Novel Technologies to Produce Cellular Polymers with TailoredCellular Structures and Properties

Technology and Innovation for Cellular Materials at Industry Service

C. Saiz-Arroyo1,2, J.A. de Saja1, M.A. Rodríguez-Pérez2

1 CellMat Technologies, Valladolid-Spain2 CellMat Laboratory-University of Valladolid, Valladolid- Spain

Hamburg-19th -21st November 2013

o CELLMAT TECHNOLOGIESo STAGES MOLDINGo ANICELLo OPENCELLMATo SUMMARY & CONCLUSIONS

CELLMAT TECHNOLOGIES

CELLULAR MATERIALS LABORATORY

UNIVERSITY OF VALLADOLID- SPAIN

• 125 scientific papers• 10 patents and several novel technologies• 12 Ph D thesis• More than 50 research projects• Strong collaborations with companies around the world

Established in 1999. International recognized laboratory in the

area of cellular materials.o Transferring knowledge and

technology on cellular materials to industrial partners.

o Advising to plastics producers in manufacturing better and cheaper materials using specific know-how.

o Producing advanced foams and/or formulations for foaming

applications

Established in October 2012.Spin-off company of the University of Valladolid.

SPECIFIC AND NOVEL KNOW-HOW AND

TECHNOLOGIES ON ADVANCED CELLULAR

MATERIALS

LICENSES TRANSFER

AGREEMENTS

CELLMAT TECHNOLOGIES

CELLMAT PRODUCTS

o IMPLEMENTATION OF FOAMING PROCESSESo TECHNICAL CONSULTANCY IN HALOGEN FREE

FLAME RETARDANCYo SPECIFIC TRAINING COURSES

CELLMAT TECHNOLOGIES

o STAGES MOULDINGo ANICELL o OPENCELLMAT

SOLID PLASTIC PARTS PRODUCERS

o OPTIMIZATION OF CELLULAR MATERIALS: PROCESS & PRODUCT

o SUBSTITUTION OF OIL-DERIVED PRODUCTS BY BIOPLASTICS

o TECHNICAL CONSULTANCY IN HALOGEN FREE FLAME RETARDANCY

o SPECIFIC TRAINING COURSES

FOAM PRODUCERS

WHAT DO WE OFFER?

o CELLMAT TECHNOLOGIESo STAGES MOLDINGo ANICELLo OPENCELLMATo SUMMARY & CONCLUSIONS

LIMITATIONS: THE ORIGIN OF STAGES MOLDING

INYECTION MOLDING• Low pressure• High pressure• Gas counter pressure• Co-injection foam molding• Mucell technology

CURRENT TECHNOLOGIES TO PRODUCE LIGHT PLASTIC PARTS

ROTOMOLDING

o Difficult to obtain relative densities below 0.75, (weight reduction lower than 25%)

o Difficult to achieve good surface qualityo Expensive moldso Size of the parts is limitedo Low filler content

o Typically powdery raw materialo Two-axis rotating machines are neededo Very simple geometries

THE PRODUCTION OF LIGHT-WEIGHT LARGE PARTS IS SOMEHOW LIMITED NOWADAYS

STAGES MOLDING: HOW IT WORKS?A NEW TECHNOLOGY TO PRODUCE LARGE LIGHTWEIGHT PLASTIC PARTS, WITH EXCELLENT SURFACE QUALITY USING SIMPLE AND CHEAP MOLDS, AND ADEQUATE FOR THE PRODUCTION OF SHORT SERIES.

THE PROCESS

Formulation of raw material

Feeding raw material into a

mold

Heating to fill the mold

Cooling and demolding

Polymer: Thermoplastics Additives: (Micro-nano,

up to 80%)Blowing agent

Self-bearing molds-Feeder-Extruder-Injection unit

LOW PRESSURES(lower than 30 bar)

KEY ASPECTS

“Carousel system”

o SPECIFIC MOLDS: SELF-BEARING MOLDS. VERY LOW FILLING PRESSURE. o EFFICIENT AND HOMOGENEOUS COOLING AND HEATING OF THE MOLDS.o SPECIFIC FORMULATIONS WITH BETTER FOAMABILITY.

STAGES MOLDING: KEY ASPECTS

o SPECIFIC FORMULATIONS WITH HIGH BETTER FOAMABILITY

Stages molding process is basically a free-foaming process using thermoplastics as raw materials, so it becomes strictly necessary to develop highly stabilized formulations.

NON-STABILIZED MATERIAL STABILIZED MATERIAL

STAGES MOLDING: ADVANTAGES

TECHNICAL ADVANTAGESo Homogeneous cellular structures, parts with excellent mechanical, thermal and acoustic properties.

