If you are searching for high-performance aluminum nitride (AlN) powder, the technical parameter "particle size distribution" is an absolutely essential factor you cannot overlook. It is not just a row of complex numbers on a data sheet but a hidden code that determines the success or failure of your final product.

So, what exactly is the particle size distribution of aluminum nitride powder? And how does it affect your production process and product performance? Let’s uncover the mystery together.

1. In Simple Terms, What Is Particle Size Distribution?

Imagine a bag of rice containing both whole grains and some broken bits. The same applies to aluminum nitride powder—it does not consist of particles all of the same size.

Particle size distribution is a scientific method to describe the proportion of particles of different sizes in this "bag of aluminum nitride powder." It tells us whether the powder is "uniform" or "varied in size."

Key metrics typically include:

D50: This is a median value. It indicates that 50% of the particles in the sample have a diameter smaller than this value, and 50% are larger. It is a core metric for measuring the "average fineness" of the powder.

D10 and D90: These represent the particle diameters below which 10% and 90% of the sample particles lie, respectively. They define the "range" of particle sizes in the powder.

Span: Calculated as (D90 - D10) / D50. A smaller Span value indicates more uniform particle sizes and a more concentrated distribution, while a larger Span value suggests greater variation in particle sizes and a wider distribution.

2. Why Is Particle Size Distribution So Important?

Particle size distribution directly affects the physical and chemical properties of the powder, thereby influencing every step from processing to the final product.

Impact on Sintering Density

Fine particles: More active and easier to fuse at high temperatures, contributing to high-density sintering at lower temperatures, saving energy.

Optimal combination: Using a "bimodal distribution" (i.e., intentionally mixing particles of two different sizes) is like combining sand and stones—small particles perfectly fill the gaps between larger ones, achieving the highest packing density and resulting in a denser, stronger product after sintering.

Decisive Influence on Thermal Conductivity

The core value of aluminum nitride lies in its exceptional thermal conductivity. Heat transfer is most hindered by "obstacles."

Pores are obstacles: Poor particle size distribution can lead to pores after sintering, severely reducing thermal efficiency.

Grain boundaries are also obstacles: Uniform and appropriately coarse particles help form larger crystal grains, reducing the "walls" (grain boundaries) between crystals. This allows heat (phonons) to flow unimpeded, maximizing thermal conductivity.

Adaptability to Production Processes

Tape casting: Requires ultra-fine powder with uniform particles (small Span value) to prepare stable, non-laminating slurry, ultimately yielding smooth and flat ceramic substrates.

Die pressing: Tolerates a wider range of particle size distributions but still requires a reasonable distribution to ensure filling rate and green strength.

About Xiamen Juci Technology Co., LTD

Xiamen Juci Technology Co., Ltd. specializes in the R&D and production of high-performance aluminum nitride (AlN) powders. Leveraging advanced preparation techniques and stringent quality control, we precisely tailor the particle size distribution of our AlN powders to ensure high uniformity and consistency. Our products feature a concentrated and narrow particle size distribution, which provides excellent flowability and sintering activity, making them ideal for applications such as thermal conductive AlN fillers, AlN ceramic substrates, and electronic packaging. We are your key material partner in enhancing the thermal performance and reliability of your products.

Media Contact:
Xiamen Juci Technology Co., Ltd.

Phone: +86 592 7080230
Email: miki_huang@chinajuci.com

Website: www.jucialnglobal.com

The lifespan of solar panels depends a lot on the materials used to seal them. That's why researchers spend a lot of time studying these materials. A comparative analysis of the aging resistance of the four mainstream encapsulation films currently on the market: Ethylene Vinyl Acetate (EVA), POE, EPE, and PVB. PolyVinyl Butyral Film (PVB film) exhibits excellent aging resistance, while EVA film exhibits good initial performance but relatively poor aging resistance.

1. Four Mainstream Encapsulation Films

EVA film: Made from ethylene-vinyl acetate copolymer resin, it is the largest market share photovoltaic module encapsulation material. Vinyl acetate groups are introduced through high-pressure polymerization. The vinyl acetate content affects film performance and is typically between 28% and 33%. EVA film technology is mature and relatively low-cost. As a photovoltaic module encapsulation film, it offers the following advantages:

• Strong adhesion to photovoltaic glass, solar cells, and backsheets
• Good melt flowability and low melting temperature
• High light transmittance
• Excellent flexibility, minimizing damage to solar cells during lamination
• Excellent weather resistance

POE film: A random copolymer elastomer formed from ethylene and 1-octene, it features a low melting point, a narrow molecular weight distribution, and long chain branches. In the ethylene-octene copolymer system, octene units can be randomly attached to the ethylene backbone, resulting in excellent mechanical properties and light transmittance.
Excellent moisture vapor barrier properties: Its moisture vapor transmission rate is approximately 1/8 that of EVA. Its stable molecular chain structure results in a slow aging process, providing better protection for solar cells from moisture corrosion in high-temperature and high-humidity environments and enhancing PID resistance in solar modules.
Excellent weather resistance: The molecular chain contains no hydrolyzable ester bonds, preventing the generation of acidic substances during aging.

