METALLIZING: Metallizing is the general name for the technique of coating metal on the surface of non-metallic objects.

VACCUM METALLIZATION: Vacuum Metalizing is the process of evaporating and deposition of metals (most commonly aluminum) inside a vacuum chamber to achieve a thin uniform metalized layer on a substrate

PURPOSE OF METALLIZATION:

Enhance barrier properties of the film so that water vapor and oxygen transmission across the film is reduced.

Depending on end use application e.g. synthetic yarn (zari), decoration, wrapping, and holography.

SCIENCE OF METALLIZATION:

In a vacuum metallization process we maintain our substrate and the material to be coated in below atmospheric (near vacuum) pressure levels. Therefore at pressures of near 5x10-5 bar the coated material (in this case aluminum) if heated to temperatures of 1500 -1600°C straightaway enter the vapor phase.

This vapor is then made to deposit via condensation over the substrate which is being rolled over a cooled drum.

A BROAD OUTLINE OF A VACCUM METALLIZER SHOWN BELOW:

THE VARIOUS SYSTAEM OF METALLIZER ARE:

Vacuum System Condensation System Evaporation & heating system Unwinder, rewinder & web handling

VARIOUS FILMS ARE METALLIZED AT THE UFLEX WAREHOUSE:

METALLIZED PET FILM METALLIZED BOPP FILM METALLIZED CPP FILM METALLIZED THERMAL FILM PLASMA TREATED METALLIZED PET FILM

COMPARISION OF BARRIER PROPERTIES BASED ON OPTICAL DENSITY (OD):

FILM O.D NORMAL PLASMAWVTR

(gm/m2/day) at 38°C 90%RH

OTR(cm2/m2/day)

at 23°C 0%RH

WVTR(gm/m2/day) at 38°C 90%RH

OTR(cm2/m2/day)

at 23°C 0%RH

BOPET

2.2 1.0 1.1 XX

2.5 0.6 1.0 XX

2.8 0.4 0.8 0.40.6

BOPP2.2 1.1 125 X

X

2.8 0.3 40 XX

CPP 2.2 3.7 650 XX

COMPARISION OF METAL BOND STRENGTH

:

FILM GRADE MET ON UT MET ON CTMET ON COATED

BOPET

F-MTG-M 175 - 200 > 200X

F-CHE-M 175 - 200 X 500

F-AUU-M 175 - 200 XX

F-AUT-M X > 200X

F-ATU-M 175 - 200 X250 – 300

F-ATT-M X > 200250 – 300

BOPP B-TVH-M X 150 - 200X

CPP C-CPM-M X 150 - 200X

RECYLING PLANT (EEMA) :

During film processing many type of wastage generated

Trim waste at TUT and slitter Jumbo roll dressing wastage Lab sample Balance length after slitting, off cut rolls at slitter. Loose film during break and any plant stoppage cast or mono film

LAB TESTING:

WHY TESTING REQUIRED? Testing is necessary to ensure:

The product is matching or surpassing the required properties for smooth usage of the product in entire chain from cradle to grave.

TEST STANDARDSTest standards are followed to maintain uniformity in testing and understanding among different people, group or companies to ensure a similar platform of product performance Common standards are:

ASTM (American)BS (British)IS (Indian)INTERNAL (Uflex)

The film properties can be broadly classified as:

DimensionalOpticalSurfacialMechanicalThermalFunctionalBarrier

1) DIMENSIONAL PROPERTIES:

The appropriate dimensions ensures uniformity during process and helps in effective cost calculation of packaging substrate.

Thickness GSMYield (α1/GSM)

THICKNESS

i) Specification : +/- 3%ii)Instrument Used: Millitroniii)Classification

a. Spot thickness : Highest accuracyb. By weight method : Average (100 cm2)c. By average gauge : Avg. of whole width

iv)Profile analysis : By graph

GSM / YIELD

i) GSM : The weight in gms of the substrate per unit square meters surface.ii) Unit : gm/mts2iii) GSM = Density * Thicknessiv) Measurement method : by weighing 100cm2 of sample in gms and multiplying by

100.

i) Yield : The area of one kg of filmii) Unit : sq.mts./ kg iii) Yield = 1000/GSM

2) OPTICAL PROPERTIES :

The optical properties makes the printed image realistic when printed from opposite side of viewing surface, properties are:

HazeTransmittanceGlossOptical DensityColour : L , a, bClarity (free from scratches, lines ,marks, patches, impurities at surface

etc.)

HAZE (ASTM D-1003): Haze is the scattering of light by a film that results in a cloudy appearance or poorer clarity of objects when viewed through the film. More technically, haze is the percentage of light transmitted through a film that is deflected more than 2.5° (degrees) from the direction of the incoming beam. This property is used to describe transparent and translucent films, not opaque films.

i) Film checked : Clear , Matteii) Specification

Clear Film : 2.0-4.0 % Matte Film: 40 -70 %

iii) Instrument used : Haze guard plus

What determines the haze level of a clear filmHaze is greatly influenced by material selections and product design. Resin characteristics, such as crystallinity and molecular weight distribution, have a key impact. Copolymers are generally hazier than homopolymers. Additives and coatings usually contribute to increased haze. All other things being equal, thicker films will be hazier than thinner films. Additional variables, like process temperatures in the different stages of film-making, can further affect haze, so they are tightly controlled.

