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The Difference Between Rotomolding PE Material And PP Material
Ingredients and Properties

‌PE material (polyethylene)‌: The main component of PE material is polyethylene, which is a thermoplastic resin that is odorless, non-toxic and feels like wax. It has good low temperature resistance, the lowest operating temperature can reach -100~-70°C, has good chemical stability, and can resist the erosion of most acids and alkalis, but is not resistant to acids with oxidizing properties.

‌PP material (polypropylene)‌: The main component of PP material is polypropylene, an odorless, tasteless, non-toxic milky white granular or powdery product. It has good mechanical properties, heat resistance and electrical insulation properties, good chemical stability, and does not interact with most chemicals.

Processing performance

‌PE material‌: It has good fluidity, low processing temperature, moderate viscosity and low decomposition temperature. It is a plastic with good processing performance. PE materials are easy to shape during processing and are suitable for blow molding, extrusion, injection molding and other methods. They are widely used in the manufacture of films, hollow products, fibers and daily sundries.

‌PP material‌: PP material has good fluidity at high temperatures and can maintain stable size and shape after cooling, so it has good formability and plasticity.

Application scope

‌PE material‌: PE material is widely used in packaging materials, containers, pipes, monofilaments, wires and cables and other fields because of its light and transparent, moisture-proof, oxygen-resistant, acid-resistant, alkali-resistant and other properties.

‌PP material‌: PP material is often used to make food turnover boxes, food bags, beverage packaging bottles, etc. due to its excellent mechanical properties and heat resistance.
2024 10 26
Research On Optimization Of Cross-linked Polyethylene(XLPE) Rotational Molding Process
1. Apply DSC to measure the thermal parameters of XLPE for rotational molding, and quantitatively analyze the non-isothermal crystallization kinetics of increases and decreases; a rotational rheometer was used to test the complex viscosity and other parameters of XLPE for rotational molding. By comparing with the complex viscosity of HDPE with only DCP added, it was shown that the starting cross-linking temperature of XLPE increased by about 10°C, broadening the processing Window; increasing the heating rate and cross-linking temperature can shorten the cross-linking reaction time and increase the cross-linking degree of the product. When the heating rate is greater than 7℃/min and the cross-linking temperature is above 190℃, products with a higher cross-linking degree can be obtained .

2. Use polarizing microscope and DSC to study the crystallization behavior of XLPE and gel.

3. Using the air temperature inside the mold as an indicator, XLPE rotational molding is divided into stages such as material preheating, material melting, bubble removal and compaction, cross-linking, cooling crystallization and solidification; the heating temperature is 270℃~290℃, and the heating time is 28min~ 32min is the optimal XLPE rotational molding process. Within a certain range of heating temperature and heating time, there is a time-temperature equivalent relationship between a 10°C increase in heating temperature and a 1-min extension in heating time; the distribution of cross-linking degree, crystallinity and crystal particle size of XLPE rotational molded products along the thickness direction was quantified.

4. The relationship between the mechanical properties of XLPE products and the degree of cross-linking, crystallinity and crystal particle size was analyzed.
2024 10 25
What Is Rotational Foam Molding And What Are Its Advantages?
Rotational foam molding is a new rotational molding process that has developed rapidly in recent years. It is based on the usual rotational molding process and combined with foaming molding technology to simultaneously complete rotational molding and rotational molding during the rotational molding process. The process of foam molding is a unique molding process to produce integrated rotational molded foam products. Rotational foam molding can be completed by the "one-step method" of inputting multiple raw materials at one time, or by two or multiple inputs. The outer surface of the obtained rotomolded foam product is dense and smooth, and there is a foam core inside. A dense inner layer can also be added to the foam core layer as needed to form a "sandwich" structure. It is also possible to mold solid foam products that are fully filled with foam layers.

Rotational foam molding is more complicated than the usual rotational molding process. If the thickness of the foam layer is controlled and the input of foam material is too small, the thickness of the foam layer will be insufficient, which will affect the function of the product, such as insufficient thermal insulation effect or insufficient density. , and also affects the strength of the product. However, if there is too much foam, it will swell and break the product or even the mold, causing greater damage.

