Abstract: According to one embodiment, a process for producing unimodal ethylene/?-olefin copolymer, the process comprising contacting ethylene and, optionally, one or more (C3-C12)?-olefin comonomers with a catalyst system in a gas-phase polymerization reactor, wherein the catalyst system comprises a chromium-based catalyst; wherein the unimodal ethylene copolymer comprises: a density from 0.942 g/cm3 to 0.950 g/cm3 according to ASTM D792-13; a flow index (I21) from 5.5 to 7.5 dg/min, when measured according to ASTM D1238 at 190° C. and a 21.6 kg load; a strain hardening modulus of 40 to 50 MPa; and a molecular weight distribution (MWD) as determined by a conventional gel permeation chromatography method or absolute gel permeation chromatography.

Abstract: According to one embodiment, a process for producing a unimodal ethylene/?-olefin copolymer, the process comprising contacting ethylene and one or more (C3-C12) ?-olefin comonomers with a chromium-based catalyst system in a gas-phase polymerization reactor to produce the unimodal ethylene/?-olefin copolymer; wherein the unimodal ethylene/?-olefin copolymer comprises: a density from 0.952 g/cm3 to 0.957 g/cm3; a flow index (I21) from 4.0 to 6.2 dg/min; a melt viscosity ratio (V0.1/V100) at 190° C. of 55 to 75; a molecular weight distribution (MWD) as calculated by the weight average molecular weight (Mw) divided by the number-average molecular weight (Mn) (Mw/Mn); and a peak molecular weight (Mp), all as measured by gel permeation chromatography.

Abstract: Embodiments of the present disclosure are directed towards method for modifying a polymer flow index. As an example, a method for modifying a polymer flow index can include providing monomers to a polymerization reactor, providing a chromium catalyst to the polymerization reactor, and providing an active amount of a flow index modifier to the polymerization reactor, wherein the flow index modifier is selected from carbon dioxide, carbon monoxide, 2,4-hexadiene, and combinations thereof.

Abstract: The present disclosure provides for a system and method for producing a polyethylene polymer (PE) that includes measuring a melt flow index (MFI) of the PE, comparing the measured value of the MFI to a predetermined desired range for the MFI, changing a catalyst feed rate to the polymerization reactor based on the compared values of the MFI, where changes in the catalyst feed rate preemptively compensate for subsequent changes in an oxygen flow rate to the polymerization reactor that maintain a predetermined residence time and bring the MFI of the PE into the predetermined desired range for the MFI; and changing the oxygen flow rate to the polymerization reactor thereby maintaining both the predetermined residence time and bringing the MFI of the PE into the predetermined desired range for the MFI. The measuring and comparing steps are repeated to ensure the measured value of the MFI is within the predetermined desired range of the MFI at the predetermined residence time.

Abstract: Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

Abstract: Embodiments of the present disclosure are directed towards methods for rating polymerization processes based upon a first cracking index value and a second cracking index value.

Abstract: The present disclosure provides for a system and method for producing a polyethylene polymer (PE) that includes measuring a melt flow index (MFI) of the PE, comparing the measured value of the MFI to a predetermined desired range for the MFI, changing a catalyst feed rate to the polymerization reactor based on the compared values of the MFI, where changes in the catalyst feed rate preemptively compensate for subsequent changes in an oxygen flow rate to the polymerization reactor that maintain a predetermined residence time and bring the MFI of the PE into the predetermined desired range for the MFI; and changing the oxygen flow rate to the polymerization reactor thereby maintaining both the predetermined residence time and bringing the MFI of the PE into the predetermined desired range for the MFI. The measuring and comparing steps are repeated to ensure the measured value of the MFI is within the predetermined desired range of the MFI at the predetermined residence time.

Abstract: Embodiments of the present disclosure are directed towards method for modifying a polymer flow index.

Abstract: The present disclosure provides for a system and method for producing a polyethylene polymer (PE) that includes measuring a melt flow index (MFI) of the PE, comparing the measured value of the MFI to a predetermined desired range for the MFI, changing a catalyst feed rate to the polymerization reactor based on the compared values of the MFI, where changes in the catalyst feed rate preemptively compensate for subsequent changes in an oxygen flow rate to the polymerization reactor that maintain a predetermined residence time and bring the MFI of the PE into the predetermined desired range for the MFI; and changing the oxygen flow rate to the polymerization reactor thereby maintaining both the predetermined residence time and bringing the MFI of the PE into the predetermined desired range for the MFI. The measuring and comparing steps are repeated to ensure the measured value of the MFI is within the predetermined desired range of the MFI at the predetermined residence time.

