Study of the Mechanical Properties of Ultra-High Molecular Weight Polyethylene Fiber Rope

Abstract

Ultra-high molecular weight polyethylene fiber (UHMWPE) exhibits outstanding strength to weight balance due to high molecular orientation, high crystallinity and low density. For these reasons, is widely used in applications demanding high strength high modulus fibers. This paper systematically studies the relationships between the mechanical properties of ropes made of ultra-high molecular weight polyethylene fiber and several attributes of the rope construction. By studying the structure of the rope, a formula relating the Young's modulus and twist angle was developed. It was found that the breaking strength and the elongation of the rope were closely related to the twist angle. Finally, the breaking strength of the rope had a positive correlation with the diameter of the rope. The retention rate of fatigue strength studied in this paper was kept above 100%. These results may provide useful guidance to the industrial production of the UHMWPE based ropes. © 2016, Association Nonwoven Fabrics Industry. All rights reserved.

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Journal of Engineered Fibers and Fabrics 9 http://www.jeffjournal.org
Volume 11, Issue 1 – 2016
Study of the Mechanical Properties of Ultra-High
Molecular Weight Polyethylene Fiber Rope
Guangting Han, Xiaowei Tao, Xianbo Li, Wei Jiang, Wenqian Zuo
Qingdao University, Laboratory of New Fiber Materials and Modern Textiles
Correspondence to:
Guangting Han email: kychgt@qdu.edu.cn
ABSTRACT
Ultra-high molecular weight polyethylene fiber
(UHMWPE) exhibits outstanding strength to weight
balance due to high molecular orientation, high
crystallinity and low density. For these reasons, is
widely used in applications demanding high
strength high modulus fibers. This paper
systematically studies the relationships between the
mechanical properties of ropes made of ultra-high
molecular weight polyethylene fiber and several
attributes of the rope construction. By studying the
structure of the rope, a formula relating the Young's
modulus and twist angle was developed. It was
found that the breaking strength and the elongation
of the rope were closely related to the twist angle.
Finally, the breaking strength of the rope had a
positive correlation with the diameter of the rope.
The retention rate of fatigue strength studied in this
paper was kept above 100%. These results may
provide useful guidance to the industrial production
of the UHMWPE based ropes.
Keywords: UHMWPE; Breaking strength;
Elongation; Fatigue strength
INTRODUCTION
Ultra-high molecular weight polyethylene
(UHMWPE) fiber exhibits an excellent balance of
excellent mechanical properties, including
ultra-high breaking strength at fine diameter, low
elongation and high anti fatigue strength [1]. Due to
UHMWPE's high rigidity, high strength [2], and
good energy absorption effect [3], it is widely used
in bulletproof armor [4-5], ballistic protective
helmets and bulletproof vest. Based on its biological
compatibility and light weight it can be applied to
bone grafts with the addition of lubricants [6-7] and
periosteum engineering by combining with carbon
nanotubes [8}. The UHMWPE's friction
performance is excellent [9], but mechanical
properties deteriorate through long-term
atmospheric exposure, as demonstrated through
weathering experiments [10]. Because of its high
molecular weight and tight molecular chain
entanglement, there are difficulties in using
conventional methods such as melt spinning to
process UHMWPE fibers [11]. Due to UHMWPE's
low surface energy and chemical inertness, it is
difficult to dye and bond to most substrates even
after various surface treatments [12]. On a more
positive note, UHMWPE has found use in low
temperature environments [13].
The Present research of high strength nanofibers
focuses on nanofibers. Poly(m-phenylene
isophthalamide) (PMIA) nanofibers can be
fabricated on a large scale via a facile combination
of relative humidity (RH)-regulated electrospinning
and multi-level aggregate reconstructing [14]. The
tensile strength of PMIA-MWCNT hybrid
nanofibers which prepared by a facile
electrospinning process can reach 316.7 MPa. The
focus of this article is the rope product made using
such high strength nanofibers [15].
UHMWPE rope is used as for mooring and towing
in the engineering such as the large ship in the
shipping industry and offshore oil drilling industries.
Its high resistance to heavy load and wear and low
friction coefficient make it useful in sport and
leisure applications [16]. It is also used as a rope
with the properties of super high load, thin diameter
and light weight in the military and marine
applications, as the warp and hand rope in the large
mid-water trawl of fisheries, and also as the cable
and anchor cable in the net cage for large-scale
mariculture applications [17-18]. The mechanical