Transmittance (ASTM D-1003) : The percent of incident light which is transmitted through the specimen.

Gloss (ASTM D-2457) : Gloss is a measurement of the relative luster or shininess of a film surface. The incident light beam strikes the film surface at a 45 degree angle from the perpendicular. A sensor measures the amount of light reflected by the film at a mirror image angle. The gloss value is the ratio of this reflected light to incident light and is reported in gloss units. Theoretically, the range of the gloss scale is 0 to 100.

Relevance to application performance : Shininess, brilliance, and sparkle are properties related to a film's gloss value. They can be valuable appearance attributes for packages, labels, or graphic arts items.

What affects film glossGloss is primarily determined by material selection and surface smoothness, which are defined during product and process development. Day-to-day process variations will have an insignificant effect on gloss. Transparent films have two reflecting surfaces. Although rare, this can lead to gloss values that exceed 100.

Optical Density: Optical density, is a representation of a material's light blocking ability. The optical density scale is unitless and logarithmic, and it enhances the data resolution for materials that transmit only a small fraction of incident light.

3) SURFACIAL PROPERTIES:

The surface properties defines the surface characteristics important for runnability, adhesion and surface morphology:

Treatment / Surface wettabilityCo-efficient of friction (α1/Slip)AdhesionSurface roughnessGloss (optical also)

Treatment (ASTM D-2578) : Wetting tension is ability of the surface to wet uniformly with a given liquid.

Liquids of different wetting level is made by mixing proper ration of water, cellusolve & formamide.

In general higher the wetting tension higher the adhesion power. Units : dyne/cm Minimum level for surfacial adhesion with ink/adhesive : 38 dyne/cm

Co-efficient of Friction (ASTM D-1894) : The resisting force that arises, when a surface of one substance slides over an adjoining surface of itself or another substance.

COF have a major role in determining the slip behavior of the film and is reciprocal in relation.

4) MECHANICAL PROPERTIES :

Mechanical property is identification of strength, flexibility / rigidity of film to understand its behavior on machine and end application:

Tensile StrengthElongationModulus of Elasticity

TENSILE STRENGTH / ELONGATION :

Tensile (ASTM D-882) : It indicates the load applied per unit cross sectional area of the specimen at the time of rupture during streching

Elongation (ASTM D-882) : It indicates the extension visa vis original length in % while stretching at the moment of rupture

5) THERMAL PROPERTIES:

The properties ensure the uses without distortion and ensure seal integrity test are;

Shrinkage Machine direction (MD) Transverse Direction (TD)

Heat seal Initiation Temperature Seal strength

Shrinkage (ASTM D-1204) : It indicate how much film got shrink in both machine and transverse direction from its original dimension when kept in hot air oven.

Test Condition : PET - 150 deg / 30 min BOPP – 120 deg / 5 min

Specification : FOR PET MD <3.0 and TD <1.0 BOPP : MD/TD :: <3.0 / <2.0

6) FUNCTIONAL PROPERTIES :

The properties ensure the product performance in special conditions which are:

Cold AntifogHot AntifogF-5Shrinkage at elevated temperatureSealing with PE film

7) BARRIER PROPERTIES:

The food have a higher shelf life when protected against environmental constrains by not allowing them to pass through the package. Barrier α 1/ Transmission rate Properties are:

O2TR (OTR) : Oxygen Transmission Rate (ASTM D-3985) WVTR(MVTR) : Water (Moisture) Vapour Transmission Rate (ASTM D-1249)

8) METALLIZED FILM TESTING :

Thin layer of Alumunium of Aprox. 200 Angstrom is deposited on film (BOPET, BOPP,CPP) and following is checked for adhesion and uniformity:

Optical DensityTape testTreatment1,2Metal Bond

9) THERMAL FILM TESTING:

Thermal Lamination grades of films are generally EVA Coated film with one side EVA Coating on the base film BOPE/BOPP.Theses grades of films are applicable for Lamination purpose and following is checked for these films:

TreatmentG.S.MTensile strength/ElongationLamination bond with fibreSeal Strength

RAW MATERIAL USED FOR THE MANUFACTURING OF BOPET/BOPP/CPP FILM:

1) Raw material used for the manufacturing of BOPET (Bi-Axially Oriented Polyethylene Terephthalate ) Film : For the Manufacturing of BOPET Film BRIGHT & SILICA are basically used.

