Prior to the advent of TPEs, soft PVC compounds or rubbers were utilized in applications requiring flexibility, elasticity, and softness. However, with the development of various TPEs, this new family quickly replaced PVC or elastomer-based competitors in many applications. This section provides a qualitative comparison between the two available options for producing soft parts such as caps, plugs, and gaskets.
PVC, an accessible and inexpensive plastic, requires various additives such as stabilizers, plasticizers, lubricants, impact modifiers, fillers, etc., to form a suitable compound for diverse part production. PVC finds applications in a broad spectrum, ranging from window gaskets to shoe soles and packaging. Initially, it is crucial to note that PVC’s primary advantage lies in its availability and affordability. Among other advantages of PVC are:
- High mechanical strength,
- Resistance to sunlight,
- High wear resistance,
- Low electrical conductivity,
- Flame resistance.
However, PVC has its drawbacks, including low thermal resistance, high weight and density, and the release of toxic gases in its molten state.
In contrast, TPEs constitute a diverse family of polymers that can operate at very high temperatures (e.g., 170 °C), possess special properties like thermal and electrical conductivity, and create various surface characteristics. TPEs are environmentally friendly and do not release toxic or harmful components throughout their life cycle. The benefits of this group encompass:
- Excellent flexibility,
- Outstanding fatigue resistance,
- High impact resistance,
- Excellent stability against chemical components,
- Low density and lightness,
- Good and cost-effective processability and formability.
However, the notable disadvantages of TPEs include their high price and aging issues, such as changing dimensions, reduced thermal resistance, creep, etc., during service.
The following tables present selected physical/mechanical properties and stability against various chemical environments for PVC and TPEs, respectively.
| PVC | TPE | |
| Tensile Strength | 2.60 N/mm² | 0.5 – 2.4 N/mm² |
| Notched Impact Strength | 2.0 – 45.0 Kj/m² | No break Kj/m² |
| Thermal Coefficient of expansion | 80 x 10-6 | 130 x 10-6 |
| Max Cont Use Temp | 60˚C / 140˚F | 140˚C / 284˚F |
| Density | 1.38g/cm3 | 0.91 – 1.3 g/cm3 |
| PVC | TPE | |
| Dilute Acid | Very good | Excellent |
| Dilute Alkalis | Very good | Excellent |
| Oils and Greases | Good (variable) | Excellent |
| Aliphatic Hydrocarbons | Very good | Excellent |
| Aromatic Hydrocarbons | Poor | Poor |
| Hydrogenated Hydrocarbons | Moderate (variable) | Poor |
| Alcohols | Good (variable) | Excellent |