Experimental Investigation on Underlying Mechanism of LLDPE Based Rotationally Molded BioComposites

ABSTRACT Large hollow seamless plastic products can be easily molded by rotational molding process. A determined thermal stability along with a broad processing window is some requisite variant requirement of resin needed to be incorporated for this technique. Though Linear Low Density Polyethylene (LLDPE) satisfies such requirements, but it deliberately depicts deficiency in application where structural strength is an essential specification. Numerous additives and reinforcements have been evinced to satiate this void. The present study investigates the effect of Sugarcane Bagasse (SCB) and Jute as an additive with LLDPE in order to ensure requisite processibility and improvised mechanical properties and even assessing the underlying mechanism to observe the fiber dispersion for rotational molding process. Fourier Transform Infrared Technique (FTIR) and Melt Flow Index (MFI) tests were considered to verify the roto moldability for the prepared bio composites in distinguished concentrations. The results obtained were then characterized mechanically based on tensile and impact strength. Thermal Stability viz. Differential Scanning Calorimeter (DSC) was also investigated to divulge the crystallinity impact of SCB and Jute with LLDPE when compared with pure matrix. Experiments revealed 5% of fiber addition manifested an improvised effect considering roto moldability and mechanical properties of end product. SUMMARY Rotational molding is a polymer manufacturing technique through which hollow and seamless parts having complex geometries can be manufactured. Polyethylene, especially Linear Low Density Polyethylene (LLDPE) is most preferred base material for rotational molding. Bio composites of jute/LLDPE and Sugar Cane Bagasse (SCB)/LLDPE prepared using rotational molding were investigated. Investigation includes processability analysis, mechanical analysis and thermal analysis.


