María Dolores Romero

Sugar Alcohol based Materials for Seasonal Storage Applications

FP7 project - SAM.SSA

Sugar Alcohol based Materials for Seasonal Storage Applications

Workshop and Onsite Demonstration– CiCenergigune

Miñano, Alava, Spain

Workshop and Onsite Demonstration ● CiCenergigune, Spain ● March 17/18, 2015

Microencapsulation of sugar alcohols by different chemical and physical procedures

Session 1, Sub Session: 2

Presented by: María Dolores Romero

AIDICO. Technological

Institute of Construction

Thomas Ballweg - FhG

María Dolores Romero - AIDICO

Contributions by:

Radu Piticescu – IMNR

Roxana Piticescu


Microencapsulation of sugar alcohols by different chemical and physical procedures

OUTLINE

1. INTRODUCTION

2. MICROENCAPSULATION OF SA WITH ORGANIC SHELLS (AIDICO)

Microencapsulation techniques Main results Conclusions

3. MICROENCAPSULATION OF SA WITH INORGANIC SHELLS (IMNR)

Description of procedure for microencapsulation Main results Conclusions

4. ENCAPSULATION OF SA WITH HYBRID SHELLS (FhG)

Description of procedure for microencapsulation Main results Conclusions

Workshop and Onsite Demonstration ● CiCenergigune, Spain ● March 17/18, 2015 Source: BASF

Source: Cryopak website

1. INTRODUCTION

THERMAL ENERGY STORAGE

Thermal Chemical

Sensible heat

Liquids Solids

Latent heat

Solid-liquid Liquid-gaseous Solid-solid

Heat reaction

Heat pumps

PCMs

AB + Q A + B

A + B AB + Q Amount of stored heat

Te

mpera

ture

Phase change

temperature

Latent heat of the

phase change

Workshop and Onsite Demonstration ● CiCenergigune, Spain ● March 17/18, 2015 Source: BASF

Source: PPL products

1. INTRODUCTION

PCM: Phase change material

Substance able to absorb, store and release energy during the phase change

High latent heat

Chemically: paraffin wax, ester, fatty acid, hydrated salt

Source: BASF website

PCM: Latent heat storage

http://www.pcmproducts.net/files/underfloor_pcm_heating.pdf


Limitations of PCMs

Dimensional instability

Corrosiveness

Low thermal conductivity

Compatibility with other materials

Encapsulation

Substances (core materials) introduced in a

matrix or shell

Macroencapsulation Microencapsulation

Nanoencapsulation

Source: BASF

PCMs in containers (cm)

Leakage

Source: PPL products website

1. INTRODUCTION

PCM: Phase change material

Workshop and Onsite Demonstration ● CiCenergigune, Spain ● March 17/18, 2015 Source: BASF Source: Cryopak website

Microencapsulation of PCMs

1. INTRODUCTION

Thermal properties

Proper phase change temperature

High latent heat storage

Proper thermal conductivity (depending on application)

Physical properties Small volume change during phase change process

Low vapor pressure

Kinetics Proper subcooling (depending on application)

Crystallization process

Chemical properties

Long term chemical stability

Compatible with container (corrosion)

No toxicity

No fire risk

Economics Available in the market

Cost effective for large scale production


Source: BASF

Microencapsulation of PCMs

1. INTRODUCTION

Physico-chemical processes

Mechanical processes

Chemical processes

Particle size, physico-chemical properties of core and shell materials

Microencapsulation techniques

Microparticles

Membrane Internal phase

Microcapsules

Active principle

Microspheres

Matrix


PCMs: Selection of Sugar Alcohol

Specifications of Sugar Alcohols :

Sugar Alcohol Melting point (ºC) Latent heat

(KJ/Kg)

Density (Kg/m3) Specific heat (KJ/Kg K)

Liquid Solid Liquid Solid

Erythritola 118 354.7 1280 1450 2.66 1.68

Dulcitolb 168-169 401 -- 1466 -- 1.31

D-Mannitolc 165.0 () 338 () -- -- -- --

Xylitold 93.20 301.12 -- -- -- --

a T. Oya et al. Applied Thermal Engineering 40 (2012) 373-377. b A. Sari et al. Solar Energy 85 (2011) 2061-2071. c C. Telang et al. Pharmaceutical Research 20 (2003) 1939-1945. d A. Biçer, A. Sari Solar Energy Materials & Solar Cells 102 (2012) 125-130.

