Photovoltaic encapsulant films comprising fumed alumina

Abstract

The present disclosure relates to a curable composition for an encapsulant film, the curable composition comprising: (A) a polyolefin; (B) a fumed alumina; (C) an organic peroxide; (D) a silane coupling agent; (E) a crosslinking co-agent; and, optionally, (F) an additive component comprising a UV stabilizer, wherein the polyolefin has a volume resistivity of less than 4.0E+15 ohm.Math.cm. The present disclosure further relates to an encapsulant film made from such a curable composition and a PV module containing such an encapsulant film.

Claims

1. A curable composition for an encapsulant film, the curable composition comprising: (A) from 80 wt % to 99 wt % of an ethylene/1-octene random copolymer with a density from 0.860 g/cc to 0.890 g/cc, and a melt index from 5 g/10 min to 20 g/10 min, based on the total weight of the curable composition; (B) from 0.01 wt % to 5 wt % of a fumed alumina with a specific surface area (BET) from greater than 50 m.sup.2/g to less than 200 m.sup.2/g, based on the total weight of the curable composition; (C) from 0.1 wt % to 5 wt % of an organic peroxide, based on the total weight of the curable composition; (D) from 0.01 wt % to 2 wt % of a silane coupling agent, based on the total weight of the curable composition; (E) from 0.01 wt % to 5 wt % of a cross-linking co-agent, based on the total weight of the curable composition; and (F) from 0 wt % to 1 wt % of an additive component comprising an antioxidant, based on the total weight of the curable composition, wherein the ethylene/1-octene random copolymer has a volume resistivity from greater than 1.0E+12 to less than 4.0E+15 ohm.Math.cm.

2. The curable composition of claim 1, wherein the ethylene/1-octene random copolymer has a melt index from 10 g/10 min to 18 g/10 min.

3. An encapsulant film comprising a crosslinked polymeric composition which is the reaction product of the curable composition of claim 1.

4. The encapsulant film of claim 3, wherein the encapsulant film has a volume resistivity from greater than 9.0E+15 ohm.Math.cm to 9.0E+16 ohm.Math.cm.

5. The encapsulant film of claim 3, wherein the encapsulant film has a maximum torque (MH) greater than or equal to 2.0 dNm.

6. The encapsulant film of claim 3, wherein the encapsulant film has a t90 less than 11 minutes.

7. The encapsulant film of claim 3, wherein the encapsulant film has an initial glass adhesion of greater than 140 N/cm.

8. The encapsulant film of claim 3, wherein the encapsulant film has a mean transmittance greater than or equal to 88%.

9. A PV module comprising a solar cell and the encapsulant film of claim 3.

Description

DETAILED DESCRIPTION

(1) Polyolefin

(2) The (A) polyolefin of the present disclosure is any olefin-based homopolymer (in which an olefin is the sole monomer) or olefin-based interpolymer, in which an olefin is the primary monomer (that is, the olefin-based interpolymer comprises greater than 50 wt % units derived from an olefin). In these embodiments in which the polyolefin is an interpolymer, the comonomer is a different C.sub.2-20 linear, branched or cyclic alpha-olefin. For purposes of this disclosure, ethylene is an alpha-olefin. Non-limiting examples of C.sub.2-20 alpha-olefins for use as comonomers include ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene.

(3) In certain embodiments, the polyolefin is an ethylene-based polymer that is an ethylene/alpha-olefin interpolymer that may be a random or block interpolymer. In further embodiments, the polyolefin is an ethylene-based polymer that is an ethylene/alpha-olefin copolymer that may be a random or block copolymer. Non-limiting examples of ethylene/alpha-olefin copolymers include copolymers of ethylene and C.sub.3-C.sub.8 alpha-olefins, or C.sub.4-C.sub.8 alpha-olefins, such as ethylene/propylene copolymers, ethylene/1-butene copolymers, ethylene/1-hexene copolymers, ethylene/l-octene copolymers, and combinations thereof.

(4) In certain embodiments, the polyolefin is an ethylene/alpha-olefin random copolymer. Examples of ethylene/alpha-olefin random copolymers include but are not limited to ethylene/propylene random copolymers, ethylene/1-butene random copolymers, ethylene/1-hexene random copolymers, ethylene/1-octene random copolymers, and combinations thereof. In certain embodiments, the polyolefin is an ethylene/alpha-olefin random copolymer, wherein the alpha-olefin is selected from 1-octene, 1-hexene, 1-butene, and propylene. In further embodiments, the polyolefin is an ethylene/1-octene random copolymer.

(5) In further embodiments, the polyolefin is an olefin block copolymer and, further, an ethylene/alpha-olefin multiblock interpolymer as defined herein.

(6) In certain embodiments, the polyolefin is absent a heteroatom. The term heteroatom, as used herein, is an atom other than carbon or hydrogen. The heteroatom can be a non-carbon atom from Groups IV, V, VI and VII of the Periodic Table. Non-limiting examples of heteroatoms include: F, N, O, P, B, S, and Si.

(7) In some embodiments, the polyolefin has a volume resistivity from greater than 1.0E+12 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than 5.0E+12 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than 1.0E+13 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than 5.0E+13 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than or equal to 1.0E+14 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than or equal to 5.0E+14 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than or equal to 5.0E+14 ohm.Math.cm to less than or equal to 3.5E+15 ohm.Math.cm, or from greater than or equal to 7.0E+14 ohm.Math.cm to less than or equal to 3.0E+15 ohm.Math.cm.

(8) In further embodiments, the polyolefin has, in accordance with the methods disclosed herein or similar methods, a volume resistivity from 1.0E+12 ohm.Math.cm, or 5.0E+12 ohm.Math.cm, or 1.0E+13 ohm.Math.cm, or 5.0E+13 ohm.Math.cm, or 1.0E+14 ohm.Math.cm, or 5.0E+14 ohm.Math.cm, or 7.0E+14 ohm.Math.cm, or 9.0E+14 ohm.Math.cm, or 1.0E+15 ohm.Math.cm to 1.5E+15 ohm.Math.cm, or 2.0E+15 ohm.Math.cm, or 2.5E+15 ohm.Math.cm, or 3.0E+15 ohm.Math.cm, or 3.5E+15 ohm.Math.cm, or less than 4.0E+15 ohm.Math.cm.

(9) In certain embodiments, the polyolefin has a density from 0.850 g/cc, or 0.855 g/cc, or 0.860 g/cc, or 0.865 g/cc, or 0.870 g/cc, or 0.875 g/cc to 0.880 g/cc, or 0.885 g/cc, or 0.890 g/cc, or 0.895 g/cc, or 0.900 g/cc, or 0.905 g/cc, or 0.910 g/cc, or 0.915 g/cc, or 0.920 g/cc, as measured in accordance with ASTM D792, Method B. For example, in certain embodiments, the polyolefin has a density from 0.850 g/cc to 0.920 g/cc, or from 0.855 g/cc to 0.910 g/cc, or from 0.860 g/cc to 0.900 g/cc, or from 0.860 g/cc to 0.895 g/cc, or from 0.860 g/cc to 0.890 g/cc, or from 0.865 g/cc to 0.885 g/cc, or from 0.865 g/cc to 0.880 g/cc, as measured in accordance with ASTM D792, Method B.