Journal of Engineered Fibers and Fabrics 10 http://www.jeffjournal.org
Volume 11, Issue 1 – 2016
properties of the rope described herein are all
positive influences related on the safety of the
applications mentioned above. The basic structure
parameters of the rope can have great influence on
its mechanical properties. In production processes,
the structure parameters of the rope are generally
determined through a combination of experience
and in-situ tests [19-20]. This paper analyzes the
breaking strength, elongation at specified load and
fatigue strength of the UHMWPE ropes with
different knitting technology and fineness.
Relationships between the basic construction
parameters and mechanical properties of the rope
are developed, with the objective of developing
data-based guidance for application to rope
production.
EXPERIMENTAL
Material And Methods
Material
The rope was braided with a plurality of strands
interspersed with crosses. In order to ensure torque
balance, two adjacent spindle strands were
pre-twisted in opposite directions- the S-twist strand
in the reverse rotation and the Z-twist in the
clockwise rotation. The rope's tightness was
controlled by the speed of equipment's drawing
mechanism's gear ratio (the weft density). When
weft density is decreased, the strands get closer, the
rising pitch weaving a circle share became lower,
and the diameter increased.
The weaving process and structure parameters of
the rope woven with UHMWPE of 105.5 tex are
shown in Table I.
TABLE I. Rope's weaving process and structure parameters.
Order number
Number of
strands
Strands of
yarn number
Pulling weft density and the yarn twist angle (°)
1# 4Z4S 80.39/ 35 0.46/28 0.52/24 0.59/23 0.73/ 21 1.04/18 1.74/11
2# 4Z4S 12 0.46/35 0.52/30 0.59/ 27 1.04/23 1.16/21 1.74/18 2.09/ 13
3# 8Z8S 10 0.59/39 1.04/29 1.16/ 27 1.57/21 1.74/20 2.09/12
4# 8Z8S 15 0.93/38 1.04/37 1.16/ 31 1.56/25 1.74/20 2.09/17
Experiment Instrument
Electronic universal testing machine CMT5105
produced by Shenzhen sans testing machine Co.,
Ltd (the largest experimental force is 100 KN, using
wheel clamp).
Methods
The rope's breaking strength, elongation and fatigue
strength were tested according to the China Testing
Standard of GB/T 8834 - 2006/ISO rope,
2307:1990.
Breaking strength: Two tags symmetric to the
sample midpoint on the test sample were marked,
the wheel clamp was used to fix the both ends of the
specimen, and the effective length of the sample
was 200 mm when clamping. A pre-tension was
applied on the sample according to the rope type,
and then the distance between the two markers was
measured.
Elongation test: Samples were elongated in a range
of 6%-10% of the original length. When the tension
of the new distance between the markers reached
75% of the breaking strength, the constant load
elongation was calculated.
Strength fracture test: A pre-stress was applied to
the rope, then the rope was stretched at a speed of
20 mm/min until broken. The rope's breaking
strength and breaking position were then recorded.
Fatigue strength test: A load of 20%-70% of the
rope's breaking strength was applied over 1000
sinusoidal cycles. The rope was then broken and the
relative strength retention was recorded.
Figure 1 represents an overall flow diagram of the
experimental protocol of this study.

Journal of Engineered Fibers and Fabrics 11 http://www.jeffjournal.org
Volume 11, Issue 1 – 2016
UHMWPE
Ropes
Elongation TestStrength Test Fatigue Test
We ave
Folded Yarns
Ply
FIGURE 1. The experiment chart.
RESULTS AND DISCUSSION
The Structure of the Rope
Theoretical Mode between Pitch and Twist Angle
(a)
(b)
(c)
FIGURE 2. 3D structure of the rope (a, b) and trajectory diagram
of the cross section (c).
The 3D model for the rope structure is shown in
Figure 2(a) and Figure 2(b). Figure 2(a) represents
the full structure and the Figure 2(b) is the model
for the single unit of the rope. The braided angle (θ)
of the rope (Figure 2(b)) can be calculated from the
cross section of the unit (Figure 2(c)). Twist angle
(β) could be introduced (( )).
A global Cartesian coordinate system(x, y, z) is
established in Figure 2(b). The equation of pitch
and twist angle is:
(1)
P: Pitch, mm. L: Projection of the cross section of
unit Pitch, mm.
(2)
As the speed of the drawing mechanism's adjusted
gear ratio (the weft density) increases [21], the axial
pitch increases, promoting a decrease in diameter.
The relationship between rope diameter and pitch is
shown in Figure 3. The regression analysis was
analyzed using SPSS, and the pitch-diameter of the
optimal fitting equation was obtained as follows: Y
=3.209+15.289/X, where Y represents diameter, X
represents pitch. The R2 of this equation is 0.981,
which implies the equation is correct and reliable. It
is noticeable from the equation that with an increase
in the rope pitch, the single strands of yarn's
movement direction tend to be consistent and the
degree of horizontal bending produced decreases,
resulting in diameter decrease and an inverse
relationship between pitch and diameter.

