A biodegradable water-repellent PLA coated jute and a process for the preparation thereof

Abstract

The present invention relates to a biodegradable water-repellent PLA coated jute and a process for the preparation thereof. The process for the preparation of the PLA coated jute comprises preparing a PLA gel, applying the gel onto at least one surface of the jute fabric using a controlled coating technique, and then curing the coated jute to form a uniform and thin PLA film thereon. Fig. 1

Specification

Description:FIELD OF THE INVENTION
The present invention relates to a biodegradable water-repellent PLA coated jute and a process for the preparation thereof.

The present invention relates to eco-friendly, biodegradable, water-repellent composite material based on jute and a process for the preparation thereof. The method involves preparing a PLA gel, applying the gel onto the jute fabric using a controlled coating technique, and then curing the coated jute to form a uniform and thin PLA film. This process significantly improves the mechanical properties of jute including stiffness, tensile strength, resistance to wear and tear, and overall structural integrity. This invention makes jute fabric suitable for a range of applications including textiles, composites, and industrial materials. PLA coating provides higher resistance to moisture and abrasion. This innovation addresses the need for improving the performance of jute materials while maintaining their eco-friendly characteristics.

BACKGROUND OF THE INVENTION
Jute is a natural fiber composed primarily of cellulose (approximately 60-70%) and lignin (about 10-15%), with small amounts of hemicellulose and other organic compounds. It is a natural, biodegradable fiber known for its flexibility, durability, and eco-friendliness, making it an excellent choice for sustainable applications. Its advantages include being cost-effective, abundant, and versatile, with a high tensile strength that supports its use in a variety of products such as bags, ropes, and textiles. It is renowned for its eco-friendly properties and has been traditionally used in various applications including textiles, packaging, and industrial materials. However, despite its environmental benefits, jute fibers suffer from limitations such as lower stiffness, reduced tensile strength, moisture absorption, and susceptibility to wear and tear.
Jute's flexible nature, while beneficial in some contexts, can be a disadvantage in others, as it may lead to reduced rigidity and structural integrity in applications where stiffness is required. This flexibility can also result in dimensional instability and difficulty in maintaining shape, limiting its use in products where consistent form and stability are critical. In addition to its stiffness, jute fabric faces a significant structural challenge due to its tendency to absorb water, which restricts its use in highly humid and rainy conditions. These shortcomings restrict their use in more demanding applications where enhanced mechanical properties and durability are required.

Previous attempts to address these issues have included various methods such as blending jute with synthetic fibers or applying different types of coatings. For example, researchers have explored the use of polymer coatings and composite materials to enhance jute's properties. Recently a lot of work has been done in applying non-biodegradable polymer coatings to jute surfaces. For example, polyethylene (PE) coatings, while effective for moisture and chemical resistance, can contribute to environmental pollution due to their non-biodegradable nature. Durable and water-resistant polypropylene (PP) coatings also pose environmental challenges as they are not easily recyclable and can persist in the environment. Plastic coatings can complicate recycling processes and may involve chemicals that affect the material's overall sustainability. Additionally, the coating process can raise production costs and contribute to environmental issues related to plastic waste.

A method for coating jute fabric using epoxy resin and PLA via solution coating and curing was proposed by Yadav and Gupta ("Development and characterization of jute composites for sustainable product: Effect of chemical treatments and polymer coating." Materials Research Express 7(1): 015306), which led to jute fabric with enhanced stiffness reduced wettability.

Another method for coating jute fibre was proposed by Gupta ("Investigations on jute fibre-reinforced polyester composites: Effect of alkali treatment and poly (lactic acid) coating." Journal of Industrial Textiles 49(7): 923-942), which involved coating the fibre with unsaturated polyester resin and PLA by immersion coating, which led to jute fabric with high water resistance and increased stiffness.

Verma and Joshi (Verma, A., K. Joshi, A. Gaur and V. Singh (2018). "Starch-jute fiber hybrid biocomposite modified with an epoxy resin coating: fabrication and experimental characterization." Journal of the Mechanical Behavior of Materials 27(5-6): 20182006) proposed a method for jute fabric coating with polyurethane along with heat setting. This led to jute fabric with increased stiffness but moderate wettability.

