Materials
In order to conduct this experimental investigation, a total of 3 kg of date seeds and tamarind seeds were obtained from Manidharma Biotech dealers in Chennai, Tamil Nadu, India. The seeds were cleaned with distilled water to eliminate any excess fruit pulp that had become stuck to them throughout the cleaning process. Tissue paper was then used to wipe away any extra water that had collected on their surfaces. Finally, they were dried for 24 hours at 60 °C in an oven. Following milling in a ball mill, a good morphology of 30–60 μm was achieved, making the fillers ready to be employed as reinforcement. GSRR Resins And Polymers, Madurai, Tamilnadu, provided the industrial bisphenol-A-epoxy vinyl ester resin (styrene - 45 percent), which had a density of 1.145 g/cm3, viscosity of 400 cps, and specific gravity of 1.09, as well as N-dimethylaniline (C8H11N - promoter), methyl ethyl ketone peroxide (C8H18O6 - catalyst) and cobalt 6% naphthenate (C20H34CoO4 - accelerator) was employed for curing purposes in accordance with the supplier's recommended ratio. Table 1 shows the chemical composition of TSF and DSF with various fillers and fibres.
Fabrication of Composites
The compounding of hybrid fillers and vinyl ester has been accomplished in this current study using a typical compression molding approach. For specimen manufacturing, different filler loadings ranging between 5 to 50 wt.% were adopted with mould specifications of approximately 200 mm long, 200 mm wide, and 3 mm thickness. The phases of preparation of the date seed filler are displayed in Fig. 1. Initially, mold removal wax (provided by Carbon black) was added to the inside surface of the mould as well as the covering plate to facilitate the removal of the cured composite plates once they had been cured. And then, a measured quantity of vinyl ester resin was Placed in a container, and 1.5 wt.% of the promoter (10 percent, N-dimethylaniline) was included in the beaker. The beaker was then agitated for another 2 minutes, and the mixture was degassed in a vacuum chamber to eliminate any air bubbles that had penetrated on where stirring procedure. A mixture of equal amounts (1.5 wt.%) of accelerator (3 wt.% Cobalt naphthenate) and catalyst (50 wt.%methyl ethyl ketone peroxide) were introduced one at a time and mixed for 2 minutes before being degassed in a vacuum chamber every after the introduction of accelerator and catalyst.
Table 1. Material characteristics of a Hybrid filler/vinyl ester (TSF/DSF) composite compared to various fillers and fiber-based composites.
Reinforcements
|
Manufacturing process
|
Tensile strength (MPa)
|
Flexural Strength
(MPa)
|
Impact strength (KJ/m2)
|
Hardness
|
References
|
TSF/DSF/Vinyl ester
|
Compression moulding
|
36.9
|
112
|
22.12
|
38.34
|
Present work
|
Nanoclay/banana/jute/polyester
|
Compression moulding
|
15 – 23.7
|
34 – 48.3
|
–
|
–
|
[22]
|
Date seed powder/Vinyl ester
|
Compression moulding
|
10.5 -- 40
|
46 -- 149
|
9.43 -- 17
|
20.33 -- 51
|
[18]
|
Boiled egg shell /Coir/Vinyl ester
|
Compression moulding
|
24
|
26
|
39.5
|
--
|
[23]
|
Tamarind seed powder/Vinyl ester
|
Compression moulding
|
10-- 34
|
47 -- 121
|
7 -- 14
|
23 -- 42
|
[17]
|
Nano Oil palm shell/(kenaf–coconut–kenaf fiber/polyester
|
Compression moulding
|
30 – 37.56
|
60 – 69.45
|
10 – 13.42
|
–
|
[24]
|
Alumina/Coir/Vinyl ester
|
Compression moulding
|
27
|
31
|
40.5
|
--
|
[23]
|
Shorearobustafiller/Polyester
|
Hand lay-up method
|
12---15
|
25--26
|
--
|
--
|
[25]
|
Rice hull/Polyethylene
|
Injection moulding
|
19--26
|
19--30
|
11--16
|
--
|
[26]
|
Polyalthialongifolia seed filler/Vinyl ester
|
Compression Molding
|
9--32
|
44--125
|
10--31
|
23--36
|
[20]
|
Rice husk/Boiled Egg shell/Coir/Polyester
|
Hand lay-up method
|
17 -- 31.5
|
18 -- 33
|
17 -- 33
|
--
|
[27]
|
Roselle fiber/Sugar Palm Fiber/Vinyl ester
|
Hand lay up
|
15--24
|
58—110.5
|
--
|
--
|
[28]
|
Date palm wood flour / glass fibre/polypropylene
|
Compression moulding
|
15--25
|
--
|
--
|
35--60
|
[29]
|
Sisal fiber/epoxy resin
|
Hand lay up
|
5--15
