In order to function as a leakproof system without a liner (one of the key advantages of our laboratory and packaging products), the surfaces of the container and closure that meet and push together when tightened must be dissimilar materials with different hardnesses. Even our polypropylene copolymer (PPCO) bottles with polypropylene homopolymer (PP) bottles are different enough to function properly. On some larger carboy products, this difference cannot be sufficiently maintained so a pliable thermoplastic elastomer (TPE) gasket is added for proper leakproof seal function.
