The difference between PP material and PS material, Which is better, PP material or PS material? PP， Polypropylene, commonly known as "hundred fold adhesive", is a semi transparent, semi crystalline thermoplastic.
PS， Polystyrene, also known as Polystyrene in English, is environmentally friendly and non-toxic. It has excellent plasticity, poor toughness, and is prone to brittleness.
How to distinguish between PP and PS materials?
1. The difference in sound: PS material is relatively hard, so the sound of tapping sounds more crisp. PP material has good toughness but insufficient hardness, so the sound is relatively dull.
2. Appearance difference: PS can be very transparent, PP has the highest transparency, but it still looks blurry, like frosted glass.
3. The difference in texture: PP has good toughness, while PS is relatively rigid, and the tactile sensation is that PP is relatively soft compared to PS.
Overall, for PP of the same thickness PS product, transparency ps>pp, hardness ps>pp, toughness pp>ps.
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　　In daily life, the plastic products we most often come into contact with include PP, PE, and PVC, among which PP, PE, and PVC are abbreviations of English names. The Chinese names are polypropylene, polyethylene, and polyvinyl chloride.
Some of the old-fashioned slippers we commonly see are made of PVC. They become soft in summer and hard in winter, which is closely related to the temperature sensitivity of PVC. PVC will decompose toxic gas chlorine at high temperatures. Among the three, PVC has the highest density.
Ordinary plastic bags are made of PE, which has good toughness. PE is also divided into HDPE (high-density polyethylene) and LDPE (low-density polyethylene), and the different densities lead to significant differences in some of its properties.
PP is a relatively safe plastic among plastics. Generally, food packaging bags are made of it, and of course, PP also has grades. The packaging used for food must be food grade. PP has the lowest density among the three and can float on the water surface.
Polymer materials like these can generally be modified by adding other materials to make their overall performance or performance superior in a certain aspect, for special purposes. Of course, the price may sometimes increase significantly after modification.
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　　Pulp molding, as a popular representative of green packaging, is favored by brand owners. In the production process of pulp molded products, the mold, as a key component, requires high development and design technology, large investment, long cycle, and high risk. So, what are the key points and precautions in the design of paper plastic molds? Below, we will share some experience in packaging structure design for you to learn and explore pulp molding mold design.
01 Characteristics of pulp molding molds
The mold design must meet the structural requirements of pulp molded products, and the structure of pulp molded products must meet the requirements of mold design and manufacturing while meeting the conditions of use and forming technology.
Therefore, before designing pulp molding molds, it is necessary to fully analyze and study the structure of pulp molding products, in order to coordinate and unify the economic rationality and technical feasibility of product design and mold design.
During the molding process of pulp molded products, they need to enter the mold multiple times before the final manufacturing process can be completed. This is because pulp molded products are formed on a single convex or concave mold, and after forming, they must be transferred in the mold cavity after the convex and concave molds are closed. The wet paper blank transferred to the shaping mold is formed by pressurizing and heating in the shaping mold.
Therefore, pulp molding molds are divided into forming molds, shaping molds, integral molds, transfer molds, and die-cutting molds. There are two types of molding processes, one is adsorption molding, and the other is compression molding. Compression molding molds are somewhat similar to rubber and plastic molds, while adsorption molding molds are more special and complex.
Moreover, the molding of pulp molded products is very different from the rubber and plastic products formed in the mold cavity. The pulp used in the molding of pulp molded products is an aqueous solution containing only about 10% fiber, and most of the water flow must be ensured to flow away. Therefore, the molding mold for pulp molded products must be a mesh mold.
02 Key points of pulp molding mold design
1. Adsorption molding mold
The structure consists of a convex mold, a concave mold, a mesh mold, a mold seat, a mold back cavity, and an air chamber. The mesh mold is the main body of the mold. As the mesh mold is woven from metal or plastic wires with a diameter of 0.15-0.25mm, it cannot be formed independently and must be attached to the surface of the mold to work.
The back cavity of a mold is a cavity composed of a certain thickness and shape that is completely synchronized with the working surface of the mold, relative to the mold seat. That is, a convex or concave mold is a shell with a certain wall thickness. The working surface of the mold is connected to the back cavity by uniformly distributed small holes.
