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Bulletproofing by using
Ultra high molecular weight poly ethylene

(Report)

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Submitted To:

Dr.Yasir Qayum

 

Submitted By:

Aqash Arshad

(2017-MS-PE-01)

 

 

University of
Engineering and Technology Lahore

1. Introduction

New material, inorganic
fullerene-like (IF) nano tungsten disulfide (IF-WS2) has been shown to have a
very high absorption of shock waves and shock absorption performance. The
strong anti shock wave feature of nano- WS2 is mainly due to its spherical nested
hollow structure. Its smooth sphere can make the stress be evenly distributed
on the particle surface and its nested hollow structure can absorb a large
amount of shock wave energy, thereby resisting anti shock wave pressures as
high as 25 GPa. In addition, the anti shock strength of this new type of IF-WS2
materials is far greater than that of the ceramic materials commonly used in
the bulletproof armor materials, such as boron carbide, silicon carbide, etc.
The combination of inorganic fullerene like nano sulfides with high elasticity
matrix materials is expected to yield composite materials with high deflection
and absorption impact characteristics, resulting in the composite materials
containing inorganic fullerene like nano sulfides and becoming one of the most
promising candidates for protection materials. UHMW PE fiber has been widely
used in the bulletproof field. Toughening and strengthening modification of
UHMW PE fibers with inorganic nano particles would further enhance the impact
resistance of its bullet proof products. In this study, by mixing the IF-WS2
and a highly elastic UHMW PE material, we prepared UHMW PE/WS2 composite fiber
materials with a homogeneous dispersion of WS2 nano particles, and studied the
influence of the IF-WS2 introduction on the structure and properties of the UH
MWPE fibers .Based on the ballistic performance test results of UHMW PE/WS2 composite
materials, we made a preliminary stud y of the bullet proof mechanism of these
UH MWPE/WS2 composite materials.

Experimental

Preparation of UH MWPE/WS2 Composite Fiber

Surface Modification of WS2 Nano particles.  An amount of 300 g of WS2 nano-particles and
24 g of a silane coupling agent (SCA) were placed in a three- necked flask with
mechanical stirring, and stirred with reflux for 2–3 h at 70–80 C with ethyl
alcohol as the solvent . The WS2 nano particles that had undergone the surface
modification by addition of the SCA were dried at 105 C for future use.      Preparation of UHMWPE/WS2 Composite
Resin. The nano- WS2, after surf ace modification, were mixed with the UHMW PE
resins with mass fractions of 1, 2, 3, and 4 wt%, and then added to a mixing
kettle with the white oil, stirring it while adding the materials. An appropriate
amount of antioxidant s was added to the suspension which had a polymer concentration
of 8 wt%. The suspension was made into a UHMWPE/WS2 composite suspension after
high temperature (100C) swelling and UHMWPE dissolving while stirring.

Preparation of UH MWPE/WS2 Compo site Fiber. The UHMW PE/WS2 composite
suspension was feed into a double screw extruder under the continuous stirring condition,
to disperse the UHMW PE/WS2 composite suspension, and then the UHMWPE/WS2
Preparation of UHMWPE /WS2 Composite Fibers 993 Downloaded by [University of
Engineering & Technology Lahore] at 09:23 07 January 2018 composite
suspension was quantitatively extruded through a metering pump and spinneret
orifice into a coagulating bath to cool down as a gel fiber. The UHMW PE/WS2
gel fibers were extracted, dried, and three level heated at 105, 110, and 108 C,
yielding the UHMW PE/WS2 composite fibers.

Characterization

The prepared UHMW PE/WS2 composite
fibers were embedded in epoxy resin and then cut to obtain transverse sections
of the composite fibers. After metal sputtering, the fiber sections were
examined with field emission scanning electron microscopy (SEM, JSM-7401F ,
JEOL, Japan).The UHMW PE/WS2 composite fiber sample s, after bullet impact,
were embedded in epoxy resin and cut into slices to observe the morphological
and structural changes of WS2 nano particles in the SEM after bullet impact.
The mechanical properties of the UHMW PE/WS2 composite fibers were tested with a
026H-250 type synthetic filament machine produced by Wenz hou Daiei Textile
Instruments Co. , Ltd. The chuck spacing was 100 mm and the tensile speed was
400 mm /min. Each sample was tested 10 time s and then the average value was
calculated. The gun used for the bullet impact test was a “54” pistol and the
projectiles were “51 type ” 7.62 mm lead-co re bullets with a shot distance of 5
m. The projectile speed was 445 § 10 m/s and its test grade was Grade II of the
Ministry of Public Security (GA141-2010).