Introduction
Rotational molding is a polymer manufacturing technique through which hollow and seamless parts having complex geometries can be manufactured. The roto molded products are usually stress free as they utilize majorly heat as a parameter for molding. The process is mainly procured for the fabrication of products ranging from a wide variety (E.g: a small toy to a large overhead tank). With rotational molding, multilayered parts can also be manufactured. This process even allows for highquality graphic formation in the product (P. L. Ramkumar and Kulkarni 2016).
Numerous thermoplastics can be utilized as a base resin for rotational molding process. However, 85% of the material incorporated in this technique is polyethylene as it provides with a wider processing window and a tremendous thermal stability. Among polyethylene, Linear Low Density Polyethylene (LLDPE) is of great interest for rotational molding process due to its inhibited features like less shear sensitivity and required melt flow characteristics (P. Gupta and Ramkumar 2021b;Ramkumar et al. 2020a). Despite this, it does have limitations including inadequate mechanical properties for some critical applications demanding structural strength on major criteria. To amend these features of polymer materials, they are reinforced by fibers, nanofillers and particulate reinforcements. In particular, natural fibers, as a reinforcement and additive, are in recent research criteria due to the variant attributes provided by them like low cost, low density along with excellent chemical resistance and biodegradability (Dou and Rodrigue 2018).
Pertaining to the benefits obtained from natural fillers, distinct literature can be reported on reinforcing them with the polymer matrix for different manufacturing processes. Hanana et al. reinforced maple wood fiber with LLDPE to form composites by rotational molding method. Their results concluded that at 30% fiber loading, tensile and flexural modulus were increased by 56% and 60% (Hanana, Yomeni Chimeni, and Rodrigue 2018). Szostak et al. (Szostak, Tomaszewska, and Kozlowski 2019) examined thermal and mechanical properties of roto molded flax and hemp fiber reinforced polyethylene matrix. They also used flame retardant and maleic anhydride as filler. Higher degree of crystallinity was observed in LLDPE filed with natural fibers compare to LDPE.
Considering the valuable literature, natural fillers were chosen as an alternative to be mixed with LLDPE as base resin to study their effect for rotational molding process (Nikita et al. 2020). Sugarcane Bagasse (SCB) and Jute were selectively made on hand for this particular study prevailing to the conclusive remark obtained from the following mentioned noteworthy research.
SCB is remaining portion of sugarcane after extraction of juice having fibrous form. It has a low cost, stable supply and is readily available (Loh et al. 2013). High degradation temperature of SCB makes it suitable for use in rotational molding (Yao et al. 2008). Agunsoye and Aigbodion formed SCB particle filled recycled polyethylene composites using compression molding. They used carbonized and uncarbonized SCB particles. Tensile and bending strength were increased up to 30% with the addition of SCB whereas the impact strength and fracture toughness decreased with the addition of SCB (Agunsoye and Aigbodion 2013). Youssef et al. investigated mechanical and physical properties of compression molded SCB reinforced LDPE and HDPE. They found significant reduction in properties at more than 50% fiber loading. Scanning Electron Microscope (SEM) graphs confirmed that electron beam radiation increased adhesion between matrix and fiber (Youssef et al. 2009).
Low cost and biodegradability make jute beneficial additive. Even for jute, it's high degradation temperature makes it suitable for use in rotational molding (Satish, Ramakrishna, and Suresh Kumar 2014). Miah et al. analyzed mechanical strength of jute fiber concentrated with LLDPE prepared by compression molding. A 33% rise in tensile strength and 50% bending strength improvement were evinced by them (Miah et al. 2005). Zaman et al. compression molded jute reinforced LLDPE and jute reinforced natural rubber composites. Tensile strength of composite was increased by 81% at 40% fiber loading (Zaman et al. 2011). A lesser known research is observed in the field of roto molding industries. Thus a wide scope of enhancement in work can be pertained in this field. LLDPE is widely used for this process, but the main challenge is increasing strength of the end product considering LLDPE as a base resin which is rarely observed in rotational molding field. Thus, the research pertains with the aim of enhancing the roto molded product's mechanical properties by mixing SCB and jute with LLDPE. However, there exists a limitation to achieve an appropriate mixing when blending a thermoplastic material with natural filler. For this purpose, determining material processability becomes important along with investigating mechanical properties of the end product so as to examine the compatibility of additive with the base resin. The processability analysis helps in obtaining an optimum range of blend from the various prepared mix of fiber concentrated with base resin to verify the potential of material sustaining roto moldability. A lesser known amount of research is available regarding the processability of LLDPE/natural filler blend for rotational molding process to the author's knowledge.
The research analysis clearly demonstrates that SCB and Jute have proved in engulfing their usage in the research field as reinforcing materials, however, their incorporation as an additive in rotational molding sector is rarely reported to the author's knowledge. This survey of literature intended to select SCB and Jute from a list of natural fillers available till date to the researchers that can be concentrated with pure LLDPE to scrutinize their effect on roto moldability and mechanical properties of the end product.
The present study is aimed to determine the synergistic effect of adding SCB and Jute in LLDPE targeting rotational molding process. Materials processibility resembles an utmost importance as this technique demands an appropriate flow of the charged resin, while maintaining the thermal stability. Fourier Transform Infrared Spectroscopy (FTIR) was utilized as a part of processibility investigation. This technique defines an optimum range wherein the characteristic infrared peaks of both, the base resin and additives, are studied. The percentage where the peaks of both the materials are evident is considered to be a blend with an appropriate mixture (Z. Yang et al. 2010). Processibility of material for roto moldability can also be determined by analyzing diverse properties such as melt flow behavior. To measure the fluidity attribute, Melt Flow Index (MFI) testing was utilized. MFI measures the flow of material in molten state. Based on results of MFI and FTIR characterization, suitable blend of an additive and base resin can be obtained. From this analysis, the devised bio composites were then analyzed by the mechanical characterization for which tensile and impact properties were considered. DSC experiment of proposed blend was performed with the aim of determining the material crystallinity and its thermal behavior when subjected to heat during roto moldability.

Materials and experimental procedure
Materials LLDPE (G3645UV) in powder form having MFI of 4.5 gram/10 min and density of 0.936 gram/cm 3 was used. This grade is predominantly used for rotational molding applications. Raw SCB is residue of sugarcane after juice extraction. SCB and jute were oven dried for 3 hours at 80°C to reduce moisture content after being pulverized.