Rotational molded foam products have many unique advantages: because they have multiple product layers, they have high mechanical properties, can be insulated, and can reduce the cost of the product. Rotational foam molding is currently mainly used to produce rotational molded products that require thermal insulation, high strength requirements, or to reduce product production costs, such as insulated boxes, boats, pontoons, etc.
2024 10 24
The Rise Of The Rotational Molding Industry
In recent years, a very popular molding method in blister molding is rotational molding. Rotational molding, also known as rotational molding, rotational molding, rotary molding, etc., is a hollow molding method for thermoplastic plastics.

Rotational molding originated in the United Kingdom in the 1940s. The first rotational molding patent was issued in 1887, and the first commercial rotational molding machine was manufactured in 1934. At first, it was only used as a supplement to injection molding, blow molding, and extrusion. With the maturity of polyethylene powdering technology, it has increasingly become a very competitive molding method in the plastic molding process.

In recent years, in developed countries in North America and Europe, the rotational molding industry has developed rapidly, and its development speed is higher than the average development speed of the entire plastics industry. And the development of the entire rotational molding industry is relatively complete. In addition to rotational molding machine manufacturers and rotational molding product manufacturers, there are also a considerable number of other professional auxiliary factories, such as rotational mold manufacturers, release agent manufacturers, rotational molding special Pigment production plants, grinding machine manufacturers, insert manufacturers, and mixing equipment manufacturers suitable for rotational molding, as well as numerous rotational molding-specific raw material supply factories, etc.

PE bucket manufactured using rotational molding process



My country's rotational molding market



According to statistics, there are more than 1,500 rotational molding product companies in my country; in the early 1970s, there were more than 500 companies engaged in the production of rotational molding products in the United States, with more than 500 rotational molding machines.
2024 10 23
How To Deal With The Problem Of Uneven Wall Thickness Of Rotomolded Products
For the problem of uneven wall thickness of rotational molded products, specific problems must be analyzed in detail. When there is a large wall thickness difference between one part of the product and other parts, if it is caused by structural problems between the rotational molded product and the mold, the structure of the mold must be changed, and the mold corners designed with too small an angle should be replaced with larger smooth arcs. to transition.

For uneven temperatures in the heating furnace, it is necessary to improve and adjust the air volume, angle and circulation path of the hot air to ensure that the mold can be heated evenly in all directions. For parts of the mold that are relatively deep and difficult for heat to reach, you can use an airflow amplifier to add heat. For problems caused by differences in heat absorption in different parts of the mold, such as the flange parts, you can preheat or reduce the heat insulation factor first. In areas where the thickness of the product is expected to be reduced, an additional layer of thin iron sheet can be welded to the corresponding part of the mold to delay the transfer of heat into the mold and reduce the molten material adhering to the mold cavity, thereby reducing the thickness of this area.

As for the uneven wall thickness caused by improper rotation speed ratio or speed control of the mold, the rotation speed of the main and secondary shafts should be appropriately adjusted to maintain a balanced proportion and uniform speed to obtain uniform coverage thickness and appropriate powder trajectory. A constant-torque or constant-speed motor that can be automatically controlled can be used to ensure that the main and secondary shafts rotate at a constant speed. When biaxial rotational molding is performed, the speed ratio of the two axes should not be an integer multiple, so that the spiral material flow traces of each rotation do not repeat each other.
2024 10 22
Precautions For Rotational Molding Mold Line
1. The position of the mold closing line should be conducive to production operations such as mold opening and closing.

2. The position of the mold closing line should take into account the aesthetic needs of the product.

3. The setting of the mold closing line can make the mold structure simpler.

4. Sometimes due to some special reasons such as the complex shape of the product, the mold closing line can also be designed to be more complicated. For example, some parts are higher or lower than the main parting line, etc.
2024 10 21
 About The First Step Of The Rotational Molding Process: Grinding Raw Materials
The first step in rotational molding is grinding, so what are the requirements for grinding?

The quality of powder is related to the pinholes on the surface of the product, the bubbles in the product wall, and of course production efficiency.

The fine powder is on the outside and the coarse powder is on the inside. When heated in this way, the fine powder close to the mold melts first to form the outer skin. If the powder is very rough, there will be gaps between the powder and air inside, which will lead to pinholes after demoulding. In addition, rough powder will trap air in it. Too much air cannot be completely melted during the heating process, and the final manifestation is bubbles in the wall.

