Synthesis and characterization of paraffin/TiO2‐P(MMA‐co‐BA) phase change material microcapsules for thermal energy storage

Microcapsules based on a phase changing paraffin core and modified titanium dioxide–poly(methyl methacrylate‐co‐butyl acrylate) [P(MMA‐co‐BA)] hybrid shell were prepared via a Pickering emulsion method in this study. The microcapsules exhibit an irregularly spherical morphology with the size range of 3–24 µm. The addition of BA can enhance the toughness of the brittle polymer poly(methyl methacrylate) and improve the thermal reliability of the phase change microcapsules. The ratio of BA/MMA is in the range of 0.09–0.14, and the ratio of the monomer/paraffin is varied from 0.45 to 0.60. These microcapsules exhibit a well‐defined morphology and good thermal stability. The actual core content of the microcapsules reaches 36.09%, with an encapsulation efficiency of 73.07%. Furthermore, the prepared microcapsules present the high thermal reliability for latent‐heat storage and release after 2000 thermal cycles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46447.     

Synthesis of melamine-formaldehyde microcapsules containing oil-based fragrances via intermediate polyacrylate bridging layers

A general and versatile strategy to prepare melamine-formaldehyde (MF) microcapsules encapsulating oil-based fragrances by combining solvent evaporation and in situ polymerization was proposed in this work. The oil-based fragrance was pre-encapsulated by an inner polyacrylate membrane via solvent evaporation, followed by in situ polymerization of MF precondensates as an outer shell. The polyacrylate membrane is used as an intermediate bridging layer to stabilize the oil-based fragrance, and to provide driving forces for in situ polymerization of MF precondensates through electrostatic attractions between carboxyl groups and ammonium ions. It was demonstrated that MF microcapsules containing clove oil were prepared successfully. The amount and the composition of the intermediate polyacrylate bridging layer were critical. Smooth and sphere-shaped MF-clove oil microcapsules were prepared when the weight ratio of polyacrylate to clove oil was over 60 wt% and the concentration of acrylic acid (AA) increased to 10 wt% in polyacrylate. In addition, MF microcapsules containing sunflower oil and hexyl salicylate were prepared by using this method. The work suggests that this new approach can be potentially used to encapsulate various core materials, tuning the shell properties of microcapsules such as thickness, mechanical strength and release properties.     

Preparation of poly(methyl methacrylate‐co‐butyl methacrylate) nanoparticles and their reinforcing effect on natural rubber

Poly(methyl methacrylate‐co‐butyl methacrylate) [P(MMA‐co‐BMA)] nanoparticles were synthesized via emulsion polymerization, and incorporated into natural rubber (NR) by latex compounding. Monodispersed, core‐shell P(MMA‐co‐BMA)/casein nanoparticles (abbreviated as PMBMA‐CA) were produced with casein (CA) as surfactant. The chemical structure of P(MMA‐co‐BMA) copolymers were confirmed by ¹H‐NMR and FTIR analyses. Transmission electron microscopy demonstrated the core–shell structure of PMBMA‐CA, and PMBMA‐CA homogenously distributed around NR particles, indicating the interaction between PMBMA‐CA and NR. As a result, the tensile strength and modulus of NR/PMBMA‐CA films were significantly enhanced. The tensile strength was increased by 100% with 10% copolymer addition, when the molar ratio of MMA:BMA was 8:2. In addition, scanning electron microscopy and atomic force microscopy results presented that the NR/PMBMA‐CA films exhibited smooth surfaces with low roughness, and PMBMA‐CA was compatible with NR. FTIR‐ATR analyses also suggested fewer PMBMA‐CA nanoparticles migrated out of NR. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43843.     