1. INTRODUCTION


Reactivity of hydroxyl group

Disadvantage of Sugar Alcohols for microencapsulation:

C CR O

H+ +

+

-

Nucleophilic Site

Electrophilic Site

Selection of microencapsulation methodology

Selection of shell

1. INTRODUCTION

Organic Hybrid Inorganic


Solvent evaporation

The size of nanoparticles can be controlled by adjusting:

Stirring rate

Type and amount of dispersing agent Viscosity of organic and aqueous phases

Temperature

Evaporation rate

Emulsification Solvent evaporation

S u r f a c t a n t O i l p h a s e

R O H

S u r f a c t a n t P o l y m e r

S o l v e n t

E v a p o r a t i o n P o l y m e r

W a t e r

Sugar Alcohol

2. MICROENCAPSULATION OF SA WITH ORGANIC SHELLS


D-Mannitol/PMMA

Surfactant concentration (1, 3, 5% Span80)

Type of surfactant

Xylitol, dulcitol, erythritol

Solvent evaporation

Solvent/non solvent

H2O

Sugar alcoholPolymer Surfactant

non solvent

n

O O

PMMA

HO

OH

OH

OH

OH

OH

D-Mannitol

Solvent evaporation



DSC

Sample Tm (ºC) ΔHm (J/g) Tc (ºC) ΔHc (J/g)

Mannitol 166 260.1 113.7 194.6

1% 159.7 78.6 99.2 48.0

3% 157.7 88.5 102.5 40.7

5% 155.6 178.3 105.6 140.8

vs

Tm D-Mannitol

Tm α (ºC) 165.5

Tm β (ºC) 165.0

Tm δ (ºC) 155

Tg (ºC) 10.7

Telang et al.

Pharmaceutical

Research, 2003,

20, 1939-1945

D-Mannitol/PMMA

Amount of oil phase surfactant

Solvent evaporation



1% Oil phase surfactant



Amount of oil phase surfactant

Solvent evaporation



Oil phase Oil phase

Hydrophilic monomer M1

H2O

Hydrophilic compounds Sugar alcohol

Addition of M2

Crosslinking reaction at the interface

NR'

NC CO O

OHR

HO

NH2R

H2N

or CO

RO

C

HN

R'

HN

C

OOO n

or C

HN

R

HN

C

HN

R'

HN

C

OOO n

Polyurethane Polyurea M1

M2

Interfacial polycondensation



1, 3 and 5 wt%

Surfactant: Lubrizol Amino-functionalized

Able to react with TDI

Type of isocianate

Type and amount of surfactant (-NH or –OH functionalities)

Isocianate/ROH ratio

Microcapsules properties (size, morphology, etc.) depend on:



NCO

NCO

HO

OH OH

OH

D-MannitolTDI

OH

OH


D-Mannitol microspheres

5% surfactant



3% surfactant

ROH/TDI = 1/1

1% surfactant


D-Mannitol

microspheres 0.5

1.0

T

5% 0.5

T

3% 0.5

1.0

T

1% 0.5

1.0

T

TDI

60

80 100

T

2000 Wavenumber (cm-1)

ROH/TDI = 1/1 Surfactant concentration



-4

-3

-2

-1

0

1

2

3

4

20 40 60 80 100 120 140 160 180 200

Hea

t F

low

(J/

g)

Temperature (ºC)

5% surfactant

3% surfactant

1% surfactant


AIR NITROGEN

-10

-5

0

5

10

15

20

20 40 60 80 100 120 140 160 180 200

Hea

t flow

(W

/g)

Temperature (ºC)