When experts encounter problems such as bubbles and pinholes, the first thing they look at is the quality of the powder. If the observed powder particles have a lot of tails, or there are a lot of large particles, then it is necessary to adjust the settings of the grinder.

So, how do we describe the quality of powder? There are three main attributes:

Dry Flow: Describes the flow rate of powder. Generally speaking, the faster, the better;

Bulk Density: Describes the accumulation of powder. Generally speaking, the bigger the better;

Particle Distribution: Describes the size distribution of powder. Generally, the finer the better.

For the results, the dry flow rate is generally between 25 seconds and 35 seconds. The higher the particle fullness, the better the fluidity; the more tails, the worse the fluidity.

Okay, so how do we control the quality of powder? Needless to say, it is a better grinder! The number of teeth of the grinding mill disc, the gap, and the working temperature of the grinding disc will all affect the above three indicators.

Regarding grinding, there are newer cutting-edge developments.
2024 10 19
Why Do Rotomolded Products Need To Be Surface Baked Before Packaging?
The purpose of roasting the surface of rotomolded products is to improve the surface gloss, reduce surface pores, and make the scratches and burrs after trimming the mold closing seam round. ‌ After roasting, the surface quality of rotomolded products is significantly improved, as shown in the following:

1‌.Improve surface gloss‌: Baking can make the surface of rotational molded products smoother, increase the gloss, and make the appearance more beautiful‌.

2‌.Reducing surface pores‌: By roasting, the pores on the surface of the product can be eliminated or reduced, improving the compactness and overall quality of the product‌.

3‌.Smooth the scratches and burrs after trimming the mold closing seam‌: Fire treatment can round the scratches and burrs after trimming the mold closing seam, reduce sharp parts, and improve the safety and aesthetics of the product‌.

Technical details and precautions for roasting:

In the rotational molding process, baking is also a link that requires technical control. Since local defects on the inner surface of the mold may cause the polyethylene melt to flow in and form bonds, it is very important to coat the inner surface of the mold with a layer of thermally stable material to prevent adhesion‌2. In addition, attention needs to be paid to controlling the temperature during the heating stage to avoid scorching of materials and ensure product quality.
2024 10 18
Can Iron Be Made Into Molds? What Are The Advantages And Disadvantages?
Good wear resistance: Specially treated iron molds, such as quenching, tempering and other heat treatment processes, can significantly improve their hardness and wear resistance, making them resistant to wear during use and extending their service life.

Excellent thermal conductivity: Iron material has good thermal conductivity, which can maintain stable temperature distribution and heat transfer during the use of the mold, helping to control product quality.

Higher strength and toughness: Iron molds perform well in terms of strength and toughness and can withstand large impact and pressure, making them suitable for some application scenarios that require higher mold strength.

Relatively low cost: Compared with some advanced alloy materials, the production cost of iron materials is low, making it convenient for small and medium-sized enterprises to manufacture molds.

Shortcoming

Higher weight: Iron material is heavier than other lightweight materials (such as aluminum alloy), which increases the difficulty of handling and installing the mold, and also limits its use in some application scenarios that require lightweight design.

Relatively poor thermal conductivity: Although iron has good thermal conductivity, its thermal conductivity still needs to be improved compared to some materials with better thermal conductivity (such as copper, aluminum, etc.). When manufacturing high-temperature products, iron molds may easily generate thermal stress, causing mold deformation and cracking.

Difficulty in processing: Iron material has high hardness and toughness, which increases its processing difficulty and cost. In the mold manufacturing process, more complex processing techniques and equipment are required to ensure the accuracy and surface quality of the mold.
2024 10 16
What Are The Advantages Of Lighting Made By Rotational Molding Process?
1. Environmental protection

Environmentally friendly materials: Rotational molding lighting usually uses environmentally friendly plastic materials, such as PE (polyethylene). These materials do not produce pollution during the manufacturing process and have good sustainability. In addition, these materials can also be recycled and reused, in line with modern environmental protection concepts.

