Thermoplastic natural rubber TPNR

Mixing of natural rubber with polyolefin is one of the methods used to prepare thermoplastic natural rubber (TPNR). TPNR behaves like vulcanized rubbers at ambient conditions, but at elevated temperatures they melt and flow like a thermoplastic material. Thus TPNR could be processed using conventional thermoplastic processing machinery without requiring vulcanization, and these materials could be reprocessed. Thus there is low level of wastage, as scrap too can be recycled. 

Thermoplastic elastomer (TPE) blends have been broadly studied as a new class of materials. TPEs offer various advantages and require no state-of-the-art processing machinery, while scrap and rejects are recyclable. Blends can be homogeneous, phase separated or both. TPEs are multi-phase polymer systems consisting of hard and soft domains that can be copolymers or mechanical blends. This phase separation leads to materials having unique and viable commercial physical properties. TPEs exhibit the thermoplastic characteristics of the hard thermoplastic phase, and resilience as a result of the rubbery domains. TPEs based on natural rubber (NR) and thermoplastic blends are known as thermoplastic natural rubber (TPNR) blends. There are two types of TPNR, namely thermoplastic polyolefin (TPO) and thermoplastic vulcanizate (TPV).3... 

Figure 17.4 SEM micrograph of thermoplastic natural rubber (TPNR).

H.N. Azlina, H. Norita, H. Anuar, S.N. Surip, N.N. Bonnia, PermeahUity properties of thermoplastic natural rubber (TPNR) nanocomposites, in ISBEIA 2012-IEEE Symposium on Business, Engineering and Industrial Apphcations, 6422983,2012, pp. 714-718. 

One of the important families of blended TPEs is thermoplastic natural rubber (TPNR), based primarily on polyolefin and natural rubber (NR). TPNR blends have attracted much attention due to their ease of processability and a broad spectrum of properties available at a competitive price. The TPNR system consists of multi-phases of hard and soft domains from blending thermoplastics with NR. Generally, TPNR is prepared with various type of polyolefin, such as PP, LDPE, LLDPE and HDPE. TPNR is usually prepared by a melt mixing process using an internal mixer or twin-screw extruder. It presents a wide range of useful properties, excellent processing abilities, and can be produced at moderate cost. 

Development of TPEs with various types of elastomers and polyolefins has been extensively reported by many researchers. Ethylene-propylene-diene monomer (EPDM) or its modified form is used as the elastomer in most polyolefin TPEs. Natural rubber (NR) and thermoplastic blends have become an area of interest only recently. These materials are known as thermoplastic natural rubber (TPNR). The development of TPNR was principally based on the criteria set by EPDM blends with thermoplastics. Two types are known, one belonging to the TPO class and the other belonging to the TPV class. 

Z. Ghazali, A. F. Johnson, K. Z. Dalhlan, Radiation crosslinked thermoplastics natural rubber (TPNR) foams, Radiation Physics and Chemistry, 1999, 55, 73-79... 

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