Confined polymers crystallize

Squeezing very thin polymer layers can cause them to form polymer single crystals that could make plastic films less permeable to gases

Macromolecular reaction engineering, the chain-of-knowledge approach

Macromolecular Science & Engineering is the paradigm of a multi-disciplinary area in Materials Science. The path from monomer via macromolecules into functional polymer materials and products travels through various disciplines: chemistry, catalysis, thermodynamics, macromolecular reaction engineering, rheology, physics, processing and product design. The successful development of novel and/or improved polymeric materials and products from laboratory into industrial practice requires an integrated approach and profound understanding of the various disciplines met en route, viz. the chain-of-knowledge approach. In the 20th Century there has been a strong chain-of-knowledge between academia and industry, a prime example in this respect was the development of i-PP by Natta c.s. in Italy in close concert with Montecatini. Nowadays the gap between academic research and industrial R&D has widened to such an extent that this chain-of-knowledge is partly broken. The polymer-producing industry is seemingly mature, no new plastics are envisaged anymore, and the focus is on cost reduction and corporate long term R&D is incompatible with short-term shareholder value. The time scale of research projects in academia, typically 3-4 years for a Ph.D., is often incompatible with the time scale of R&D projects in industry. In the current academic domain, macromolecular science and engineering is becoming more and more fragmented and novel results are published in numerous non-overlapping disciplinary journals. The question is: can we repair this broken chain-of-knowledge between academia and the plastics-producing industry or will academic research make a new chain-of-knowledge by establishing a platform for new industrial activities, exploiting the ultimate properties of the macromolecular chain, also beyond the covalent bond, and in novel sophisticated applications

Sterke vezels

no abstract

Structured polymer blends

The morphol. of model incompatible HDPE fiber-polystyrene blends was studied as functions of processing conditions and processing aids. Modeling of extrusion processes and continuous mixers yielded expressions for the shear rate and shear stress as well as the limited residence time and no. of reorientation. These results could be combined with knowledge of distributive and dispersive mixing process to predict morphol. development. Morphol. of nylon 6 blends with LDPE and ethylene-vinyl alc. copolymer including the effect of electron beam was also studied. [on SciFinder (R)

Crystallization phenomena in bacterial poly[(R)-3-hydroxybutyrate]. 2. Embrittlement and rejuvenation

Poly[(R)-3-hydroxybutyrate] (I) (Biopol) is a bacterial storage polymer, currently receiving much attention because of its potential as a biodegradable plastic. A major drawback of I is its intrinsic brittleness. Although as-molded I shows ductile behavior, upon storage at ambient temp. is detrimental aging process seriously embrittles the material and restricts its application possibilities. This remarkable embrittlement is delineated in the present study and could be attributed to progressive crystn. By using a simple annealing treatment I can be rejuvenated while subsequent aging is prevented to a large extent. This observation might considerably enlarge the applicability of

Chain-extended flexible polymers

\u3cp\u3eHigh‐strength/high‐modulus structures such as fibres, tapes and rods can be produced currently on the basis of intrinsically flexible macromolecules. The prime example amongst these new developments is gelspinning of high‐molecular‐weight polyethylene resulting in fibrous structures possessing tenacities of 3–4 GPa and corresponding moduli up to appr. 150 GPa. The basic aspects of chain‐extension for polyethylene will be discussed in relation to the various routes toward oriented/extended PE structures as well as recent developments concerning the utilization of other flexible polymeric systems for the production of high‐strength/high‐modulus fibres.\u3c/p\u3