Preparation and photocatalytic activity of zinc sulfide/polymer nanocomposites

ZnS nanoparticles were prepared on the surface of polyacrylonitrile (PAN) and methyl methacrylate (MMA)/butyl methacrylate (BMA)/acrylic acid (AA) copolymer nanofibers. The MMA–BMA–AA copolymer was synthesized by bulk radical polymerization using 2,2′‐azobisisobutyronitrile as the initiator. The PAN and MMA–BMA–AA copolymer nanofibers were prepared by electrospinning. Zinc ions were introduced onto the surface of the nanofibers by coordination with the carboxyl of AA. Then, sulfide ions were added to react with zinc ions to form ZnS nanoparticles. The average diameter of the nanofibers was about 300 nm, and the diameter of the ZnS nanoparticles was about 10 nm. The band position of the photoluminescence spectrum of the ZnS/PAN and MMA–BMA–AA nanocomposites had an 80‐nm blueshift in comparison with that of the corresponding bulk ZnS sample. The ZnS/PAN and MMA–BMA–AA nanocomposites had high photocatalytic activity for the degradation of phenol under ultraviolet irradiation; the photocatalytic activity changed indistinctively after it was used repeatedly (6 times). The nanofibers of PAN and MMA–BMA–AA not only dispersed but also stabilized the ZnS nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of mixing protocol on morphology and properties of PA6/ABS blends compatibilized with MMA‐MA

The effect of different mixing protocols in the preparation of PA6/ABS/MMA‐MA (57.5/37.5/5 wt %) blends on their morphological, rheological, thermal, thermomechanical, and mechanical behavior were studied. Despite the second‐phase size reduction due to copolymer incorporation, mixing sequence seems to play an important role in the properties of the blends. When PA6 is blended with the pre‐blended ABS/MMA‐MA system, compatibilizer is preferentially located in ABS phase and a co‐continuous structure is formed. The co‐continuity is believed to be responsible for the enhancements in toughness, but excessive presence of MMA‐MA in ABS phase seems to hamper thermomechanical properties. On the other hand, when ABS is blended with the PA6/MMA‐MA system previously prepared, compatibilizer is preferentially located in PA6 phase and a particle‐in‐matrix morphology is observed. The absence of excessive amount of MMA‐MA in ABS phase avoids the negative effect on thermomechanical resistance, however enhancements in toughness are not so pronounced. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43612.     

Fragrance‐Containing Microcapsules Based on Interfacial Thiol‐Ene Polymerization

In this study, microcapsules containing fragrance oils as active agent were synthesized by interfacial thiol‐ene polymerization in oil‐in‐water emulsion. One water‐soluble dithiol and four oil‐soluble acrylates were used as “click”able monomers. The polymerization kinetics was studied by HPLC and ¹H‐NMR. The size and morphology of the microcapsules were characterized by means of light scattering, optical microscope, and scanning electron microscope, and their thermal property was examined by TGA. The encapsulation efficiency and stability of the microcapsules were monitored at room temperature and 45 °C for 1 month. In general, this interfacial thiol‐ene polymerization was demonstrated to be a facile and efficient approach for fragrance microencapsulation with new and stable shell materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43905.     

Heat‐resistant sustained‐release fragrance microcapsules

In this study, fragrance microcapsules were prepared by a spray‐drying method, in which the osmanthus flower fragrance acted as the core material and gum arabic and maltodextrin acted as shell materials. Scanning electron microscopy images showed that the microcapsules were approximately spherical in shape with a concave surface. Fourier transform infrared spectroscopy was used to prove the formations of the microcapsules. The fragrance retention rate at high temperatures (80–120°C) after a short heating time (30 min) reached 85.20 ± 2.72% and the retention rate after a long heating time (a week) at 60°C reached 95.40 ± 2.88%. The retention rate after 100 days exceeded 90%, and the transdermal release experiments showed that on the surface of the skin, the fragrance in the microcapsules stayed longer than in the pure fragrance oil. These results indicate that the fragrance microcapsules had an excellent aroma‐reserving ability. The results of the release test proved that the transport mechanism of the fragrance microcapsules conformed to the Weibull equation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40053.     

Preparation and characterization of flame retardant phase change materials by microencapsulated paraffin and diethyl ethylphosphonate with poly(methacrylic acid‐co‐ethyl methacrylate) shell

Microcapsules containing paraffin and diethyl ethylphosphonate (DEEP) flame retardant with uncrosslinked and crosslinked poly (methacrylic acid‐co‐ethyl methacrylate) (P(MAA‐co‐EMA)) shell were fabricated by suspension‐like polymerization. The surface morphologies of the microencapsulated phase change materials (microPCMs) were studied by scanning electron microscopy. The thermal properties and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The flame retarding performances of the microcapsule‐treated foams were calculated by using an oxygen index instrument. The DSC results showed that the crosslinking of the polymer shell led to an increase in the melting enthalpies of the microcapsule by more than 15%. The crosslinked P(MAA‐co‐EMA) microcapsules with DEEP and without DEEP have melting enthalpies of 67.2 and 102.9 J/g, respectively. The TGA results indicated that the thermal resistant temperature of the crosslinked microcapsules with DEEP was up to 171°C, which was higher than that of its uncrosslinked counterpart by ～20°C. The incorporation of DEEP into the microPCM increased the limiting oxygen index value of the microcapsule‐treated foams by over 5%. Thermal images showed that both microcapsule‐treated foams with and without DEEP possessed favorably temperature‐regulated properties. As a result, the microPCMs with paraffin and DEEP as core and P(MAA‐co‐EMA) as shell have good thermal energy storage and thermal regulation potentials, such as thermal‐regulated foams heat insulation materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41880.     

