Liquid crystal polymer compositions, articles and methods of making
Described herein are polymer compositions including at least 20 wt. % of a liquid crystal polymer (“LCP”); 10 wt. % to 40 wt. % of a flat glass fiber and 15 wt. % to 50 wt. % of boron nitride and/or zinc oxide. It was surprisingly discovered that polymer compositions including an LCP in conjunction with a combination of flat glass fibers and boron nitride and/or zinc oxide had improved thermal conductivity and flexural properties, relative to analogous polymer compositions having round glass fibers in place of the flat glass fibers.
1 . A polymer composition consisting of:
at least 20 wt. % and at most 60 wt. %, based on the total weight of the polymer composition, of a liquid crystal polymer formed from the polycondensation of the following monomers: terephthalic acid, 4,4′-biphenol, isophthalic acid, and 4-hydroxybenzoic acid;
from 10 wt. % to 40 wt. %, based on the total weight of the polymer composition, of a flat glass fiber; and
boron nitride and zinc oxide, wherein the total concentration of boron nitride and zinc oxide is from 15 wt. % to 50 wt. %, based on the total weight of the polymer composition;
optionally an additive selected from the group consisting of tougheners, plasticizers, colorants, pigments, antistatic agents, dyes, lubricants, thermal stabilizers, light stabilizers, nucleating agents, and antioxidants;
wherein the relative concentration of boron nitride to zinc oxide expressed as weight of boron nitride in the polymer composition/weight of zinc oxide in the polymer composition is from 0.5 to 2,
wherein the flat glass fiber is E-glass fiber and the composition is free of additional glass fibers;
wherein the flat glass fiber has an aspect ratio of at least 2 and at most 8;
wherein the flat glass fiber has an average length of from 3 mm to 50 mm wherein the average length is the average length of the glass fiber prior to incorporation into the polymer composition or the average length of the glass fiber in the polymer composition; and
wherein the composition has an apparent viscosity from 90 Pa.s to 300 Pa.s at a shear rate of 100 s-1, as measured according to ASTM D3835.
2 . The polymer composition of claim 1 , wherein the polymer composition has a through-plane thermal conductivity of from 0.20 W/m-K to 0.9 W/m-k, as measured by Laser Flash according to ASTM E1461-13.
3 . The polymer composition of claim 1 , wherein the polymer composition has a flexural strength of from 100 MPa to 250 MPa, according to ASTM D790.
4 . The polymer composition of claim 1 , wherein the polymer composition has a flexural strain of from 100 MPa to 190 MPa, as measured according to ASTM D790.
5 . The polymer composition of claim 1 , wherein polymer composition has an apparent viscosity of from 35 Pa.s to 150 Pa.s at a shear rate of 500 s −1 ; or of from 25 Pa.s to 100 Pa.s at a shear rate of 1000 s −1 ; as measured according to ASTM D3835.
6 . The polymer composition of claim 1 , wherein the concentration of the flat glass fiber is from 10 wt. % to 30 wt. %, based on the total weight of the polymer composition.
7 . The polymer composition of claim 1 , wherein the glass fiber has an aspect ratio, defined as the average ratio between the length and the largest of the width and thickness, of at least 5.
8 . The polymer composition of claim 1 , wherein the additive is selected from the group consisting of tougheners, plasticizers, colorants, antistatic agents, dyes, lubricants, thermal stabilizers, light stabilizers, nucleating agents, and antioxidants.