(10) In certain embodiments, the polyolefin has a melt index (MI) from 0.1 g/10 min, or 0.5 g/10 min, or 1 g/10 min, or 5 g/10 min, or 10 g/10 min, or 12 g/10 min to 18 g/10 min, or 20 g/10 min, or 25 g/10 min, or 30 g/10 min, or 50 g/10 min, or 75 g/10 min, or 100 g/10 min, as measured in accordance with ASTM D1238, at 190 C./2.16 kg. For example, in certain embodiments, the polyolefin has a melt index (MI) from 0.1 g/10 min to 100 g/10 min, or from 0.5 g/10 min to 100 g/10 min, or from 1 g/10 min to 100 g/10 min, or from 1 g/10 min to 75 g/10 min, or from 1 g/10 min to 50 g/10 min, or from 1 g/10 min to 30 g/10 min, or from 5 g/10 min to 30 g/10 min, or from 5 g/10 min to 20 g/10 min, as measured in accordance with ASTM D1238, at 190 C./2.16 kg.

(11) In certain embodiments, the polyolefin has a melting point (Tm) from 55 C., or 60 C., or 75 C., or 90 C., or 95 C., or 100 C. to 105 C., or 110 C., as measured using DSC.

(12) In certain embodiment, the olefin-based polymer has a glass transition temperature, Tg, from 30 C., or 35 C. to 40 C., or 45 C., or 50 C., or 60 C., as measured using DSC.

(13) In an embodiment, the olefin-based polymer has a flexural modulus (2% secant) from greater than or equal to 500 psi, or greater than or equal to 750 psi, or greater than or equal to 1000 psi to 2000 psi, or 3000 psi, or 3500 psi, or 4000 psi, or less than 6000 psi, as measured in accordance with ASTM D790.

(14) Suitable polyolefins in accordance with the present disclosure include but are not limited to those available as ENGAGE polyolefin elastomers and INFUSE olefin block copolymers from The Dow Chemical Company, those available as Exact plastomers from ExxonMobil Chemical Company, and those available as LUCENE polyolefins from LG Chemical.

(15) Blends of any of the polyolefins described above may also be used, so long as the volume resistivity of the blend is less than 4.0E+15 ohm.Math.cm. The polyolefin or blends thereof may be blended or diluted with one or more other polymers to the extent that the polyolefin(s) and other polymer(s) are (i) miscible with one another, (ii) the other polymer(s) have little, if any, impact on the desirable properties of the polyolefin (i.e., optics and low modulus), and (iii) the content of polyolefin(s) constitute greater than 50 wt %, or 60 wt %, or 70 wt %, or 75 wt %, or 80 wt % to 90 wt %, or 95 wt %, or 98 wt %, or 99 wt %, or less than 100 wt % of the blend based on the total weight of the blend.

(16) The polyolefin of the present disclosure may be any combination of embodiments disclosed herein.

(17) Fumed Alumina

(18) The fumed alumina (aluminum oxide) is a type of synthetic alumina. As a synthetic alumina, the fumed alumina of the present disclosure has a high degree of chemical purity and a high specific surface area. In further embodiments, the fumed alumina may be prepared by flame hydrolysis processes known in the art, such as processes similar to the AEROSIL process. The flame hydrolysis processes for preparing the fumed alumina can be controlled by varying the concentration of the reactants, the flame temperature, and certain dwell times. This will affect the particle size, particle size distribution, specific surface area, and the surface properties of the fumed alumina products. In other words, different fumed alumina products can be made depending on how the process is controlled.

(19) The fumed alumina particles prepared by flame hydrolysis processes are by nature hydrophilic unless specifically treated. To form hydrophobic fumed alumina particles, the hydrophilic fumed alumina particles are subjected to chemical post-treatment with a hydrophobic agent. Suitable hydrophobic agents include but are not limited to organosilane compounds, such as alkoxysilanes, silazanes, and siloxanes. The term hydrophobic-treated fumed alumina, as used herein, is fumed alumina in particle form, with a hydrophobic agent bonded to the particle surface by way of one or more oxygen covalent bonds.

(20) In certain embodiments, the fumed alumina of the present disclosure is hydrophilic fumed alumina. In further embodiments, the fumed alumina of the present disclosure is hydrophobic-treated fumed alumina. The fumed alumina of the present disclosure may be in the thermodynamically stable alpha form or the metastable gamma form, including the gamma, delta, and theta forms.

(21) In certain embodiments, the fumed alumina has a specific surface area (BET) from greater than 50 m.sup.2/g to less than 200 m.sup.2/g. In certain embodiments, the fumed alumina has a specific surface area (BET) from 55 m.sup.2/g to 150 m.sup.2/g, or from 60 m.sup.2/g to 140 m.sup.2/g, or from 65 m.sup.2/g to 130 m.sup.2/g. in further embodiments, the fumed alumina has a specific surface area (BET) of 55 m.sup.2/g, or 60 m.sup.2/g, or 65 m.sup.2/g, or 70 m.sup.2/g, or 75 m.sup.2/g, or 80 m.sup.2/g, or 85 m.sup.2/g to 95 m.sup.2/g, or 100 m.sup.2/g, or 105 m.sup.2/g, or 110 m.sup.2/g, or 115 m.sup.2/g, or 120 m.sup.2/g, or 130 m.sup.2/g, or 140 m.sup.2/g, or 150 m.sup.2/g, or less than 200 m.sup.2/g.

(22) Non-limiting examples of hydrophilic fumed alumina are those available as AEROXIDE Alu 65 and Alu 130 from Evonik Industries. Non-limiting examples of hydrophobic-treated fumed alumina are those available as AEROXIDE Alu C from Evonik Industries.

(23) The fumed alumina of the present disclosure may be a blend of a hydrophilic fumed alumina and a hydrophobic-treated fumed alumina or may be blend of more than hydrophilic fumed alumina.

(24) The fumed alumina of the present disclosure may be any combination of embodiments disclosed herein.

