Biodegradable films made from low density polyethylene (LDPE), wheat starch and soluble starch for food packaging applications. Part 2

The food packaging material is expected to provide optimum protective properties so that the product it encloses remains in satisfactory condition for its anticipated shelf life. The packaging tech...

Totally and Partially Biodegradable Polymer Blends Based on Natural and Synthetic Macromolecules: Preparation, Physical Properties, and Potential as Food Packaging Materials

Intercrystalline molecular connections in semicrystalline polymers have been the subject of numerous discussions and controversies. Nevertheless, there is one point of agreement: such intercrystalline tie molecules have a prime role in the mechanical and use properties of the materials, notably the resistance to slow crack growth. This article is a critical review of the mechanisms of generation of the tie molecules during the stage of crystallization and of the experimental and theoretical assessment of their concentration. Polyethylene and related materials are mainly studied. The contribution of chain entanglements is also discussed in parallel with tie molecules. Particular attention is paid to Huang and Brown's statistical approach, which appears to be the most appropriate one for predictive purposes and has aroused much interest from various authors. Attempts are made to provide solutions to the shortcomings of this model.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/polb.20414

Critical review of the molecular topology of semicrystalline polymers: The origin and assessment of intercrystalline tie molecules and chain entanglements

Time resolved simultaneous small- and wide-angle X-ray scattering during polyethylene deformation—II. Cold drawing of linear polyethylene

The disclosed ethylene polymer compositions have et least one homogeneously branched substantially linear ethylene/α-olefin interpolymer and at least one heterogeneously branched ethylene polymer. The homogeneously branched linear or substantially linear ethylene/α-olefin interpolymer has a density from about 0.88 to about 0.935 g/cm3 and a slope of strain hardening coefficient greater than or equal to about 1.3. Films made from such formulated compositions have surprisingly good impact and tensile properties, and have an especially good combination of modulus and toughness.

Fabricated articles made from ethylene polymer blends

A fundamental theory for slow crack growth in polyethylene

Slow crack growth in a wide variety of polyethylenes have been investigated. The quantitative relationship between: (1) the external variables such as stress, temperature, stress intensity and J-integral; (2) the morphological variable such as density and crystal size and (3) molecular variables such as molecular weight, branch density and branch distribution and the rate and time to failure for slow crack growth will be presented. The kinetics of slow crack growth is correlated with the microstructural changes. A fundamental description of slow crack growth is given in terms of tie molecules and the stress field on the boundary of the craze from which fracture initiates.

Slow crack growth in polyethylene ‐ a review

The mechanism of slow crack growth in polyethylene by an environmental stress cracking agent

The ductile-brittle transition of an ethylene-hexene copolymer was measured from 80 to 24° C. The basic curves of stress against time to failure could all be unified in terms of a single equation based on normalizing the stress relative to the transition stress between the ductile and brittle regions and using a single thermal activation parameter. This unity is based on the observations which show that the ductile and brittle failure processes are both associated with a shear process. The unifying equation is 
$$\left( {\frac{\sigma }{{\sigma _{\text{c}} }}} \right)^n = \left( {\frac{{t_{\text{R}} }}{{t_{\text{f}} }}} \right){\text{ exp }}\left[ {{\text{85 500/}}R\left( {\frac{1}{T} - \frac{1}{{T_{\text{R}} }}} \right)} \right]$$

 where σ
c is the minimum stress for ductile failure at an arbitrary temperature, T
R; t
R is the time to failure at an arbitrary reference temperature T
R; n equals 34 and 3.3 for the ductile and brittle regions, respectively and R is in J mol−1 K−1.

Xici Lu

Papers

A fundamental theory for slow crack growth in polyethylene

Slow crack growth in polyethylene ‐ a review

The mechanism of slow crack growth in polyethylene by an environmental stress cracking agent

The ductile-brittle transition in a polyethylene copolymer

The effect of crystallinity on fracture and yielding of polyethylenes