EPE Co-extruded Film: This encapsulation film was developed to address the application challenges of POE films. POE films are prone to additive precipitation during lamination, resulting in slippage during use and affecting product yield. Therefore, EVA and POE are co-extruded in multiple layers to create EVA/POE/EVA multilayer co-extruded films.
This film combines the advantages of both materials: it possesses the water barrier and PID resistance of POE with the high adhesion of EVA.
Process control is challenging: Polyolefin elastomers are non-polar molecules, while ethylene-vinyl acetate copolymers are polar molecules. The two resins exhibit significant differences in cross-linking reactivity, melt viscosity, and shear melt heating rate, making it difficult to effectively control quality through a simple co-extrusion process.

PVB Film: This film offers significant advantages in photovoltaic module encapsulation, particularly for building-integrated photovoltaic (BIPV) modules. This thermoplastic polymer is formed by the acid-catalyzed condensation of polyvinyl alcohol (PVA) generated by the hydrolysis or alcoholysis of polyvinyl acetate and n-butyraldehyde. It is recyclable and reprocessable, and does not require a cross-linking reaction.
Strong Adhesion and Mechanical Properties: It exhibits strong adhesion to glass and high mechanical strength.
Excellent Aging Resistance: It exhibits exceptional environmental aging resistance, making it more resilient for outdoor use and capable of lasting up to four years without compromising performance. Its adhesion to glass and impact resistance are superior to those of EVA film, and its aging resistance is also superior to that of EVA film.

2. Aging Resistance - UV Accelerated Aging Test

The UV accelerated aging test verifies atmospheric light aging resistance. After lamination, the prepared materials are placed in a UV aging chamber under controlled test conditions. After aging, the peel strength and yellowing index of the film against glass are measured.

UV radiation damages the film's adhesive properties, but the effect is less severe than in high temperature and high humidity environments. EVA exhibits significant yellowing after UV irradiation. Peel Strength Change: UV irradiation does affect the peel strength between the film and glass to some extent, but the effect is less pronounced than in high-temperature, high-humidity environments. Different films exhibit different peel strength change trends after UV irradiation. For example, samples 1# (EVA), 2# (POE), 3# (EPE), and 4# Polyvinyl Butyral (PVB) all show a decrease in peel strength after UV irradiation, but the degree of decrease varies.

Yellowing Index Change: EVA exhibits significant yellowing after UV irradiation. This is because residual crosslinkers in the EVA decompose under the influence of light, generating reactive free radicals that react with the antioxidant (UV absorber) to form chromophores. The yellowing index of other films also changes after UV irradiation, but to a lesser extent than that of EVA.

3. Aging Resistance - High-Temperature, High-Humidity Aging Test

The laminated samples were placed in a constant temperature and humidity chamber at a temperature of (85±2)°C and a relative humidity of 85%±5% for 1000 hours.

The peel strength of all four samples against glass decreased after hygrothermal aging. PVB exhibited superior hygrothermal aging resistance, while EPE fell between EVA and POE. EVA was more susceptible to yellowing under high temperature and high humidity conditions.

Peel Strength Change: The peel strength of samples 1#, 2#, 3#, and 4# against glass decreased after hygrothermal aging, and this continued to decline with increasing hygrothermal aging time.

Yellowing Index Change: The yellowing index of all samples increased with increasing hygrothermal aging time, with EVA showing the largest increase, indicating that EVA is more susceptible to yellowing under high temperature and high humidity conditions.

4. Aging Resistance - Humidity-Freeze Aging Test

Laminated specimens were placed in a temperature-humidity cycling test chamber. The cycle conditions were characterized by specific temperature and humidity variations, as shown in the figure below. The number of cycles was 20.

Peel Strength Change: As shown in the figure, the humidity-freeze cycle had little effect on the peel strength between films 1#, 2#, 3#, and 4 and the glass. The peel strength of the four films remained relatively stable during the humidity-freeze cycle, with no significant decrease.

Yellowing Index Change: The four films showed low yellowing after the humidity-freeze cycle, demonstrating that they maintain high performance despite frequent temperature fluctuations and exhibit good resistance to yellowing. Their optical properties remained relatively stable in environments with high humidity and large temperature fluctuations.

Mechanical tests showed that PVB has the best properties, while EVA is mechanically stronger than POE, with EPE in between. Overall, PVB film resists aging best, while EVA is good at first but ages faster. EVA is still popular because it's affordable. As tech gets better, POE and EPE will likely become more common alongside EVA, giving more choices for sealing solar panels.

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Modified phenolic resin overcome the shortcomings of phenolic resin, such as poor heat resistance and low mechanical strength. They offer excellent mechanical properties, strong heat resistance, strong bonding, and chemical stability. They are widely used in compression molding powders, coatings, glues, fibers, anti-corrosion, and thermal insulation applications.