Possible to generate skin-core morphology.o Parts with no joints, no internal stresses or skin marks. Excellent surface quality.o Very high density reductions (up to 75%) which are associated to economic and environmental

advantages.o Molds up to 100 times cheaper than the ones used in conventional injection molding. Low filling

pressures, (lower than 30 bar). SHORT SERIES AT LOW COST.o Intrinsic characteristics of the process together with self-bearing molds: no need of an injection unit. o Possible to produce large parts with complex geometries. Up to 2m x 1.5 m. Thickness from 2 mm to

60 mm.o Suitable for any thermoplastic polymer. Possible to make co-injection using different polymers. o Very versatile in terms of fillers, possible to use micro or nanofillers and up to very high contents

(80%). Possible to use also recycled polymers.

59 cm

STAGES MOLDING: APPLICATIONS

APPLICATIONS o Building & Constructiono Automotiveo Biotechnologyo Consumption

o Aeronauticso Packagingo Energetic sector.o Naval industry

ANY INDUSTRY USING PLASTIC AS RAW MATERIAL

STAGES MOLDING: A TECHNICAL & LOW COST SOLUTION

HIGH WEIGHT REDUCTIONS, UP TO 80%WEIGHT, RAW MATERIAL &

COST REDUCTIONSELF-BEARING & LOW PRESSURE MOLDS

COST REDUCTION & LOW INVESTMENTS FOR IMPLEMENTATION

NO INJECTION UNITLARGE PARTS, GOOD SURFACE QUALITYNO SECONDARY PROCESSES & LESS DISCARDED PRODUCTS THERMOPLASTICS & ANY FILLER

RECYCLED AND/OR HIGH FILLER CONTENTLOWER COST PER PART

(SHORT SERIES)

o CELLMAT TECHNOLOGIESo STAGES MOLDINGo ANICELLo OPENCELLMATo SUMMARY & CONCLUSIONS

FOAMS & STRUCTURAL APPLICATIONS

o BUILDING AND CONSTRUCTIONo AUTOMOTIVEo RENEWABLE ENERGIESo AERONAUTICSo NAVAL INDUSTRYo TRAINSo ETC…

SEVERAL STRATEGIC SECTORS USE FOAMS AS STRUCTURAL ELEMENTS

Panels or core of sandwich panels

BALSA WOOD• Natural resource, lack of

homogeneity.• Not suitable where water

absorption must be avoided.• Shortage of supply problems• Environmental concerns

CROSSLINKED PVC• High cost.• Need to crosslink PVC to reach

low densities.• Few companies around the

world involved in its production.• Non-recyclability after end-use.

POLYURETHANE• Environmental concerns.• Thermoset: Non-recyclable• Fire resistance reached using

halogenated products.• Not as good mechanical

performance as technical polymers.

THE ICM ROUTE: THE ORIGIN OF ANICELL

Production of a solid precursor

Foaming of precursor material under

controlled pressure and temperature in a closed

mould

Cooling of foamedmaterial

Mixing raw materials in a twin-screw extruder

THE ICM ROUTE

THE PRESSURE APPLIED DURING THE FOAMING STEP

SELF-EXPANDABLE MOULDS

• Defined (simple) geometry.• Very high accuracy in density

control.

NON-CROSSLINKED FOAMED PRODUCTS AND AN INDEPENDENT CONTROL OF DENSITY AND CELLULAR

STRUCTURE. SIMILAR DENSITIES BUT DIFFERENT CELLULAR STRUCTURES

APPROPIATE TUNING OF FOAMING PARAMETERS AND CHEMICAL COMPOSITION

ANICELL CLOSED CELLANICELL FLAME RETARDANTANICELL OPEN CELL

ANICELL SOLUTIONS

ANICELL CLOSED CELLo Foamed cores with high specific mechanical properties due to the combination of a closed cell

cellular structure and high anisotropy ratios, (higher than 2). o Depending on the final application density can be varied between 90 and 500 kg/m3

ANICELL CC 180 Kg/m3

ANICELL CC 150 Kg/m3

Elastic Modulus (Mpa) 180 120Collapse Stress (MPa) 2.8 1.6Open Cell Content (%) < 20 < 20

Anisotropy Ratio 2.3 2.6ANICELL FLAME RETARDANTo The ICM route and halogen free flame retardant technology can be combined to generate a new

class of lightweight fire resistant cores and panels.o Density range: Between 250 and 300 kg/m3.

