阅读说明：本技术 一种密胺树脂壳层相变微胶囊及其制备方法 (Melamine resin shell phase change microcapsule and preparation method thereof ) 是由 杨晶磊 孙赛玲 安金亮 于 2021-09-17 设计创作，主要内容包括：本申请提供一种PMF壳层相变微胶囊及其制备方法。该PMF壳层相变微胶囊的内壳层为PUF,外壳层为PMF。制备方法包括下列步骤：准备PUF相变微胶囊；制备n批PMF预聚液,其中n为大于或等于2的自然数；在pH为2.8-3.5,温度为30-50℃的条件下,在15-60分钟内将一批PMF预聚液缓慢滴加至PUF相变微胶囊乳液中,搅拌速度200rpm～600rpm,滴加完成后反应1-2小时,然后升温至80-85℃,再反应1.5-4小时；重复n次上述单次PMF壳层制备的步骤,直至滴加完所有的n批PMF预聚液。本申请PMF壳层MEPCMs的制备方法过程稳定,制得的MEPCMs胶囊间分散性好,壁材利用率高,在长时间高温下也具有优异的耐热性能,壳材致密性好；PMF壳层MEPCMs与常规树脂基体混合后,制得的混合物粘度低,流动性好。(The application provides a PMF shell phase change microcapsule and a preparation method thereof. The PMF shell phase change microcapsule has an inner shell layer of PUF and an outer shell layer of PMF. The preparation method comprises the following steps: preparing PUF phase change microcapsules; preparing n batches of PMF pre-polymerization liquid, wherein n is a natural number more than or equal to 2; slowly dripping a batch of PMF prepolymer solution into the PUF phase change microcapsule emulsion within 15-60 minutes under the conditions that the pH is 2.8-3.5 and the temperature is 30-50 ℃, stirring at 200-600 rpm, reacting for 1-2 hours after dripping is finished, then heating to 80-85 ℃, and reacting for 1.5-4 hours; repeating the step of preparing the PMF shell layer for n times until all n batches of PMF pre-polymerization liquid are dripped. The preparation method of the PMF shell MEPCMs has the advantages that the process is stable, the prepared MEPCMs have good dispersity among capsules, the utilization rate of wall materials is high, the prepared MEPCMs have excellent heat resistance at high temperature for a long time, and the compactness of shell materials is good; after PMF shell MEPCMs are mixed with a conventional resin matrix, the prepared mixture has low viscosity and good fluidity.)

1. A melamine resin shell phase change microcapsule is characterized in that the inner shell layer of the phase change microcapsule is urea formaldehyde resin, and the outer shell layer of the phase change microcapsule is melamine resin.

2. A method for preparing a phase-change microcapsule according to claim 1, comprising the steps of:

preparing urea-formaldehyde resin phase-change microcapsule emulsion;

preparing n batches of melamine resin pre-polymerization liquid; n is a natural number greater than or equal to 2; the preparation method of each batch of the melamine resin pre-polymerization solution comprises the following steps: mixing 0.2-0.6 part by mass of melamine, 0.5-1.5 parts by mass of 37% -40% formaldehyde aqueous solution and 5-10 parts by mass of deionized water together, adjusting the pH value to 8.5-9.5, keeping the temperature at 50-70 ℃, and reacting for 8-15 minutes at the stirring speed of 100-300 rpm;

preparing a melamine resin shell layer for one time; the preparation of the single melamine resin shell layer comprises the following steps: dropwise adding a batch of melamine resin pre-polymerization liquid into urea-formaldehyde resin phase-change microcapsule emulsion containing 6-10 parts by mass of urea-formaldehyde resin phase-change microcapsules at a constant speed within 15-60 minutes under the conditions that the pH is 2.8-3.5 and the temperature is 30-50 ℃, stirring at a stirring speed of 200-600 rpm, reacting for 1-2 hours after dropwise adding, heating to 80-85 ℃, and reacting for 1.5-4 hours;

repeating the step of preparing the single melamine resin shell layer for n times until all n batches of the melamine resin pre-polymerization liquid are dripped.