1. Applications of Modified Phenolic Resins in Compression Molding Powders

Compression molding powders are essential for the production of molded products. They are primarily made from modified phenolic resins. In manufacturing, a common method involves using both roller compaction and twin-screw extrusion. Wood is used as a filler to impregnate the resin, and other reagents are then added and mixed thoroughly. The powder is then pulverized to produce compression molding powder. Materials such as quartz can be added to produce compression molding powders with enhanced insulation and heat resistance. Compression molding powders are a raw material for various plastic products, which can be manufactured industrially through injection molding or compression molding. Figure 2 shows the application of modified phenolic resin in compression molding powders. Compression molding powders are primarily used in electrical components such as switches and plugs for household items.

2. Application of Modified Phenolic Resins in Coatings

For 70 years, coatings have used phenolic resins. Rosin-modified phenolic resins or 4-tert-Butylphenol formaldehyde resin are the main ones in phenolic coatings. These resins make coatings better at resisting acid and heat, so they're common in lots of engineering projects. Still, because they give things a yellow color, you can't use them if you want a light-colored finish. Besides being mixed with tung oil, they can also be blended with other resins. To increase a coating's alkali resistance and air-dried hardness, alkyd resins can be added to improve the coating's alkali resistance and hardness. For coatings requiring acid and alkali resistance and good adhesion, epoxy resins can be added to enhance the coating's performance. Figure 3 illustrates the application of modified phenolic resins in coatings.

3. Application of Modified Phenolic Resins in Phenolic Adhesives

Phenolic adhesives are mainly made from modified thermosetting phenolic resins. If phenolic resin is used to create adhesives, its viscosity can be a problem, restricting it to plywood bonding. But, modifying phenolic resin with polymers can improve its heat resistance and adhesion. Phenolic-nitrile adhesives can even have good mechanical strength and toughness, especially when it comes to impact resistance.

4. Application of Modified Phenolic Resins in Fibers

Phenolic resins also have a wide range of applications in the fiber industry. Phenolic resin is melted and drawn into fibers, which are then treated in polyoxymethylene. After a period of time, the filaments solidify, resulting in a fiber with a solid structure. To further enhance the fiber's strength and modulus, the modified phenolic resin can be mixed with molten low-concentration polyamide and drawn into fibers, as shown in Figure 4. The spun fibers are typically yellow and possess high strength. They will not melt or burn even at temperatures of 8,000°C. It will also self-extinguish in these harsh environments, preventing fires from occurring at the source. At room temperature, polyamide-modified phenolic resin fibers are highly resistant to concentrated hydrochloric and hydrofluoric acids, but less resistant to strong acids and bases such as sulfuric acid and nitric acid. These products are primarily used in factory protective clothing and interior decoration, minimizing employee injuries and fatalities in the event of a fire. They are also commonly used as insulation and thermal insulation materials in engineering projects.

5. Application of Modified Phenolic Resins in Anti-Corrosion Materials

Phenolic resins are used to make anti-corrosion stuff, but the modified versions are more common. You'll often see these as phenolic resin mastics, phenolic-epoxy composite fiberglass, or phenolic-epoxy coatings. A good example is phenolic-epoxy coatings, which mix the acid resistance of phenolic resins with the alkali resistance and stickiness of epoxy resins. This mix makes them great for protecting pipelines and vehicles from corrosion.

6. Application of Modified Phenolic Resin in Thermal Insulating Materials

Because modified phenolic resin offers superior heat resistance compared to pure phenolic resin, modified phenolic resin foams occupy a prominent position in the thermal insulation market, as shown in Figure 5. Modified phenolic resin foams also offer thermal insulation, are lightweight, and are difficult to spontaneously ignite. Furthermore, when exposed to flames, they do not drip, effectively preventing the spread of fire. Consequently, they are widely used in thermal insulation color-coated steel sheets, room insulation, central air conditioning, and pipes requiring low temperatures. Currently, polystyrene foam is the most widely used insulation material on the market, but its performance is far inferior to that of modified phenolic resin foam. Modified phenolic resin foam, due to its low thermal conductivity and excellent thermal insulation, has earned it the title of "King of Insulation" in the insulation industry.

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For outdoor environments, you should choose EPDM. Nitrile suits oil and fuel contact best. For mixed chemical resistance, select neoprene and chloroprene. Evaluate your project’s environmental exposure, chemical compatibility, and temperature requirements. These factors will help you make the right material choice for reliable, long-term performance.

1. Comparison Overview

Key Properties

When you compare Chloroprene Rubber(such as Polychloroprene Rubber CR2440) , EPDM, and Nitrile Rubber, you need to focus on several critical properties. These include oil resistance, weathering, ozone/UV resistance, fire performance, temperature range, and cost. The table below summarizes how each material performs in these areas:

Property

Ozone and Weathering Resistance Table

Fire Resistance Classification Table

2. Pros and Cons

You should weigh the advantages and disadvantages of each material before making your selection.