(25) Organic Peroxide

(26) The organic peroxide is a molecule containing carbon atoms, hydrogen atoms, and two or more oxygen atoms, and having at least one OO group, such that when there are more than one OO group, each OO group is bonded indirectly to another OO group via one or more carbon atoms, or collection of such molecules. The organic peroxide may be a monoperoxide of formula R.sup.OOOR.sup.O, wherein each R.sup.O independently is a (C.sub.1-C.sub.20)alkyl group or (C.sub.6-C.sub.20)aryl group. Each (C.sub.1-C.sub.20)alkyl group independently is unsubstituted or substituted with 1 or 2 (C.sub.6-C.sub.12)aryl groups. Each (C.sub.6-C.sub.20)aryl group is unsubstituted or substituted with 1 to 4 (C.sub.1-C.sub.10)alkyl groups. Alternatively, the organic peroxide may be a diperoxide of formula R.sup.OOOROOR.sup.O, wherein R is a divalent hydrocarbon group such as a (C.sub.2-C.sub.10)alkylene, (C.sub.3-C.sub.10)cycloalkylene, or phenylene, and each R.sup.O is as defined above. Suitable organic peroxides include but not limited to alkyl peroxides, aryl peroxides, peroxyesters, peroxycarbonates, diacylperoxides, peroxyketals, cyclic peroxides, dialkyl peroxides, peroxy esters, peroxy dicarbonates, or combinations of two or more thereof.

(27) Examples of suitable organic peroxides include but are not limited to dicumyl peroxide; lauryl peroxide; benzoyl peroxide; tertiary butyl perbenzoate; di(tertiary-butyl) peroxide; cumene hydroperoxide; 2,5-dimethyl-2,5-di(t-butyl-peroxy)hexyne-3; 2,-5-di-methyl-2,5-di(t-butyl-peroxy)hexane; tertiary butyl hydroperoxide; isopropyl percarbonate; alpha,alpha-bis(tertiary-butylperoxy)diisopropylbenzene; t-butylperoxy-2-ethylhexyl-monocarbonate; 1,1-bis(t-butylperoxy)-3,5,5-trimethyl cyclohexane; 2,5-dimethyl-2,5-dihydroxyperoxide; t-butylcumylperoxide; alpha,alpha-bis(t-butylperoxy)-p-diisopropyl benzene; bis(1,1-dimethylethyl) peroxide; bis(1,1-dimethylpropyl) peroxide; 2,5-dimethyl-2,5-bis(1,1-dimethylethylperoxy) hexane; 2,5-dimethyl-2,5-bis(1,1-dimethylethylperoxy) hexyne; 4,4-bis(1,1-dimethylethylperoxy) valeric acid; butyl ester; 1,1-bis(1,1-dimethylethylperoxy)-3,3,5-trimethylcyclohexane; benzoyl peroxide; tert-butyl peroxybenzoate; di-tert-amyl peroxide (DTAP); bis(alpha-t-butyl-peroxyisopropyl) benzene

(28) (BIPB); isopropylcumyl t-butyl peroxide; t-butylcumylperoxide; di-t-butyl peroxide; 2,5-bis(tbutylperoxy)-2,5-dimethylhexane; 2,5-bis(t-butylperoxy)-2,5-dimethylhexyne-3,1,1-bis(tbutylperoxy)-3,3,5-trimethylcyclohexane; isopropylcumyl cumylperoxide; butyl 4,4-di(tertbutylperoxy) valerate; di(isopropylcumyl) peroxide; and combinations thereof.

(29) Non-limiting examples of suitable commercially available organic peroxides include TRIGONOX from AkzoNobel and LUPEROX TBEC from ARKEMA.

(30) Silane Coupling Agent

(31) In some embodiments, the silane coupling agent contains at least one alkoxy group. Non-limiting examples of suitable silane coupling agents include -chloropropyl trimethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, vinyl-tris-(-methoxy)silane, allyltrimethoxysilane, -methacryloxypropyl trimethoxysilane, -(3,4-ethoxy-cyclohexyl)ethyl trimethoxysilane, -glycidoxypropyl trimethoxysilane, -mercaptopropyltrimethoxysilane, -aminopropyl trimethoxysilane, N--(aminoethyl)--aminopropyl trimethoxysilane, and 3-(trimethoxysilyl)propylmethacrylate, vinyl triacetoxysilane, -(meth)acryloxy, propyl trimethoxysilane, and combinations thereof.

(32) In some embodiments, the silane coupling agent is vinyl trimethoxysilane (VTMS) or 3-(trimethoxysilyl)propylmethacrylate (VMMS) or allyltrimethoxysilane.

(33) Crosslinking Co-Agent

(34) The crosslinking co-agent can be any one, or a mixture, of co-agents, including, but not limited to, an ester, ether, ketone, cyanurate, isocyanurate, phosphate, ortho formate, aliphatic or aromatic ether containing at least 2, and preferably 3, unsaturated groups such as allyl, vinyl or acrylate. The number of carbon atoms in the co-agent can be in the range of 9 to 40 or more, and is preferably 9 to 20.

(35) Specific examples of co-agents include, but are not limited to, triallyl cyanurate (TAC); triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione also known as triallyl isocyanturate (TAIC); hexaallyl melamine; triallyl phosphate (TAP); triallyl ortho formate; tetra-allyloxy-ethane; triallyl benzene-1,3,5-tricarboxylate; diallyl phthalate; zinc dimethacrylate; ethoxylated bisphenol A dimethacrylate; methacrylate terminated monomer with average chain length of C14 or C15; pentaerythritol tetraacrylate; depentaerythritol pentaacrylate; pentaerythritol triacrylate; dimethylolpropane tetraacrylate; ethoxylated trimethylolpropane triacrylate; trimethylolpropane triacrylate; 2,4,6-triallyl-1,3,5-trione; 2,4-diphentyl-4-methyl-1-pentene; triallyl trimellitate (TATM); 3,9-divinyl-2,4,8,10-tetra-oxaspiro[5.5]undecane (DVS); alpha-methyl styrene dimer (AMSD); and combinations thereof.

(36) In certain embodiments, the crosslinking co-agent may be selected from the group consisting of TAIC, TAC, TAP, vinyl cyclic siloxanes, and combinations thereof.

(37) Additive Component

(38) The curable compositions of the present disclosure may contain one or more additives. Non-limiting examples of suitable additives include other polymers, metal oxides, antioxidants, fillers, UV stabilizers, flame retardants, plasticizers or oils, colorants or pigments, tackifiers, reinforcing agents, fatty acids and salts thereof, ignition resistant additives, scorch inhibitors, stabilizers, blowing agents, lubricants, processing aids, extrusion aids, nucleating agents, scavengers, waxes, curing additives, accelerants, and combinations thereof.

(39) In certain embodiments, the curable compositions of the present disclosure comprises an additive component comprising an antioxidant and/or a UV stabilizer. Accordingly, the additive component may comprise a UV stabilizer. Or, the additive component may comprise an antioxidant. Further, the additive component may comprise an antioxidant and a UV stabilizer.

(40) Non-limiting examples of suitable UV stabilizers include hindered phenols, phophites, hindered amine light stabilizers (HALS), UV absorbers, hindered benzoates, and combinations of these. Suitable UV stabilizers include but are not limited to T770 available from TCI; UV 531 available from TCI; Cynergy A400, A430 and R350; Cyasorb UV-3529; Cyasorb UV-3346; Cyasorb UV-3583; Hostavin N30; Univil 4050; Univin 5050; Chimassorb UV-119; Chimassorb 944 LD; Tinuvin 622 LD; benzophenones, benzotriazoles, triazines, and combinations of these, such as Tinuvin 328 or Cyasorb UV-1164; and the like.