3. The method for preparing phase-change microcapsules according to claim 2, wherein n is 3 or 4.

4. The method for preparing phase-change microcapsules according to claim 3, wherein n is 4.

5. The method for preparing phase-change microcapsules according to claim 2, wherein the single melamine resin shell preparation has a pH of 3.

6. The method for preparing phase-change microcapsules according to claim 2, wherein the method for preparing the urea resin phase-change microcapsule emulsion comprises the following steps:

adding 0.2-1 part by mass of emulsifier into 50-80 parts by mass of deionized water, stirring and mixing uniformly at the temperature of 40-80 ℃ and the rotating speed of 200-500 rpm, adding 0.6-1 part by mass of urea, stirring uniformly, and adjusting the pH value to 2.8-3.5 to obtain a water phase mixture;

weighing 5-8 parts by mass of a phase-change material, heating to obtain a liquid phase-change material, adding the liquid phase-change material into the water phase mixture, and reacting at a stirring speed of 500-6000 rpm to obtain a uniform and stable oil-in-water phase-change emulsion;

under the condition of the rotating speed of 200rpm-1000rpm, adding 1.5-2.6 parts of formaldehyde aqueous solution with the mass fraction of 37% -40%, and reacting at 45-70 ℃ for 40-60 minutes to obtain the urea-formaldehyde resin phase-change microcapsule emulsion.

7. The method for preparing phase-change microcapsules according to claim 6, wherein the aqueous phase mixture further comprises 0.1 to 0.6 parts by mass of a polyhydric phenol and 0 to 0.2 parts by mass of ammonium chloride.

8. The method for preparing phase-change microcapsules according to claim 6, wherein the polyhydric phenol is one or more of resorcinol, hydroquinone, pyrogallol, phloroglucinol, catechol, and dopamine.

9. The method for preparing phase-change microcapsules according to claim 6, wherein the oil-in-water phase-change emulsion further comprises an antifoaming agent with a mass fraction of not more than 2%.

10. The method for preparing phase-change microcapsules according to claim 9, wherein the antifoaming agent is one or more of n-octanol, n-butanol, silicone emulsion, higher alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glycerol ether and polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane.

Technical Field

The application relates to the field of phase change microcapsules, in particular to melamine resin shell layer phase change microcapsules and a preparation method thereof.

Background

Electronic packaging means that packaging glue is used for sealing, encapsulating or encapsulating some electronic components, so that the purposes of water resistance, moisture resistance, shock resistance, dust resistance and corrosion resistance are achieved, and the accuracy and stability of electronic components can be improved. Common packaging adhesives include epoxy, silicone, polyurethane, and ultraviolet light curing packaging adhesives.

The common packaging adhesive is a poor thermal conductor, and the heat-conducting property of the packaging adhesive can be improved by adding a proper heat-conducting filler. However, the heat-conducting filler and the heat-conducting medium are limited in thermal conductivity, which results in poor heat dissipation.

In recent years, microcapsule phase change materials are applied to packaging adhesives as heat conduction and temperature control additives, when the temperature of an electronic component rises to the phase change temperature of a phase change core material, the core material can generate phase change to absorb a large amount of heat, and the heating part of the electronic component can be rapidly radiated. In addition, the microcapsule has a large specific surface area and a large heat transfer area, so that the heat conduction performance of the material is improved to a certain extent, and the heat is dissipated quickly; the normal operation of the electronic product is ensured, the uniformity of the temperature of the product can be improved, the local overheating is avoided, the accuracy and the stability of the electronic device are improved, and the service life of the electronic device is prolonged.

The field of electronic packaging requires that the packaging adhesive has good fluidity. However, the phase-change microcapsules are very fine powders, which have small density and large volume, and when added into the matrix, the phase-change microcapsules greatly increase the viscosity of the matrix material, thereby affecting the fluidity of the whole system and being not beneficial to the realization of the encapsulation effect. Meanwhile, the addition amount of the phase-change microcapsules is limited, and the effectiveness of the phase-change microcapsules is greatly reduced. The fluidity of the phase-change microcapsule added into the matrix is improved, and the phase-change microcapsule and other materials can be blended, so that the adding process in the fields of phase-change microcapsule spinning, building and the like can be simplified, and the cost is reduced.