Preparation of reduction-triggered degradable microcapsules for intracellular delivery of anti-cancer drug and gene

The reduction-triggered degradable poly(methacrylic acid-co-N,N-bis(acryloyl)cystamine)/polyethyleneimine (P(MAA-co-BAC)/PEI) microcapsules were prepared by distillation–precipitation polymerization for delivery of anti-cancer drug and gene. N,N-bis(acryloyl)cystamine (BAC) as a crosslinker containing a disulfide bond can be triggered by reductive agents, such as glutathione (GSH) and dithiothreitol (DTT), to endow the functional microcapsules with reduction-triggered drug release. The P(MAA-co-BAC)/PEI microcapsules were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), laser particle size analyzer and elemental analysis. The degradable behavior of microcapsules was investigated by analysis of UV-vis spectroscopy. The controlled drug release behavior for P(MAA-co-BAC)/PEI microcapsules was strongly dependent on the absence/presence of GSH and the pH values with doxorubicin hydrochloride (DOX) as a model drug molecule. The in vitro gene transfection ability was evaluated by Hela cells with the transfection of plasmid DNA (pDNA) encoded with green fluorescent protein (GFP) and the transfection efficiency was determined by confocal fluorescence microscopy. Furthermore, the cytotoxicities of (P(MAA-co-BAC)/PEI) microcapsules before and after loading of DOX were assessed via WST-1 assay. The P(MAA-co-BAC)/PEI microcapsules provide the potential novel vectors for delivery of drugs and genes, promising for future applications in anticancer drug and gene combined therapy.     

Microencapsulated ammonium polyphosphate with boron‐modified phenolic resin

Ammonium polyphosphate (APP) was encapsulated with boron‐modified phenolic resin (BPF) by in situ polymerization with the goal of improving its hydrophobicity, thermal stability, and compatibility in polymers. The chemical and physical features of APP microcapsules were characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, scanning electron microscopy, inductively coupled plasma, and laser particle sizing. The hydrophobicity was assessed by the water contact angle. The residues from thermogravimetric analyzer and muffle burner were investigated. The results showed that the APP microcapsules with BPF shell had been achieved successfully. The shell encapsulation rate mainly depended on the amount of crosslinking agent when the ratio of APP/BPF was constant. The mean particle size increased and the particle size distribution became more narrow. The hydrophobicity of APP was improved and the improvement degree mainly depended on the amount and adding rate of crosslinking agent and the conditions of heat curing. A good thermal stability and high residue char rate at high temperature were noticed for APP microcapsules. It suggests that these microcapsules might be used as an intrinsic flame retardant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43720.     

Preparation and characterization of microcapsules containing capsaicin

With urea‐formaldehyde (UF) resin as walls and capsaicin as core substances, microcapsules were prepared based on in situ polymerization process. The morphology and size distribution of the microcapsules were analyzed by Fourier transform infrared spectroscopy, laser particle size analyzer, and scanning electron microscopy. The microcapsulated capsaicin (MC) agents had a mean diameter of about 30–50 μm. Moreover, the thermal properties of the MC agents were measured by differential scanning calorimetry and thermogravimetric analysis. It was demonstrated that the melting point and thermal stability of the MC agents were greatly improved compared with that of the uncovered capsaicin, which were caused by the encapsulating crosslinked UF resin over the surface. The shell formation mechanism and the effects of the process conditions such as U/F ratio, shearing force, and acidification time on the particle size of the MC agents were discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of phase‐change heat‐storage UV curable polyurethane acrylate coating

