Molded polymeric article with low haze and high clarity
The present disclosure provides a molded article composed of a polymeric composition and processes for producing the same. The polymeric composition includes from about 60 wt % to about 99 wt % of a matrix of a propylene-based polymer. The propylene-based polymer has a refractive index (n1). The polymeric composition also includes from about 40 wt % to about 1 wt % of elongated elastomer particles dispersed in the propylene-based polymer. The elongated elastomer particles have a refractive index (n2). The propylene-based polymer and the elongated elastomer particles exhibit a refractive index mismatch whereby |n1−n2|>0.002. The molded article has a haze value less than about 20% and optionally a viscosity ratio (VR) greater than 0.28.
1. A process comprising:
selecting from 80 wt % to 90 wt % of a propylene-based polymer having a refractive index (n1) from 1.495 to 1.505 as measured in accordance with ASTM D 542 and a melt flow rate (MFR) measured in accordance with ASTM D 1238 230° C./2.161kg and 20 wt% to 10 wt% of an elastomer that is an ethylene-based polymer consisting of (i) a majority weight percent polymerized ethylene monomer and (ii) polymerized butene comonomer or polymerized octene comonomer, the elastomer having a refractive index (n2) from 1.470 to 1.497 as measured in accordance with ASTM D 542 and a molt index (MI) measured in accordance with ASTM D 1238 190°C./2.16kg, such that
MI
×
2.8
MFR
is greater than 1.0 to 7.0 and
|n1−n2| is from greater than or equal to 0.015 to 0.025;
blending particles of the elastomer into a matrix of the propylene-based polymer;
subjecting the blend to a shear rate from 8,000 sec −1 to 12,000 sec −1 to form elongated particles of the elastomer particles; and
injecting the blend into a mold to form an injection molded article having a haze value less than 15% as measured in accordance with ASTM D 1003.
2. The process of claim 1 wherein the elongated elastomer particles have an average length at least 10 times the average particle width.
3. An injected molded article comprising:
a polymeric composition comprising about 80 wt% to 90 wt% of a matrix of a propylene-based polymer with a refractive index (n1) from 1,495 to 1,505 and a melt flow rate (MFR) measured in accordance with ASTM D 1238, 230°C./2.16 kg;
from 20 wt % to 10 wt % of elongated elastomer particles dispersed in the propylene-basal polymer, the elastomer is an ethylene-based polymer consisting of (i) a majority weight percent polymerized ethylene monomer and (ii) polymerized butene comonomer or polymerized octene comonomer, the elastomer having a refractive index (n2) from 1.470 to 1.497 and a melt index (MI) measured in accordance with ASTM D 1238 190° C./2.16 kg dispersed on the propylene-based polymer;
wherein |n1−n2| is from greater than or equal to 0.015 to 0.025, and the injected molded article has a haze value less than 15% as measured in accordance with ASTM D 1003 and a viscosity ratio (VR) greater than 1.0 to 7.0 wherein
VR
=
MI
×
2.8
MFR
.
4. The injected molded article of claim 3 wherein the elongated elastomer particles have an average length at least 10 times the average particle width from a sectional view taken along a mold flowpath of the article.
5. The injected molded article of claim 3 wherein the elongated elastomer particles have an average width from 5 nm to 200 nm.
6. The injected molded article of claim 3 wherein the propylene-based polymer is a nucleated random propylene/ethylene copolymer.
7. The injected molded article of claim 3 having a haze value loss than 10%.
8. The injected molded article of claim 3 having a clarity value greater than or equal to 98% as measured in accordance with ASTM D 1746.