Patent ID: 8368504

Claim:
A PTC circuit protection device comprising: a PTC polymer material; and two electrodes attached to said PTC polymer material; wherein said PTC polymer material includes a polymer matrix and a particulate conductive filler dispersed in said polymer matrix and having a resistivity less than that of carbon black; wherein said polymer matrix is made from a polymer composition that contains at least a primary polymer unit and a reinforcing polyolefin, said primary polymer unit containing a base polyolefin and optionally a grafted polyolefin, said reinforcing polyolefin having a weight average molecular weight greater than that of said base polyolefin, said primary polymer unit and said reinforcing polyolefin being co-melted together and then solidified to form said polymer matrix; wherein said base polyolefin has a melt flow rate ranging from 10 g/10 min to 100 g/10 min measured according to ASTM D-1238 under a temperature of 230° C. and a load of 12.6 Kg, and said reinforcing polyolefin has a melt flow rate ranging from 0.01 g/10 min to 1 g/10 min measured according to ASTM D-1238 under a temperature of 230° C. and a load of 12.6 Kg; and wherein said primary polymer unit is in an amount ranging from 50 to 95 wt % based on the weight of said polymer composition, and said reinforcing polyolefin is in an amount ranging from 5 to 50 wt % based on the weight of said polymer composition.