D-Mannitol - Cycle 1 - N2


5% surfactant - Cycle 1 - N2

5% surfactant - Cycle 30 - N2

-15

-10

-5

0

5

10

15

20

25

20 40 60 80 100 120 140 160 180 200

Hea

t flow

(W

/g)

Temperature (ºC)

D-Mannitol - Cycle 1-AIR

D-Mannitol - Cycle 30 - AIR

5% Surfactant - Cycle 1 - AIR

5% surfactant - Cycle 30 - AIR




The decrease of thermal energy storage capacity is not only due to the oxidation by the air, but also the temperature increase in thermal cycles, which favors the reaction between the prepolymer and the sugar alcohol: -OH of the SA react with the polymer when increasing temperature during thermal cycles

This effect has been produced both in D-Mannitol and Erythritol, which have different melting and crystallization temperatures and also different chemical structure and number of –OH groups

Although it is possible to obtain sugar alcohols microcapsules by interfacial polycondensation, thermal stability of the capsules during thermal cycling can be improved by studying how to finish the reaction of the prepolymer

Polyurethane and polyurea bonds can be formed between the –OH or –NH2 of the surfactant and the isocianate

-OH containing surfactant is not a good solution (reaction between isocianate and D-Mannitol is also produced). A different surfactant with different chemical groups, competing with –OH from sugar alcohol is required to react with TDI

Interfacial polycondensation - Conclusions



SOL-GEL

3. MICROENCAPSULATION OF SA WITH INORGANIC SHELLS

• SiO2 as TEOS. Mannitol in spheres from spray drying

D-Mannitol in benzyl alcohol

TEOS SiO2 as TEOS

D-Mannitol as spheres from spray drying (not dissolution, but dispersion)

Water-free process. Hydrolysis of TEOS with benzyl alcohol

D-Mannitol : TEOS = 1 : 1 and 1 : 3 (wt)


SOL-GEL



632

700 888

1019

1086

1287 1424

1641

D-Mannitol from spray drying

2909

2970

3284

0.0

0.5

1.0

1.5

Abs

700

732 1007

1086

1208

1451

1496 2871

3029

3302

Encapsulations with SiO2

-0.00

0.02

0.04

0.06

0.08

0.10

Abs

2000

Wavenumber (cm-1)

D-Mannitol

SiO2


SOL-GEL


D-Mannitol from spray drying

Encapsulations with SiO2



SOL-GEL


-10

-5

0

5

10

15

20

25

30

0 50 100 150 200

He

at f

low

(W

/g)

Temperature (ºC)

D-Mannitol Spray drying

D-Mannitol:TEOS = 1:1 (wt)

D-Mannitol:TEOS = 1:3 (wt)

DSC – air atmosphere

Tm (ºC) ΔHm (J/g) Tc (ºC) ΔHc (J/g)

D-Mannitol spray drying

167.0 260.9 117.6 204.0

Encapsulation with SiO2 (1:1)

163.6 67.6 106.5 57.7

Encapsulation with SiO2 (1:3)

163.8 84.9 107.9 70.6



SOL-GEL



-3

-2

-1

0

1

2

3

4

5

0 20 40 60 80 100 120 140 160 180 200

He

at flo

w (

W/g

)

Temperature (ºC)

Cycle 1. Melting

Cycle 1. Crystallization

Cycle 10. Melting


Cycle 20. Melting


Cycle 30. Melting


Mannitol:TEOS = 1:1

-4

-2

0

2

4

6

8

0 20 40 60 80 100 120 140 160 180 200

He

at flo

w (

W/g

)

Temperature (ºC)

Cycle 1. Melting


Cycle 10. Melting


Cycle 20. Melting


Cycle 30. Melting


Mannitol:TEOS = 1:3

Thermal cycle 1 Thermal cycle 30


SOL-GEL


a)

b) c)



SOL-GEL


D-Mannitol (spheres from spray drying)

Benzyl alcohol

Ti precursor

-OH groups

-OH groups Hydrolysis of Ti

Orange solution: Ti compounds

- TiO2 . Mannitol dispersed in organic solvent: avoid water


SOL-GEL



D-Mannitol 166.0 260.1 113.7 194.6

Encapsulation with TiO2

166.4 239.0 120.4 179.9

DSC – air atmosphere

-15

-10

-5

0

5

10

15

20

25

0 50 100 150 200

He

at f

low

(W

/g)