Chloroprene Rubber

• Pros: Offers balanced resistance to oil, chemicals, and weathering; Performs well in outdoor and marine environments; Less flammable than many other rubbers.
• Cons: Faces supply chain risks due to regulatory restrictions; Ozone resistance is lower than EPDM or Nitrile; Cost can be higher than EPDM.

EPDM

• Pros: Excels in outdoor, UV, and ozone-exposed applications; Maintains flexibility at low temperatures; New formulations provide flame resistance and self-healing properties; Cost-effective for large-scale projects.
• Cons: Poor resistance to oils and fuel; Requires additives for optimal fire performance; Not suitable for applications involving petroleum-based fluids.

Nitrile Rubber

• Pros: Outstanding oil and fuel resistance; Enhanced heat resistance in modern compounds; Can be blended for specialized performance, such as static dissipation; Eco-friendly options are emerging.
• Cons: Weathering and ozone resistance are lower than EPDM; Not inherently flame retardant; Flexibility decreases at low temperatures.

3. Choosing the Right Material

Environmental Factors

You need to assess the environment where your rubber material will operate. Outdoor exposure, sunlight, ozone, and weathering can quickly degrade some rubbers. EPDM stands out for its excellent resistance to ozone and sunlight, making it the top choice for outdoor applications. You benefit from EPDM’s ability to withstand harsh weather, UV rays, and temperature swings. This material can last up to 20 years or more in outdoor conditions. If your project involves exposure to oils or solvents, Chloroprene Rubber (such as Neoprene AD-20) offers good oil resistance and performs well in parts exposed to chemicals. EPDM is also more environmentally friendly because it is non-toxic and recyclable, while Neoprene (Chloroprene Rubber) is less sustainable.

Chemical Resistance

You must match the rubber’s chemical resistance profile to your application. Each material reacts differently to oils, fuels, and industrial chemicals. Nitrile Rubber provides high oil resistance but performs poorly against weather and ozone. Chloroprene Rubber offers moderate oil resistance and excellent weather resistance. EPDM does not resist oils but excels in weather and ozone resistance.

You should always check the chemicals your project will encounter. Select Nitrile Rubber for oil and fuel contact. Use Chloroprene Rubber for balanced resistance to chemicals and weather. Choose EPDM for applications with no oil exposure but high weathering demands.

4. Summary

Choosing the right rubber material for your project depends on matching its properties to your application’s demands. You need to consider oil resistance, weathering, ozone and UV exposure, and the specific environment where the rubber will perform. Each rubber type offers unique strengths that make it ideal for certain uses.

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Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer with excellent film-forming properties, surface activity, and strong adhesion to inorganic and cellulosic materials. Global annual PVA production is approximately 1.05 million tons, with Japan producing approximately 300,000 tons. Approximately 14,100 tons of this is used as a paper processing chemical, a surface sizing agent for plain paper, a sizing agent for coated and coated paper, a fluorescent brightener, an inkjet ink absorber, an adhesive for inorganic fillers, and a silicone sealant for release paper.

The paper business faces challenges like using different types of wood pulp and faster, bigger machines for making paper and printing. Because of this, they need better water-soluble polymers with special features. These polymers are important for making fancy specialty papers and papers used in tech. To adapt to these fundamental changes in the papermaking industry, Kuraray Japan has developed and mastered the properties of modified PVA with novel properties. This article will focus on two specialty PVA: the silanol-modified "R-series PVA" and the high-barrier "Exceval PVA" with the introduction of special hydrophobic groups. The two types will be discussed, along with their properties and applications in paper processing additives.

2. PVA Properties and Dissolution Methods

Industrially, PVA is produced by polymerizing and then saponifying polyvinyl acetate. Its fundamental properties depend on its degree of polymerization and saponification. Most commercially available PVAs had a degree of polymerization of 200 to 4000 and a degree of saponification of 30% to 99.9% by mole fraction. The main varieties of PVA produced by Kuraray (Kuraray PVA) are shown in Tables 1 and 2.

3. Specialty Kuraray PVA

To date, Kuraray has produced a variety of Kuraray PVAs with varying degrees of polymerization and saponification, which are used in a wide range of applications. As demand grows for better PVA and more varied uses, just tweaking the polymerization and saponification degrees isn't enough anymore. So, Kuraray PVA now comes with special groups added to give it extra function.

This article will introduce two types of functionalized PVA: the "R-series PVA," modified with silanol groups, and the "Exceval PVA (Exceval HR-3010)," which incorporates special hydrophobic groups for high barrier properties.

3.1 Silanol-Modified R-series PVA

The R-series is a modified PVA with silanol groups. Table 3 lists the quality standards for the R-series products.

