pps proceeding - Abstract Preview
pps proceeding
Symposium: S02 - Polymer Blends and Alloys
Poster Presentation
 
 

Polypropylene blends for raffia tapes with improved toughness

Lotti Cybele (1), Bulhões Carolina Cerqueira (2), Campbell Richard A (3)*

(1) Braskem SA - Porto Alegre, RS - Brazil, (2) Braskem SA - Sao Paulo, SP - Brazil, (3) Braskem SA - Pittsburgh , PA - USA

Polypropylene is a preferred polymer for the production of raffia bags. In developing countries, they are used to packaging of wide range goods, including agricultural products. The high molecular orientation achieved during processing of polypropylene results in tapes with high tenacity, as requested by the final application. In recent years, raffia bag customers are requesting lighter, tougher, more puncture resistant bags, motivated by the worldwide driver sustainability. Tape tenacity can be improved by increasing molecular orientation. However, the tape’s elongation can be compromised. As a result, there is a reduction in the overall raffia bags’ performance. One attempt to increase raffia elongation in highly oriented tapes is by blending another polymer, forming a dispersed second phase in polypropylene matrix, such as LLDPE, polypropylene based-elastomers or ethylene/alfa-olefin copolymers. The aim of this work is evaluate the influence of different modifiers to polypropylene matrix in the tenacity and elongation of raffia tapes. Blends with 5%wt of LLPDE (0.916g/cc), ethylene-butylene copolymer Engage 7467 (0.86g/cc) and linear triblock copolymer based on styrene and ethylene-butylene SEBS Kraton G1643 (0.90g/cc) were dry blended with a 3.5 MFR homopolymer polypropylene. Raffia tapes were produced on a pilot raffia line in three different draw ratios and tensile properties were evaluated. As expected, with increasing draw ratio, an increase in tenacity and a reduction in elongation were observed for all samples. The polymer blends allowed higher draw ratios and in general produced lower tenacity but higher elongation than the neat polypropylene. Both in low and high draw ratios, no significant difference in tenacity could be observed for blends with LLDPE and Engage 7467. However, blends with Kraton G1643 showed the lower tenacities. Changes in the tenacity-elongation relationship will be explained by changes in the system morphology.