Temperature (ºC)

Heating D-Mannitol

Cooling D-Mannitol

Heating - Encapsulation with TiO2

Cooling - Encapsulation with TiO2



SOL-GEL


-10

-5

0

5

10

15

20

25

0 50 100 150 200

He

at f

low

(W

/g)

Temperature (ºC)



Encapsulation - Cycle 1 - N2

Encapsulation - Cycle 30 - N2


Cycle 1 165.2 202.0 112.7 106.2

Cycle 30 165.6 202.1 115.1 152.6


Cycle 1 166.0 209.9 120.7 157.4

Cycle 30 166.6 195.5 124.4 161.6

D-Mannitol

Encapsulations with TiO2



SOL-GEL



Tª = 30 ºC Tª = 105 ºC Tª = 160 ºC

Tª = 167 ºC Tª = 183 ºC Tª = 30 ºC


SOL-GEL


CONCLUSIONS

SiO2

TiO2

- Water free process required

- By using aqueous solutions of Mannitol, hydrolysis of TiO2 is produced, but Mannitol is removed with the aqueous phase

- Possible procedure for encapsulations with TiO2 (heat storage capacity, subcooling, durability under thermal cycles).

Deeper analysis is being currently done.

- SiO2 particles do not anchor with the D-Mannitol, as the sugar alcohol stays with the aqueous phase

- Hydrolysis of SiO2 has to be done in water-free process

- Microencapsulation of D-Mannitol seems to be suitable by sol-gel procedures in water-free processes



Elaboration of a hydrothermal /solvothermal process to encapsulate sugar alcohols

in zinc oxide shell as an alternative to the chemical process of simple or complex coacervation

Investigate the influence of pressure on the formation of ZnO-sugar alcohols

composites (crystal growth process, crystallisation, crystal shape and morphology)

OBJECTIVES

HYDROTHERMAL / SOLVOTHERMAL

Preparation and characterization of core/shell structures based on mannitol and ZnO

Mathematical model of ZnO-Mannitol hydrothermal synthesis process at high pressures

Preparation and characterization of core/shell structures based on erythritol and ZnO

RESULTS



Characterization methods: - Chemical analysis: ICP-OES (Agilent

Technology) - Particle sizes, Zeta Potential:

Malvern ZS 90 - XRD (Brucker D8 Advance) - FT-IR (ABB) - SEM: HITACHI S2600N (Centre 3MN) - Thermal analysis: DSC Netzch F3 Maya DSC-TG Setsys Setaram

Water soluble Zn salt Spray dried S.A.

S-A encapsulated in ZnO nanomatrices

Synthesis pressure: 100 – 3000 bar T < 100 deg.C



Micro-encapsulation of D-Mannitol in ZnO nanomatrices

DSC-TG curve for ZnO M8-1 (ZnO : mannitol =10:1), P=100 bar

SEM of ZnO 10:1

(P=100 bar)




DSC-TG curve for ZnO : mannitol = 4:1, P=1000 bar

SEM ZnO :Mannitol 4:1, P=1000 bar)




FT-IR spectra for ZnO : mannitol = 4:1, P=1000 bar




DSC-TG curve and SEM for ZnO : mannitol = 4:1, P=3000 bar




FT-IR curve for ZnO : mannitol = 4:1, P=3000 bar



Micro-encapsulation of Erythritol in ZnO nanomatrices

4000 3500 3000 2500 2000 1500 1000 500

10

20

30

40

50

60

70

80

90

100

T [

%]

Wavenumber [cm-1]

erythritol

ZnO-Er2

FT-IR of ZnO-Er2 sample

(ZnO:erythritol=4:1,100 atm.)

SEM of ZnO-Er2 sample

(ZnO:erythritol=4:1, 100 atm.)

Succesful encapsulation clear observed.



