Process-Oriented Structure Tuning of PBT/PTHF Thermoplastic Elastomers

Abstract

The multiscale structure of thermoplastic elastomers (TPEs) made of poly(butylene terephthalate)/ polytetrahydrofuran (PBT/PTHF) segmented block copolymers is investigated in a systematic way with the aim to characterize the impact of the processing route on it. By means of atomic force microscopy and small-angle scattering techniques, we first evidence the presence of thick (ca. 11 nm) and well-aligned ribbons in hot-pressed samples, whereas thinner and branched filaments (ca. 5 nm) are observed when solvent casting is used. Besides, differential scanning calorimetry suggests that all the so-formed structures can "remember" their initial state after being melted, a property that we assign to the persistent phase separation of the constituents in the viscoelastic liquid. At a smaller length scale, combining transmission and reflection wide-angle X-ray scattering experiments further reveals the influence of the processing method on the molecular order within the crystallites. In particular, it makes emerge the pronounced orthotropic character of the whole samples set, being to our knowledge totally ignored in the TPE's literature. In light of this extensive characterization, we end the article with a discussion on the relationship between the crystalline network's structure and the corresponding chains topology.

Morphological origins of temperature and rate dependent mechanical properties of model soft thermoplastic elastomers

“…Thermal transitions observed via DSC and DMTA yield a consistent picture (note that the measurements are performed as slightly different heating rates). We will next describe briefly the major transitions observed with increasing temperature based on these results as well as on the extensive previous literature 1,3,4,13 …”

“…They all share the feature of having a low glass transition (T g ) of the soft blocks (SBs) combined with physically associating hard blocks (HBs). Their mechanical properties are governed by the interplay of the different dynamics present in the system (e.g., hard block associations and soft block mobility) as well as by their morphology, that is, the physical arrangement of the polymer chains 1–7,9,10,12–18 …”

Coarse-Grained Molecular Dynamics Modeling of Segmented Block Copolymers: Impact of the Chain Architecture on Crystallization and Morphology

“…60,61 In the present work, we propose to combine this technique to the simulation of segmented copolymers to model the structuring behavior of semicrystalline TPE previously studied from the experimental point of view. 8,62,63 The article is organized as follows: After explaining the different methods and modeling aspects in section 2,w e present and discuss the results in three sections. First, results concerning the properties of the neat soft and hard homopolymers are presented in section 3.1.…”

Synthesis and Nonisothermal Crystallization Kinetics of Poly(Butylene Terephthalate-co-Tetramethylene Ether Glycol) Copolyesters

“…PBT-based TPEE has been developed, such as poly(butylene terephthalate- co -polyethylene glycol) (PBT- co -PEG) [ 16 , 31 ] and poly(butylene terephthalate- co -polypropylene glycol) (PBT- co -PPG) [ 32 ], revealing varied characteristics depending on different compositions. Poly(butylene terephthalate- co -tetramethylene ether glycol) (PBT- co -PTMEG) copolymer was first commercialized under the trademark “Hytrel” (Du pont, Wilmington, DE, United States) as engineering plastics in 1972 [ 33 , 34 , 35 ], and the morphology [ 17 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ], properties [ 45 , 46 , 47 , 48 , 49 ], interactions between hard segments and soft segments [ 50 , 51 ], and structure of the crystalline [ 36 , 38 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ] and amorphous phase [ 5 , 17 , 49 , 59 ] have been studied extensively. The crystalline regions of PBT- co -PTMEG copolymers are continuous and highly interconnected, dispersing in a continuous amorphous region [ 52 , 60 ].…”