Standard Prpoerties of PET Chips:

Molecular formula (C10H8O4)n Density 1370 kg/m3 Young's modulus (E)2800–3100 MPa Tensile strength (σt)55–75 MPa

Elastic limit50–150%notch test3.6 kJ/m2 Glass temperature 75 °C melting point 260 °C Vicat B170 °C

Thermal conductivity0.24 W/(m·K) linear expansion coefficient (α) 7×10−5/K Specific heat (c)1.0 kJ/(kg·K)Water absorption (ASTM)0.16 Refractive Index 1.5750

Method of making Polyester

PET resin can be formed by two different reactions. The starting material for the first reaction is Terephthalic Acid which can be converted in a condensation reaction with Ethylene Glycol to form Bis(hydroxyethyl)-terephthalate and Water (TPA - Route). The other possibility is to start the condensation reaction with Di-m ethyl- terephthalate and Ethylene Glycol to achieve Bis(hydroxyethyl)-terephthalate and Methanol (DMT - Route). In the next step, The PET is formed by transesterification and gives some amount of Ethylene Glycol back, which can be used in the first step again.

TYPICAL STRUCTURE OF PET CHIPS:

Basic Process flow chart for Manufacturing of BOPET Film :

1) Raw material used for the manufacturing of BOPP (Bi-Axially Oriented Polypropylene ) Film : For the Manufacturing of BOPP Film HOMOPOLYMER & COPOLYMER are generally used.

The abbreviation BOPP stands for Bi-axially Oriented Polypropylene. By stretching the film, i.e. by orienting the macro-molecules of the polypropylene, it’s properties are altered as follows.

Properties of Polypropylene

Molecular Formula : (C3H6)xDensity: Amorphous (0.85 g/cm3) Crystalline (0.95 g/cm3)Melting Point: 165°C

PP is a crystalline solid produced by polymerization of propylene monomers

PP HOMOPLYMER:

Steps followed in producing PP homopolymer: Washing out the catalyst/drying of solvent(only for slurry

process) PP powder, additives, granulating PP granulate

The following reaction agents are put into the reactor: Propylene as a monomer to achieve polymerization. Hexane as a solvent.

Molecular Weight:

• The hydrogen constituent in the process is responsible for the mean molecular weight, which in turn determines the melt viscosity and thus the ability of the melt to flow through the die.

• The capability of the melt to maintain it’s form upon leaving the extruder die is improved by increasing the molecular weight.

MFI (Melt flow index):

• Indicates the flow property of the polymer melt and is related with the molecular weight of the polymer.

• Polypropylene is tested for MFI usually at 230 degrees C with a testing weight of 2.16 kg. For BOPP production process a MFI of 1.5-3.5 g/10min is chosen. The numerical value of MFR is inversely proportional to the viscosity.

• The iso-tactic portion influences the crystallinity, though crystallinity is also influenced by cooling rate.

Crystallinity

affects the density of the polypropylene. For a crystallinity of 30-60%, the density is 0.91kg/cm3 and the melting point of the PP homopolymer is 165-175 degree C.

Additives: • They are added to the PP powder to form granulates

• Anti-oxidation agents and thermo-stabilizers to prevent the degradation of molecules during further processing.

• Calcium-stearate or hydrotalcid serves to neutralize non-washed out catalyst deposits. Catalyst deposits like chlorine compounds affect the which affect the roll surface. Calcium stearate also acts slip agent.

PP Copolymer

• Is produced by polymerizing together propylene, ethylene –P-E-P-E-P-E-P-P-E-P-P-E-P-P-E- (Random Copolymer).

• The ethylene portion of the random copolymer is 3-5%. • The ethylene portion determines the melting pt. of the copolymer.

• Higher the percentage of ethylene , lower is the melting point. Though, a very high percentage of ethylene may cause increase in haze.

• Generally the melting point of copolymer is 138 degree C. The MFI of random copolymer is appox 5-7 g/10min

ADDITIVES

Masterbatch is a PP granulate with additives introduced into the homopolymer, copolymer system through a dosing system. Additives in masterbatch form guarantees homogenous distribution in the granulate and also the film.

The additives are added subject to application:

Slip agentsAnti-statics agentsAnti-blocking agents

SLIP Agents are applied in order to obtain a smooth-slipping film with low coeff. of friction. It also improves the extruder output capacity while decreasing extruder power input.

• Erucamide is a chief agent in anti slip additives.•For plain film 250-750 ppm of slip agent is added, while for coextruded film 1000-2000 ppm of slip agent is added to homopolymer and 1000ppm for copolymer.1-2 weeks of migration time is required to make the slip agent effective on the film’s surface.

Anti-Static Agents are used to reduce electrostatic charge on the film.This is tested by finding out the half-life of the accumulated charge to get discharged.

• The agent is bipolar , so while migrating to film surface , the unpolar portion stays with the PP, while the polar portion attaches humidity.

Anti-blocking agents are used to prevent blocking of film on winder which is

caused by the following reasons.•Short-polymer chains migrate to the film surface and get pasted with the other film.•If the film surface is too smooth, great adhesive strength originates between two films.•Therefore anti-blocking agents like silicic acid agents are added to artificially roughen the film surface. 2 and 4 μm particle size of silicic acid in a concentration of 200-1000ppm is added. •Thinner film requires more antiblocking agent. Silicic acid is chosen since it is amorphous, has high refraction index, and is a soft material.•Since this is an inorganic product, it doesn’t migrate and is fully effective right after migration.The store-up of water, facilitates easier discharge of electrostatic charge from the film. These are especially for co-ex film with a concentration 300 ppm. Appropriate migration is required, 1-2 weeks