Evaluation and stability of PET resin mechanical properties.

摘要

Mechanical properties of materials differ by their chemistry and, processing conditions. Polymers are no exception. Poly(ethylene Terephthalate) (PET), an aromatic-polyester made from renewable sources (feedstock) is making an impact on the environment due to the required volumes (13 Mega tons/annum). PET's properties make it the market's choice for packaging. The amount of PET recycled is less than 30% leaving virgin resin consumption to make up the majority of product. An emphasis on environmental responsibility is one factor driving the plastics industry towards use of renewable materials and light-weighting. Differences in micro-structure achieved through processing changes can provide a range of properties. This highlights the importance of testing samples processed under actual processing conditions when considering improved designs. In the packaging industry, a superior product can be obtained through usage of efficient part geometry and materials. Customer acceptance is also an issue. The addition of nanoparticles is to obtain an ecologically-friendlier and improved performance material. Even 1 wt% addition has been shown to significantly improve stiffness.The goal of the work is to examine the typical PET resins available (I.V. 0.74-0.84 dL/g) and obtain baseline performance data on mechanical properties. To compare the material properties, injection molded amorphous samples were collected on industrial-scale equipment. Before this study, mechanical property data of samples processed at quenching and flow rates typically used in industry is not available. A convenient method for precise mechanical testing of these samples was developed. This new method, including a custom fixture, accommodates the preform shape used as an intermediate in packaging production. Along with this new tensile testing method, nanoindentation was performed along the length of industrially produced films. Nanoindentation is another potentially useful method for measuring properties from material samples. The preform samples were verified to be amorphous through DSC and X-ray diffraction analysis.Outcomes of this work show a 13-27% performance range in modulus between the resins. This is notable since it is within the typical property improvements reported by 1 wt% nano-particle reinforcements. The results correlate the yield strength and Young's modulus with a ratio of 0.015. These results also highlight the industry's need for forming a record of resins available for resin selection.