Abstract: Embodiments of the present disclosure are directed towards method for modifying a polymer flow index. As an example, a method for modifying a polymer flow index can include providing monomers to a polymerization reactor, providing a chromium catalyst to the polymerization reactor, and providing an active amount of a flow index modifier to the polymerization reactor, wherein the flow index modifier is selected from carbon dioxide, carbon monoxide, 2,4-hexadiene, and combinations thereof.

Abstract: Embodiments of the present disclosure are directed towards methods for rating polymerization processes based upon a first cracking index (value and a second cracking index value.

Abstract: The present disclosure provides for a system and method for producing a polyethylene polymer (PE) that includes measuring a melt flow index (MFI) of the PE, comparing the measured value of the MFI to a predetermined desired range for the MFI, changing a catalyst feed rate to the polymerization reactor based on the compared values of the MFI, where changes in the catalyst feed rate preemptively compensate for subsequent changes in an oxygen flow rate to the polymerization reactor that maintain a predetermined residence time and bring the MFI of the PE into the predetermined desired range for the MFI; and changing the oxygen flow rate to the polymerization reactor thereby maintaining both the predetermined residence time and bringing the MFI of the PE into the predetermined desired range for the MFI. The measuring and comparing steps are repeated to ensure the measured value of the MFI is within the predetermined desired range of the MFI at the predetermined residence time.

Abstract: Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

Abstract: Embodiments of the present disclosure are directed towards method for modifying a polymer flow index. As an example, a method for modifying a polymer flow index can include providing monomers to a polymerization reactor, providing a chromium catalyst to the polymerization reactor, and providing an active amount of a flow index modifier to the polymerization reactor, wherein the flow index modifier is selected from carbon dioxide, carbon monoxide, 2,4-hexadiene, and combinations thereof.

Abstract: Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

Abstract: Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

Abstract: A semiconductor optical device such as a laser or semiconductor optical amplifier (SOA) based on an indium phosphide substrate or equivalent buffer layer. The active layer of the device is based on conventional InGaAs(P) alloy, but additionally includes N in order to increase the operating wavelength to greater than 1.5 ?m, preferably to a wavelength lying in the C- or L-band. The active layer composition may thus be denoted In1-xGaxAsyNzPp with x?0.48, y?1?z?p, z?0.05, p?0. The active layer may include a quantum well or multi-quantum wells in which case its thickness is preferably less than the critical thickness for lattice relaxation. In other embodiments the active layer is a “massive” layer with quasi-bulk properties. The active layer may advantageously be under tensile stress, preferably roughly between 1% and 2.2%, to manipulate the light and heavy hole bands. The active layer is typically bounded by barrier layers made of a suitable semiconductor alloy, such as AlInAs or InGaAs(P).

Abstract: A semiconductor optical device such as a laser or semiconductor optical amplifier (SOA) based on an indium phosphide substrate or equivalent buffer layer. The active layer of the device is based on conventional InGaAs(P) alloy, but additionally includes N in order to increase the operating wavelength to greater than 1.5 ?m, preferably to a wavelength lying in the C- or L-band. The active layer composition may thus be denoted In1-xGaxAsyNzPp with x?0.48, y?1-z-p, z?0.05, p?0. The active layer may include a quantum well or multi-quantum wells in which case its thickness is preferably less than the critical thickness for lattice relaxation. In other embodiments the active layer is a “massive” layer with quasi-bulk properties. The active layer may advantageously be under tensile stress, preferably roughly between 1% and 2.2%, to manipulate the light and heavy hole bands. The active layer is typically bounded by barrier layers made of a suitable semiconductor alloy, such as AlInAs or InGaAs(P).

Abstract: A process for preparing high density polyethylene in the gas phase comprising contacting a mixture comprising ethylene and one or more alpha-olefins with the supported reaction product of a bis-hydrocarbylsilyl chromate and a hydrocarbylaluminum compound or a hydrocarbyl boron compound in a fluidized bed reactor having a recycle gas line, under particularly defined polymerization conditions, including, but not limited to, the following provisos:(i) oxygen and/or another catalyst poison is introduced into the reactor in the range of about 0.005 to about 0.5 part by volume of catalyst poison per million parts by volume of ethylene; and(ii) a relatively low boiling inert hydrocarbon is introduced into the recycle gas line in an amount sufficient to raise the dew point of the recycle gas, which is comprised of alpha-olefins and other reactor gases, and the recycle gas is partially condensed and recycled to the reactor where it promotes cooling by evaporation.

Abstract: Process for producing a transistor, particularly a heterojunction bipolar transistor, of the type comprising the known stages consisting in producing layers forming the collector, base and emitter, as well as collector, base and emitter ohmic contacts. The emitter producing stage consists in depositing, on the base layer, two superposed layers making up the emitter, the first of which is a thin layer made up of a first material having a large energy gap, and the second made up of a second material also having a high energy gap. The base ohmic contact is deposited on the first layer of the emitter. The invention also relates to the transistors obtained.