Processibility analysis
Fourier transform infrared spectroscopy FTIR characterization was performed on the distinguished blends in powder form. Perkin Elmer spectrum two instrument was utilized for the analysis. FTIR spectra were made in the attenuated total reflectance (ATR) mode. Absorption spectrum was recorded in range of 450 cm −1 to 4000 cm −1 at an interval of 1 cm −1 . Appropriate amount of force was applied on material to maintain contact with ATR diamond crystal. Crystal was cleared with acetone after each experiment to remove traces of material. Obtained data was plotted in a graph from which characteristic peaks were identified for each compound present.

Melt flow index test
This test is meant to examine the melt behavior of the composite. For rotational molding, the value must be in the range of 3 grams/10 minutes − 8 grams/10 minutes(P. L. Ramkumar et al. 2014). Melt flow properties of material were investigated using MFI test apparatus which is performed according to ASTM D1238. As per the standard, mixture was heated at 190°C with a load of 2.16 kg being applied on top of piston. Force on piston pressurizes material within cylinder to flow through small diameter orifice. Weight of material flowed through orifice per 10 min is measured using high precision weighing machine. Measured weight indicates MFI of material. Each blend was tested three time and average value was considered for analysis.

Mechanical characterization
The various stages of the development cycle for the rotationally molded bio composite LLDPE/SCB and LLDPE/Jute are illustrated schematically in Figure 1.
Initially, the fibers were dried and then sewn with a set of metal sieves to obtain particles averaging 125 mm in size. Although melt blending produced marginally better properties than dry blending in terms of limiting potential material degradation (mechanical, thermal, and oxidative) while lowering processing costs and time, the latter is more appealing in terms of limiting potential material degradation (mechanical, thermal, and oxidative) while lowering processing costs and time (Shaker and Rodrigue 2019). The mixture was weighed according to 3 mm thickness and placed into a dimensional mold. The mold utilized particularly for this experiment in rotational molding was of stainless steel with 160/160/30 mm 3 dimension. The bio composites were manufactured with the aid of rotational molding machine setting the parameter at 180°C for almost 20 minutes. Major axis to minor axis speed ratio of equipment was maintained at 4:1. The composite part was cooled with forced air at room temperature before the mold removal. SCB and Jute were added in the concentration ranging from 0% to 40% each respectively with LLDPE.
The composites were cut from the cube mold into plates in order to get the necessary dimensions as per ASTM requirements to conduct experiments for characterization. Tensile testing was carried out according to ASTM D 638, with a total of five samples evaluated with LLDPE for each concentration to get the average tensile strength value. Impact strength was investigated as per ASTM D256 to research the effect of natural fillers. Pendulum having maximum energy capacity of 10 Joules was used for experiments. While maintaining the impact speed as 3.46 m/s. The samples for tensile and impact as per the standards are shown in Figures 2 and 3 respectively,

Thermal analysis
The thermal properties can be analyzed by Differential Scanning Calorimeter. It helps in determining the heat flow of materials in terms of temperature and time. Various temperature parameters like melting point, glass transition temperature, crystallization temperature, and enthalpy of fusion are the distinct data that can be obtained by DSC experimentation. A 75 µl aluminum crucible was utilized to perform the thermal analysis tests using DSC setline instrument. A sample of around 5 mg was investigated in the nitrogen atmosphere with 20 ml/min heat flow rate. The heating and cooling rate were maintained as 10°C/min. Graphs obtained in form of endothermic and exothermic peaks were evaluated by means of calisto software. The equation to calculate %crystallinity is mentioned below: Where, ΔH m = experimental melting enthalpy, ΔH 0 m ¼ 293J=g is the melting enthalpy and W f = weight ratio of polyethylene in composite (Khanam, Mariam, and Almaadeed n.d;Saci et al. 2016).