Other methods of modifying jute surface have also been proposed (Das, D., M. Datta, R. Chavan and S. Datta (2005). "Coating of jute with natural rubber." Journal of applied polymer science 98(1): 484-489), which include dip-coating and thermal reduction of jute fabric with graphene oxide which lead to jute fabric with increased stiffness and reduced wettability, or coating jute fibre with acrylic polymer Jabbar, A., J. Militký, J. Wiener, B. M. Kale, U. Ali and S. Rwawiire (2017). "Nanocellulose coated woven jute/green epoxy composites: Characterization of mechanical and dynamic mechanical behavior." Composite Structures 161: 340-349) to yield jute fibres with moderate stiffness and reduced wettability.

However, many of these approaches involve non-biodegradable polymers or complex processing techniques that can compromise jute's eco-friendly nature or introduce additional costs. However, very few researchers prioritize the significance of both biodegradability and stiffness. Hence, an effective method needs to be developed to enhance these properties while preserving the eco-friendliness of jute.

Therefore, the need exists in the art to propose a method for coating jute fabric which will enhance the performance of jute fabric for various applications while maintaining its eco-friendly characteristics, by enhancing the mechanical strength, physical appearance, water/moisture resistance, and environmental sustainability of jute without altering its biodegradability.

OBJECTS OF THE INVENTION
It is therefore an object of this invention to propose a biodegradable water-repellent PLA coated jute and a process for the preparation thereof.

It is a further object of this invention to propose a biodegradable water-repellent PLA coated jute which is prepared by an efficient, simple, eco-friendly, and sustainable process.

A still further object of the invention is to propose a biodegradable water-repellent PLA coated jute, which enhances the eco-friendliness of traditional materials.

Another object of this invention is to propose a biodegradable water-repellent PLA coated jute, which is produced by a process which is viable and cost-effective, does not require any pre or post-treatment or complicated equipment and maintains green manufacturing principles.

Yet another object of this invention is to propose a biodegradable water-repellent PLA coated jute, which offers superior mechanical properties compared to untreated jute.

A further object of this invention is to propose a biodegradable water-repellent PLA coated jute, which enhances the modified jute's performance in highly humid and rainy conditions.

A still further object of this invention is to propose a biodegradable water-repellent PLA coated jute, which improves its appearance with a transparent and smooth finish.

These and other objects and advantages of the invention will be apparent from the ensuing description, when read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
This invention can be better understood with reference to the following detailed description together with the appended illustrative drawing showing various aspects related to synthesis reaction and preferred embodiments.
Fig. 1 Schematic representation of the fabrication process for applying a thin PLA film to jute fabric.

SUMMARY OF THE INVENTION
The present invention relates to a biodegradable water-repellent composite material based on jute. This invention further relates to a process for the preparation of the biodegradable water-repellent composite material which involves preparing a PLA gel, applying the gel onto the jute fabric using a controlled coating technique, and then curing the coated jute to form a uniform and thin PLA film.

DETAILED DESCRIPTION OF THE INVENTION
According to this invention is provided a biodegradable water-repellent PLA coated jute.

According to this invention is further provided, a process for the preparation of the
a biodegradable water-repellent PLA coated jute.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without some of these specific details.
Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the spirit and scope of the invention.
As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

In the application, where an element or component is said to be selected from a list of recited elements or components, it should be understood that the element or component can be any one of the recited elements or components, or the element or component can be selected from a group consisting of two or more of the recited elements or components. Further, it should be understood that elements and/or features of a composition or a method described herein can be combined in a variety of ways without departing from the spirit and scope of the present teachings, whether explicit or implicit herein.
The use of the terms "include," "includes", "including," "have," "has," or "having" should be generally understood as open-ended and non-limiting unless specifically stated otherwise.
Throughout the application, where compositions are described as having, including, or comprising specific components, or where processes are described as having, including, or comprising specific process steps, it is contemplated that compositions of the present teachings can also consist essentially of, or consist of, the recited components, and that the processes of the present teachings can also consist essentially of, or consist of, the recited process steps.
In interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non- exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.
It will be understood by those skilled in the art with respect to any chemical group containing one or more substituents that such groups are not intended to introduce any substitution or substitution patterns that are sterically impractical and/or physically non-feasible.
Where a range of values is provided, it is to be understood that each intervening value, including the limiting values, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter.
The technical expressions as used herein are standard expressions which will be apparent to a person skilled in the art as being a part of standard terminology. However, in order to lend further clarity to the description, some of the expressions are defined hereinbelow.