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Volume 11, Issue 1 – 2016
FIGURE 3. Relationship between pitch and rope diameter.
Theoretical Mode and Verification for Twist
Angle and Young's Modulus
Twist angle describes the relationship between
diameter and pitch [22]. Eq. (1) above resulted from
analysis of this study. By the same token, Eq. (3)
results from the research on the initial modulus and
the breaking strength of yarn [23].
If a single strand rope is viewed as a cylinder
structure under ideal state:
(3)
is the strain of the fiber, is the stress of the
single strand rope, and is the dip angle
between the fiber axe and the Single strand rope
axe. This shows that the strain of the fiber in the
middle of the single strand rope is the same as the
strain of the single strand rope. When the dip
angle becomes , the Strain becomes .
According to the Hooke's law, the tension:
(4)
Where is the elastic modulus of the fiber, r is
the radius of the fiber, the contribution of each fiber
in Single strand rope is
(5)
The numerator refers to the effective axial
component force of . The denominator describes
the effective axial area. By applying this equation to
the cross section of Single strand rope, the stress of
the Single strand rope can be obtained through
integration.
(6)
Where is the twist angle, the Young's modulus E
of the rope is
(7)
Young's modulus is defined as the ratio of the stress
(F/S) along an axis to the strain (ΔL/L) along that
axis in the range of stress in which Hooke's law
holds. The formula is . Where E is
Young's modulus, is the stress, is the strain.
Then, the measured value of Young’s modulus can
be calculated by the stress value and strain value.
The measured value and the theoretical value
calculated from the Eq. (7) show similar trends
(Figure 4), which implies that the Eq. (7) is
reasonable and capable to analyze the Young’s
modulus.
510 15 20 25 30 35 40
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Measured curve (GPa)
Twist angle (°)
Measured curve
Theoretical curve
FIGURE 4. Comparison of theoretical data and measured data.

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Volume 11, Issue 1 – 2016
The Relationship Between Twist Angle And
Tensile Properties
(a)
(b)
(c)
(d)
FIGURE 5. The relationship of the rope twist angle and the
breaking strength, elongation (a: 4 mm, b: 6 mm, c: 8 mm, d: 10
mm).
Figure 5 represents the rope strength and elongation
results based on the weaving parameters of Table I.
The increasing of the drawing speed causes the
twist angle of the strands to change, which changes
the structural parameters of the rope, and ultimately
affects the magnitude of the rope's strength and
elongation.
It is observed from Figure 5 that the rope breaking
strength increases as the twist angle decreases.
When the twist angle decreases to a certain value,
the curve tends to be stable; the breaking strength
tends to a constant value. This is because as the
twist angle increases, the rope's axial deviation
angle becomes larger, dispersion of fibers into the
ropes axial tensile strength decreases, effectively
decreasing the rope strength. Secondly, as the twist
angle increases, the rope becomes more compact,
and the pitch number in the same length increases.
With the rope force increasing, fibers can't be
completely straight under the action of external
force, the pitch pressure is also increasing, which
leads to a higher tangential pressure, causing the
rope to break on the pitch point. When the twist
angle is reduced to a certain value, the rope
structure is not as compact, plied yarns are easy to
transfer, and the fiber is almost straight to axial rope.
Thus, breaking strength plateaus to a fixed value.
In the twist angle-elongation plots, the rope fixed
load elongation decreases continuously with the
decrease in the twist angle. When the twist angle
decreases to a certain value, the elongation tends to
a constant value. The elongation is higher at high
twist angle stage because the first stage of
elongation is the extension and elongation of the
spiral rope. The ropes with the larger twist angle
contain longer piled yarns in a given length; in the
initial stages of tensile stress the tensile force
increases gradually and the piled yarns in the rope
become completely straight and elongate. As load
continues to increase, the elongation of the rope
mainly becomes monofilament elongation resulting
from chain slippage of molecules of individual
fibers. Therefore, with the decrease of the twist
angle rope, rope elongation decreases gradually to a
given value.
Comprehensively analysis of the relationship of
twist angle, breaking strength and elongation from
Figure 5 shows that when the yarn woven twist
angle is about 25 degrees, breaking strength of the