Fourier transform infrared spectroscopy
In FTIR spectroscopy, infrared rays having different wavelengths are imparted on material. Infrared rays transmit through atoms and atomic bonds. Each bond has its specific vibrational characteristic. It absorbs specific wavenumber of infrared rays and characteristic peak at that wavenumber. By comparing peaks of original substances and blend, we can analyze significance of each substance in the composite. Pure LLDPE, SCB and jute were characterized by FTIR. Attained FTIR characteristic curves were compared with data available in literature.
SCB contains lignin, hemicellulose and cellulose. Figure 5 illustrates FTIR curve for pure SCB. At 3330 cm −1 , strong peak is found because of axial deformation of O-H bond. Band at 1239 cm −1 represents C-O-C bond in cellulose chain. Peak at 1159 cm −1 is due to asymmetric deformation of C-O-C of cellulose and hemicellulose. Strong peak at 1033 cm −1 represents C-O bond stretching of cellulose (Guilherme et al. 2015;Mothé and De Miranda 2009;Singh et al. 2005;Zhanying et al. 2011).
Pure jute was also characterized to notice its significant peaks as shown in Figure 6. Peak values from spectra were identified and compared with literature. Band attained at 3330 cm −1 represents O-H bond stretching vibration of cellulose which remarks as the major constituent in jute. C-H stretching vibration gives peak at 2920 cm −1 . C=O stretching vibration of hemicellulose is responsible for peak at 1728 cm −1 . Peak at 1233 cm −1 represents C-O stretching vibration in lignin. C-O-C asymmetric stretching is represented by peak at 1155 cm −1 . Peak at 1029 cm −1 is due to stretching vibration of C-O bond (Goriparthi, Suman, and Mohan Rao 2012;Mwaikambo and Ansell 2002;Rana et al. 1997;Samal et al. 2001).
SCB was blended with LLDPE in range of 10%wt to 40%wt at an interval of 10%wt and characterized by FTIR. Mixture having apparent peaks of both LLDPE and SCB is considered as a blend with an appropriate mix. By analyzing curves obtained, it is noticeable that blend having 10% SCB has no significant peaks of SCB which signifies negligible presence of SCB in blend. Similarly, blend containing 40% SCB has no particular peaks of LLDPE. It demonstrates that at 40% LLDPE/SCB prepared composite, SCB is dominant over LLDPE. Hence, optimal blend cannot be obtained above 40% SCB   concentrated with LLDPE. FTIR characterization of blends having 20% and 30% SCB was then further analyzed that showed significant peaks of both LLDPE and SCB as shown in Figure 7.
Thus, less than 40% SCB concentrated with LLDPE can be considered as a blend having presence of both the resins.
Similarly, Jute was blended with LLDPE at 10%wt, 20%wt, 30%wt, 40%wt. Mixture of jute and LLDPE was analyzed using FTIR as shown in Figure 8. The particular concentration wherein both LLDPE and jute resembles evidence of their characteristic peaks are considered to be an appropriate blend. Analysis of results suggested that blend having 10% jute has no significant peaks of jute. It indicates dominance of LLDPE in mixture, whereas, 40% jute mixed with LLDPE has no significant peaks of LLDPE. It implies that at 40% jute mixture, jute is dominant over LLDPE. Hence, blend having significance of both materials will be obtained in mixture having jute less than 40%.
This in particular concludes to further process the composites for less than 40% LLDPE/jute mixture. Hence, the further experiments were conducted for SCB and jute-based LLDPE bio composites for the fillers concentration below 40% with the base matrix.
For analyzing processibility of material for rotational molding, blend having optimum amount of additive was further characterized by MFI to account for the flow characteristic.