AniCell PP Flame Retardant coreThere is no flame propagation

when it is directly applied to the material

No FR PP core

Parallel to expansion direction

ANICELL OC ARE NOVEL MATERIALS THAT COMBINE HIGH SPECIFIC MECHANICAL PROPERTIES WITH

AN OPEN CELL STRUCTURE: EXCELLENT STRUCTURAL FOAMS FOR

ACOUSTIC ABSORPTION OR FILTRATION PURPOSES.

BIMODAL & 100% OPEN CELL CELLULAR STRUCTUREANISOTROPY RATIO: 2.3-2.5

ANICELL SOLUTIONS

ANICELL OPEN CELLo The combination of a 100% open cell content and high specific mechanical properties.o The use of the ICM route together with the use of nanoreinforcements has facilitated the generation

of a novel class of materials: Open cell polypropylene foams with a very high mechanical response.

Perpendicular

COMPRESSIVE MODULUS

ANICELL & THE MARKET

CrosslinkedPVC foams

AniCell CC (closed cell)

AniCell OC (open cell)

Rigid PU

ANICELL products are FULLY RECYCLABLE The ICM route does not imply crosslinking of polymer matrix even when products with densities around 90kg/m3 are produced.

MECHANICAL RESPONSE COMPARABLE to that of commercial products based on crosslinked PVC or rigid PU.

ANICELL is based in a POLYMER, HIGH MELT STRENGTH POLYPROPYLENE, (Daploy WB135 HMS).Currently working in technical polymers, (SAN, PET)

Possible to generate HALOGEN FREE FLAME RETARDANT products.The ICM route permits including high amounts of fillers, (up to 40-50%)

o CELLMAT TECHNOLOGIESo STAGES MOLDINGo ANICELLo OPENCELLMATo SUMMARY & CONCLUSIONS

WHY OPENCELLMAT?

CLOSED CELL FOAMS

OPEN CELL FOAMS

VERY LOW RELATIVE DENSITIES0.01 < ρR < 0.1

LOW DENSITY CROSSLINKED POLYOLEFIN FOAMS

FLEXIBLE POLYURETHANE

FLEXIBLE FOAMS

o Resistant to moisture and chemicals. o Thermofoamable.o Can not cover open-cell foam

applications, (sound absorption, filtration, seats and mattresses, …)

o Not resistant to moisture.o Not UV resistanto Not environmentally friendly

OPENCELLMATLOW DENSITY OPEN CELL POLYOLEFIN BASED FOAMS

OPENCELLMAT

BASE POLYMER • Crosslinked low density polyethylene, (XL-LDPE)• Ethylene vinyl copolymer, (EVA)

PRODUCTION• Batch: Two-steps compression molding process.

MICROSTRUCTURE & PHYSICAL PROPERTIES

OPENCELLMAT FLEXIBLE POLYURETHANECOMMERCIAL_CLOSEDCELLCOMMERCIAL_OPENCELL

• XL-LDPE• OC: 99%• ρ: 26 kg/m3

• XL-LDPE & EVA• OC: 95%• ρ: 26 kg/m3

• XL-LDPE • OC: ∼7%• ρ: 25 kg/m3

• PU• OC: ∼97%• ρ: 25 kg/m3

Two-steps compression molding process

OPENCELLMAT: MICROSTRUCTURE

o Exhibits a cellular structure similar to that of commercial opencell foam, this is something between flexible polyurethane and commercial closed cell foams but with smaller holes in the walls.

o OpenCellMat present struts, edges and walls with small holes.

OPENCELLMAT

Material Cell Size (μm) Tortuosity

Flexible Polyurethane 355 1.76

Commercial Closed Cell 255 -

Commercial Open Cell 630 25.4

OPENCELLMAT 670 35.2

Microstructure of OpenCellMat foam is an hybrid between commercial open and closed cell materials

with the particularity of a completely interconnected and high tortuous cellular structure.

OPENCELLMAT: MECHANICAL PROPERTIES

III I

II

III

I. Elastic RegionII. Plateau RegionIII. Densification Region

IIIcσ

-ε: Strain- ρf: Density of foamed material- ρs: Density of the corresponding solid

COMPRESSION TESTS: STRESS-STRAIN CURVES Compression tests up to 75% strain, strain rate 0.1s-1. 5 cycles without recovery time.

- σ: Stress- σc: Collapse stress- P0: Pressure of the gas enclosed in the cells.