Journal of Engineered Fibers and Fabrics 14 http://www.jeffjournal.org
Volume 11, Issue 1 – 2016
rope is high, but the elongation is low. Therefore, in
order to produce ropes of high strength and low
elongation, the pulling speed should be controlled
such that the twist angle of 25 degrees.
The Relationship Between Diameter and
Strength
FIGURE 6. Relationship between rope diameter and breaking
strength.
Using the parameters listed in Table I (number of
strands, the stock yarn number and twist angle of
about 21 degrees) four ropes of different diameters
were woven. Figure 6 shows breaking strength
values of the four ropes. The results of numerical
analysis and linear regression equation show that
rope diameter and breaking strength is exponential,
and the correlation coefficient R2 is 0.972. This
relation can be used to predict the breaking strength
of the ropes with different diameters, and provide a
theoretical basis for production guidance.
Rope Fatigue Test
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
0
2
4
6
8
10
12
Strength
(KN)
Weft density
Static tensile strength
Ultimate strength
40
60
80
100
The retention rate of strength(%)
The retention rate of
strength(%)
FIGURE 7. Anti-fatigue strength retention rates of ropes of
various pitches.
From the strength retention of Figure 7, it can be
seen that the rope does not decrease its breaking
strength by loading for 20%-70% of the fracture
strength, after repeated for 1000 cycles of sinusoidal
fatigue testing. In fact, the strength after cycling
increases to about 100-110% of the original value.
This is because after repeated stretching of the
UHMWPE rope, resulting slippage of molecular
chains results in enhanced orientation of the fibers,
effectively increasing the strength of the strands and
the rope [24]. At the same time, this repeated
fatigue draft increases the uniformity of orientation
of the individual UHMWPE fibers, maximizing the
strength of the rope. This tends to confirm that the
high strength of UHMWPE fibers results from the
numerous covalent bonds of the carbon atoms in the
axial direction [25], resulting in high anti-fatigue
performance of the rope woven from such fibers.
CONCLUSION
1) The mechanical properties of the UHMWPE rope
are closely related to the twist angle. A formula
relating the Young's modulus and twist angle was
developed.
2) The weft density value affects the tightness of the
rope, with the diameter getting smaller, the rope
becoming more compact, the pitches per unit length
decreasing. Rope diameter and section spacing have
a reciprocal equation.
3) The increase of twist angle decreases the
structural stability of the rope; lowering the
effective utilization of individual fiber strength. The
optimum weaving twisting angle for high strength,
low elongation rope should be controlled to 25
degrees. The rope diameter and tensile strength
have an exponential relationship.
4) Tensile fatigue test loading and unloading of
ultra-high molecular weight polyethylene fiber
ropes tended to improve breaking strength.
ACKNOWLEDGEMENT
The authors are grateful for the funding of National
Natural Science Foundation of Shandong Province
(ZR2014EMQ010), Qingdao Sci-Tech Planning
Project (13-1-4-215-jch), Taishan Scholars
Construction Engineering of Shandong Province,
and Program for Scientific Research Innovation
Team in Colleges and Universities of Shandong
Province.