Melt flow characterization
Rotational molding process uses heat as a parameter. Negligible pressure is applied during moldability. Thus, material flow property in mold is very crucial. Molten polymer flow could be characterized by MFI. It represents flow characteristics of polymer efficiently. For rotational molding process, MFI value of material should be in range of 3 grams/10 min to 8grams/10 min (Crawford and Throne 2002;Gupta and Ramkumar 2020). LLDPE with MFI value 4.5 gm/10 min is incorporated in present study. This test was certainly premeditated for samples having an additive 10%wt, 20%, 30%, 40%, as obtained as conclusive remarks from FTIR analysis. Nevertheless, at 20% additive, MFI value was Transmittance (%) excessively low as shown in Table 1. Additives in powder form having high melting temperature restrict the flow of polymer. Besides, fibrous form of additive plays vital role in melt flow behavior of material (Ramaraj 2007). Similar trend was observed in rice husk and kenaf reinforced High Density Polyethylene (HDPE) by Noor Zuhaira et al. (Zuhaira, Aziz, and Mohamed 2013). Reduction in MFI might be due to weak interfacial interaction causing increase in viscosity of composite.
As rotational molding process requires MFI between 3 to 8 grams/10 min, SCB and jute could be blended in LLDPE only up to 10%. Therefore, blend having 3%, 5% and 7% additives was further characterized by MFI. Investigation shows that MFI decreases linearly with increase in the percentage of additives. At higher concentration of natural fillers, flow restriction becomes more evident. Hence, it can be said that additive reduces melt flow property of blend.  Results suggests that SCB and jute could be blended in LLDPE in 3%, 5% and 7% ratio for rotational molding application. Further investigations need to be fulfilled to analyze mechanical and thermal behavior of material in mold.

Mechanical properties
(a) Tensile Strength Figure 9 displays bio composite tensile strength as opposed to pure LLDPE. For 3% SCB added to LLDPE, the value obtained is 16.8 MPa, which shows a decrease in tensile strength of 4% when compared with pure LLDPE. Similar conclusion was revealed for 5% and 7% which examined a decrease of 8% and 13% respectively. This is obviously noteworthy that the plastic deformation (ductility) decreases sharply when SCB is applied to the LLDPE matrix. The decrease in value is due to the effect of the rigid character of SCB particles that limits bio composite plastic behavior compared to virgin matrix. When the SCB concentration increases, the bio composite passes from a phase of ductility to fragile behavior.
The addition of the SCB particles tends to decrease the average tension at breakage. The particles actually create stress concentration zones around them and in this case, they act as defects. Similar trend was observed by Ramaraj in SCB reinforced PP composite (Ramaraj 2007).
On the other hand, when jute is blended with pure LLDPE, the tensile strength for 3% was found to be 20.2 MPa which showed an increase of 15.5% when compared to that of pure LLDPE (17.5 MPa). Similarly, a rise in tensile strength of 9.7% was observed for 5% jute added to LLDPE (19.2 MPa). 7% LLDPE/jute composite also evinced an improvised value (18.2 MPa-4%) but signified to be decreased from its counterpart of 5% jute filler. This variation is depicted in Figure 9. Jute increases the toughness of the component when combined with the base resin, and the rigid nature of bio composites is affected by the jute fiber (Mohammed 2014;Naghmouchi et al. 2015). Furthermore, jute powder serves as a particle reinforcement, lowering the elasticity of LLDPE and rendering the composite less ductile. Decrease in the mechanical properties at high additive loading may certainly co-relate to the non-uniform stress transfer due to additive agglomeration within the matrix (Gupta and Ramkumar 2021a;Mohanty, Verma, and Nayak 2006). A similarity in trend was observed in past literature, with the incorporation of other natural fillers (Boujelben et al. 2021;Ramaraj 2007).