|
22--61
|
5--13
|
--
|
[30]
|
Sawdust/ Recycled Plastics
|
Hand lay up
|
9--13
|
21--35
|
--
|
--
|
[31]
|
carbon fiber/cement dust/vinyl ester
|
Hand lay up
|
10--19
|
28--34
|
--
|
--
|
[32]
|
wood flour/pulp fiber/Polyvinyl Chloride
|
Hand lay up
|
6--17
|
18--42
|
--
|
--
|
[33]
|
Sawdust Flour/Polypropylene
|
Hand lay up
|
25--30
|
50--54
|
--
|
--
|
[34]
|
Afterward, the produced mixture was started pouring into the mould, and the mould was covered with the help of a cover plate to complete the process. It was necessary to cure the composite specimen for 24 hours at atmospheric temperature before removing it from the mould and post-curing it for approximately 2 hours at 80 degrees Celsius in the oven. The cured TSF/DSF hybrid-VE composite plate was extracted from the chamber of the mould. The same process has been used to produce the hybrid-VE composite with various filler loadings.
Experimental Details
Mechanical Testing
A saw cutter was used to cut the fabricated composite plates to the desired shapes for different test specimens. Tensile and flexural experiments were carried out at room temperature, utilizing a universal testing machine (Tinius OlsenH50K). To check the repeatability of the results obtained, three specimens with respect to each weight percentage were tested. According to ASTM D638 (165 × 10 × 3 mm) test standard, a tensile test was carried out on specimens, using a set crosshead speed of 1 mm/min 17. Flexural testing was carried out using the three-point bending technique with a potential of 50 kN and crosshead rate of 2 mm/min for all samples with the following dimensions: 127 mm in length, 12.7 mm in width, and 3 mm thick in accordance with ASTM D790-10 standard 18. The impact strength was determined using the Charpy measurement technique in accordance with the ASTM D-256 (65 x 13 x 3 mm3) standards, and the results were analyzed. The hardness of the material was also assessed using a Barcol Hardness analyzer (Model: VBH2) in accordance with the ASTM 2583 standard. The hardness for each sample was found as the mean of 7 measurements. With the use of a Zeiss EVO 18 scanning electron microscope performing at 25 KV, the morphology and failure mechanism of the samples were investigated 19.
Heat Deflection Temperature Tests
In order to perform the heat deflection temperature (HDT) measurement in accordance with the ASTM D648 standard (60×12×3 mm3), an HDT-TSP type analyzer (6012mm3mm) was utilized for composites containing 0–50 wt.% hybrid filler loading. In this experiment, the loading pressure and consistent temperature range were 455 kPa and 2°C/min, respectively. Once the testing bar deformed under flexural load, the HDT was recorded; this is a normal deflection under flexural load 20.
Water absorption behavior
The testing samples are cut from the composite plates that had been produced in accordance with the ASTM D570-99 standard. Rectangular samples with dimensions of 39 x 10 x 3 mm3 were used in this study. The materials were dried for 24 hours at 105 degrees Celsius in an oven. Following that, they were submerged in water that was at normal temperature. In each sample, three samples were immersed in four distinct watery environments, namely warm water, cold water, seawater, and normal water. The results were compared. Each of the specimens was immersed in water for two hours, twenty-four hours, twenty-four hours, and twenty-four hours at atmospheric temperature, respectively. Utilizing an electronic weighing balance with a precision of up to 10-4 g, the weight of every specimen previously they were immersed in water was measured. Before every examination, a wiping cloth was utilized to wipe away the water droplets from the surfaces of all of the specimens once they were removed from the water 20.
The absorbed water content of each of the specimens was determined using Eq. (1).
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Where Wt indicates the weight of the sample after a specific soaking period and Wo means the weight of the specimen after being oven-dried.