(41) Suitable antioxidants include but are not limited to those selected from the group consisting of Cyanox 2777; Irganox 1010; Irganox 1076; Irganox B215; Irganox B225; PEPQ; Weston 399; TNPP; Irgafos 168; and Devoerphos 9228.

(42) Curable Composition

(43) The present disclosure relates to a curable composition for an encapsulant film, the curable composition comprising: (A) a polyolefin; (B) a fumed alumina; (C) an organic peroxide; (D) a silane coupling agent; (E) a crosslinking co-agent; and, optionally (F) an additive component comprising an antioxidant and/or a UV stabilizer, wherein the polyolefin has a volume resistivity of less than 4.0E+15 ohm.Math.cm.

(44) The (A) polyolefin having a volume resistivity of less than 4.0E+15 ohm.Math.cm may be present in the curable composition in an amount from 80 wt % to 99 wt %, or from 85 wt % to 99 wt %, or from 90 wt % to 99 wt %, or from 95 wt % to 99 wt %, based on the total weight of the curable composition.

(45) The (B) fumed alumina may be present in the curable composition in an amount from 0.01 wt % to 5 wt %, or from 0.05 to 2 wt %, or from 0.1 wt % to 1 wt %, or from 0.25 wt % to 1 wt %, based on the total weight of the curable composition.

(46) The (C) organic peroxide may be present in the curable composition in an amount from 0.1 wt % to 5 wt %, or from 0.1 wt % to 3 wt %, or from 0.5 wt % to 2 wt %, based on the total weight of the curable composition.

(47) The (D) silane coupling agent may be present in the curable composition in an amount from 0.01 wt % to 2 wt %, or from 0.05 wt % to 1 wt %, or from 0.1 wt % to 0.5 wt %, based on the total weight of the curable composition.

(48) The (E) crosslinking co-agent may be present in the curable composition in an amount from 0.01 wt % to 5 wt %, or from 0.1 wt % to 3 wt %, or from 0.2 wt % to 1 wt %, based on the total weight of the curable composition.

(49) The (F) additive component comprising an antioxidant and/or a UV stabilizer may be present in the curable composition in an amount from 0 wt % to 5 wt %, or from 0 wt % to 3 wt %, or from 0 wt % to 1 wt %, or from 0.01 wt % to 1 wt %, based on the total weight of the curable composition.

(50) In certain embodiments, the curable composition of the present disclosure may further comprise one or more polymers other than the (A) polyolefin. That is, the (A) polyolefin may blended with one or more polymers. Accordingly, the curable composition of the present disclosure (as well as the crosslinked polymer composition comprising the reaction product of the curable composition) may further comprise one or more polymers, including but not limited to unsaturated polyolefins (another EPDM, polybutadiene, etc.), saturated polyolefins (PE, PP, ethylene/alpha-olefin interpolymers, propylene/alpha-olefin interpolymers, olefin block copolymers, etc.), other elastomers (SBCs, PVC, EVA, etc.) and other engineering thermoplastics (styrenics, polyamides, polyesters, etc.).

(51) In certain embodiments, the polyolefin is not blended with other polymers. In certain embodiments, the curable composition is absent (or does not comprise of) any polymers other than the (A) polyolefin.

(52) The curable composition of the present disclosure may be cured to form a crosslinked polymeric composition. The crosslinked polymeric composition is the reaction product of the curable composition that results from curing.

(53) In some embodiments, the crosslinked polymeric composition has, in accordance with the methods disclosed herein or similar methods, a volume resistivity greater than 1.0E+15 ohm.Math.cm, or greater than 5.0E+15 ohm.Math.cm, or greater than or equal to 9.0E+15 ohm.Math.cm, or greater than or equal to 1.0E+16 ohm.Math.cm, or greater than or equal to 2.0E+16 ohm.Math.cm, or greater than or equal to 5.0E+16 ohm.Math.cm, or greater than or equal to 8.0E+16 ohm.Math.cm, or greater than or equal to 1.0E+17 ohm.Math.cm, or greater than or equal to 5.0E+17 ohm.Math.cm, or greater than or equal to 1.0E+18 ohm.Math.cm, or greater than or equal to 1.0E+19 ohm.Math.cm.

(54) In further embodiments, the crosslinked polymeric composition has, in accordance with the methods disclosed herein or similar methods, a volume resistivity from 1.0E+15 ohm.Math.cm, or 5.0E+15 ohm.Math.cm, or 9.0E+15 ohm.Math.cm to 1.0E+16 ohm.Math.cm, or 2.0E+16 ohm.Math.cm, or 5.0E+16 ohm.Math.cm, or 8.0E+16 ohm.Math.cm, or 9.0E+16 ohm.Math.cm, or 1.0E+17 ohm.Math.cm, or 5.0E+17 ohm.com, or 1.0E+18 ohm.Math.cm, or 1.0E+19 ohm.Math.cm. For example, in certain embodiments, the crosslinked polymeric composition has a volume resistivity from greater than 1.0E+15 ohm.Math.cm to 1.0E+19 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 1.0E+18 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 5.0E+17 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 1.0E+17 ohm.Math.cm, or from greater than 5.0E+15 ohm.Math.cm to 1.0E+17, or from greater than 9.0E+15 ohm.Math.cm to 9.0E+16 ohm.Math.cm.

(55) Each of the curable composition and the crosslinked polymeric composition may have any combination of embodiments described herein.

(56) Encapsulant Films or Film Layers

(57) The present disclosure provides an encapsulant film or film layer that may be incorporated in an electronic device, such as a PV module. The encapsulant film or film layer is made from the curable composition or crosslinked polymeric composition described herein. In certain embodiments, the present disclosure relates to an encapsulant film or film layer comprising a crosslinked polymeric composition that is the reaction product of a curable composition comprising: (A) a polyolefin; (B) a fumed alumina; (C) an organic peroxide; (D) a silane coupling agent; (E) a crosslinking co-agent; and, optionally (F) an additive component comprising an antioxidant and/or a UV stabilizer, wherein the polyolefin has a volume resistivity of less than 4.0E+15 ohm.Math.cm. In certain embodiments, the encapsulant film or film layer is the crosslinked polymeric composition.