Melamine resins are considered as preferable phase change microcapsule wall materials because of their properties such as water resistance, acid and alkali resistance, flame retardancy, high mechanical strength, and good storage stability. However, in the preparation stage of the melamine shell (PMF) microcapsule, the problems of conglutination and agglomeration of shell materials are easy to occur, so that the problems of implosion, agglomeration and the like are caused, the quality of the microcapsule product is poor, even the microcapsule product is broken, and the application of the melamine shell phase-change microcapsule is greatly influenced. Therefore, the melamine resin shell phase-change microcapsule with more stable preparation process and better product fluidity is urgently needed.

Disclosure of Invention

In view of the above technical problems, the present invention aims to provide a melamine resin shell phase change microcapsule, which has good fluidity and thermal stability.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a melamine resin shell phase change microcapsule, wherein the inner shell layer is urea resin, and the outer shell layer is melamine resin.

The invention also aims to provide a preparation method of the melamine resin shell phase-change microcapsule.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of melamine resin shell phase change microcapsules, which comprises the following steps:

preparing urea-formaldehyde resin phase-change microcapsule emulsion;

preparing n batches of melamine resin (PMF) pre-polymerization liquid; wherein n is a natural number greater than or equal to 2; the preparation method of each batch of melamine resin pre-polymerization solution comprises the following steps: mixing 0.2-0.6 part by mass of melamine, 0.5-1.5 parts by mass of 37% -40% formaldehyde aqueous solution and 5-10 parts by mass of deionized water together, adjusting the pH value to 8.5-9.5, keeping the temperature at 50-70 ℃, and reacting for 8-15 minutes at the stirring speed of 100-300 rpm;

preparing a melamine resin shell layer for one time; the preparation of the single melamine resin shell layer comprises the following steps: dropwise adding a batch of melamine resin prepolymer solution into the urea-formaldehyde resin phase-change microcapsule emulsion containing 6-10 parts by mass of urea-formaldehyde resin phase-change microcapsules at a constant speed within 15-60 minutes under the conditions that the pH value is 2.8-3.5 and the temperature is 30-50 ℃, stirring at a stirring speed of 200-600 rpm, reacting for 1-2 hours after dropwise adding, heating to 80-85 ℃, and reacting for 1.5-4 hours;

repeating the step of preparing the melamine resin shell layer for n times until all n batches of melamine resin pre-polymerization liquid are dripped.

The preparation of the PMF shell material is carried out on a urea-formaldehyde resin (PUF) inner shell layer, the smooth PUF inner shell layer provides a stable place for the deposition of the PMF shell material, the adhesion and agglomeration caused by the fact that the PMF shell material prepolymer is directly deposited on the surface of an emulsified core material liquid drop at a too high deposition rate are avoided, the shell material is porous and not compact, and the core material precipitation caused by the fact that the PMF shell material prepolymer is deposited too slowly is also avoided.

In this application, the adoption is earlier prepared the PMF of having diluted the concentration and is polymerized in batches to reaction rate when the prepolymer polycondensation has been slowed down, avoids because PMF explodes and gathers, leads to capsule adhesion reunion caking, rough surface, and PMF is from gathering impurity many.

Further, n is 3 or 4.

Further, n is 4.

Further, in the single melamine resin shell preparation, the pH was 3.

Further, the preparation method of the urea resin phase-change microcapsule emulsion comprises the following steps:

adding 0.2-1 part by mass of emulsifier into 50-80 parts by mass of deionized water, stirring and mixing uniformly at the temperature of 40-80 ℃ and the rotating speed of 200-500 rpm, adding 0.6-1 part by mass of urea, stirring uniformly, and adjusting the pH value to 2.8-3.5 to obtain a water phase mixture;

weighing 5-8 parts by mass of a phase-change material, heating to obtain a liquid phase-change material, adding the liquid phase-change material into the water phase mixture, and reacting at a stirring speed of 500-6000 rpm to obtain a uniform and stable oil-in-water phase-change emulsion;

under the condition of the rotating speed of 200rpm-1000rpm, adding 1.5-2.6 parts of formaldehyde aqueous solution with the mass fraction of 37% -40%, and reacting at 45-70 ℃ for 40-60 minutes to obtain the urea-formaldehyde resin phase-change microcapsule emulsion.