WCA: The Water Contact Angle (WCA) measures how a liquid, such as water, wets a solid surface. Mathematically, it is defined as the angle at the point where the liquid, gas, and solid intersect. Essentially, the WCA illustrates the interplay between the surface's physical properties and its chemical characteristics.
Hydrophilic surfaces: In this context, "hydrophilic" refers to surfaces with water contact angles significantly below 90°.
Hydrophobic surfaces: These surfaces are hydrophobic, characterized by low surface energy that causes them to repel water and resist wetting. A surface is classified as hydrophobic if the water droplet contact angle exceeds 90°.
Fabric stiffness: Stiffness is a measure of a material's resistance to deformation under applied force. It quantifies how much a material will bend, stretch, or compress in response to a load, with higher stiffness indicating less deformation for a given force.
Flexural rigidity: Flexural rigidity, or bending stiffness, quantifies a fabric's resistance to bending under external forces.
Biodegradable: Biodegradable refers to the ability of a substance to break down naturally through the action of micro-organisms such as bacteria and fungi into simpler, non-toxic components that are assimilated into the environment. This process typically occurs over a relatively short period of time, reducing environmental impact and contributing to ecological balance.
It is to be understood that, for a clear understanding, the description of the present invention has been simplified to illustrate the relevant elements only. For the sake of clarity, other details that may be well-known are omitted.
The present invention relates to biodegradable water-repellent PLA coated jute and a process for the preparation thereof. The present invention provides a novel process for applying a polylactic acid (PLA) coating to jute fabric to enhance its stiffness, water repellency, and durability. The method involves preparing a PLA gel, applying the gel onto the jute fabric using a controlled coating technique, and then curing the coated jute to form a uniform and thin PLA film. This process significantly improves the mechanical properties of jute including stiffness, tensile strength, resistance to wear and tear, and overall structural integrity. This invention makes jute fabric suitable for a range of applications including textiles, composites, and industrial materials. PLA coating provides higher resistance to moisture and abrasion. This innovation addresses the need to improve the performance of jute materials while maintaining their eco-friendly characteristics.

In accordance with this invention, the biodegradable water-repellent composite material based on jute comprises biodegradable PLA and sustainable woven jute fabric.
In accordance with this invention, the process for the preparation of the biodegradable water-repellent PLA coated jute involves preparing a PLA gel, applying the gel onto at least one surface of the jute fabric using a controlled coating technique, and then curing the coated jute to form a uniform and thin PLA film.

The PLA gel is prepared by dissolving PLA pellets in a solvent to create a PLA gel and stirring the solution continuously at 40 ℃ until the PLA behaves like gel, ensuring a homogeneous mixture.
The solvent used for preparing the PLA gel is selected from tetrahydrofuran (THF), chloroform, and dichloromethane.
Applying PLA film to single or both sides of the jute fabric improves its appearance with a transparent and smooth finish. For a single-side thin coating, first, the jute fabric is laid on a flat glass surface. Next, prepared homogeneous PLA gel is applied to the jute. Another flat glass plate is then placed on top of the PLA gel and pressed slowly until the gel spreads uniformly over the jute surface without forming any air bubbles between the jute fabric and the top glass.

For application of the thin film coating on both sides, first, the PLA gel is applied to the bottom glass plate, then the jute fabric is placed on top. After that, the PLA gel is applied to the other surface of the jute. Another flat glass plate is then placed on top of the PLA gel and it is pressed slowly until the gel spreads uniformly over the jute surface without forming any air bubbles between the jute fabric and the top glass
After coating, the pressed jute with glass is heated at 90 ℃ for 10 minutes to remove the solvent. Finally, the assembly is removed from the oven, the glass plates are separated, resulting in a transparent thin film PLA coating on one or both sides of the jute surface depending on the requirement.

Fig. 1 shows a schematic representation of fabrication process for applying a thin PLA film to jute fabric. It includes the following steps:
1-PLA gel preparation,
2-Adhesion process of the PLA gel,
3-Use of glass plates to ensure a uniform and smooth film,
4-Application of an external compression object,
5-Pouring PLA gel onto the jute fabric,
6-Placement of the woven jute fabric,
7-Curing at 90°C for 10 minutes in a hot air oven,
8-The hot air oven process,
9-Removal of the glass plates, and
10-Formation of the stiffened thin PLA film on jute.

