formation of new rubber. Changes in the low molecular weight fraction were also detected. Gravimetric analysis revealed ∼30% mass gain after the in vitro synthesis. The overall gel content was found to be reduced, which further supported the formation of new rubber. This is the first report that utilizes high-resolution SEC to monitor the in vitro NR growth without the use of radiolabeling.

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