Phase‐change heat‐storage UV curable polyurethane acrylate (PUA) coating was prepared by applying microencapsulated phase change materials (microPCMs) to PUA coating. MicroPCMs containing paraffin core with melamine‐formaldehyde shell were synthesized by in situ polymerization. The effect of stirring speed, emulsification time, emulsifier amount, and core/shell mass ratio on particle size, morphology, and phase change properties of the microPCMs was studied by using laser particle size analyzer, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopic analysis, scanning electron microscopy, and differential scanning calorimetry. The results showed that the diameter of the microcapsules decreased with the increase of stirring speed, emulsification time, and emulsifier amount. When the mass ratio of emulsifier to paraffin is 6%, microcapsules fabricated with a core/shell ratio of 75/25 have a compact surface and a mean particle size of 30 μm. The sample made under the above conditions has a higher efficiency of microencapsulation than other samples and was applied to PUA coating. The dispersion of microPCMs in coating and heat‐storage properties of the coating were investigated. The results illustrated that the phase‐change heat‐storage UV curable PUA coating can store energy and insulate heat. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41266.     

Latent Heat Enhancement of Paraffin Wax in Poly(divinylbenzene-co-methyl methacrylate) Microcapsule

The preparation of divinylbenzene (DVB)-methyl methacrylate (MMA) copolymer microcapsule encapsulated Rubitherm27 (RT27) P(DVB-co-MMA)/RT27 used as heat storage material by the microsuspension polymerization was studied to improve the latent heats of the encapsulated RT27 with sufficient polymer shell strength. Percent loading of RT27 and DVB:MMA ratio were optimized. The optimal condition was 30% loading of RT27 and 30:70 (% w/w) of DVB:MMA ratio. The nonspherical microcapsules with a dent having core-shell morphology were obtained. The thermal properties of the encapsulated RT27 in the P(DVB-co-MMA)/RT27 capsules were measured by thermogravimetric analyzer and differential scanning calorimeter. The heats of melting (ΔH_m; 153 J/g-RT27) and crystallization (ΔH_c; 164 J/g-RT27) of the encapsulated RT27 in the prepared copolymer capsules were higher than those in PDVB and closed to those of bulk RT27 (162 and 168 J/g-RT27 for ΔH_m and ΔH_c, respectively).     

聚乳酸-石蜡微胶囊相变材料的制备及表征

制备了以聚乳酸(PLA)为壁材、石蜡为芯材的相变储能微胶囊。采用红外光谱、扫描电镜、热失重分析仪和差示扫描量热仪分析了微胶囊的结构及性能。结果表明:PLA已包覆到石蜡上,该微胶囊的粒径为5~10μm;微胶囊的热稳定性能在一定范围内得到了较大程度的提高,在300℃以下无质量损失;微胶囊的储热能力高达170.52 J/g。     

Aqueous polyacrylate/poly(silicone‐co‐acrylate) emulsion coated fertilizers for slow nutrient‐release application

Waterborne polyacrylate/poly(silicone‐co‐acrylate) emulsions were synthesized to develop coated fertilizers. The effects of the n‐butyl acrylate (BA)/methyl methacrylate (MMA) ratio, vinyltriethoxysilane, and synthesis method on the water resistance, glass‐transition temperature, mechanical properties, and nutrient‐release profiles were investigated. The results show that miniemulsion polymerization with a BA/MMA ratio of 55:45 was the most suitable for slow nutrient‐release applications. Under these conditions, the preliminary solubility rate of the nutrient was about 3%, and the 30‐day cumulative nutrient release was 15% at 25°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40369.     

Preparation of paraffin-based phase-change microcapsules and application in geopolymer coating

A type of paraffin phase-change microcapsule for thermal insulation of exterior walls was prepared by in situ polymerization of low-softening-point paraffin (46°C) as core material and acrylic copolymer as shell. The surface morphology, phase-change thermal properties, and thermal stability were characterized by scanning electron microscopy, laser particle size distribution analysis, differential scanning calorimetry, and thermogravimetric analysis, respectively. The results showed that, for polymerization reaction temperature of 75°C and paraffin/acrylic copolymer mass ratio of 1.8, the microcapsules prepared at rotation speed of 1600 r/min with 8% emulsifiers were spherical particles with smooth surface and average particle size of 0.68 μm. The phase-change temperature and latent heat storage capacity of the microcapsules were 47.8°C and 174 J/g, respectively. The paraffin phase-change microcapsules obtained using the optimum synthesis condition were mixed in a metakaolin-based geopolymer coating at different proportions, and the thermal insulation ability of the resulting phase-change thermal energy storage coating characterized.     

