Injection Molded PP Foams Using Food Ingredients for Food Packaging Applications.

A new approach to the creation of polypropylene (PP) based foaming materials was developed using food grade foaming agents that were coated on the PP pellets. More specifically, sodium bicarbonate and organic acids were used to coat PP pellets using either polyethyleneoxide (PEO) or lipid esters as coating stabilizers. In order to overcome the problem of the thermal decomposition of sodium bicarbonate at temperatures lower than the PP melting temperature, which makes the direct foaming during melt mixing impossible, the proposed methodology was proved quite efficient. Thus, new PP masterbatches were prepared, where the foaming agents were incorporated as coating at PP pellets at contents up to 10%, and initially used in Lab scale injection machines in order to find the best combination of materials that resulted in the production of foamed articles. Subsequently selected material combinations were tested in an industrial scale injection molding machine, where an optimization of the injection parameters was attempted. The outcome of this was the production of PP articles with significantly increased void fraction, up to 14%, decreased thermal conductivity, up to 20%, and various pore sizes as was observed via microscopic examination using SEM and CLSM.

Polymeric Coatings Based on Water-Soluble Trimethylammonium Copolymers for Antifouling Applications.

Crosslinked polymeric materials based on a quaternary trimethylammonium compound were developed and evaluated as potential antifouling coatings. For this purpose, two water-soluble random copolymers, poly(4-vinylbenzyltrimethylammonium chloride-co-acrylic acid) P(VBCTMAM-co-AAx) and poly(N,N-dimethylacrylamide-co-glycidylmethacrylate) P(DMAm-co-GMAx), were synthesized via free radical polymerization. A water based approach for the synthesis of P(VBCTMAM-co-AAx) copolymer was used. Coatings of the complementary reactive copolymers in different compositions were obtained by curing at 120 °C for one day and were used to coat aquaculture nets. These nets were evaluated in respect to their release rate using Total Organic Carbon (TOC) and Total Nitrogen (TN) measurements. Finally, the antifouling efficacy of these newly-composed durable coatings was investigated for 14 days in accelerated conditions. The results showed that this novel polymeric material provides contact-killing antifouling activity for a short time period, whereas it functions efficiently in biofouling removal after high-pressure cleaning.