L.J. Gibson, M.F. Ashby. Cellular Solids: Structure and Properties. 2nd Edition, Cambridge University Press, United Kingdom, (1997).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

ELAS

TIC

MO

DULU

S (M

Pa)

Elastic Modulus Cycle#1

OPENCELLMAT: MECHANICAL PROPERTIES

COMPRESSION TESTS: ELASTIC MODULUS

FLEXIBLE POLYURETHANECOMMERCIAL_OPENCELL COMMERCIAL_CLOSEDCELLOPENCELLMAT

BENDING OF EDGES

STRETCHING OF CELL WALLS

GAS CONTRIBUTION

Ef: Foam Elastic ModulusEs:Solid Elastic Modulusfs: Mass fraction in the strutsP0: Pressure into the cellsυ: Poisson’s ratioρf:: Foam Densityρs: Solid DensityC: Constant

OpenCellMat is stiffer than open-celled commercial products based on blends of LDPE & EVA or in PUF

L.J. Gibson, M.F. Ashby. Cellular Solids: Structure and Properties. 2nd Edition, Cambridge University Press, United Kingdom, (1997).

OPENCELLMAT: MECHANICAL PROPERTIES

COMPRESSION SET

0 4 8 12 16 20 240

2

4

6

8

10

12

14

Rem

anen

t Stra

in (%

)

Time (Hours)

OpenCellMat Commercial Open Cell Commercial Closed Cell Flexible Polyurethane

Remanent strain of samples has been measured after compressing them at 25% strain during 22 hours. Dimensions (thickness) of the materials have been measured at different times, between0.5 and 24 hours after removing the compressive force, (according to ISO 1856/80B standard)

L0: Initial thickness of the sample.L: Thickness of the sample after deformation, measured at different times.

OpenCellMat is a slow-recover material, with a behavior similar to viscoelastic polyurethane. This behavior is the direct result of its very tortuous cellular structure with very small holes in cell walls.

OPENCELLMAT: THERMAL PROPERTIES

Thermal conductivity of samples has been measured at 25ºC, (according to UNE 12667)

Material Thermal Conductivity (mW/mK)

Flexible Polyurethane 38.5

Commercial Closed Cell 37.8

Commercial Open Cell 37.5

OPENCELLMAT 38

λs : Conduction through solid phaseλg : Conduction through gas phaseλc : Convectionλr : Radiation

THERMAL CONDUCTIVITY

Thermal conductivity of OpenCellMat is similar to the one exhibited by the other products.The presence of small holes in the walls is not enough to activate the convection mechanism and therefore conductivities of all materials are very similar.

OPENCELLMAT: THERMAL PROPERTIES

THERMAL STABILITYDimensional stability of polyolefin based samples has been measured by subjecting them to 100ºC during 24 hours.

L0: Initial thickness of the sample.L: Thickness of the sample after being @100ºC during 24h.

OpenCellMat exhibits a behavior similar to closed cell products.As cell opening takes place during the foaming step, no biaxial stresses remains in cell walls.

0

2

4

6

8

10

12

14

SHRI

NKA

GE

(%)

97%

OPENCELLMAT COMMERCIALCLOSEDCELL

COMMERCIALOPENCELL

OPENCELLMAT: ACOUSTIC PERFORMANCE

Typical performance of an open cell foam, so better sound absorption capability than closed cell material.Higher absorption capability than flexible polyurethane and commercial open cell foams at low frequencies.At high frequencies, similar performance than polyurethane and higher than that of open cell foams.

1000 2000 3000 4000 5000 60000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Norm

al In

ciden

ce A

cous

tic A

bsor

ptio

n Co

effic

ient

Frequency (Hz)

Flexible polyurethane Commercial Open Cell Polyolefin based Foam Commercial Closed Cell Polyolefin based Foam OpenCellMat

Normal incidence acoustic absorption coefficient has been measured in an impedance tube, Brüel & Kjaer model UA-1630. Frequency range: 500-6400 Hz. (ISO 10534-2)

o CELLMAT TECHNOLOGIESo STAGES MOLDINGo ANICELLo OPENCELLMATo SUMMARY & CONCLUSIONS

SUMMARY & CONCLUSIONS

STAGES MOLDING ANICELL

OPENCELLMAT

CELLMAT TECHNOLOGIES S.L.CENTRO DE TRANSFERENCIAS Y TECNOLOGÍAS

APLICADAS (CTTA)PASEO DE BELÉN 9A OFFICE 105

47011, VALLADOLID-SPAIN

Phone:+34 983 189 197c.saiz@cellmattechnologies.comwww.cellmattechnologies.com

ACKNOWLEDGEMENTSo University of Valladolido Prof. Miguel Angel Rodríguez-Pérezo Alberto López-Gil, Josías Tirado, Javier Escudero.

THANK YOU SO MUCH FOR YOUR ATTENTION!!