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 latex composition including a polystyrene-polyisoprene-polystyrene (SIS) latex, at least one sulfur donor, and at least one dithiocarbamate;
prevulcanizing the compounded latex composition at a temperature and for a time period effective to form a prevulcanized compounded latex composition having a relaxed modulus of about 0.50 MPa to about 0.61 MPa;
dipping a former into the prevulcanized compounded latex composition to form at least one layer of the prevulcanized compounded latex composition thereon; and
curing the at least one layer of the prevulcanized compounded latex composition on the former to provide the elastomeric article.
2. The method of claim 1 , wherein the at least one sulfur donor is a thiuram compound.
3. The method of claim 1 , wherein the at least one sulfur donor includes one or both of dipentamethylenethiuram tetrasulfide (DPTT) and dipentamethylenethiuram hexasulfide (DPTTH).
4. The method of claim 1 , wherein the compounded latex composition further includes one or both of an amphoteric surfactant and an antioxidant.
5. The method of claim 1 , comprising prevulcanizing the compounded latex composition at a first temperature for a first time period and then at a second, lower temperature for a second time period.
6. The method of claim 5 , wherein the first temperature is in a range of about 32° C. to about 38° C., and the first time period is in a range of about 0.5 hours to about 18 hours.
7. The method of claim 5 , wherein the second temperature is in a range of about 26° C. to about 32° C., and the second time period is in a range of about 2 hours to about 36 hours.
8. The method of claim 5 , wherein the first temperature and the second temperature are separated by at least 2° C.
9. 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 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 )/2M
wherein F is the load in Newtons, d is a density of the 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 latex ring in grams.
10. The method of claim 1 , further comprising drying the at least one layer of the prevulcanized compounded 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.
11. The method of claim 10 , wherein the drying is carried out after the dipping and before the curing.
12. The method of claim 1 , wherein the dipping comprises a first dipping effective to form a first layer of the prevulcanized compounded latex composition and a second effective to form a second layer of the prevulcanized compounded latex composition on the first layer of the prevulcanized compounded latex composition.
13. The method of claim 12 , comprising a first drying that is carried out after the first dipping and before the second dipping and a second drying that is carried out after the second dipping.
14. The method of claim 13 , wherein the first drying is carried out at a first temperature, the second drying is carried out at a second temperature, and the second temperature is higher than the first temperature.
15. The method of claim 13 , 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.
16. The method of claim 13 , 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.