Common phase change materials are suitable for use in the present invention, including but not limited to mixtures of one or more of organic paraffins, alkanes, fatty acids, fatty alcohols, and fatty acid esters.

Preferably, the emulsifier is one or more of ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, Gum Arabic (GA), polyvinyl alcohol (PVA), alkylphenol polyoxyethylene ether (OP-10), Sodium Dodecylbenzenesulfonate (SDBS), Sodium Dodecyl Sulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), and sorbitan fatty acid ester.

Further, the aqueous phase mixture also comprises 0.1 to 0.6 part by mass of polyhydric phenol and 0 to 0.2 part by mass of ammonium chloride. And the polyphenol is used as a trapping agent of free formaldehyde and a PUF cross-linking agent, so that the PUF shell is deposited on the surface of the core material, and the compactness of the shell material is improved through curing and cross-linking. Ammonium chloride acts as a curing agent, which accelerates the formation of PUF shells. The polyphenol and the ammonium chloride are beneficial to the PUF to quickly form a relatively compact shell layer (instead of self-polymerization in solution) on the surface of the phase-change material to coat the phase-change material and prevent the phase-change core material from being separated out, so that the coating rate of the core material is influenced, and the subsequent PMF shell forming is also influenced.

Further, the polyhydric phenol is at least one of resorcinol, hydroquinone, pyrogallol, catechol, and dopamine.

Further, the oil-in-water phase-change emulsion also comprises an antifoaming agent with the mass fraction not more than 2%, wherein the mass fraction is the mass ratio of the antifoaming agent to the phase-change microcapsule core material.

Further, the defoaming agent is one or more of n-octanol, n-butanol, emulsified silicone oil, a higher alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether and polydimethylsiloxane.

The invention has the beneficial effects that:

1. the preparation method of the melamine resin shell phase change microcapsule has the advantages that the process is stable, the prepared phase change microcapsule has good dispersity among capsules, the utilization rate of wall materials is high, and the prepared phase change microcapsule has high fluidity;

2. the melamine resin shell phase change microcapsule prepared by the method has excellent heat resistance, good shell material compactness and good thermal stability at high temperature for a long time, and ensures that the core material cannot leak;

3. after the melamine resin shell phase change microcapsule prepared by the method is mixed with a conventional resin matrix, the prepared mixture is low in viscosity and good in fluidity, and when the melamine resin shell phase change microcapsule is applied to packaging glue, the fluidity is greatly improved, and the application range is widened.

Drawings

FIG. 1 is a DSC curve of melamine resin shell phase change microcapsules prepared in example 1;

FIG. 2 is a DSC curve of melamine resin shell phase change microcapsules prepared in example 1 after being baked at a high temperature of 100 ℃ for 6 hours;

FIG. 3 is an SEM photograph of melamine resin shell phase change microcapsules prepared in example 1;

FIG. 4 is an SEM image of melamine resin shell phase change microcapsules prepared in a comparative example;

fig. 5 viscosity of the mixture of phase-change microcapsules prepared in example 1 and comparative example with a resin matrix.

Detailed Description

The invention will be described in detail with reference to the drawings and specific embodiments, which are illustrative and not limiting.

Example 1

Preparing urea resin phase-change microcapsules: 60g of deionized water, 0.48g of ethylene-maleic anhydride copolymer and 0.09g of polyvinyl alcohol were mixed uniformly at 50 ℃ while maintaining the mechanical stirring speed at 300 rpm. 0.1g of resorcinol, 0.1g of ammonium chloride and 0.8g of urea were added, stirred to dissolve, and then the pH was adjusted to 3.0 with an acid or an alkali to obtain an aqueous phase mixture. Weighing 5g of phase-change paraffin (phase-change temperature 38 ℃), heating to obtain liquid phase-change paraffin, adding the liquid phase-change paraffin into the water phase mixture at the rotation speed of 1000rpm, adding 0.015g of n-octanol, and carrying out an emulsion reaction for 13 minutes to obtain a uniform and stable oil-in-water (O/W) phase-change emulsion. Adjusting the rotating speed to 400rpm, adding 2g of formaldehyde water solution with the mass fraction of 37-40%, and reacting for 60 minutes at 50 ℃ to obtain the urea-formaldehyde resin phase-change microcapsule emulsion.