Innovation with respect to the state of the art: Hydrothermal / solvothermal process is used to encapsulate sugar alcohols (D-

mannitol and Erythritol) in ZnO shell as an alternative to the chemical process of simple or complex coacervation.

Hydrothermal / solvothermal synthesis advantages: the possibility to work at low

temperatures (<1000 C) and high pressures ( 100-3000 atm), single, one step process, controlled composition, morphology and microstructure.

ZnO – nano was selected due to its versatility and compatibility with SA (in particular D-mannitol or erythritol)

Modelling of the encapsulation process of mannitol in ZnO shell by hydrothermal

process at pressures between 100 and 3000 atm, revealed that 1000 atm is enough for obtaining a good encapsulation degree.

Improved handling and good thermal stability in the final product expected.

CONCLUSIONS


Participants: Thomas Ballweg, Doris Hanselmann

Encapsulation by Way of UV-curable Hybridpolymeric and Monomeric Building Blocks

Principle

• Vibration assisted microdrop generation through a concentric nozzle combination

• „Cold“ UV-curing with short residence time in the radiation field ( < 1/10 s)

• Encapsulation of sugar alcohol supersaturated aqueous solutions or sugar alcohol melts collector

UV-curing

shell material core material

ring nozzle

Scheme of the encapsulation process

4. ENCAPSULATION OF SA WITH HYBRID POLYMERS


General Properties

• Capsules size range: 0.5 – 5 mm

• Adjustable wall thickness

• Monomodal size distribution

• Core-shell-type morphology

• Transparency of the shell allowing the visual control of the physical condition of the sugar alcohol

High speed photographs of the encapsulation process showing the vibration assisted drop

generation

Encapsulation by Way of UV-curable Hybridpolymeric and Monomeric Building Blocks



Capsule Quality and Wall Thickness Control

High capsule quality and good wall thickness control attainable

Core:Shell ratio = 5:1 Core:Shell ratio = 2:1



Monomeric Di- and Trifunctional Monomeric and Hybrid Polymeric Building Blocks for High Strength Shells

Trimethacrylato- (3-mercaptopropyl)methyldimethoxysilane

Trimethylpropanetriacrylate (TMPTA)

Urethanedioldimethacrylate (UDMA)



Encapsulation of Xylitol-Erythritol Eutectic Melt by 2-Stage Curing

Xylitol-Erythritol-filled Capsules before and after crystallisation

Process-related challenges solved by means of 2-stage curing of

acrylate-methacrylate based shell material combinations



On the Destructive Power of Sugar Alcohol Crystallisation

Images: © Fraunhofer

Typical crystallisation-induced defects

• Process-related challenges solved…., but crystallization-related challenges remained

• 5 MPa uniaxial pressure resistance isn’t enough to withstand crystallization forces

ca. 5 MPa

(50 bar)



Elastomeric Shell Material Alternatives for Sugar Alcohol Encapsulation

Capsule Size: 3,0 0,1 mm Compr. Strength: 20,7 2,1 N Deform. at break: 54,5 1,5 %

Composition:


1 : 2


• Gas bubbles

Motivation:

• MASA-modifications for short time cycling (day-night) application

• Running MASA-PCMs in the not-subcooling mode

Results:

• Integration of encapsulation-compatible trigger mechanisms possible

• Low acceleration of crystallization

• Solvents • Particles

Integration of Nucleation Promoters



Conclusions and Outlook

• Encapsulation of sugar alcohols melts by means of vibration assisted microdrop generation and UV-curing successfully realized

• Capsule size in the mm-range complementary to true microencapsulation

• Monomodal size distribution with controllable wall thickness

• Core-shell-type morphology

• Building blocks for high strength and flexible elastomeric shells applicable

• Integration of nucleating agents (particles, solvents, gas bubbles) demonstrated

Outlook

• Optimization of thermo-chemical & mechanical stability at cycling

• Further development of nucleation agents for promoting short time cycling

• Increase of the processing temperature beyond 120 °C



The SAM.SSA project The SAM.SSA project

Thank you very much for your attention

María Dolores Romero

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