(b) Impact Strength
Impact strength is a measure of ability of material to resist suddenly applied load. It indicates maximum amount of energy that material can absorb. Impact strength property of a material is of prime importance as it finds application in daily usage products. In present study, Izod impact testing was used. As material is thermoplastic composite, brittle fracture was observed in every specimen.
Impact strength of composite was decreased with the increase in the concentration of an additive. At 3% LLDPE/SCB composite, there was 26.05% reduction in impact strength. This reduction may be attributed to change from ductile to brittle fracture behavior due to filler agglomeration which also is the reason for stress concentration requiring less energy to initiate crack This is evident from Figure 10 that further increase in SCB percentage causes minor increase in impact strength. At 5% additive, there was 13.64% decrease in the value. This may be caused by reinforcing effect of additive and better particle distribution in matrix. At 7% additive, there was marginal decrease in impact strength caused by additive -matrix adhesion, which caused crack formation at the interface (Ito et al. 2009).
Similarly, impact strength was found to be decreased with increase in jute additive as evident from Figure 10. At 3% jute concentration, impact strength was reduced by 30.67%. This may be explained by that particle additives plays the role of impurities, which raises the stress concentration points and initiates fracture from these points (Kunal et al. 2010). At 5% and 7% loading, impact strength was decreased by 20.22% and 18.89%, respectively. Nevertheless, the reduction in impact strength was not marginal. The effect may be caused by better distribution of additives. It is expected that at higher % additive, impact strength will increase. However, as previous studies have reported, after a specific amount of additive, more fiber concentration decreases impact strength (Mohanty and Nayak 2006b;Smita and Nayak 2006a). Our findings were found to be consistent with previous studies on other natural fibers López-Bañuelos et al. 2012). Up to 5 wt% fiber addition with LLDPE, this maintains the properties without significantly depreciating the roto moldability. Figures 11 and 12 are the microstructure images obtained for 3% and 7% LLDPE/SCB composites from the optical microscope respectively. A uniform fiber distribution is evident for 3% when viewed from the mold's inner surface. The hydrophilic aspect of natural fiber on the polymer matrix affects 7% of SCB combined with LLDPE. As shown in Figure 12 numerous pores were visible due to excessive fiber agglomeration. That is one of the key reasons for 7% of the mechanical properties being degraded. Likewise, microstructural images for LLDPE/jute composites for 3% and 7% jute concentration are illustrated in Figures 13,14, 15, 16 respectively For higher fiber loading, the surface becomes susceptible to pore formation and thus fragility increase, lowering the product's ductility.
The experiments clearly state that in rotational molding process a simple accommodation of up to 5% of natural filler (SCB and jute) is possible without any loss of property and a gain in mechanical properties. However, any further additions can result in poor mechanical properties, so they are less recommended. Furthermore fiber addition will have a negative effect on the mechanical strength.  These findings are a complement to the preliminary research done to determine the processibility needed for roto moldability. The product characterization shows that in terms of both roto moldability of material and mechanical characterization of the product, 5% SCB and 5% jute concentrated with LLDPE is sufficient.    Figure 15(a,b) shows the morphology of fractured surface of 10% LLDPE/Jute and 5% LLDPE/Jute rotomolded product. It is evident that at 10% jute fiber loading over LLDPE surface is greatly susceptible to the pulling out of fibers, thus making and holding a poor fiber adhesion with the polymer matrix when subjected to rotational molding process. On the other hand for 5% LLDPE/Jute rotomolded product, a uniform distribution of fiber can be evinced. This is quite acceptable due to the fact that the hydrophilic nature of natural fiber is not affecting much as there is a uniform layer of fiber being dispersed over LLDPE matrix for rotomolded product being fabricated. From figure 16(a,b), it can be seen that SCB has been positioned out unswervingly over the LLDPE surface in various orientations. This shows how SCB may provide mechanical support to LLDPE in order for it to withstand any external load. Micro fibril breaking has a small effect on the shattered specimen produced from impact testing, as shown in Figure 16(b). Because the SCB generates a solid threedimensional structure that prevents crack propagation within the surface, the energy saved until fracture for 5% LLDPE/SCB rotomolded composites is higher. Apart from that, SCB has a bridge function, in which a visible extension of fiber from one fracture surface to another is seen, delaying failure and so preventing LLDPE cracking (Q. Yang et al. 2020). Figure 16(b) clearly shows the elongation of the SCB. This indicates that SCB adheres to LLDPE properly. The elongating fibers indicate that the fibers are traveling in the same direction as the LLDPE without breaking. This is why rotationally molded composites containing 5% LLDPE/SCB have greater tensile characteristics than unreinforced LLDPE. As a result, effective interface bonding between fiber and matrix can be guaranteed (Naghmouchi et al. 2015).

Characterization of underlying mechanism of LLDPE bio composites
The fact that this robust bonding can withstand high shearing stress while simultaneously enhancing the deformation and load bearing performance of LLDPE is related to an interface between natural fibers and LLDPE (Agunsoye and Aigbodion 2013; Gupta and Ramkumar 2021a). The surface has a smooth aesthetic appearance with no void formation or lumps visible.
Finally, the interface improvement mechanism of the LLDPE bio composite, which can not only endure but also re-distribute stress, is responsible for the stable three-dimensional network structure, bridging properties, and elongating behavior of natural fillers. This improves LLDPE's deformation tolerance as well as its load-bearing capabilities. When subjected to the rotational molding process, however, a larger fiber dust addition is not a desirable alternative since the density difference ensures a lower affinity between fiber dust and resin.
The thermal behavior of the composites were further analyzed to confirm the stability of natural fibers over the polymer matrix in terms of withstanding the temperature analysis during rotomoldability which is mentioned in the subsequent section.