(58) In further embodiments, the present disclosure relates to an encapsulant film or film layer comprising a crosslinked polymeric composition that is the reaction product of a curable composition comprising: (A) from 80 wt % to 99 wt %, or from 85 wt % to 99 wt %, or from 90 wt % to 99 wt %, or from 95 wt % to 99 wt % of a polyolefin having a volume resistivity of less than 4.0E+15 ohm.Math.cm, based on the total weight of the curable composition; (B) from 0.01 wt % to 5 wt %, or from 0.05 to 2 wt %, or from 0.1 wt % to 1 wt %, or from 0.25 wt % to 1 wt % of a fumed alumina, based on the total weight of the curable composition; (C) from 0.1 wt % to 5 wt %, or from 0.1 wt % to 3 wt %, or from 0.5 wt % to 2 wt % of an organic peroxide, based on the total weight of the curable composition; (D) from 0.01 wt % to 2 wt %, or from 0.05 wt % to 1 wt %, or from 0.1 wt % to 0.5 wt % of a silane coupling agent, based on the total weight of the curable composition; (E) from 0.01 wt % to 5 wt %, or from 0.1 wt % to 3 wt %, or from 0.2 wt % to 1 wt % of a crosslinking co-agent, based on the total weight of the curable composition; and (F) from 0 wt % to 5 wt %, or from 0 wt % to 3 wt %, or from 0 wt % to 1 wt %, or from 0.01 wt % to 1 wt % of an additive component comprising an antioxidant and/or a UV stabilizer, based on the total weight of the curable composition.

(59) The encapsulant film or film layer may be formed by any means known in the art. In some embodiments, the encapsulant film or film layer is prepared by extruding some or all components of the curable composition via various types of mixers or extruders, such as single or twin screw types, followed by curing or crosslinking during molding and/or lamination. A typical extruder has a hopper at its upstream end and a die at its downstream end. Components of the curable composition may be fed to the hopper, and then melted and extruded at a temperature less than 120 C. so as to not initiate curing or crosslinking. In certain embodiments, extrusion may be performed at a temperature from 85 C. to 115 C. at a rotor speed from 20 rpm to 40 rpm.

(60) The components (A) to (F) of the curable composition may be added to or combined with each other in any order prior to curing or crosslinking. For example, components (B) to (F) may each be gradually added to the (A) polyolefin in an extruder. In some embodiments, the (A) polyolefin may be soaked with components (C) to (E) prior to extrusion during which the other components may be added. In further embodiments, the (A) polyolefin may be mixed or extruded with components (B) and (F) followed by soaking with components (C) to (E).

(61) It is desirable to avoid or limit curing or crosslinking of the curable composition until the steps following extrusion. Premature curing or crosslinking may result in the encapsulant film or film layer having decreased glass adhesion. Accordingly, in certain embodiments, curing or crosslinking the curable composition occurs after extrusion and during molding and/or lamination at elevated temperatures (such as greater than 120 C. to 160 C.). In other words, the encapsulant film remains active until molding and/or lamination, at which point curing or crosslinking is initiated resulting in the encapsulant film or film layer comprising a crosslinked polymeric composition which is the reaction product of a curable composition comprising: (A) a polyolefin having a volume resistivity of less than 4.0E+15 ohm.Math.cm; (B) a fumed alumina; (C) an organic peroxide; (D) a silane coupling agent; (E) a crosslinking co-agent; and, optionally (F) an additive component comprising an antioxidant and/or a UV stabilizer.

(62) The encapsulant film or film layer may have any thickness that is suitable for its inclusion in an electronic device, such as a PV module. In certain embodiments, the encapsulant film or film layer has a thickness from 100 m, or 150 m, or 200 m, or 250 m, or 300 m, or 350 m, or 400 m to 450 m, or 500 m, or 550 m, or 600 m, or 650 m, or 700 m, or 800 m.

(63) In some embodiments, the encapsulant film or film layer of the present disclosure has, in accordance with the methods disclosed herein or similar methods, a volume resistivity of greater than 1.0E+15 ohm.Math.cm, or greater than 5.0E+15 ohm.Math.cm, or greater than or equal to 9.0E+15 ohm.Math.cm, or greater than or equal to 1.0E+16 ohm.Math.cm, or greater than or equal to 2.0E+16 ohm.Math.cm, or greater than or equal to 5.0E+16 ohm.Math.cm, or greater than or equal to 8.0E+16 ohm.Math.cm, or greater than or equal to 1.0E+17 ohm.Math.cm, or greater than or equal to 5.0E+17 ohm.Math.cm, or greater than or equal to 1.0E+18 ohm.Math.cm, or greater than or equal to 1.0E+19 ohm.Math.cm.

(64) In further embodiments, the encapsulant film or film layer of the present disclosure has, in accordance with the methods disclosed herein or similar methods, a volume resistivity from 1.0E+15 ohm.Math.cm, or 5.0E+15 ohm.Math.cm, or 9.0E+15 ohm.Math.cm to 1.0E+16 ohm.Math.cm, or 2.0E+16 ohm.Math.cm, or 5.0E+16 ohm.Math.cm, or 8.0E+16 ohm.Math.cm, or 9.0E+16 ohm.Math.cm, or 1.0E+17 ohm.Math.cm, or 5.0E+17 ohm.Math.com, or 1.0E+18 ohm.Math.cm, or 1.0E+19 ohm.Math.cm. For example, the encapsulant film or film layer has a volume resistivity from greater than 1.0E+15 ohm.Math.cm to 1.0E+19 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 1.0E+18 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 5.0E+17 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 1.0E+17 ohm.Math.cm, or from greater than 5.0E+15 ohm.Math.cm to 1.0E+17, or from greater than 9.0E+15 ohm.Math.cm to 9.0E+16 ohm.Math.cm.

(65) In certain embodiments, the encapsulant film or film layer of the present disclosure has a maximum torque (MH) greater than or equal to 2.0 dNm, or greater than or equal to 2.5 dNm, or greater than or equal to 3.0 dNm, or greater than or equal to 3.5 dNm, or greater than or equal to 3.6 dNm, or greater than or equal to 3.7 dNm.

(66) In further embodiments, the encapsulant film or film layer has a t90 less than 15 minutes, or less than 13 minutes, or less than 11 minutes, or less than 10.9 minutes, or less than or equal to 10.8 minutes, or less than or equal to 10.7 minutes.

(67) In some embodiments, the encapsulant film or film layer has an initial glass adhesion greater than 100 N/cm, or greater than 110 N/cm, or greater than 120 N/cm, or greater than 130 N/cm, or greater than 140 N/cm, or greater than 145 N/cm, or greater than or equal to 146 N/cm, or greater than or equal to 149 N/cm, or greater than or equal to 150 N/cm. In certain embodiments, the encapsulant film or film layer has, in accordance with the methods disclosed herein or similar methods, an initial glass adhesion from greater than 100 N/cm to 200 N/cm, or from greater than 100 N/cm to 180 N/cm, or from greater than 100 N/cm to 160 N/cm, or from greater than 120 N/cm to 160 N/cm, or from greater than 130 N/cm to 150 N/cm.

(68) In certain embodiments, the encapsulant film or film layer has, in accordance with the methods disclosed herein or similar methods, a mean transmittance greater than or equal to 88%, or greater than or equal to 88.5%, or greater than or equal to 89%, or greater than or equal to 89.5%, or greater than or equal to 90%.

(69) The encapsulant film or film layer of the present disclosure may be any combination of embodiments disclosed herein.