3.2 High Barrier Exceval PVA

Exceval PVA is a PVA containing special hydrophobic groups. The introduction of hydrophobic groups enhances the crystallinity of the solid polymer, resolving the dilemma of achieving both high water resistance and stable aqueous solution viscosity, which is difficult to achieve with standard PVA. The use of PVA is increasing annually. PVA is usually used as a stabilizer in adhesives that need to resist water. But, when used in food packaging films, PVA doesn't block oxygen well when it's humid. Exceval PVA is also being developed as an improved material. In coated paper applications, Exceval PVA has also been successfully used when higher water resistance than PVA is required.

This article reports on the results of a new application study for Exceval PVA, specifically its use as an oil-resistant agent in food packaging. The product specifications of the Exceval PVA used in this study are shown in Table 4.

Table 5 shows that coating with Exceval PVA RS-2117 achieves air resistance roughly equivalent to that achieved with partially saponified PVA-217, while significantly reducing water absorption. Paper coated with partially saponified PVA exhibits higher air resistance. This is because the highly hydrophobic, partially saponified PVA has a lower surface tension in aqueous solution, inhibiting penetration into the paper. However, partially saponified PVA suffers from a significant reduction in water resistance. While Exceval PVA, modified with a special hydrophobic group, is fully saponified, it still exhibits the same permeability as partially saponified PVA, offering both improved water resistance and air impermeability.

R-series PVA contains highly reactive silanol groups, which improve adhesion to various inorganic materials. Using the R-series in inkjet media reduces the amount of polyvinyl alcohol used as a binder for silica particles, improving print quality. Even without a crosslinker, the R-series provides high water resistance. Exceval PVA is a modified, hydrophobic polyvinyl alcohol that offers excellent water resistance and gas barrier properties under high humidity conditions. The lower air permeability of coated paper provides a higher barrier to oils and greases than fully water-soluble polyvinyl alcohol, a property further enhanced when used with flake minerals. Exceval is now FDA-registered as safe for contact with food, opening doors for its use in food packaging paper.

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Carbon foam, a functional carbonaceous material with a honeycomb structure, not only boasts excellent properties such as low density, high strength, oxidation resistance, and adjustable thermal conductivity, but also boasts excellent processability. Therefore, it can be used as a thermal conductor, insulator, catalyst carrier, biosolidifier, and absorber. It holds broad application prospects in military applications, energy-saving building insulation, chemical catalysis, biological wastewater treatment, and energy. Carbon foam can be sorted into two kinds—one that lets heat pass through easily (thermally conductive) and another that stops heat from passing through (thermally insulating). The difference lies in how much the original carbon material has been turned into graphite. Mesophase pitch and phenolic resin are two typical carbonaceous precursors for producing high- and low-thermal-conductivity carbon foams, respectively. Currently, both thermosetting and thermoplastic phenolic resins are high-quality carbonaceous precursors for producing low-thermal-conductivity carbon foam. Using phenolic resin as the raw material, a phenolic resin foam can be produced by adding a blowing agent and a curing agent and foaming at normal pressure. Carbon foam is then produced by high-temperature carbonization. The compressive strength of this carbon foam is below 0.5 MPa, which restricts how it can be used.

When Phenolic Resin 2402 is used as the raw material, the pores of the carbon foam produced at different foaming pressures are all nearly spherical (Figure 6). Since no foaming agent is added, the foaming process follows a self-foaming mechanism, whereby the matrix material undergoes a cracking reaction at a certain temperature, generating corresponding small molecular gases. As gases form, they gather and grow into pores. The viscosity, structure, volume, shape, and gas production rate of the base material change as cracking gas is produced. This means the structure of pores in carbon foam depends on the base material's viscosity, gas production rate, volume, how quickly its viscosity changes, and outside pressure within the foaming temperature range.

At foaming temperatures between 300 and 425°C, 2402 phenolic resin makes lots of cracking gas (Figure 3(a)) and has low viscosity (<2×104Pa·s, Figure 4(d)). Because of this, surface tension causes the pores to be round. When the foaming pressure is 1.0 MPa, the low outside pressure causes bubbles to merge and grow, leading to larger pore sizes (500-800 μm). Also, the larger pores mean the carbon foam has thinner connections and many pores are close to becoming open cells (Figure 6(a)).

When the foaming pressure goes up to 3.5 MPa, the pore size of the carbon foam goes down (300-500 μm), the connections get thicker, and the pore structure is more consistent (Figure 6(b)). If the foaming pressure keeps increasing to 5.0 MPa, the pore size keeps going down, but the consistency of the pore structure starts to get worse (Figure 6(c)). At a foaming pressure of 6.5 MPa, the pore structure of the carbon foam keeps getting worse, but the pore density goes up (Figure 6(d)).

When the foaming temperature goes above 425°C, the viscosity of the 2402 phenolic resin quickly goes up. The foaming pressure clearly has an important impact on how consistent the pore structure is and how dense the carbon foam is. If the foaming pressure is less than the pressure inside the bubble, the cracking gas produced later can still overcome the base material's viscosity and keep gathering and growing in the already formed bubble. This results in a fairly consistent pore structure in the bubble, but no new bubbles will form. But, if the foaming pressure is high enough, the cracking gas produced later can only form new, smaller bubbles at the connections of the already formed bubbles or in the base material, which makes the pore structure of the foamed carbon worse and increases the pore density.