原位三元共聚制备高亮度水性铝颜料

为提高铝颜料在水性介质中的耐蚀性能,以丙烯酸(AA)、甲基丙烯酸甲酯(MMA)、甲基丙烯酸丁酯(BMA)为单体,过氧化二苯甲酰(BPO)为引发剂,丙二醇甲醚(PM)为溶剂,通过三元共聚反应在片状铝粉表面包覆致密薄膜,制备了高亮度水性铝颜料。结果表明,当m(丙烯酸)∶m(甲基丙烯酸甲酯)∶m(甲基丙烯酸丁酯)∶m(过氧化二苯甲酰)∶m(丙二醇甲醚)∶m(片状铝粉)=0.083∶0.083∶0.083∶0.015∶40∶1,85℃反应6 h时,水性铝颜料的缓蚀效率为97.2%,涂层光泽度为109.9 Gs。激光粒度分析、SEM和FTIR分析表明,AA、MMA和BMA三种单体通过原位三元共聚在片状铝粉表面形成了致密共聚物薄膜。     

Membrane properties of microporous structures prepared from polyethylene/polymethacrylate IPN

Polyethylene/polymethacrylate interpenetrating polymer networks (PE/PMA IPN) form a matrix–particle or a co‐continuous morphology that can be adjusted by the composition and synthesis conditions. Based on the fact that PMA degrades whereas PE crosslinks when they are exposed to energetic irradiation, we developed a new approach to create a porous structure by electron beam irradiation. IPN systems that differ in the methacrylate components and composition were studied. One system contains poly(butyl methacrylate‐co‐methyl methacrylate) (BMA‐co‐MMA) and the other contains poly(dodecyl methacrylate‐co‐ethyl methacrylate) (DMA‐co‐EMA) as the PMA phase. After electron beam irradiation followed by extraction with xylene, both IPN systems have a porous structure that is permeable to water. However, the structure and size of the pores depend on the PMA components and the synthesis conditions. PMAs with long aliphatic side chains degrade less than PMAs containing only short aliphatic pendant groups. Therefore, the PE/BMA‐co‐MMA IPN forms bigger pores than PE/DMA‐co‐EMA, resulting in a higher water flux. The molecular cutoffs of the IPN are characteristic for microfiltration or ultrafiltration.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1976–1982, 2003     

Microencapsulation of triglycidyl isocyanurate by solvent evaporation method for UV and thermal dual‐cured coatings

Triglycidyl isocyanurate (TGIC), a thermal curing agent, was encapsulated with poly(methyl methacrylate) with small particle size and narrow distribution for the application in acrylic resins to prepare one‐package UV and thermal dual‐cured coatings. Investigation of the wettability and thermal properties suggests that the microcapsules have better compatibility with acrylic resins and thermal stability as compared to pure TGIC. Results of the release performance experiments indicate good storage stability at 25°C and a quick release of vast TGIC at 120°C for the microcapsules. The UV‐thermal dual‐cured coatings prepared with the microcapsules exhibit a fast, even and complete hardening at 130°C together with an excellent adhesion to the mild steel panels. The results presented here show an application potential of the microcapsules in UV and thermal dual‐cured paints. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41008.     

Morphologies and dynamic mechanical properties of core‐shell emulsifier‐free latexes and their copolymers for P(BA/MMA)/P(MMA/BA) and P(BA/MMA)/PSt systems in the presence of AHPS

Different poly(methyl methacrylate/n‐butyl acrylate)/poly(n‐butyl acrylate/methyl methacrylate) [P(BA/MMA)/P(MMA/BA)] and poly(n‐butyl acrylate/methyl methacrylate)/polystyrene [P(BA/MMA)/PSt] core‐shell structured latexes were prepared by emulsifier‐free emulsion polymerization in the presence of hydrophilic monomer 3‐allyloxy‐2‐hydroxyl‐propanesulfonic salt (AHPS). The particle morphologies of the final latexes and dynamic mechanical properties of the copolymers from final latexes were investigated in detail. With the addition of AHPS, a latex of stable and high‐solid content (60 wt %) was prepared. The diameters of the latex particles are ～0.26 μm for the P(BA/MMA)/P(MMA/BA) system and 0.22–0.24 μm for the P(BA/MMA)/PSt system. All copolymers from the final latexes are two‐phase structure polymers, shown as two glass transition temperatures (T_gs) on dynamic mechanical analysis spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3078–3084, 2002