The invention will now be explained in greater detail with the help of the following non-limiting embodiments. However, such examples are merely for the purpose of explaining the invention and are not to be construed as limiting the scope of the invention.
EXAMPLES:
Materials and Methods
Materials
Polylactic acid (PLA) was purchased from Banka Bioloo Ltd., India. While Tetrahydrofuran (THF) was purchased from TCI Pvt. Ltd. Chloroform and Dichloromethane were procured from SRL Pvt. Ltd. All the chemicals were used as obtained without any further processing.
EXAMPLE 1: The prepared homogeneous PLA gel using tetrahydrofuran (THF) with a concentration of 10% (w/v) is applied to jute fabric. A flat glass plate is positioned on top of the PLA gel and pressed down, ensuring that the gel spreads evenly over the jute surface without trapping any air bubbles between the jute fabric and the glass plate. After that, the glass-pressed jute was heated at 90 ℃ for 10 minutes to remove the solvent and generate a thin transparent layer of PLA over the jute fabric.

EXAMPLE 2: The prepared homogeneous PLA gel using chloroform with a concentration of 10% (w/v) is applied to jute fabric. A flat glass plate is positioned on top of the PLA gel and pressed down, ensuring that the gel spreads evenly over the jute surface without trapping any air bubbles between the jute fabric and the glass plate. After that, the pressed jute was heated with glass at 90 ℃ for 10 minutes to remove the solvent and generate a thin transparent layer of PLA over the jute fabric.

EXAMPLE 3: The prepared homogeneous PLA gel using dichloromethane with a concentration of 10% (w/v) is applied to jute fabric. A flat glass plate is positioned on top of the PLA gel and pressed down, ensuring that the gel spreads evenly over the jute surface without trapping any air bubbles between the jute fabric and the glass plate. After that, the pressed jute was heated with glass at 90 ℃ for 10 minutes to remove the solvent and generate a thin transparent layer of PLA over the jute fabric.

EXAMPLE 4: For double-sided film coating, we first apply the PLA gel to the bottom glass plate and then position the jute fabric on top. Following this, we proceed with the procedure detailed in any of EXAMPLES 1, 2, or 3.
Following the application of a coating, the packaging material was subjected to testing in order to evaluate its properties and qualities.

The redesigned surface was measured to have a water contact angle of 95±3° using a goniometer. The surface morphology of the treated samples was analyzed using field emission scanning electron microscopy (FE-SEM). Additionally, the functionality of the coating was assessed through Fourier transform infrared spectroscopy (FTIR).

In the water absorption test, the untreated jute fabric quickly sank, while the PLA film-coated (single or double-sided) fabric remained buoyant for a prolonged period due to the presence of the PLA layer. Remarkably, PLA-coated jute retained its stiffness and water-repellent properties even after exposure to UV radiation. The proposed PLA-coated jute fabric demonstrated excellent chemical stability across different pH levels, as supported by the literature and its compositions. Additionally, the adhesion of the PLA film was tested by attempting to peel the film off the coated jute. It was observed that the film did not come off easily, indicating that it has adhesive properties even without the use of epoxy resin.

The integration of PLA coating on jute fabric resulted in significant improvements in mechanical properties and surface characteristics. The tensile strength of the single-side and double-side coated jute fabric was assessed using a universal testing machine (UTM). It was found that the tensile strength was the same in the case of single-sided and minor increment in the case of double-sided PLA-coated jute fabric compared to the uncoated jute fabric. Furthermore, bending stiffness tests showed a significant enhancement in stiffness, with the coated jute displaying an eightfold increase for single-sided coating and a twelvefold increase for double-sided coating compared to the unmodified fabric. This significant enhancement in stiffness is attributed to the PLA coating, which added rigidity to the jute fibers. Despite the increased stiffness, the beneficial properties of the coating were maintained, indicating that it effectively enhanced the mechanical properties without compromising the desired surface characteristics.

In the biodegradability test, the uncoated and coated jute samples were buried beneath the wet soil for one month. As a result, the uncoated jute fabric shrinks under the biodegradation analysis. In contrast, the PLA film on coated jute was as original with the same stiffness, even after the 30-day burial period. Biodegradability tests demonstrated that the shelf-life is increased to five times as long as that of the untreated jute, suggesting that the PLA coating not only improved the mechanical properties but also contributed to the longevity of the material. The enhanced durability did not interfere with the natural biodegradation process of the jute, making the coated fabric a sustainable option for various applications. Extended shelf-life is particularly advantageous for products like shopping bags, where both durability and environmental impact are crucial considerations.

