Raychem Limited

The Hong Kong University of Science and Technology

Tyco Electronics Corporation

Other

Chi-Ming Chan

Shou-Mean Fang

Daniel A Chandler

Pradeep Barma

Kai-Mo Ng

Ying Kit Cheung

Dennis C Siden

Mark S Thompson

Catherine Yuen-Chien Wong

Michael T Zhang

Nachum Rosenzweig

Manoochehr Mohebban

Vijay K Dhingra

Gregory A Graves

David D Liu

David J Chazan

Edward F Chu

Eugen L Kurjatko

Ann Banich

Michael Mengruo Zhang

Steven Sunshine

Robert Ives

Yongli Mi

Qipeng Cuo

Xiaoya Chen

Catherine Yuen Chien Wong

Jiarui Shen

Zhi Wang

The invention provides a process for preparing an overvoltage protection material comprising:

Overvoltage protection materials and process for preparing same

An electrical device which comprises first and second laminar electrodes and a laminar PTC resistive element sandwiched between them, the device comprising

Electrical devices

The present invention provides a method for creating durable blends of polystyrene and polyolefin. The blends of the present invention have improved mechanical properties evidenced by measurement of impact strength, tensile strength, and elongation at break. Polyolefin is first crosslinked by creating a melt of polyolefin and a small amount of peroxide in a mixer at elevated temperature. The crosslinked polyolefin is then melt-blended with polystyrene at elevated temperature. Finally, a styrene-butadiene-styrene block copolymer is mixed into the melt. The method of the present invention can be applied to various blend systems of otherwise incompatible polymers provided it contains at least one component and a compatibilizer that are crosslinkable.

Stable polymer blends from a two-step crosslinking process

There are disclosed novel composite materials in which polypropylene is reinforced by the inclusion of bamboo fibers. Preferably the polypropylene may be maleated prior to inclusion of the bamboo fibers in order to promote bonding between the bamboo fibers and the polypropylene matrix.

Bamboo fiber reinforced polypropylene composites

A circuit protection device which comprises first and second laminar electrodes; a laminar PTC conductive polymer resistive element sandwiched between the electrodes; a third laminar conductive member which is secured to the same face of the PTC element as the second electrode but is separated therefrom; and an electrical connector which connects the third conductive member and the first electrode. This permits connection to both electrodes from the same side of the device, so that the device can be connected flat on a printed circuit board, with the first electrode on top, without any need for leads. The connector is preferably a cross-conductor which passes through an aperture in the PTC element, because this makes it possible to carry out the steps for preparing the devices on an assembly which corresponds to a number of individual devices, with division of the assembly as the final step.

A conductive polymer composition which has a resistivity of less than 10 ohm-cm and which exhibits PTC behavior comprises a polymeric component and a particulate conductive filler. The polymeric component comprises a first crystalline fluorinated polymer having a first melting point T.sub.m1 and a second crystalline fluorinated polymer having a second melting point T.sub.m2 which is from (T.sub.m1 +25).degree. C. to (T.sub.m1 +100).degree. C. The composition exhibits one of a number of characteristics, including a relatively high PTC anomaly. The composition is useful in circuit protection devices to be used at high ambient conditions.

Electrical device comprising a conductive polymer composition

An electrical device in which a conductive terminal is physically and electrically attached directly or indirectly to a face of a laminar PTC resistive element. The terminal comprises a laminar portion and a non-laminar shaped portion which lies within a projection of the periphery of the PTC resistive element. The shaped portion serves to improve thermal transfer between the PTC element and the atmosphere surrounding the device. Devices of the invention are useful as circuit protection devices.

Electrical device

An electrical device in which a first connection element is in electrical contact with a resistive element. The first connection element defines a cavity into which, when the cavity is empty, a second connection element can be inserted. The second connection element, which may be connected to a source of electrical power, is partially within the cavity, makes physical and electrical contact with the first connection element, and protrudes from the cavity. Such devices can be made in a continuous process by a method of the invention. They are particularly suitable for insertion into a circuit board.

Connection device for resistive elements

A composition which comprises a matrix polymer and, distributed therein, a particulate conductive filler. At least some of the filler particles are composed of a conductive polymer composition and/or the matrix comprises a sintered polymer. The matrix polymer and the filler particles and the method of distributing the particles are such that the particles maintain their identity in the matrix. For example, the particles are preferably highly cross-linked so that they have a hot modulus of at least 250 psi if the composition is prepared by melt extrusion or another process involving a high degree of shear; or a low-shear process such as sintering can be used. Preferably the matrix polymer is capable of coating the filler particles; for example, the matrix polymer and the filler polymer may be chemically similar. The invention is particularly useful for preparing compositions which have high resistivities, eg. 1000 ohm.cm or more, and which can be prepared with a high degree of reproduceability. The compositions can exhibit PTC, ZTC or NTC behavior, depending on the nature of the conductive filler, and their resistivity is dependent on the electric field. The compositions are particularly useful as resistive materials in sheet heaters and as stress-grading materials for high voltage apparatus.

Conductive polymer composition

Growing community of inventors

Hong Kong, China

Chi-Ming Chan