Conclusion

(1) The way thermoplastic phenolic resin (resin for refractory) foams is based on its own reaction. How well it foams depends on the conditions (pressure, temperature, and time). It's also influenced by how the molecules interact, considering their size, distribution, how they lose weight when heated, and how their viscosity changes with temperature. Viscosity and temperature are key.

(2) When heated to 300-420°C, 2402 Phenoic formaldehyde resin breaks down fast, making a lot of gas. If the material's viscosity is below 2×104 Pa·s at this point, the resulting foamed carbon has good bubbles that are round and evenly spaced.

(3) Lower pressures when foaming help make foamed carbon with consistent pores. Higher pressures stop the gas from clumping together and getting bigger, which causes more bubbles to form. This makes the pore structure uneven and increases how many bubbles there are.

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In today's industry, new materials are boosting how well products work. Polyvinyl Alcohol (PVA) is one of these. It's a special kind of synthetic polymer that's becoming very important for making glues, coatings, and films. PVA is great at forming films, sticking things together, dissolving in water, and blocking stuff from getting through. All these things make products better and more competitive.

1. PVA in Adhesives: The Cornerstone of Strong Adhesion

PVA stands out because it sticks things together very well. Its molecular structure contains numerous hydroxyl (-OH) groups, which form strong hydrogen bonds with a variety of substrates, resulting in a secure bond.

How PVA Works in Adhesives:

• Excellent Adhesive Properties: PVA's hydroxyl groups allow it to wet and stick to things like paper, wood, cloth, leather, and certain plastics, creating a strong bond.
• Excellent Film-Forming Properties: When PVA solution dries, it makes a continuous, smooth, and very flexible film. This film helps the glue stick better. It also spreads stress evenly on the surface, which lowers stress points and makes the bond stronger and last longer.
• Excellent Cohesive Strength: Hydrogen bonding between PVA molecular chains also imparts high cohesive strength to the adhesive layer, making the bond less susceptible to breakage when subjected to external forces.
• Modified Polymer Adhesives: PVA is often used as a modifier for polymer adhesives such as polyvinyl acetate (PVAc) emulsions. The addition of PVA significantly increases the viscosity, cohesive strength, wet adhesion, and initial tack of PVAc-based adhesives, while also improving their film-forming properties.

Typical Product Applications:

• Paper and Packaging: PVA is a key adhesive component in the production of products such as paperboard, corrugated boxes, envelopes, and tapes. Its rapid cure and high bond strength meet the demands of high-speed production lines.
• Wood and Furniture: In the woodworking industry, PVA-based adhesives are favored for their excellent adhesion to wood and relatively low cost. Textiles: PVA can be used as a textile adhesive for non-woven fabric production and garment lamination.

2. PVA in Coatings: Improving Performance and Aesthetics

PVA is also widely used in coatings. It not only serves as a film-forming agent but also as an additive, significantly improving the coating's application performance and final film finish.

Mechanisms of PVA in Coatings:

• Enhancing Adhesion: Similar to its role in adhesives, PVA helps the coating adhere better to the substrate surface, reducing flaking and blistering, and improving coating durability.
• Improving Leveling and Uniformity: PVA's film-forming properties help create a smooth, uniform coating. In paper coatings, PVA acts as a carrier, helping evenly distribute pigments and optical brighteners, enhancing the paper's gloss and printability.
• Thickening and Stabilization: In water-based coatings, PVA acts as a thickener, adjusting the viscosity and making it easier to apply. It also acts as a protective colloid, stabilizing pigment dispersions and preventing settling.
• Optical Enhancement: In paper or textile coatings, PVA is an excellent carrier for optical brighteners. It helps the agents distribute more evenly and anchor them to the surface, effectively absorbing UV light and reflecting bluish-white light, significantly improving the product's whiteness and brightness.

Typical Product Applications:

• Paper Coating: CCP Polyvinyl Alcohol BP-05 (CCP BP 05), a partially hydrolyzed form of PVA, exhibits both hydrophilic and hydrophobic properties, making it ideal as a component in paper coatings. It improves paper's smoothness, printability, ink bleed resistance, and surface strength. BP-05 is recommended for paper coating, indicating its specialized application in this area.
• Architectural Coatings: In building materials such as cement mortar and gypsum board, PVA can be used as an additive to improve flexibility, bonding strength, and crack resistance.
• Specialty Coatings: PVA can also be used to create high-performance coatings, such as packaging coatings with excellent barrier properties, or as a surface treatment for leather, making it smoother and easier to print.

3. PVA in Films: A Model of Versatility

PVA film is very useful because of its special mix of features. It can be used in many areas, especially for packaging and things that are thrown away after use.

