Polymer compositions and products formed therewith
The present disclosure provides compositions and products formed therefrom. In particular, the disclosure provides elastomeric latex articles, such as gloves and condoms, that can be prepared utilizing a styrene-polyisoprene-styrene (SIS) latex. The elastomeric articles can exhibit desired tensile properties while being substantially or completely free of undesired components, such as sulfur and zinc oxide, which can be allergens. The disclosure further provides methods of preparing elastomeric latex articles.
1 . A method for preparing an elastomeric article, the method comprising:
preparing a compounded polymer latex composition including a polystyrene-polyisoprene-polystyrene (SIS) polymer latex;
prevulcanizing the compounded polymer latex composition at a first temperature for a first time period and then at a second, lower temperature for a second time period effective so that the prevulcanized compounded polymer latex composition has a relaxed modulus of about 0.50 MPa to about 0.61 MPa, wherein the first temperature and the second temperature are separated by at least 4° C.;
dipping a former into the prevulcanized compounded polymer latex composition to form at least one layer of the prevulcanized compounded polymer latex composition thereon; and
curing the at least one layer of the prevulcanized compounded polymer latex composition on the former to provide the elastomeric article.
2 . The method of claim 1 , wherein the first temperature is in a range of about 32°° C. to about 38° C.
3 . The method of claim 2 , wherein the first time period is in a range of about 0.5 hours to about 18 hours.
4 . The method of claim 1 , wherein the second temperature is in a range of about 26° C. to about 32° C.
5 . The method of claim 4 , wherein the second time period is in a range of about 2 hours to about 36 hours.
6 . The method of claim 1 , further comprising drying the at least one layer of the prevulcanized compounded polymer latex composition at a temperature in a range of about 80° C. to about 120°° C. for a time of about 1 minute to about 10 minutes.
7 . The method of claim 6 , wherein the drying is carried out after the dipping and before the curing.
8 . The method of claim 1 , wherein the dipping comprises a first dipping effective to form a first layer of the prevulcanized compounded polymer latex composition and a second dipping effective to form a second layer of the prevulcanized compounded polymer latex composition on the first layer of the prevulcanized compounded polymer latex composition, wherein a first drying is carried out after the first dipping and before the second dipping, and wherein a second drying is carried out after the second dipping.
9 . The method of claim 8 , wherein the first drying is carried at a first temperature, the second drying is carried out at a second temperature, and the second temperature is higher than the first temperature.
10 . The method of claim 8 , wherein the first drying is carried out at a temperature in a range of about 80° C. to about 100° C. for a time of about 1 minute to about 10 minutes, and wherein the second drying is carried out at a temperature in a range of about 100° C. to about 120° C. for a time of about 1 minute to about 10 minutes.
11 . The method of claim 1 , wherein the relaxed modulus is measurable according to a test comprising:
preparing a tube-shaped film of the prevulcanized compounded polymer latex composition on a dipping structure;
rolling the tube shaped film to form a ring;
stretching the ring using a tensile tester to about 100% extension for about 1 minute to identify a load; and
calculating the relaxed modulus using the formula:
Relaxed Modulus (MPa)=( F×d×C )/2 M
wherein F is the load in Newtons, d is a density of the polymer latex ring in grams per cubic centimeter, C is an external circumference of the dipping structure in centimeters, and M is the mass of the polymer latex ring in grams.
12 . The method of claim 1 , wherein preparing the compounded polymer latex composition comprising compounding the SIS polymer latex with at least one sulfur donor and at least one dithiocarbamate.
13 . The method of claim 12 , wherein preparing the compounded polymer latex composition further comprises compounding the SIS polymer latex with one or both of an amphoteric surfactant and an antioxidant.
14 . The method of claim 1 , wherein the method is effective to provide the elastomeric article with one or more of: a tensile strength of about 25 MPa or greater when measured in accordance with ASTM D412; a tensile modulus at 500% elongation of less than 2.5 MPa when measured in accordance with ASTM D412; a tear strength of at least 1.5 N/mm when measured in accordance with ASTM D624-000; a Young's modulus (E′) that is less than 1 MPa at a frequency of 1 Hz and that is greater than 1 MPa at a frequency of 21.5 Hz; and an elongation at break of about 1100% or greater.