What is the thickness of molded pulp

Table of Contents

The thickness of molded pulp products typically ranges from 0.8 mm to 5 mm, depending on their intended use and material composition.

Factors Influencing Molded Pulp Thickness

Thickness is a crucial parameter of the molded pulp products determining their performance, durability, and cost effectiveness. The following factors affect the final thickness of molded pulp products.

Material composition . The type and quality of fibers used in the pulp mixture directly influence the thickness of the products. The fibers from the hardwood trees are longer, which makes such molded pulp products denser and thicker than those made of the short fibers derived mostly from recycled papers . In addition, the use of binders or fillers can also influence the thickness because the additives alter the pulp consistency.

Pulp density is an equally important factor because a denser pulp results in the thicker final product. The higher pulp density is achieved with the larger number of fibers per volume unit, making the product thicker after drying.

Molding pressure . The pressure during molding can also influence the thickness by the pressing of the fibers in the pulp. The increase in pressure results in the thinner product. At a molding pressure of 0.7 MPa, the final product could have a thickness of 1.5 mm. The rejection of pressure to 0.5 MPa would increase the product thickness to 2 mm.

Drying method and time . Drying the pulp after molding also influences the thickness. If the product is dried via the hot air production, the resulting product is extendable thinner because the method shrinks the pulp more than other methods, such as vacuum. Thus, the drying conditions should be controlled, including temperature and time. The pressure exerted on the upper sections of the product is also important during the drying.

Product application . Different application determines different thickness of the molded pulp products. For example, packaging for electronics is thicker than that for ends or shoes because they need more cushion in the packaging of the products. In this way, thinner packaging materials are used to save the amounts of the materials and to cut down costs.

In addition to these factors, other circumstances can also influence the product thickness: the prevailing environment factors, namely humidity and temperature because they affect the water content in the pulp; different manufacturing conditions and tools. Thus, all these factors should be taken into account while choosing the thickness for molded pulp products to maintain the balance between their performance and cost.


Measuring Techniques for Pulp Thickness

Correct measurement of the thickness of pulp plays a vital role in the production of molded pulp items. Multiple techniques are known to the industry, each of which has benefits as well as serious limitations.

  1. Micrometer measurement. The most common method for measuring the thickness of pulp uses a micrometer. Readings of this tool are precise: a digital micrometer defines the thickness with an accuracy up to 0.001 mm. At the same time, it is crucial to apply uniform pressure, as the measurement of compressed pulp can yield false results.

  2. Ultrasonic thickness gauge. It is a contactless method that measures the pulp’s thickness with an ultrasound wave. The method is widely employed for measuring wet pulp items, as the majority of other types of measurement are inapplicable in this case . For instance, the ultrasonic gauge can measure the thickness with the accuracy of ≈ ±0.01 mm, although sometimes calibration is required to accommodate different types of pulp.

  3. Optical measurement systems. The industry also benefits from using advanced optical tools such as laser micrometers. They allow to measure the thickness of a sample without touching it . This method is also highly precise, with instruments being able to define thickness with precision ≈ 0.001 mm.

  4. Using a caliper. To obtain a rough measurement of the thickness of a pulp product, one may use a hand tool, such as a caliper. It is less precise than a micrometer but allows for an acceptable precision ≈ ±0.1 mm . Generally, the method is employed in routine operations for obtaining a quick estimate of the thickness.

  5. Using a CT scan machine. It allows for a non-invasive, highly precise, and detailed image of the interior of the sample, including the thickness of the pulp. As the technique is expensive, complicated, and used mainly for scientific purposes, it does not see much use in the routine operations of manufacturing.

  6. A manometer. In some cases, an abbreviated manometer with predetermined settings of the quantity of pulp surrounded is used for feeling the approximate thickness of the item. However, the method’s accuracy is low.

Each method of thickness measurement has its role in the industry, depending on the required precision, type of pulp item, and the specifics of production. Manufacturers often use more than one method to ensure the pulp products adhere to the requirements of the thickness.


Standard Thickness Ranges for Molded Pulp Products

The thickness of molded pulp products varies, depending on their intended use and the material used for their production. However, one may describe some standard thickness ranges by categories of products in a general way. For instance:

  • Packaging Inserts : Such protective packaging inserts as those used for electronics or fragile items usually have a thickness of 1.5 to 3 mm. It ensures the sufficient cushioning and shock-absorbing effect for careful transportation and handling.

  • Food Service Items : Those include such items as plates, bowls, or trays and tend to have a thickness of 0.8 to 2 mm. It allows attaining a reasonable balance between the required degree of durability and rigidity, on one hand, and the use of material, on the other, making the products cost-efficient.

  • Egg Cartons : Egg cartons made of molded pulp tend to be 1.2 to 2.5 mm thick. It is enough to make the articles rigid while keeping them light at the same time.

  • Industrial Trays : Those used for such applications as automotive parts trays or tool packaging may have a thickness of 2 to 4 mm. A higher degree of thickness is required due to special emphasis on strength and durability of these products.

  • Medical Products : Items from this category, such as kidney trays or bedpans, may be 2 to 3.5 mm thick. Such thickness is high enough to ensure their strength for the intended handling while following the requirements for preserving hygiene.

  • Decorative . Sculptures, wall panels, and other decorative items may have very different thicknesses and range from 2 to 5 mm or more.

76Thickness Variations in Different Product Categories

Molded pulp products find their application in multiple industries, and there are distinctive applications of different thicknesses. For example, consumer electronics packaging utilizes relatively thin molded pulp trays to provide protection for smartphones, tablets, or other fragile items. The typical thickness for these applications is in the range from 1.5 mm to 3 mm, as thinner trays would not provide adequate safety from impacts and vibrations in these goods’ shipping.

One of the widely spread applications of molded pulp, food packaging, also utilizes products of various thicknesses. They can include containers for fresh produce, such as fruits, vegetables, or eggs, which typically range in thickness from 0.8 mm to 2.5 mm. The difference in this case is determined both by the desired level of protection and by the weight of the contents, with heavier items requiring the thicker packaging. The medical industry, in turn, utilizes molded pulp for various disposable items, including bed pans, urinals, kidney trays, and others. These products usually are 2 mm to 3.5 mm thick to provide sufficient sturdiness for handling the weight of liquids contained in them and to avoid leaking.

In industrial applications, such as transportation of automotive parts and hardware, molded pulp can range in thickness from 2 mm to 4 mm to withstand the heavier weighted and provide adequate protection. Finally, molded pulp seedling trays and flower pots in agriculture typically range in thickness from 1 mm to 2 mm, balancing durability with minimal material use. In some cases, when the aesthetic quality of the product needs to be higher, such as in the cases of wall panels or other art pieces, the thickness can be significantly increased, averaging around 2 mm to 5 mm or more.

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