2. Aesthetics

Variety of options: The rotational molding process provides a wide range of options for lighting design, including a variety of colors and styles, which can be customized according to different decorative needs.

Smooth appearance: Rotomolded lighting has a smooth surface and high transparency, which can show unique light and shadow effects and become a beautiful landscape for indoor or outdoor decoration.

3. Durability

Anti-corrosion and collision resistance: Rotational molding products are anti-corrosion and collision-resistant, which means that rotational molding lighting can maintain good performance and extend service life in harsh environments.

Strong adaptability: The rotational molding process can produce lighting fixtures of various shapes and sizes to meet the decorative effects of different scenes and needs.

4. Practicality

Uniform light effect: The rotational molding lighting has uniform light effect and good light transmittance, which can create a comfortable and harmonious lighting environment.

Easy to clean: The surface of rotomolded lighting is smooth and not easy to adhere to dust. It is very convenient to clean. Just wipe it gently with a cloth.

5. Innovation

Large design space: The rotational molding process provides designers with a larger design space, and they can boldly turn their imagination into reality and create a variety of unique and novel lighting products.
2024 10 15
Rotomolding Products May Undergo Cooling Shrinkage And Deformation And There May Be Certain Errors In Size
1. Optimize cooling methods

Choose appropriate cooling intensity: Try to choose a method with low cooling intensity to avoid uneven shrinkage caused by too fast cooling rate. Although fan cooling is faster than room temperature cooling, it should be used with caution to avoid aggravating shrinkage and deformation.

Uniform cooling: During the cooling process, the rotation of the mold should be maintained to ensure that all parts of the product are cooled evenly. For products with large thickness differences, local air cooling or local reheating can be used to adjust the temperature difference to avoid large deformation.

2. Control the demoulding temperature

Extend the cooling time in the mold: A longer cooling time in the mold can reduce the shrinkage rate.

Control the demoulding temperature: On the premise of ensuring easy demoulding, the lower the demoulding temperature, the better, so as to minimize the risk of shrinkage and deformation.

3. Adjust process parameters

Adjust the rotation speed of the main and auxiliary shafts: Make the rotation speed ratio balanced and the rotation speed uniform, which will help the wall thickness of the molded products to be uniform, thereby reducing shrinkage and deformation.

Improve the heating process: Appropriately increasing the heating temperature can improve the density of the product and help reduce shrinkage and deformation during the cooling process.

4. Optimize mold design

Correct the mold structure: Correct the structures, narrow spaces, sharp angles, etc. in the mold that may cause shrinkage and deformation of the product to reduce the risk of deformation.

Keep the mold vents clear: If necessary, inert gas can be introduced into the mold to improve the temperature distribution and cooling effect inside the product.
2024 10 14
Why Do Motorcycles Use Plastic Fuel Tanks?
As a common means of transportation, motorcycles need to store fuel during driving, so it is necessary to choose a suitable fuel storage device. In modern motorcycles, plastic fuel tanks are becoming more and more common. Why?

First of all, plastic fuel tanks are lighter and easier to manufacture than metal fuel tanks. Plastic materials have good toughness and impact resistance. While being wear-resistant and durable, they can also reduce the weight of the car body. This reduces the overall weight of the motorcycle and improves maneuverability and agility.

Secondly, plastic fuel tanks are more convenient to manufacture and maintain than metal fuel tanks. Making a plastic fuel tank is relatively simple and only requires injection molding, blow molding or extrusion molding. There is no excess waste produced during the production process and the cost is relatively low. In addition, plastic fuel tanks also have better leakage performance, getting rid of the common oil leakage problems of metal fuel tanks. At the same time, the plastic fuel tank design is more concise and fashionable, meeting the aesthetic needs of different consumers.

However, compared with metal fuel tanks, plastic fuel tanks also have some disadvantages. Plastic fuel tanks have a slightly shorter service life than metal tanks, and plastics are not as resistant to chemicals as metal tanks, so they may have an impact on the fuel. Moreover, plastic fuel tanks are prone to aging, being exposed to the sun, rain, and high temperatures. If left outdoors for a long time, they are prone to deformation, cracking, and other problems. Therefore, certain maintenance measures need to be taken during daily use.
2024 10 11
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