In conclusion, the PLA coating significantly improved the tensile strength, stiffness, and biodegradability of the jute fabric while maintaining its beneficial properties. These enhancements make the coated jute fabric an excellent candidate for applications requiring durability, mechanical strength, water-repellent, and environmental sustainability such as shopping bags and other textile products.

The experimental data from various tests conducted on coated and uncoated samples is presented in Table 1 below.







Table 1: Experimental data from various tests conducted on coated and uncoated
samples.
Properties Uncoated Coated
One-sided coated Double-sided coated
Water contact angle (WCA) 0° 95±3° (Coated side) 95±3°
Bouncy/Floating test Sank immediately Floating (for more than 10 min) Floating (for more than 10 min)
Tensile stress at Maximum Force [MPa] 18.53 18.68 20.32
Average Flexural Rigidity, G (mg cm) 1579 12596 19025
Biodegradability test (Buried underneath the wet soil for one month) ~90 % decomposed Minor changes in dimension and weight No changes in dimension and weight


In conclusion, the PLA coating significantly improved the tensile strength, stiffness, and biodegradability of the jute fabric while maintaining its beneficial properties. These enhancements make the coated jute fabric an excellent candidate for applications requiring durability, mechanical strength, water-repellent, and environmental sustainability such as shopping bags and other textile products.
The developed thin PLA-coated stiff jute fabric has potential industrial applications of the are the follows:
a. Packaging materials: Used for durable and water-resistant packaging solutions, including bags and sacks.
b. Construction materials: Employed in construction for reinforcement and protection, such as in geotextiles and erosion control fabrics.
c. Agricultural products: Utilized in agriculture for protective covers, mulch mats, and seedling bags.
d. Industrial applications: Applied in industrial settings for protective barriers, mats, and conveyor belts.
e. Outdoor furniture: Used in outdoor furniture and accessories where moisture resistance and stiffness are beneficial.
f. Flooring and carpets: Incorporated into flooring and carpets for added durability and resistance to environmental factors.

The proposed PLA-coated jute fabric stands out for its unique ability to achieve water repellency, transparency, smoothness, and stiffness while preserving the fabric's strength. Previous research efforts have struggled to combine these essential characteristics in a single textile using biodegradable coatings. Notably, the cost of coating 1 square meter of fabric on single side and double sides was estimated at approximately 10 Rs and 15 Rs, respectively. These costs could be further reduced through large-scale production or by using more affordable solvents. The coating process is both cost-effective and straightforward, requiring minimal post-treatment. , Claims:CLAIMS:

1. A biodegradable water-repellent PLA coated jute comprising biodegradable PLA and sustainable woven jute fabric.
2. The PLA coated jute as claimed in claim 1, wherein the PLA is coated on at least one surface of the jute fabric.

3. A process for preparing a biodegradable water-repellent PLA coated jute, comprising preparing a PLA gel, applying the gel onto at least one surface of the jute fabric using a controlled coating technique, and then curing the coated jute to form a uniform and thin PLA film thereon.

4. The process as claimed in claim 3, wherein the PLA gel is prepared by dissolving PLA pellets in a solvent to create a PLA gel and stirring the solution continuously at 40 ℃ until the PLA behaves like gel, ensuring a homogeneous mixture.

5. The process as claimed in claim 3, wherein the solvent used for preparing the PLA gel is selected from tetrahydrofuran (THF), chloroform and dichloromethane.

6. The process as claimed in claim 3, wherein application of a single-side thin coating on the jute fabric comprises laying the jute fabric on a flat glass surface and applying the prepared homogeneous PLA gel to the jute, placing another flat glass plate on top of the PLA gel and pressing it slowly until the gel spreads uniformly over the jute surface without forming any air bubbles between the jute fabric and the top glass.

7. The process as claimed in claim 3, wherein application of the thin film coating on both sides of the jute fabric comprises applying the PLA gel to the bottom glass plate, placing the jute fabric thereon, followed by applying the PLA gel to the other surface of jute, placing another flat glass plate on top of the PLA gel and pressing it slowly until the gel spreads uniformly over the jute surface without forming any air bubbles between the jute fabric and the top glass.

8. The process as claimed in claim 3, wherein after coating, the pressed jute with glass is heated at 90 ℃ for 10 minutes to remove the solvent.

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