Properties of PVA Film:

• High Barrier: PVA film keeps oxygen and smells out well. This makes it a good option for keeping safe things that are easily changed or have strong smells.
• Water Solubility and Biodegradability: One of the best things about PVA film is that it can dissolve in water. Also, it can break down under certain conditions, which is good for the environment. This helps meet the rising needs for eco-friendly products. This gives it unique advantages in disposable and water-soluble film applications.
• Controllable Water Solubility: By controlling the degree of polymerization and hydrolysis of PVA, its dissolution rate and temperature in water can be precisely tailored to meet the needs of various applications.
• Chemical Stability: PVA exhibits excellent resistance to oils, greases, and most organic solvents.

Typical Product Applications:

• Soluble Packaging: Selvol Polyvinyl Alcohol 205 (Celvol 205), a partially hydrolyzed PVA with low viscosity, sees main application across adhesives, papermaking, and textile sectors. Its low viscosity can make it more useful in some film and coating processes. A common use involves creating packaging films for things like laundry detergent and dishwashing tabs. People can just put the whole package in water, and it will dissolve. This makes things easier and cuts down on plastic waste.
• Agricultural Film: Controlled-release PVA films can be used to encapsulate pesticides or fertilizers, slowly releasing them under specific conditions to reduce environmental pollution.
• Medical Applications: PVA's biocompatibility and controllable properties also offer potential applications in the medical field, such as drug delivery vehicles and contact lenses.

4. The Future of PVA

Polyvinyl alcohol (PVA), with its unique chemical structure and physical properties, plays a vital role in three major areas: adhesives, coatings, and films. From providing strong adhesion, enhancing the decorative and protective properties of coatings, to creating environmentally friendly and convenient packaging solutions, PVA's applications are continuously deepening and expanding.

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Polyvinyl alcohol (PVA) is a widely used synthetic material. PVA ability to dissolve in water and break down naturally makes it a good choice for packaging films. The main production methods for PVA film are aqueous solution coating and melt blow molding. PVA is hard to shape with heat because it melts at a higher temperature than it decomposes. This is due to the strong links between its molecules and its crystal structure. Therefore, the most important factor in the processing of PVA film is the selection of appropriate additives.

1. Effect of Plasticizer Amount on Tensile Strength, Tear Strength, and Elongation at Break of Polyvinyl Alcohol Film

As shown in Figure 1, film ability to resist breaking lessens as more plasticizer is added. This suggests that plasticizers reduce how strong the film is. The plasticizer gel theory explains that when the plasticizer mixes with the resin, it loosens the points where the resin molecules connect. These connections have different strengths. The plasticizer pulls them apart and hides the forces that hold the polymer together. This reduces the secondary forces between the polymer macromolecules, increases the flexibility of the macromolecular chains, and accelerates the relaxation process. Tensile strength goes down as you add more plasticizer.

As the amount of plasticizer is increased, the film becomes more flexible and stretches further before breaking. This suggests that plasticizers make the film more pliable. Plasticizers achieve this by weakening the attraction between the large molecules in the polymer. This increased flexibility and longer relaxation period lead to the film ability to stretch further.

The data indicates that as more plasticizer is added, the film becomes easier to tear. This likely happens as the plasticizer reduces the film's surface energy and lessens the energy needed for both plastic flow and lasting deformation. These factors, in turn, contribute to the film's reduced resistance to tearing.

2. Effect of Crosslinker Amount on the Tensile Strength, Elongation at Break, and Tear Strength of PVA Film

As shown in Figure 3, the film's tensile strength goes up gradually as the amount of crosslinker is increased, during which the elongation at break goes down gradually. When a certain point is reached, the film's tensile strength goes down gradually, while the elongation at break goes up gradually. At first, as more crosslinker is added, the number of working polymer chains goes up, intermolecular forces get stronger, and the polymer chains become less flexible. The ability of the large molecular chains to change shape and rearrange decreases while the chain relaxation is difficult. So, the tensile strength goes up, while the elongation at break goes down. Continuing the use of crosslinkers causes degradation and branching to increase gradually, which decreases the number of working polymer chains, and increases the flexibility of the polymer chains. The ability of the large molecular chains to change shape and rearrange increases, while the chain relaxation becomes easier. As a result, the tensile strength starts to go down again, while the elongation at break goes back up.

As shown in Figure 4, the tear strength of the film changes with the amount of crosslinker. At first, it goes up, but then it starts to go down. This happens because when crosslinking starts, more crosslinker helps the polymer network form. This makes the film's surface energy go up gradually. It then needs more energy to spread plastic flow and irreversible viscoelastic processes. Because of this, the film's tear strength gets better as crosslinking happens. But, if there is too much crosslinker with too much polymer broken down, and there are more branching reactions, the tear strength gets worse.

3. Conclusions

• When you add more plasticizer, PVA film becomes less strong but stretches and tears more easily.
• When you add more crosslinker, film strength and resistance to tearing improve at first, but then weaken, while its ability to stretch keeps getting better.