Preparation of melamine resin (PMF) prepolymer fluid: 0.3g of melamine, 0.75g of aqueous formaldehyde solution with the mass fraction of 37-40% and 8g of deionized water are mixed, the pH value is adjusted to 8.6, and the mixture reacts for 9 minutes at 60 ℃ under the stirring speed of 200rpm to obtain 1 batch of melamine resin pre-polymerization solution. The above steps were repeated 4 times to prepare a total of 4 batches of melamine resin prepolymer solution.

Adjusting the reaction temperature to 40 ℃, adjusting the pH value to 3.0, dripping the 1 st batch of PMF prepolymer solution into the urea-formaldehyde resin phase-change microcapsule emulsion at a constant speed within 45 minutes, stirring at a stirring speed of 400rpm, reacting for 1 hour after finishing dripping, then heating to 85 ℃, and reacting for 2 hours. The reaction temperature is reduced to 40 ℃, the 2 nd batch of PMF prepolymerization solution is dripped into the mixture at a constant speed within 60 minutes for reaction for 1 hour, and then the temperature is increased to 85 ℃ for reaction for 2 hours. The reaction temperature is reduced to 40 ℃, the 3 rd batch of PMF pre-polymerization solution is dripped at a constant speed within 60 minutes for reaction for 1 hour, then the temperature is raised to 85 ℃, and the reaction is carried out for 2 hours. The reaction temperature is reduced to 40 ℃, the 4 th batch of PMF pre-polymerization solution is dripped at a constant speed within 60 minutes for reaction for 1 hour, then the temperature is raised to 85 ℃, and the reaction is carried out for 2 hours. And washing the emulsion obtained by the reaction with water, filtering, and naturally drying to obtain melamine resin (PMF) shell phase change microcapsules (MEPCMs).

Example 2

Preparing urea resin phase-change microcapsules: 80g of deionized water and 1g of styrene-maleic anhydride copolymer were mixed uniformly at 80 ℃ while maintaining the mechanical stirring speed at 500 rpm. 0.6g of hydroquinone, 0.2g of ammonium chloride and 1g of urea are added, and after stirring and dissolution, the pH value is adjusted to 2.8 by acid or alkali, thus obtaining an aqueous phase mixture. Weighing 8g of phase-change paraffin, heating to obtain liquid phase-change paraffin, adding the liquid phase-change paraffin into the water phase mixture at the rotating speed of 3000rpm, adding 0.015g of n-octanol, and carrying out an emulsion reaction for 13 minutes to obtain a uniform and stable oil-in-water (O/W) phase-change emulsion. Adjusting the rotating speed to 1000rpm, adding 2.6g of formaldehyde water solution with the mass fraction of 37-40%, and reacting for 60 minutes at 45 ℃ to obtain the urea-formaldehyde resin phase-change microcapsule emulsion.

Preparation of melamine resin (PMF) prepolymer fluid: 0.6g of melamine, 1.5g of aqueous solution of formaldehyde with the mass fraction of 37-40% and 10g of deionized water are mixed, the pH value is adjusted to 9.5, and the mixture reacts for 15 minutes at 70 ℃ under the stirring speed of 300rpm to obtain 1 batch of melamine resin prepolymer solution. The above steps were repeated 3 times to prepare a total of 3 batches of melamine resin prepolymer solution.