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REFERENCES
[1] Luyu Zhou, Xianbo Li. A Comparative study
of UHMWPE Multifilament and Aramid
Multifilament [J]. Advanced Materials
Research, 2013, 709, 84-88.
[2] G. Liu, M.D. Thouless, V.S. Deshpande, et al.
Collapse of a composite beam made from
ultra-high molecular-weight polyethylene
fibers [J]. Journal of the Mechanics and
Physics of Solids, 2014, 63, 320-335.
[3] Wei Zhang, Zihan Hu, Yan Zhang, et al.
Gel-spun fibers from magnesium hydroxide
nanoparticles and UHMWPE
nanocomposite: The physical and
flammability properties [J]. Composites:
Part B, 2013, 51, 276-281.
[4] Long H. Nguyen, Shannon Ryan, Stephen J.
Cimpoeru, et al. The effect of target
thickness on the ballistic performance of
ultra-high molecular weight polyethylene
composite [J]. International Journal of
Impact Engineering, 2015, 75, 174-183.
[5] Rui Miranda Guedes, Celeste M.C. Pereira,
Alexandra Fonseca, et al. The effect of
carbon nanotubes on viscoelastic behaviour
of biomedical grade ultra-high molecular
weight polyethylene [J]. Composite
Structures, 2013, 105, 263-268.
[6] Dariush Firouzi, Aya Youssef, Momen Amer,
et al. A new technique to improve the
mechanical and biological performance of
ultra-high molecular weight polyethylene
using a nylon coating [J]. Journal of the
mechanical behavior of biomedical
materials, 2014, 32, 198-209.
[7] Ruofan Ma, Jie Xu, Yan Chen, et al. An in
vivo rat model of self-control continuous
intramedullary infusion of ultra-high
molecular weight polyethylene particles by
osmotic pumps[J]. Journal of Orthopaedic
Translation, 2013, 1, 49-56.
[8] Masanori Kobayashi, Takayuki Koide,
Suong-Hyu Hyon, et al. Tribological
characteristics of polyethylene glycol (PEG)
as a lubricant for wear resistance of
ultra-high-molecular-weight polyethylene
(UHMWPE ) in artificial knee join[J].
Journal of the mechanical behavior of
biomedical materials, 2014, 38, 33-38.
[9] A. Wang, V. K. Polineni, C. Stark, et al. Effect
of Femoral Head Surface Roughness on the
Wear of Ultrahigh Molecular Weight
Polyethylene Acetabular Cups[J]. The
Journal of Arthroplasty, 1998, 13, 615-620.
[10] Chang-Sheng Li, Mao-Sheng Zhan,
Xian-Cong Huang, et al. Degradation
behavior of ultra-high molecular weight
polyethylene fibers under artificial
accelerated weathering[J]. Polymer Testing,
2012, 31, 938-943.
[11] Zhipei You, Dagang Li. Highly filled bamboo
charcoal powder reinforced ultra-high
molecular weight polyethylene[J]. Materials
Letters, 2014, 122, 121-124.
[12] Ichiro Enomoto, Yosuke Katsumura, Hisaaki
Kudo, Masayuki Sekiguchi. The role of
hydroperoxides as a precursor in the
radiation-induced graft polymerization of
methyl methacrylate to ultra-high molecular
weight polyethylene[J]. Radiation Physics
and Chemistry, 2010, 79, 718-724.
[13] Liu Hongtao, Ji Hongmin, Wang Xuemei.
Tribological properties of ultra-high
molecular weight polyethylene at ultra-low
temperature [J]. Cryogenics, 2013, 58, 1-4.
[14] K Chen, S C Zhang, B W Liu, et al.
Large-scale fabrication of highly aligned
poly(m-phenylene isophthalamide)
nanofibers with robust mechanical
strength[J]. RSC Advances, 2014, 4,
45760-45767.
[15] X Wang, Y Si, X Wang, et al. Tuning
hierarchically aligned structures for
high-strength PMIA-MWCNT hybrid
nanofibers [J]. Nanoscale, 2013, 5, 886-889.
[16] M.T. Mathew, J. Novo, L.A. Rocha, J.A.
Covas, et al. Tribological, rheological and
mechanical characterization of polymer
blends for ropes and nets[J]. Tribology
International, 2010, 43, 1400-1409.
[17] Yiping Guo, Haiyou Ma , Lisheng Mao. The
performance and selection of fiber rope in
deep water net cage [C].2004.
[18] Haiyou Ma, Yiping Guo, Lisheng Mao. Study
on Marine Fisheries anti wave cage of
ultra-high molecular weight polyethylene
composite rope [J]. marine fishery, 2005,
27.
[19] Shenghua Lv, Jieliang Wang, Yang He,
Guozheng Liang, et al. Study on ropes of
high strength rope UHMWPE
fiber[J].engineering plastic, 2003, 31.

Journal of Engineered Fibers and Fabrics 16 http://www.jeffjournal.org
Volume 11, Issue 1 – 2016
[20] Lisheng Mao, Yiping Guo, Haiyou Ma, et al.
The elongation measurement of the
UHMWPE rope [J]. China Fisheries
Science, 2004, 11.
[21] Lizhen Chen, Haofeng Yu, Shanyuan Wang.
Study of process on high strength polyester
three strand rope[J]. Journal of China
Textile University, 1994, 20, 45-52.
[22] Suoting Yang, et al. Spinning technology[M].
Beijing. China Textile Press. 2004: 251-253.
[23] Weidong Yu, et al. Textile materials[M].
Beijing. China Textile Press. 2008:228-229.
[24] Edin Suljovrujic, Maja Micic, Dejan Milicevic.
Structural Changes and Dielectric
Relaxation Behavior of Uniaxially Oriented
High Density Polyethylene[J]. Journal of
Engineered Fibers and Fabrics, 2013, 3,
131-143.
[25] Fangtao Ruan, Limin Bao. Mechanical
Enhancement of UHMWPE Fibers by
Coating with Carbon Nanoparticles[J].
Fibers and Polymers, 2014, 15, 723-728.
AUTHORS’ ADDRESSES
Guangting Han
Xiaowei Tao
Xianbo Li
Wei Jiang
Wenqian Zuo
Qingdao University
Laboratory of New Fiber Materials and Modern
Textiles