The mold is installed on the template of the molding machine through the mold seat, and an air chamber is installed on the other side of the template. The air chamber is connected to the back cavity, and there are also two channels for compressed air and vacuum on it.
Reserve amount for adsorption molding molds:
The reserved amount of adsorption molding molds is the key to mold design
Pulp molded products shrink from wet paper blanks to finished products due to the precipitation of water. The different and irregular shrinkage rates at different positions of the same product result in multi-directional and variable shrinkage changes during the molding process, making it difficult to determine the reserved amount in mold design. Fortunately, the current packaging industry does not have high requirements for the manufacturing accuracy of pulp molded products, and empirical design methods can still meet the requirements.
2 pulp molding and shaping molds
The shaping mold is a mold that directly enters the wet paper blank after it is formed and has functions of heating, pressurization, and dehydration. The products manufactured with the shaping mold have a smooth surface, accurate dimensions, solidity, and good rigidity. Disposable tableware is made using this mold. In industrial packaging, some small, precise, and large quantities of small items are packaged layer by layer, with packaging products used for positioning between each layer. If pulp molded products are used, they need to be manufactured using shaping molds.
Most industrial inner packaging products are single-sided and do not require heat setting. They can be dried directly. The structure of the shaping mold includes a convex mold, a concave mold, a mesh mold, and a heating element. The convex or concave mold with a mesh mold has drainage and exhaust holes. During operation, the wet paper blank is first squeezed in the shaping mold, and 20% of the water is squeezed and discharged. At this time, the water content of the wet paper blank is 50-55%, which vaporizes and discharges the remaining water after being heated in the mold. The wet paper blank is pressed, dried, and shaped to form a product.
The mesh mold in the shaping mold will cause mesh marks on the surface of the product, and the mesh mold will quickly damage during frequent squeezing. To solve this problem, a mold designer has designed a mesh free mold, which is manufactured using copper based spherical powder metallurgy. Over the past two years, through multiple structural improvements and the selection of appropriate powder particle size, the lifespan of the meshless shaping mold manufactured is 10 times longer than that of the mesh mold, with a 50% cost reduction. The paper products produced have high precision and smooth inner and outer surfaces.
3 pulp molding and shaping molds
After drying, wet paper blanks may undergo deformation. Some parts may undergo severe deformation, or high precision is required for the appearance of the product. The product needs to go through a shaping process, and the mold used is called a shaping mold. This type of mold also requires heating elements, but it can be done without a mesh mold. Products that require shaping should retain 25-30% moisture content during drying to facilitate shaping.
In production practice, due to the difficulty in controlling water content, it is difficult for products to meet quality requirements. A manufacturer has designed a spray shaping mold, and spray holes are made on the mold corresponding to the parts that need shaping. When working, the products are put into the shaping mold after being thoroughly dried. At the same time, the spray hole on the mold is used for spray hot pressing the products. This mold is somewhat similar to the spray iron in the clothing industry.
4 Transfer mold
The transfer mold is the last workstation of the entire process, and its main function is to safely transfer the product from the integral auxiliary mold to the receiving tray. For the transfer mold, its structural design needs to be as simple as possible, with evenly arranged suction holes to ensure that the product can be smoothly adsorbed on the mold bonding surface.
5 pulp molding and die-cutting molds
In order to make paper molded products clean and beautiful, paper molded products with high appearance requirements are equipped with edge cutting processes. Die cutting molds are used to trim the rough edges of paper molded products, also known as edge cutting molds.
The New Favorite of Paper Mold and Plastic Tool Design - Public Mold
Pulp molding is the use of molds to shape paper products in the pulp state, therefore, molds are the key to pulp molding technology. Using paper plastic molds to produce disposable tableware, gift box packaging, beauty packaging, etc., due to their simple shape, they have a certain degree of universality.
