Mohd Hafiz Zainol
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Preferred name
Mohd Hafiz Zainol
Official Name
Mohd Hafiz, Zainol
Alternative Name
Mohd, H. Z.
Zainol, Mohd
Zainol, M. H.
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Scopus Author ID
57201736993
Researcher ID
CGX-4416-2022

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Self-healable and recyclable nitrile rubber based on thermoreversible ionic crosslink network

2022-04-15 , Mohd Hafiz Zainol , Ariff Z.M. , Mohd Firdaus Omar , Ping T.M. , Shuib R.K.

In this work, commercial carboxylated nitrile butadiene rubber (XNBR) was ionically crosslinked with zinc thiolate forming reversible ionic salt bonding between carboxy groups (COOH) in XNBR chains and Zn2+ ions from zinc thiolate. The reversible nature of the ionic crosslinks allows rearrangement of rubber molecular chains under an external heat and provides self-healing capability to the materials. The amount of zinc thiolate was varied at five levels (10, 20, 30, 40, and 50 per hundred rubber (phr) to assess the maximum reaction between COOH and Zn2+ ion for the formation of ionic crosslink networks. Evidence that ionic crosslinks formed within the materials was determined by the increased of curing torque and the chemical interaction was identified by Fourier transform infrared spectroscopy. An equilibrium swelling testing quantitatively measured the ionic crosslink density within the material and XNBR with 30-phr zinc thiolate showed the highest ionic crosslink density. The results revealed that, damaged XNBR with 30 phr zinc thiolate able to recover 98% of its initial properties under thermal healing at 150°C for 10 min. Furthermore, the material can be reprocessed and recycled for three times without compromising its initial properties. Perhaps, the tensile strength increased 360% at approximately 23 MPa, after third recycling process. In addition, the self-healing XNBR also have excellent weldability on the damage sample, which shows high potential for repairing of existing rubber products installed in heavy engineering applications.

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Effect of multi-walled carbon nanotubes reinforcement on self-healing performance of natural rubber

2024-01-01 , Mohd Sani N.F. , Shuib R.K. , Mohd Hafiz Zainol , Othman N. , Tran D.L.

This work is motivated by the desire to restore the quality of rubber-based product properties with the intention of prolonging the service life period, thus helping create a sustainable environment by proposing effective rubber waste management. This study experimentally investigated an intrinsically self-healing zinc thiolate grafted natural rubber (NRZT) compound filled with multi-walled carbon nanotubes (MWCNT) to assess its influence on mechanical properties and self-healing performance. The MWCNT loading varied to 0, 2, 4, 6, and 8 phr. The Equilibrium swelling test was used to quantify the amount of ionic and covalent crosslinks formed. Fourier Transform Infrared (FTIR) spectra were used to detect the presence of MWCNT in the compound. The mechanical properties computed by the tensile and tear strength tests showed that the incorporation of MWCNT increased both properties up to three and twofold, respectively. However, as expected, the elongation at break (Eb) value was reduced. The unfilled sample showed that it can heal up to ∼98 %, measured from the tensile strength. However, the healing efficiency obtained from tensile strength reduces to ∼88 % by incorporating 2 phr MWCNT. The Eb and its self-healing efficiency gradually decreased as the MWCNT amount increased. All samples showed outstanding properties under the tearing mode, where the healed samples produced higher tear strength (>100 % healing) than the initial value. Scanning Electron Microscopy (SEM) micrographs revealed a noticeable gap along the healed cut line with increased MWCNT numbers, possibly due to the lower reaction between polymerized zinc thiolate (PZTh) radicals with zinc thiolate (ZT) and rubber molecules. The work aims to investigate the influence of MWCNTs on the mechanical and healing performance of self-healing NR composites by comparing them to their unfilled sample.

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Self-healing magnetorheological elastomer for vibration damping

2020-01-01 , Shuib R.K. , Thajudin N.L.N. , Mohd Hafiz Zainol

In this work, magnetorheological elastomers (MRE) based on nickel zinc ferrite and natural rubber were prepared. Self-healing capability was employed to the MRE by peroxide induced graft polymerization between zinc thiolate and natural rubber to produce reversible ionic crosslinks that can recover the properties of the fracture materials. Evidence that reversible ionic crosslinks occurred was determined by tensile test of original and healed sample. The results revealed that the tensile strength of the MRE recovered 56% in a minute and almost 100% in 10 minutes at room temperature. The morphology of the fractured surface also showed the fracture area was recovered after the healing processed. The dynamic mechanical analysis of the MREs under cyclic loading were also examined with parallel plate rheometer.

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The effect of ionic cross linker on Self-healing natural rubber

2020-09-21 , Mohd Hafiz Zainol , Shuib R.K.

The performance of rubber used for engineering purposed are depending on the selection of raw materials, followed by the processing of the rubber into final products. Although the products been made as robust as possible, rubber still failed through crack and fatigue. In this work, the effect of ionic cross linker by association of different amount of Zinc thiolate has been investigated to emerge autonomous self-healing ability to the materials. The self-healing mechanism of the materials was evidence by FTIR and swelling analysis. Healing performance and efficiency has been carried out using tensile test to investigate the self-healing ability. The results revealed that the material recovered its initial properties in 10 minutes and the tensile strength recovered almost 90% after healing process at room temperature without any external stimulus. The SEM observation showed that the intermolecular diffusion occurred between the fractured surfaces and healed the materials.

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