Results and Discussion

Distribution of IF -WS2 Nano particles in UHMWPE Fibers

In order to investigate the dispersion
of WS2 nano particles in the UH MWPE fiber, SEM analysis was conducted on the
transverse sections of pure UHMW PE fibers without adding WS2 nano particles
and the UHMW PE/WS2 composite fibers adding the WS2 nano particles. Figure 1(a)
is the SEM image of a transverse section of the pure UHMW PE fibers; the fiber
section structure was uniform in cross section, without any nano particles.
Figur e 1(b) is the SEM image of a transverse section of the UHMW PE/WS2 composite
fibers. In the figure, a number of evenly distributed spherical particles can
be seen clearly;

Mechanical Properties of UHMWPE/WS2Composite Materials

Table 1 shows the mechanical
properties of the UHMWPE fiber and UH MWPE/WS2 composite fibers when the drawing
multiple was 40. As it shows, when the content of WS2 nano particles in UH
MWPE/WS2 composite fibers was 1 or 2 wt %, the composite fibers displayed
mechanical properties superior to the pure UHMW PE fibers ; in particular, when
the content of WS2 nano particles was 1 wt%, the tensile strength of UH
MWPE/WS2 composite fiber was higher than that of pure UHMW PE fibers by 7%.More
over, with the increase of content of WS2 nano particles in the composite
fibers, their tensile moduli increased obviously. When the added amount of WS2
nano particles was 4 wt%, the tensile modulus of the UHMW PE fibers was increased
from 1203 to 1326 cN/ dtex , an increas e by 10%, suggesting that, with the
adding of WS2 nano particles, the tensile strength and tensile modulus of
UHMWPE were increased. When the WS2 nano particles, with special molecular
structure after surface modification, was added to the UHMWPE matrix, the
stress could be transferred to WS 2 through the interface in the extension
process due to good interaction between the WS2 nano particles and UHMW PE
matrix, thereby enhancing the mechanical properties of the composite fibers.
However, with the addition of increased amounts of WS2 nano particles, the tensile
strength of the UHMW PE/WS2 composite fibers showed a gradual decreasing trend,
upto 4 wt% WS2, it is noted when the WS2 nano particles percentage exceeded 4
wt%, the UH MWPE/WS2 composite solution could not undergo continuous fiber
formation. This was because, with the increase in the WS 2 nano particles mass
percentage, the dispersion uniformity of WS2 nano particles in the matrix was
reduced, and the agglomerated WS2 nano particles became the focal points of
stress , leading to easy fracture when stretched during process

Bullet proof Mechanism of UHMW PE/WS2 Composite Materials

Figure 2 shows the SEM and TEM
images of the IF-W S2 nano particles. According to the images , the particle
size of the IF-WS2 nano particles was about 100 nm. Figure 3 shows the HRTEM
image of the IF WS2 nano particles with the nested torispherical layered
closure structure. Figure 3(a) shows the shape of the IF-W S2 nano particles;
Figure 3(b) shows an enlarged image of part of Fig. 3(a). As shown from the
image, the IF-WS2 nano particles have a typical nested torispherical layered
closure structure. From the illustration, it can be seen that the distance
between the layers for the IF-WS2 nano particles closure structure was about
0.63 nm. According to the literature, such a kind of IF-WS2

Nano particles, with nested
torispherical layered closure structure, could resist a shock pressure up to 25 GPa while
maintaining the overall morphology of the material, which is not completely destroyed. The super anti shock wave features of
the WS2 nanoparticles can be attributed
to its nested torispherical hollow structure . The smooth sphere could make the stress distribute on the
particle’s surface evenly and the nested hollow structure could absorb a large amount of shock wave energy. Figure 4 is the
HRTEM image of the WS2 nano particles of the UHMW PE/WS2 composite materials
after being shocked by 51 type 7.62 mm lead-core bullets emitted from“54”
pistol. The WS2 nano particles in the UH MWPE/WS2 composite materials were partially
destroyed after being shocked b y the high-speed bullets. Their layered shell
structures were damaged partially (as indicated by the arrows). According to
the bullet proof

performance test results of the
UHMW PE/WS2 composite materials, it could be inferred that, by the damage of
the layered structure of the IF-WS2 nano particles, the IF-WS2 nano particles
can absorb a large amount of impact energy of bullets fired against the UH
MWPE/WS2 composite target slices , and thus effectively slow the damage to the
UH MWPE/WS2 composite materials by the bullets impact. Figure 5 illustrates the
bulletproof mechanism of the UHMW PE/WS2 composite materials. When the UHMW
PE/WS2 composite materials were subject to the bullet impact, the torispherical
structure of IF-WS2 nano particles could make the external force distribute on
the particle surface evenly; moreover, the nested hollow layered structure of
the IF-WS2 nano particles could absorb a large amount of energy, to effectively
suppress the damage cause d by the impact from bullets.

Conclusions

By adding the surface modified
IF-WS2 to the UHMW PE spinning solution, we prepared a series of WS2 nano
particles enhanced UHMW PE composite fiber materials using a gel spinning
technique. The SEM, HRTEM, strength testing, and bullet test results showed
that the WS2 nanoparticles could be homogeneously dispersed in the composite
fibers and the adding of the WS2 nano particles could effectively enhance the
mechanical properties. When the added amounts of nano meter WS2 was 4 wt%, the
maximum permitting gel- spinning , the UHMW PE fiber tensile modulus was
increased from 1203 to 1326 cN/dtex , an increase by 10%. The IF-WS2 nested torispherical
enclosure structure could absorb a large amount of impact energy and thus effectively
inhibit the damage of bullet impact on the UHMWP E/WS2 composite materials. This
stud y showed that, compared with the pure UHMW PE fiber, the UHMW PE/WS 2
composite materials have excellent bulletproof performance ; therefore, we hope
that the UHMW PE/WS2 composite materials prepared by our institute will have a
great development value and good application prospect in new bullet resistant
materials, and can be extensively applied in individual protective armor,
vehicle arm

 

 

 

or, and other fields.

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