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　　On March 28th, the China Consumers Association released a report on research on excessive packaging of goods and consumer perception survey. The report shows that consumers highly support the current standards set by relevant departments to restrict excessive packaging of five categories of products: edible agricultural products, tea, toys, baby and child products, and electronic products. Consumers are most concerned about the issue of excessive packaging of tea, with 40.7% of them believing that there may be an issue of excessive packaging; More than 20% of consumers believe that there may be excessive packaging issues with electronic products and edible agricultural products. Consumers hope that packaging can protect their right to information, choice, and fair trade. For example, consumers hope that packaging for agricultural products can not only be fresh and easy to carry, but also open an effective visual "skylight".
It is reported that relevant departments are currently formulating mandatory standards for excessive packaging restrictions on edible agricultural products and tea, and recommending standards for excessive packaging restrictions on toys, infant and child products, and electronic products. The research on excessive packaging of products and consumer perception survey organized by the China Consumers Association also targeted the functional needs of consumers for packaging of edible agricultural products, tea, toys, infant and child products, electronic products, and other products, as well as their perception of excessive packaging in these categories, in order to provide feedback to the standard setting department on reasonable consumer demands.
According to a survey conducted by the China Consumers Association, the proportion of consumers who believe that electronic products, edible agricultural products, infant and child products, and toys are suspected to have excessive packaging is 23.5%, 20.5%, 15.3%, and 14.6%, respectively. Professional investigators organized by the China Consumers Association conducted a search for suspected excessive packaging issues in four product categories on mainstream e-commerce platforms, namely edible agricultural products, tea, toys, and baby and child products, from the perspective of actual consumer consumption. Through subjective judgment based on high visual packaging voids, a total of 6160 products, including 2830 tea leaves, 900 edible agricultural products, 920 toys, and 1510 baby and child products, were identified. The preliminary judgment showed that the proportion of suspected excessive packaging problems in mainstream e-commerce platform tea was 11.2%, while the proportion of suspected excessive packaging problems in edible agricultural products and toys was 8.9%. The proportion of suspected excessive packaging problems in baby and child products was the lowest, only 4.4%.
The China Consumers Association found that the main functional requirement of consumers for packaging of edible agricultural products is preservation (78.8%). After harvesting, a series of changes occur in the quality and maturity of agricultural products, such as respiration and water transpiration, which affect their storage life. Therefore, agricultural product packaging should have preservation function to maintain good quality during transportation, storage, and distribution; Due to the large volume and weight of agricultural products, 73.1% of consumers hope that the packaging of edible agricultural products can be easily carried, for example, it is best to have handles and handles for packaging large agricultural products; 60.8% of consumers believe that the packaging of edible agricultural products should be "visible (with transparent windows to determine freshness)". Consumers can judge the quality and maturity of agricultural products by observing their appearance, such as size, color, and damage, and decide whether to purchase them. "Visible packaging" can facilitate consumers to accurately understand the quality and maturity of agricultural products, protect their right to know, and let consumers buy with confidence.
The survey shows that the main functional requirements of consumers for tea packaging are as follows: "ensuring the quality of tea, preventing moisture and spoilage" (76.9%), "good storage performance after opening" (75.8%), and "convenient access" (62.5%); The main demand of consumers for the packaging function of infant and child products is "safety" (78.4%), and the main demand for the packaging function of toys is "guidance on gameplay and improvement of fun" (63.4%); The main demands of consumers for the packaging functions of electronic products are as follows: "moisture-proof, anti-collision, shockproof and other protective functions" (82.2%), "reflecting the brand and having anti-counterfeiting functions" (61.9%), and "convenient portability" (59.9%).
The China Consumers Association hopes that relevant departments can fully consider the reasonable demands of consumers in the process of formulating relevant standards, so that product packaging is not only environmentally friendly and simple, but also close to actual living needs, and can also protect consumers right to know; It is suggested that when formulating tea packaging standards, reference should be made to the requirements of the new standard for moon cake Zongzi in terms of the number of packaging layers, packaging cost ratio, and packaging materials, considering that the minimum weight of a single small package should not be less than the amount of tea brewed at one time, and enterprises should be encouraged to provide at least one small package with transparent windows so that consumers can see the quality of tea; It is recommended that when formulating standards for packaging of edible agricultural products, transparent skylights should be installed on the packaging or the goods can be seen without damage to the packaging, in order to facilitate consumers to accurately understand the quality and maturity of agricultural products, protect their right to know, and let consumers buy with confidence.

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