Adjusting the reaction temperature to 30 ℃, adjusting the pH value to 3.5, dripping the 1 st batch of PMF prepolymer solution into the urea-formaldehyde resin phase-change microcapsule emulsion at a constant speed within 60 minutes, stirring at a stirring speed of 600rpm, reacting for 2 hours after finishing dripping, then heating to 80 ℃, and reacting for 4 hours. The reaction temperature is reduced to 30 ℃, the 2 nd batch of PMF pre-polymerization solution is dripped at a constant speed within 60 minutes for reaction for 2 hours, and then the temperature is increased to 80 ℃ for reaction for 4 hours. The reaction temperature is reduced to 30 ℃, the 3 rd batch of PMF pre-polymerization solution is dripped at a constant speed within 60 minutes for reaction for 2 hours, then the temperature is raised to 80 ℃, and the reaction is carried out for 4 hours. And washing the emulsion obtained by the reaction with water, filtering, and naturally drying to obtain melamine resin (PMF) shell phase change microcapsules (MEPCMs).

Example 3

Preparing urea resin phase-change microcapsules: 50g of deionized water and 0.2g of gum arabic were mixed uniformly at 40 ℃ with the mechanical stirring speed kept at 200 rpm. Adding 0.3g of phenol and 0.6g of urea, stirring to dissolve, and adjusting the pH value to 3.0 with acid or alkali to obtain an aqueous phase mixture. Weighing 6g of phase-change paraffin (phase-change temperature 38 ℃), heating to obtain liquid phase-change paraffin, adding the liquid phase-change paraffin into the water phase mixture at the rotation speed of 500rpm, adding 0.015g of n-octanol, and carrying out an emulsion reaction for 13 minutes to obtain a uniform and stable oil-in-water (O/W) phase-change emulsion. Adjusting the rotating speed to 200rpm, adding 1.5g of formaldehyde aqueous solution with the mass fraction of 37-40%, and reacting at 70 ℃ for 40 minutes to obtain the urea-formaldehyde resin phase-change microcapsule emulsion.

Preparation of melamine resin (PMF) prepolymer fluid: 0.2g of melamine, 0.5g of aqueous solution of formaldehyde with the mass fraction of 37-40% and 5g of deionized water are mixed, the pH value is adjusted to 8.6, and the mixture reacts for 9 minutes at 60 ℃ under the stirring speed of 200rpm to obtain 1 batch of melamine resin pre-polymerization solution. The above steps were repeated 4 times to prepare a total of 4 batches of melamine resin prepolymer solution.

Adjusting the reaction temperature to 30 ℃, adjusting the pH value to 2.8, dripping the 1 st batch of PMF prepolymer solution into the urea-formaldehyde resin phase-change microcapsule emulsion at a constant speed within 15 minutes, stirring at a stirring speed of 200rpm, reacting for 1 hour after finishing dripping, then heating to 85 ℃, and reacting for 1.5 hours. The reaction temperature is reduced to 30 ℃, the 2 nd batch of PMF prepolymerization solution is dripped into the mixture at a constant speed within 15 minutes for reaction for 1 hour, and then the temperature is increased to 85 ℃ for reaction for 1.5 hours. The reaction temperature is reduced to 30 ℃, the 3 rd batch of PMF pre-polymerization solution is dripped at a constant speed within 15 minutes for reaction for 1 hour, and then the temperature is increased to 85 ℃ for reaction for 1.5 hours. The reaction temperature is reduced to 30 ℃, the 4 th batch of PMF pre-polymerization solution is dripped at a constant speed within 15 minutes for reaction for 1 hour, and then the temperature is increased to 85 ℃ for reaction for 1.5 hours. And washing the emulsion obtained by the reaction with water, filtering, and naturally drying to obtain melamine resin (PMF) shell phase change microcapsules (MEPCMs).

Comparative example

6g of melamine, 11g of formaldehyde aqueous solution with the mass fraction of 37-40% and 11g of deionized water are uniformly mixed, the pH value is adjusted to 8.5 by triethanolamine, and the mixture is stirred and reacted for 1 hour at 250rpm in a water bath at 70 ℃ to obtain a transparent PMF (polymethylene diamine) pre-polymerization solution.

And emulsifying 30g of phase-change paraffin (phase-change temperature 38 ℃), 360g of deionized water and 2.88g of ethylene-maleic anhydride copolymer for 8 minutes at the water bath temperature of 70 ℃ and the stirring speed of 1000rpm to obtain the phase-change emulsion.