(70) Electronic Device

(71) The encapsulant film of the present disclosure may be incorporated in the construction of an electronic device, such as a PV module. The encapsulant film may be used as one or more layers for a PV module. The encapsulant film may be applied to one or both face surfaces of an electronic device, e.g., as a front encapsulant film or rear encapsulant film, or as both the front encapsulant film and the rear encapsulant film, e.g., in which the electronic device is totally enclosed within the material.

(72) A photovoltaic module or PV module is a laminated structure that may include the following layer components but is not limited in such way: 1. Light receiving and transmitting layer; 2. A front encapsulant film layer (transparent); 3. One or more photovoltaic cell; 4. A rear encapsulant film layer; and 5. A backseet.

(73) In an embodiment, the light receiving and transmitting layer is glass, acrylic resin, polycarbonate, polyester or fluorine-containing resin. In an embodiment, the light receiving and transmitting layer is glass.

(74) The number of photovoltaic cells in a given photovoltaic module will vary depending on the nature and use of the electronic device utilizing the photovoltaic module. In an embodiment, at least one photovoltaic cell is in direct contact with the front encapsulant film layer and rear encapsulant film layer.

(75) In an embodiment, the backsheet is a polymer backsheet or a glass backsheet.

(76) The layers (1)-(5) of the PV module with laminated structure described above are bonded through lamination. Through lamination, the top sheet is brought into direct contact with the front encapsulant film layer, and the backsheet is brought into direct contact with the rear encapsulant film layer. The photovoltaic cells are secured between, and in direct contact with, the front encapsulant film layer and the rear encapsulant film layer. As a result, portions of the front encapsulant film and the rear encapsulant film are in direct contact with each other.

(77) In an embodiment, the present disclosure provides a PV module. The PV module includes an encapsulant film layer of the present disclosure. The film layer of the present disclosure can be a front encapsulant film layer, a rear encapsulant film layer, a backsheet film layer, and combinations thereof. In other embodiments, the present film layer can be the entire film, or are or more discrete sublayers of a film.

(78) In an embodiment, both the front encapsulant film layer and the rear encapsulant film layer are film layers as disclosed herein. Each of the front encapsulant film layer and the rear encapsulant film layer directly contact the photovoltaic cell. A portion of the front encapsulant film layer also directly contacts a portion of the rear encapsulant film layer. The front encapsulant film layer and the rear encapsulant film layer can be as previously described.

(79) In an embodiment, the film layer(s) comprising the compositions of this disclosure are applied to an electronic device by one or more lamination techniques. Through lamination, the cover sheet is brought in direct contact with a first facial surface of the encapsulant film layer, and the electronic device is brought in direct contact with a second facial surface of the encapsulant film layer. In another embodiment, the cover sheet is brought into direct contact with a first facial surface of the front encapsulant film layer, the back sheet is brought in direct contact with a second facial surface of the rear encapsulant film layer, and the electronic device(s) is secured between, and in direct contact with the second facial surface of the front encapsulant film layer and the first facial surface of the rear encapsulant film layer.

(80) In an embodiment, the lamination temperature is sufficient to activate the organic peroxide and crosslink the curable composition, that is, the curable composition comprising (A) a polyolefin having a volume resistivity less than 4.0E+15 ohm.Math.cm, (B) a fumed alumina, (C) an organic peroxide, (D) a silane coupling agent, (E) a crosslinking co-agent, and, optionally, (F) an additive component comprising an antioxidant and/or a UV stabilizer, such as disclosed herein remains reactive until lamination when crosslinking occurs. After lamination, the crosslinked polymeric composition is formed as a reaction product of the curable composition comprising (A) a polyolefin having a volume resistivity less than 4.0E+15 ohm.Math.cm, (B) a fumed alumina, (C) an organic peroxide, (D) a silane coupling agent, (E) a crosslinking co-agent, and, optionally, (F) an additive component comprising an antioxidant and/or a UV stabilizer.

(81) In an embodiment, the lamination temperature for producing an electronic device is from 130 C., or 135 C., or 140 C., or 145 C. to 150 C., or 155 C., or 160 C. In an embodiment, the lamination time is from 8 minutes, or 10 minutes, or 12 minutes, or 15 minutes to 18 minutes, or 20 minutes, or 22 minutes, or 25 minutes.

(82) Specific embodiments of the present disclosure include but are not limited to the following:

(83) 1. A curable composition for an encapsulant film, the curable composition comprising: (A) a polyolefin; (B) a fumed alumina; (C) an organic peroxide; (D) a silane coupling agent; (E) a crosslinking co-agent; and, optionally, (F) an additive component comprising an antioxidant and/or a UV stabilizer, wherein the polyolefin has a volume resistivity of less than 4.0E+15 ohm.Math.cm.

(84) 2. The curable composition of embodiment 1, wherein the curable composition comprises: (A) from 80 wt % to 99 wt %, or from 85 wt % to 99 wt %, or from 90 wt % to 99 wt %, or from 95 wt % to 99 wt % of the polyolefin, based on the total weight of the curable composition; (B) from 0.01 wt % to 5 wt %, or from 0.05 to 2 wt %, or from 0.1 wt % to 1 wt %, or from 0.25 wt % to 1 wt % of the fumed alumina, based on the total weight of the curable composition; (C) from 0.1 wt % to 5 wt %, or from 0.1 wt % to 3 wt %, or from 0.5 wt % to 2 wt % of the organic peroxide, based on the total weight of the curable composition; (D) from 0.01 wt % to 2 wt %, or from 0.05 wt % to 1 wt %, or from 0.1 wt % to 0.5 wt % of the silane coupling agent, based on the total weight of the curable composition; (E) from 0.01 wt % to 5 wt %, or from 0.1 wt % to 3 wt %, or from 0.2 wt % to 1 wt %, based on the total weight of the curable composition; and (F) from 0 wt % to 5 wt %, or from 0 wt % to 3 wt %, or from 0 wt % to 1 wt %, or from 0.01 wt % to 1 wt % of a UV stabilizer, based on the total weight of the curable composition.

(85) 3. The curable composition of embodiment 1 or 2, wherein the polyolefin has a volume resistivity from greater than 1.0E+12 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than 5.0E+12 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than 1.0E+13 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than 5.0E+13 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than or equal to 1.0E+14 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than or equal to 5.0E+14 ohm.Math.cm to less than 4.0E+15 ohm.Math.cm, or from greater than or equal to 5.0E+14 ohm.Math.cm to less than or equal to 3.5E+15 ohm.Math.cm, or from greater than or equal to 7.0E+14 ohm.Math.cm to less than or equal to 3.0E+15 ohm.Math.cm.

(86) 4. The curable composition of any of the previous embodiments, wherein the polyolefin has a density from 0.850 g/cc to 0.920 g/cc, or from 0.855 g/cc to 0.910 g/cc, or from 0.860 g/cc to 0.900 g/cc, or from 0.860 g/cc to 0.895 g/cc, or from 0.860 g/cc to 0.890 g/cc, or from 0.865 g/cc to 0.885 g/cc, or from 0.865 g/cc to 0.880 g/cc, as measured in accordance with ASTM D792, Method B.

