What are the properties of Moulded paper pulp

Table of Contents

Moulded paper pulp is lightweight, biodegradable, with a density of 0.15-0.25 g/cm³, and can absorb up to 24% of its weight in water.

Physical Properties

One of the ordinary characteristics of the moulded paper pulp is its low weight since its density usually varies between 0.15 and 0.25 grams per cubic centimeter. Such properties are crucial for packing applications since they reduce the weight of every item significantly. As for the porosity, it highly depends on the process of manufacturing and the materials used before it. Particularly, the moulded paper pulp materials designed for shock absorption, such as egg cartons, can have the increased level of porosity.

It is one of the main reasons for the extensive use of the material as the porosity and the resulting density can be adjusted as required. Overall, low-density, high-porosity pulp forms are used to pack fragile items and absorb the shock applied during the transportation or handling.

The tensile strength, compression strength, and tear resistance remain to be crucial to the strength of the moulded paper pulp. For instance, a typical packaging tray from the moulded paper pulp can withstand up to 200 kilograms of the added load before deforming. The reasonable tensile strength of the added stress in either direction is typical for all the trays, holders, or other products made of the material.

Typically, such parameters highly depend on the bonding of the fibers of the better alignment of the fibers. It is reasonable to note that better products usually use multidirectional bonding and include fibers aligned in various directions to guarantee the same level of strength in different directions.

The moisture content of the moulded paper pulp is typically between 5 and 12%, which directly relates to the provided flexibility and strength of the material. At the same time, absorption varies from 14% to 24%, which is crucial for transportation applications since every tray should protect the material from spilling or leaking. Some adjustments are regularly made to reduce the rate of absorption. These adjustments include the applications of wax or a biodegradable coating which is essential to bring this rate to 12-14% or even lower. Thus, moulded paper pulp can perform as needed at different levels of water resistance.

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Chemical Properties

I. Fiber Composition

Primarily, the base material for moulded paper pulp is recycled paper fibers. The most commonly reused materials are newspaper, cardboard, and office paper . The choice of fiber is essential for the properties of the final product, as such materials as cardboard are characterized by long fibers and can provide greater strength and durability. The longest fibers in these materials are cellulose. Delivery of particles and refining methods contribute to their final size and structure. The chemical composition of the fiber consists mostly of cellulose and is reported to be around 60-70%, while hemicellulose and lignin also constitute the fibers and together account for 30%. Long fibers are important for the strength of the paper product.

II. Resistance to Chemicals

Moulded paper pulp has natural resistance to chemicals and, therefore, is suitable for various applications. Depending on the chemical substance, the pulp may or may not degrade. As the substance becomes more acidic or alkaline, the resistance of the pulp decreases . At a specific with relatively low pH, the paper losses its resistance to acids in 26% of cases and is gradual on average. Regarding alkalis, the pulp is resistant up to the pH of 10-11 and degrades with a pH of 12.5. Cellulose fibers are resistant to different substances since no molecule can affect them significantly. The pulp can be made resistant to other chemicals by adding treatments on some stages of its production. For example, adding substances at the paper making stage can help it to be resistant to both weak acids and bases, and if this substance is further added to the coating, the pulp will be resistant to stronger acids and bases. Therefore, if moulded paper pulp has such surface treatment, it can be used in various industrial applications and laboratories.

 

Manufacturing Process

Raw Material Selection

The first and one of the most important stages of the manufacturing process of moulded paper pulp is raw material selection. Manufacturers typically use recycled paper products such as newspaper, corrugated fiberboard, and office paper . The choice is based on the final product’s characteristics, such as strength, flexibility, and appearance. For example, corrugated fiberboard is preferred for its long fibers, improving the product’s durability and strength. The cost of raw materials may differ; for example, the use of recycled paper will decrease the costs and add to the environmental sustainability. Moreover, the purity and quality of the paper are critical for the pulping process’ efficiency and the quality of moulded pulp products.

Pulp Preparation and Moulding Techniques

First, the raw material is shredded into small pieces, mixed with water, and cooked into a slurry . The slurry is then blended to make the pulp homogeneous. The consistency of the pulp is altered to adjust the thickness and strength of the final product. Moulding techniques include both traditional wet press and modern methods such as thermoforming. The latter provides more room for design decal and is used for producing electronic packaging, which needs to be precise and strong, which is achieved by thermoforming to shape the pulp into various forms .

Drying and Finishing

Finally, the products must be dried, as their strength and durability are greatly dependent on the fact how dry they are. They are typically dried in special drying rooms, and the method used can vary . Some manufacturers use energy-efficient approaches such as solar drying to reduce costs and ensure they are utilizing renewable energy sources . After that, the product is finished. For example, it can be pressed for smoothness. Coatings and other finishing treatments are applied to make the product resistant to moisture. For example, biodegradable coating can be added, which will make the packaging water-resistant but will not affect its biodegradable properties. Each step is tailored to meet the requirements of the end use, such as food safety, strength, and lack of moisture for food packaging. Thus, the versatile nature of this material and its ability to be fine-tuned for each case make it a viable and sustainable choice for producing a variety of products from packaging to disposable items.

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Environmental Impact

Sustainability Considerations

Moulded paper pulp production and use contribute to sustainability in many ways; the most important reasons come from the product’s reliance on recycled materials and its low environmental impact due to biodegradability . The use of recycled paper as a raw material helps preserve natural resources and reduce the demand for virgin fiber, a factor that prevents deforestation and habitat destruction. Furthermore, recycling paper requires much less energy than producing new paper from trees, a factor that contributes to lower greenhouse gas emissions. At the same time, moulded paper pulp is 100% biodegradable and compostable, which makes it much more sustainable than plastic regarding the environmental footprint . When disposed of, moulded paper pulp decomposes within a few months, enriching soil without releasing toxic substances, as plastics often do following much longer decomposition times of hundreds of years.

Recycling and Waste Management

Moulded paper pulp benefits from environmentally friendly recycling and waste management processes. The industry mainly applies the so-called closed-loop recycling system, which allows for waste paper to be collected, processed, and reused in the production of new products . Such an approach has plenty of benefits because apart from decreased waste, it reduces the consumption of water and energy needed for making new materials. However, despite its biodegradability, the end-of-life disposal of moulded paper pulp and paper products has to abide by the official rules for environmentally responsible waste management. Composting is a desirable way of disposing of these products as it allows the materials to return nutrients to the soil and supports the circular economy principle. It is thus indispensable for the communities and businesses to include composting programs in their waste management strategies to ensure the biodegradable products go to the landfills as little as possible. The role of moulded paper pulp in the sustainable environment is considerable, and the ability to ensure waste reduction, resource preservation, smart production, and proper disposal supports this claim.

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