Thermal Properties Of Plastic Packaging Systems
The conduct of most plastic products and polymers, specifically thermoplastics, is reliant upon temperature during production, application processes, storage and distribution. The major thermal properties which are crucial in the plastic packaging area include not only fundamental thermal properties such as decomposition temperature, glass transition, crystallization temperature, but also include relevant thermodynamic properties such as HDT (heat deformation temperature) and HET (heat expansion rate). These features are ordinarily estimated by specialized devices called thermal analyzers: such as thermomechanical analyzer (TMA); differential scanning calorimetry (DSC); dynamic mechanical analyzer; and thermogravimetric analyzer (TGA). In this section, basic thermal features and practical thermal features shall be shortly explained, and several examination techniques that are frequently used in the real packaging world will be brought in.
The melting procedures of polymers that are made of plastic is abbreviated as Tm, the obverse of crystallization and is more complex than both the melting point of lower molar/molecular crystals. In technical language, a session transition at a temperature range from a semi-crystalline or a crystalline structure to a solid amorphous structure is referred to as the plastic polymer’s melting point. The reason behind a wide MW dispersion, and structural and chemical features, the session transition is not kept at identical temperatures but is usually kept at a range of varying temperatures. In polymers consisting of plastic packaging, exclusive semi-crystalline or solidification (which is not possible in the live world) of thermoplastics can have a melting point. Plastic packaging materials under the thermosetting will also have separate decomposition temperatures apart from melting. Another session transformation of thermoplastic polymers is also an ordinary characteristic in below melting temperature.
A session transition generally, from a glass to rubber-like state is termed as glass transition, and is reversible in nature especially in the amorphous region within the amorphous plastic polymers and semi-crystalline structures. Generally, the polyesters having a higher value of Tm are more brittle, and are frequently used in the rigid packaging due to its durability and tough nature. The temperature of glass transition can be altered by changing the level of cross-connecting or branching of the polymer or additives in the form of plasticizers and filters.
The thermal testing method is the “Change of Energy Absorption or Release”
Features: To find out the several thermal features of plastic packaging materials, a calorimetry method using DSC is broadly utilized in the area of packaging. The below-mentioned criteria are often gauged by DSC:
- Specific heat capability or heat capability
- Fusion heat
- Glass transition temperature (Tg)
- Crystalline phase transformation energy and temperature
- Latent heat of melting
- Oxidation induction time
- Reaction energy and temperature
- Melting temperature (Tm)
- Precipitation energy and temperature
- Bio-polymeric packaging substance’s denaturation temperatures
On the basis of these findings, the exothermal energy of polymer cure (as in epoxy adhesives), general thermal stability, the reaction kinetics of materials and the level and rate of cure could be ascertained. Additionally, the process could also be used as one of the several methods to pinpoint an unknown substance or has to confirm what is being hoped for from the material.
Heat Distortion Temperature (HDT)
The plastic packaging products and thermal stability is often expressed with the help of HDT. The thermal stability of plastic items can be enhanced with morphological alteration such as the use of advanced stabilizers and fiberglass. It can also be controlled by the degree of semi-crystalline and crystalline regions. The maximum degree of thermal stability can be estimated by understanding the temperature in which under controlled stressful environment, the polymer becomes distorted.