(87) 5. The curable composition of any of the previous embodiments, wherein the polyolefin has a melt index from 0.1 g/10 min to 100 g/10 min, or from 0.5 g/10 min to 100 g/10 min, or from 1 g/10 min to 100 g/10 min, or from 1 g/10 min to 75 g/10 min, or from 1 g/10 min to 50 g/10 min, or from 1 g/10 min to 30 g/10 min, or from 5 g/10 min to 30 g/10 min, or from 5 g/10 min to 20 g/10 min, as measured in accordance with ASTM D1238, at 190 C./2.16 kg.

(88) 6. The curable composition of any of the previous embodiments, wherein the polyolefin has a melting point (Tm) from 55 C., or 60 C., or 75 C., or 90 C., or 95 C., or 100 C. to 105 C., or 110 C., as measured using DSC.

(89) 7. The curable composition of any of the previous embodiments, wherein the polyolefin has a glass transition temperature, Tg, from 30 C., or 35 C. to 40 C., or 45 C., or 50 C., or 60 C., as measured using DSC.

(90) 8. The curable composition of any of the previous embodiments, wherein the polyolefin has a flexural modulus (2% secant) from greater than or equal to 500 psi, or greater than or equal to 750 psi, or greater than or equal to 1000 psi to 2000 psi, or 3000 psi, or 3500 psi, or 4000 psi, or less than 6000 psi, as measured in accordance with ASTM D790.

(91) 9. The curable composition of any of the previous embodiments, wherein the polyolefin is an ethylene/alpha-olefin interpolymer.

(92) 10. The curable composition of any of the previous embodiments, wherein the polyolefin is an ethylene/alpha-olefin copolymer.

(93) 11. The curable composition of any of the previous embodiments, wherein the polyolefin is an ethylene/alpha-olefin random copolymer.

(94) 12. The curable composition of any of the previous embodiments, wherein the polyolefin is an ethylene/1-octene copolymer.

(95) 13. The curable composition of any of the previous embodiments, wherein the fumed alumina is hydrophilic.

(96) 14. The curable composition of any of the previous embodiments, wherein the fumed alumina has a specific surface area (BET) from greater than 50 m.sup.2/g to less than 200 m.sup.2/g, or from 55 m.sup.2/g to 150 m.sup.2/g, or from 60 m.sup.2/g to 140 m.sup.2/g, or from 65 m.sup.2/g to 130 m.sup.2/g.

(97) 15. The curable composition of any of the previous embodiments, wherein the organic peroxide is selected from the group consisting of tert-Butylperoxy 2-ethylhexyl carbonate, dicumyl peroxide, lauryl peroxide, benzoyl peroxide, tertiary butyl perbenzoate, di(tertiary-butyl) peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butyl-peroxy)hexyne-3, 2,-5-di-methyl-2,5-di(t-butyl-peroxy)hexane, tertiary butyl hydroperoxide, isopropyl percarbonate, alpha,alpha-bis(tertiary-butylperoxy)diisopropylbenzene, 1,1-bis(t-butylperoxy)-3,5,5-trimethyl cyclohexane, 2,5-dimethyl-2,5-dihydroxyperoxide, t-butylcumylperoxide, alpha,alpha-bis(t-butylperoxy)-p-diisopropyl benzene, and combinations thereof.

(98) 16. The curable composition of any of the previous embodiments, wherein the silane coupling agent is selected from the group consisting of 3-(trimethoxysilyl)propylmethacrylate, vinyl trimethoxysilane, allyltrimethoxysilane, and combinations thereof.

(99) 17. The curable composition of any of the previous embodiments, wherein the cross-linking co-agent is selected from the group consisting of triallyl isocyanurate, triaryl cyanurate, triallyl phosphate, and combinations thereof.

(100) 18. An encapsulant film comprising a crosslinked polymeric composition that is the reaction product of the curable composition of any of the previous embodiments.

(101) 19. An encapsulant film comprising the curable composition of any of embodiments 1-17.

(102) 20. An encapsulant film comprising the reaction product of the curable composition of any embodiments 1-17.

(103) 21. The encapsulant film of any of embodiments 18-20, wherein the encapsulant film has a volume resistivity greater than 1.0E+15 ohm.Math.cm, or greater than 5.0E+15 ohm.Math.cm, or greater than or equal to 9.0E+15 ohm.Math.cm, or greater than or equal to 1.0E+16 ohm.Math.cm, or greater than or equal to 2.0E+16 ohm.Math.cm, or greater than or equal to 5.0E+16 ohm.Math.cm, or greater than or equal to 8.0E+16 ohm.Math.cm, or greater than or equal to 1.0E+17 ohm.Math.cm, or greater than or equal to 5.0E+17 ohm.Math.cm, or greater than or equal to 1.0E+18 ohm.Math.cm, or greater than or equal to 1.0E+19 ohm.Math.cm.

(104) 22. The encapsulant film of any of embodiments 18-21, wherein the encapsulant film has a volume resistivity from greater than 1.0E+15 ohm.Math.cm to 1.0E+19 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 1.0E+18 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 5.0E+17 ohm.Math.cm, or from greater than 1.0E+15 ohm.Math.cm to 1.0E+17 ohm.Math.cm, or from greater than 5.0E+15 ohm.Math.cm to 1.0E+17, or from greater than 9.0E+15 ohm.Math.cm to 9.0E+16 ohm.Math.cm.

(105) 23. The encapsulant film of any of embodiments 18-22, wherein the encapsulant film has a maximum torque (MH) greater than or equal to 2.0 dNm, or greater than or equal to 2.5 dNm, or greater than or equal to 3.0 dNm, or greater than or equal to 3.5 dNm, or greater than or equal to 3.6 dNm, or greater than or equal to 3.7 dNm.

(106) 24. The encapsulant film of any of embodiments 18-23, wherein the encapsulant film has has a t90 less than 15 minutes, or less than 13 minutes, or less than 11 minutes, or less than 10.9 minutes, or less than or equal to 10.8 minutes, or less than or equal to 10.7 minutes.

(107) 25. The encapsulant film of any of embodiments 18-24, wherein the encapsulant film has an initial glass adhesion from greater than 100 N/cm to 200 N/cm, or from greater than 120 N/cm to 180 N/cm, or from greater than 130 N/cm to 170 N/cm, or from greater than 130 N/cm to 150 N/cm, or greater than 100 N/cm, or greater than 110 N/cm, or greater than 120 N/cm, or greater than 130 N/cm, or greater than 140 N/cm, or greater than 145 N/cm, or greater than or equal to 146 N/cm, or greater than or equal to 149 N/cm, or greater than or equal to 150 N/cm.