And dropwise adding the PMF prepolymer into the obtained emulsion within 10 minutes, adjusting the pH value of the system to be 3.2 by using citric acid, reacting for 2 hours at 70 ℃ to obtain PMF shell MEPCMs, centrifuging, washing and drying to obtain a powder sample.

Test results of example 1 and comparative example

Thermal stability

The melamine resin shell phase change microcapsules prepared in example 1 were tested by DSC, and the DSC curve obtained is shown in fig. 1. The melamine resin shell phase change microcapsules prepared in example 1 were baked at a high temperature of 100 ℃ for 6 hours and then tested by DSC, and the DSC curve obtained is shown in fig. 2.

As can be seen from fig. 1: melting enthalpy (. DELTA.H) of MEPCMs prepared in example 1_m) At 140.9J/g, enthalpy of crystallization (. DELTA.H)_c) It was 139.3J/g. As can be seen from fig. 2: the enthalpy of fusion (. DELTA.H) measured after baking the MEPCMs prepared in example 1 at a high temperature of 100 ℃ for 6 hours_m) 140.8J/g, enthalpy of crystallization (. DELTA.H)_c) It was 138.7J/g. It can be seen thatAfter the high temperature test, the core material of the prepared MEPCMs has no leakage, which shows that the phase change microcapsules prepared in example 1 have excellent thermal stability.

The PMF shell MEPCMs prepared in the comparative example were respectively baked at room temperature and at a high temperature of 100 ℃ and then tested by DSC. At ambient temperature, heat of fusion (. DELTA.H)_m) 123J/g, enthalpy of crystallization (. DELTA.H)_c) The concentration was 121.9J/g. After baking at 100 ℃ for 1 hour, the heat of fusion (. DELTA.H) was measured_m) 52.6J/g, enthalpy of crystallization (. DELTA.H)_c) 52J/g and 57.2% of core material leakage rate, so that the shell material of the microcapsule in the comparative example has poor compactness, and a large amount of leakage can be generated after the microcapsule is baked at 100 ℃ for 1 hour.

Dispersibility

As can be seen from fig. 3, the melamine resin shell phase change microcapsules prepared in example 1 have good capsule dispersibility, and the obtained product has substantially no impurity particles and smooth capsule surface. As can be seen from fig. 4, in the melamine resin shell phase change microcapsule prepared in the comparative example, the melamine resin (PMF) shell material in the reaction product was self-polymerized to generate a lot of impurities, and the obtained capsule was easily adhered and had a rough surface.

The melamine resin shell phase change microcapsules prepared in example 1 and comparative example were tested for density. The specific test method comprises the following steps: with a 25ml measuring cylinder, 5g of the microcapsule powder was weighed, the volume of the powder contained was read, and the density of the microcapsules was calculated by the following formula: the density of the microcapsules is mass/volume of microcapsule powder. The test results are: PMF/PUF Shell MEPCs prepared in example 1, having a Density of 0.52g/cm³PMF shell MEPCMs prepared in comparative example, having a density of less than 0.3g/cm³。

Viscosity of mixture of phase-change microcapsules and resin matrix

The melamine resin shell phase change microcapsules prepared in example 1 and the melamine resin shell phase change microcapsules prepared in comparative example are mixed with heat-conducting silicone grease (which is a heat-conducting interface material with a heat conductivity coefficient of not less than 1W/(m.K), a density of 2.2g/cm3 and a viscosity of about 42.6 Pa.s) with a model number of HT1101 of Hubei Suitian New materials, according to a mass ratio of 2:8 to obtain a mixture, and then a rheometer with a model number of AR2000ex of TA is used for viscosity test, wherein the test conditions are as follows: room temperature, steady state mode, shear rate of 10HZ, 30s over time. Figure 5 shows the viscosity of two mixtures, the viscosity of the mixture of example 1 being 48.99pa.s and the viscosity of the mixture of the comparative example being 89.53 pa.s.

It should be understood that the above-mentioned examples of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. It is not intended to be exhaustive or to limit all embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. All obvious changes and modifications which are within the technical scope of the invention are covered by the invention.