Thermal behavior of material
DSC characterization was used to analyze thermal behavior of material in mold. DSC reveals thermal properties such as melting temperature (Tm), crystallization temperature (Tc), % crystallinity, glass transition temperature (Tg), enthalpy of fusion (∆Hm), etc. Samples were put through first heating cycle, cooling cycle and second heating cycle. First heating cycle removed thermal traces in material. During cooling cycle, endothermic peak was observed indicating melting temperature. Exothermic peak was detected in second heating cycle representing crystallization temperature. Glass transition temperature (Tg) could not be detected as Tg of virgin polyethylene are generally below −100°C (Wang et al. 2007). Crystallization of Polyethylene composites occurs in certain stages. First stage is nucleation in which new nuclei are formed. In polymers, it involves rearrangement of chains. In second stage, nucleus grows and forms crystalline region. Changes in nucleating agents occur as fiber/fillers are blended in polyethylene, resulting in changes in melting and crystallization temperatures, as well as the percentage of crystallization (Khanam, Mariam, and Almaadeed n.d).
Thermal properties obtained from DSC are shown in Table 2. Melting point temperature of the LLDPE was increased due to the additives. Increase in melting temperature may be accredited to the plasticization effect of the additives diffused into LLDPE (Wang et al. 2007). % crystallinity was reduced due to additives. Change in melting temperature and %crystallinity with additives was not magnanimous. From DSC thermograph analysis, it can be said that properties of blended LLDPE were comparable with that of neat LLDPE used in rotational molding. Jute blended LLDPE and SCB blended LLDPE can be used for rotational molding processes as it does not degrade in processing temperature range.

Conclusion
LLDPE is used as a base resin in rotational molding, which is a plastic manufacturing technique. Additives play a vital role in enhancing mechanical properties targeting certain applications which require strength on major criteria. To improve it, various additives, fillers and reinforcements can be used. In this study we aimed at exploiting and valuing Sugarcane Bagasse (SCB) and jute fiber and this is due to their use as micrometric additives in thermoplastic matrices to obtain better bio composites. Additives were added in different proportions from 0% to 40%. In order to obtain blend having significance of base resin and additive, FTIR characterization was employed. SCB and jute were mixed with LLDPE in different proportions at 10% interval. Attained FTIR curves were compared with FTIR curves of pure LLDPE, jute, and SCB, which concluded that less than 40% of fiber loading is suitable to utilize for further processing as below 40% concentration embarks the peaks of base resin and additives both. To investigate melt flow behavior of optimum blend, MFI characterization was investigated. MFI analysis proposed that jute and SCB could be blended in LLDPE in range of 0% to 10% as requisite for roto moldability. The addition of SCB and jute to polymeric materials is a promising avenue, as it improves the material's overall mechanical properties. Mechanical characterization proved that the addition till 5% fiber can enhance the properties of roto molded product, beyond which the results showed negative impact. Low fiber wt percent has also been found to provide homogeneous microstructure and strong particles adherence for bio composites -interface matrix whereas high percentages of natural fiber generate microstructural defects as observed from the underlying mechanism. Further investigation was carried out by DSC characterization in order to analyze thermal behavior of material having 3% and 5% additives. When compared to pure LLDPE, % crystallinity was found to be decreased. However, the change in melting temperature was negligibly differentiable and thus can be sustained in processing range for rotational molding process. Experimental investigation proved the benefits of the prepared roto molded composites (LLDPE/SCB and LLDPE/jute) till 5% of natural filler addition. The future perspective can be extensively preferred using various additives and supporting the results with distinct experiments.

Disclosure statement
No potential conflict of interest was reported by the author(s).