Process for preparing thermally conductive oriented UHMWPE products and products obtained therefrom
The present disclosure relates to a process for preparing of high thermal conductivity and high heat capacity oriented ultrahigh molecular weight polyethylene (UHMWPE) product. The process includes feeding UHMWPE through rollers to obtain a pre-laminate which is further hot stretched to obtain the oriented UHMWPE product having high thermal conductivity and high heat capacity. The temperature of stretching is maintained below the melt temperature of the UHMWPE throughout the entire process. There is also provided a high thermal conductivity and high heat capacity oriented UHMWPE product prepared by the process of the present disclosure. The oriented UHMWPE product is characterized in the axial thermal conductivity in the range of 70 to 200 W/mK, transverse direction thermal conductivity in the range of 0.022 to 0.045 W/mK and heat capacity in the range of 6 to 25 MJ/m 3 K.
1. A process for preparing a high axial thermal conductivity and high heat capacity oriented ultrahigh molecular weight polyethylene (UHMWPE) product; said process comprising the following steps:
a. feeding UHMWPE at the nip of at least one set of first rollers having a first pre-determined roller speed and a first pre-determined temperature to obtain a pre-laminate; and
b. hot stretching said pre-laminate using at least one set of second rollers at a second pre-determined roller speed and a second pre-determined temperature to obtain the oriented UHMWPE product having high thermal conductivity and high heat capacity;
wherein said hot stretching of the pre-laminate is in the range of 10 to 80 mm/minute;
wherein the axial thermal conductivity of the UHMWPE product is in the range of 70 to 200 W/mK;
wherein the heat capacity of the UHMWPE product is in the range of 6 to 25 MJ/m 3 K;
wherein the stretch ratio of the length of the hot stretched product and the pre-laminate is in the range of 30 to 250; and
wherein the molecular weight distribution of said UHMWPE is at least 12.3.
2. The process as claimed in claim 1 , wherein the UHMWPE is disentangled.
3. The process as claimed in claim 1 , wherein the UHMWPE is in the form of one of UHMWPE powder and compressed UHMWPE preform.
4. The process as claimed in claim 1 , wherein said first pre-determined roller speed and second pre-determined roller speed are independently in the range of 2 to 200 cm/min.
5. The process as claimed in claim 1 , wherein said first pre-determined temperature and said second predetermined temperature is less than the melt temperature of UHMWPE and independently in the range of 125° C. to 155° C.
6. The process as claimed in claim 1 , further includes incorporating at least one additive in the UHMWPE fed at the nip of at least one pair of rollers.
7. The process as claimed in claim 6 , wherein said additive is at least one selected from the group consisting of carbon nanotubes, graphene, carbon black, aluminum powder and boron nitride.
8. The process as claimed in claim 1 , wherein the stretch ratio of the length of the hot stretched product and the pre-laminate is in the range of 30 to 130.
9. A high conductivity and high heat capacity oriented UHMWPE product prepared by the process as claimed in claim 1 , characterized by the following properties:
a. axial thermal conductivity in the range of 70 to 200 W/m;
b. transverse direction thermal conductivity in the range of 0.022 to 0.045 W/mK;
c. heat capacity in the range of 6 to 25 MJ/m 3 K; and
d. crystallinity in the range of 85 to 95%.
10. The high conductivity and high heat capacity oriented UHMWPE product as claimed in claim 9 , wherein said product is obtained in a form selected from the group consisting of sheets, tapes, fibers and films.