(108) 26. The encapsulant film of any of embodiments 18 to 25, wherein the encapsulant film has a mean transmittance greater than or equal to 88%, or greater than or equal to 88.5%, or greater than or equal to 89%, or greater than or equal to 89.5%, or greater than or equal to 90%.

(109) 27. A PV module comprising a solar cell and the encapsulant film of any of embodiments 18-26.

(110) 28. A PV module comprising a solar cell and at least one layer that is the encapsulant film of any of embodiments 18-26.

EXAMPLES

(111) Materials

(112) The materials used in the following examples are described below.

(113) POE 1: An ethylene/1-octene copolymer that is available as ENGAGE 8411 from The Dow Chemical Company and has: a density of 0.880 g/cc (ASTM D792); a melt index of 18.0 g/10 min (ASTM D1238 at 190 C./2.16 kg); a Tm of 76 C.; and a 2% secant=20.5 Mpa. POE 1 used herein (and available upon request from The Dow Chemical Company) has a volume resistivity of 1.0E+15 ohm.Math.cm, in accordance with the methods disclosed herein.

(114) POE A: An ethylene/1-octene copolymer that is available from The Dow Chemical Company and has: a density of 0.880 g/cc (ASTM D792) and a melt index of 18.0 g/10 min (ASTM D1238 at 190 C./2.16 kg); a Tm of 76 C.; and a 2% secant=20.5 Mpa and a volume resistivity of 4.0E+16 ohm.Math.cm in accordance with the methods disclosed herein.

(115) Peroxide: Tert-Butylperoxy 2-ethylhexyl carbonate (TBEC) available from J&K Scientific Ltd.

(116) Coagent: Triallyl isocyanurate (TAIC) available from Fangruida Chemicals Co., Ltd.

(117) Alumina 1: Fumed alumina available as Aeroxide Alu 130 from Evonik Industries.

(118) Alumina 2: Fumed alumina available as Aeroxide Alu 65 from Evonik Industries.

(119) Silica: A fumed silica available as Aerosil R812S from Evonik Industries.

(120) UV Stabilizer: Bis(2,2,6,6-tetramethyl-4-piperidyl) Sebacate available as T770 from TCI.

(121) Silane Coupling Agent (Silane): 3-(trimethoxysilyl)propylmethacrylate available as VMMS from Dow Corning.

(122) Sample Preparation

(123) Each of the comparative samples (CS1 to CS6) and inventive examples (IE1 to IE4) are prepared as described below and in accordance with the formulations of Table 1.

(124) Ethylene/1-octene copolymer pellets are fed into a Brabender mixer at a temperature of 130 C. with a rotor speed of 10 rpm. Fumed alumina or fumed silica (depending on the formulations of Table 1) are then added. The final mixing is conducted at 130 C. and a rotor speed of 80 rpm for 5 minutes. The resulting compound is collected and cut into small pieces.

(125) The small pieces of ethylene/l-octene copolymer and alumina/silica (or, if no alumina or silica is added, just ethylene/1-octene copolymer) are fed into the hopper of a Brabender single extruder. The small pieces are extruded to melt stand at 110 C. with a screw speed of 25 rpm. The melt strand is fed into the Brabender pelletizer to prepare pellets.

(126) The silane coupling agent, organic peroxide, co-agent, and any additional additives, such as UV stabilizer and/or antioxidant, are weighed and mixed in a sealable plastic bottle in accordance with Table 1, below. The pellets are weighed in accordance with Table 1 and added to the plastic bottle. To ensure a homogenous distribution, and complete soaking, the plastic bottle was first tumbled for 1 minute and then placed on a running roller for further homogenization in an oven at 40 C. for 15-20 hours before using.

(127) Film Preparation

(128) After soaking, the pellets are fed into a Brabender single screw mixer at 105 C. with a rotor speed of 30 rpm. Films with a thickness of approximately 0.5 mm are prepared and stored in sealed aluminum foil bags for testing.

(129) Compression Molding

(130) Cast films are compression molded into a 0.5 mm film. The samples are placed in a mold, preheated to 120 C. for 5 minutes, and then degassed via 8 cycles of pressure loading/releasing. The degassed samples are then pressed at 150 C. for 15 minutes and cooled to room temperature. The compression molded sheets are used for the volume resistivity and transmittance tests.

(131) Lamination

(132) 46 glass plates are cleaned using water and dried before use. The backsheets are cut into four 6-inch squares. The film samples are cut into pieces to fit the size of the glass and backsheet. The backsheet, film samples, and glass are layered together to form a backsheet/film sample/glass structure and then laminated on a PENERGY L036 laminator at 150 C. for 20 minutes (4 minutes of vacuum and 16 minutes pressing). The laminated samples are used for the glass adhesion test.

(133) TABLE-US-00001 TABLE 1 Component CE1 CE2 CE3 IE1 IE2 IE3 IE4 CE4 CE5 CE6 Sample Compositions (wt %) POE 1 98.18 97.18 97.93 97.68 97.18 97.18 POE A 98.18 97.93 97.68 97.18 Peroxide 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Silane 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 Coagent 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 UV Stabilizer 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 0.07 Alumina 1 0.25 0.5 1.0 0.25 0.5 1.0 Alumina 2 1.0 Silica 1.0 Total (wt %) 100 100 100 100 100 100 100 100 100 100 Performance Results MH/dNm 3.63 3.05 3.76 3.68 3.66 2.91 2.65 t90/min 11.14 12.7 10.78 10.68 10.66 11.3 11.3 Initial glass adhesion 152.8 147.5 146.4 149.6 153.8 151.9 (N/cm) Mean Transmittance 90.89 91.23 90.08 89.39 88.51 90.60 89.74 88.78 (380-1100 nm)% VR at RT 7.73E+14 8.71E+14 4.28E+17 9.73E+15 2.37E+16 8.09E+16 1.50E+16 1.30E+18 1.20E+18 7.43E+17 (ohm .Math. cm)

(134) Comparative Example 1 (CE1) is an encapsulant film based on an ethylene/alpha-olefin copolymer having a volume resistivity of 1.0E+15 ohm cm. As seen with Comparative Example 2 (CE2), the addition of fumed silica with the same level of additives does not provide for a significant VR improvement. Similarly, as seen with Comparative Examples 3-6 (CE3 to CE6), the addition of fumed alumina (with the same level of additives) based on an ethylene/alpha-olefin copolymer having a higher VR (a volume resistivity of 4.0E+16 ohm cm) does not provide for significant VR improvement.

(135) In contrast, Inventive Examples 1-4 (IE1 to IE4) surprisingly show that the addition of fumed alumina with the same level of additives provide for significant VR improvement while maintaining other key properties, such as good curing performance and good adhesion performance Indeed, IE1 to IE4 show a VR improvement by greater than 10 times and even as much as greater than 100 times (2 orders of magnitude) while also maintaining similar or comparable curing and adhesion performance as CE1. This tremendous improvement of VR for a formulation based on an ethylene/alpha-olefin copolymer having a low VR without affecting curing and adhesion is surprising and unexpected.