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Polyvinyl alcohol (PVA) is a fundamental raw material for vinylon production and is also used in the production of adhesives, emulsifiers, and other products. In the PVA production process, solution polymerization is used to ensure a narrow degree of polymerization distribution, low branching, and good crystallinity. The VAM polymerization rate is strictly controlled at approximately 60%. Due to the control of the polymerization rate during the VAM polymerization process, approximately 40% of the Vinyl Acetate Monomer (VAM) remains unpolymerized and requires separation, recovery, and reuse. Therefore, research on VAM recovery process is a crucial component of the PVA production process. There is a polymer-monomer relationship between Ethylene Vinyl Acetate (EVA) and vinyl acetate monomer (VAM). Vinyl acetate monomer is one of the basic raw materials for making ethylene vinyl acetate polymer.

This paper uses the chemical simulation software Aspen Plus to simulate and optimize the VAM recovery process. We studied how process settings in the first, second, and third polymerization towers affect the production unit. We found the best settings to save water used for extraction and lower energy consumption. These parameters provide an important theoretical basis for the design and operation of VAM recovery.

1 Vinyl Acetate Monomer Recovery Process

1.1 Simulation Process

This process includes the first, second, and third polymerization towers in the vinyl acetate monomer recovery process. The detailed flow diagram is shown in Figure 1.

1.2 Thermodynamic Model and Module Selection

The vinyl acetate monomer recovery unit of the polyvinyl alcohol plant primarily processes a polar system consisting of vinyl acetate, methanol, water, methyl acetate, acetone, and acetaldehyde, with liquid-liquid separation between vinyl acetate and water. The main equipment in the vinyl acetate monomer recovery unit of the polyvinyl alcohol plant was simulated using Aspen Plus software. The RadFrac module was employed for the distillation tower, and the Decanter module for the phase separator.

2 Simulation Results

We ran a process simulation on the vinyl acetate monomer recovery unit in the polyvinyl alcohol plant. Table 3 shows a comparison of the simulation results and actual values for the main logistics. As shown in Table 3, the simulation results are in good agreement with the actual values, so this model can be used to further optimize the process parameters and process flow.

3 Process Parameter Optimization

3.1 Determination of the Amount of Stripping Methanol

Polymerization Tower 1 takes out vinyl acetate monomer (VAM) from the stream that remains after polymerization. It uses methanol vapor at the bottom for heat. The right amount of methanol is important for how well the tower works. This study looks at how different amounts of methanol affect the mass fraction of PVA at the tower's bottom and the mass fraction of VAM at the top, assuming the feed stays the same and the tower's design is constant.

As shown in Figure 2, when the heat capacity needed for separation in Polymerization Tower 1 is satisfied, raising the stripping methanol amount lowers the PVA mass fraction at the bottom and the VAM mass fraction at the top. The stripping methanol amount has a linear relationship with the PVA mass fraction at the bottom and the VAM mass fraction at the top.

3.2 Optimization of the Feed Position in Polymerization Tower 2

In Polymerization Tower 2, an extractive distillation tower, the locations where the solvent and feed enter greatly affect how well the separation works. This column uses extractive distillation. Based on the physical properties of the extractant and the mixed feed, the extractant should be added from the top of the column. Figure 3 shows how the mixture feed position affects the methanol mass fraction at the top and the reboiler load at the bottom, keeping other simulation settings the same.

3.3 Optimizing the Extraction Water Amount in Polymerization Column 2

In Polymerization Column 2, extractive distillation is used to separate vinyl acetate and methanol azeotrope. By adding water to the top of the column, the azeotrope is disrupted, allowing for the separation of the two substances. The extract water flow rate has a big impact on how well Polymerization Column 2 separates these materials. With consistent simulation settings, I looked at how the amount of extract water affected the methanol mass fraction at the top and the reboiler load at the bottom of the column. The results are shown in Figure 4.

3.4 Optimizing the Reflux Ratio in Polymerization Column 3

In Polymerization Column 3, the reflux ratio is important for separating vinyl acetate from lighter substances like methyl acetate and trace water. This boosts the quality of vinyl acetate obtained from the side stream. We kept the simulation settings constant and studied how the reflux ratio affects both the mass fraction of vinyl acetate from the side stream and the reboiler load. The calculation results are shown in Figure 6. Maintaining the polymerization tower's reflux ratio around 4 helps ensure the vinyl acetate from the side line meets quality standards and keeps the reboiler load low.

4. Conclusion

(1) Using AspenPlus software, a suitable thermodynamic model is selected to simulate the entire process of vinyl acetate monomer recovery of the polyvinyl alcohol plant. The simulation results are in good agreement with the actual values and can be used to guide the process design and production optimization of the plant.

(2) Based on the establishment of a correct process simulation, the influence of the process parameters of the polymerization tower 1, polymerization tower 2, and polymerization tower 3 on the plant is investigated, and the optimal process parameters are determined. When vinyl acetate meets the needed separation standards, we can save on extraction water and lower energy use.

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