Investigation of Degradation of Structural Adhesives under Influence of Chemicals

Structural adhesives are used for joining materials also under conditions, where they through the application will be influenced by many different chemicals. The adhesives can – if not protected from the chemical influence – be degradated of the chemicals. The degradation can because of the different structures of the polymers in the adhesives result in lower strength of the joining area, but can also give higher strength but brittleness. Information of the structures of the structural adhesives used in the project have been taken from the data sheets from the manufacturers and have been compared with investigation of the structures by FTIR and DSC. In the laboratory the HSP's (Hansen Solubility Parameters) of the adhesives has been determined and compared with the theoretically estimated HSP's. The estimation has mainly been done by Lydersens group contribution method. The chemical resistance of the adhesives have been foreseen by using HSP's of the adheisves and compared them with the HSP's of the chemicals. The structural adhesives were most of the epoxy types and of the polyurethane types with different curing systems. The structural adhesives should all have high strength and an opening time of more than 30 minutes. They were in the laboratory cured up after the specifications from the manufacturer and were stored one week after curing before they were influenced by hte chosen chemicals. The chemicals were chosen from their functional groups. In the laboratory the adhesives were influenced by different chemicals at room temperarture and under elevated temperature and under different periods to develope the degradation curves for the different chemicals and to foresee the degradation time of the adhesives before their properties were not acceptable any more. The structure after influence of the chemicals is studied by FTIR. The results of the investigations have been that it is possible to estimate the degradation by using the HSP's of the adhesives and the chemicals, but to estimate the time before degradation has been so serious that the properties of the adhesives are not acceptable any more, it is necessary to add laboratory investigations to the HSP comparisons of adhesives and chemicals. The comparison of the HSP and of the chemicals by which the adhesives can be in its lifetime has seen to be usefull especially if the chemicals are pesticides.     

Intrinsic route to melt fracture in polymer extrusion: a weakly nonlinear subcritical instability of viscoelastic poiseuille flow

As is well known, the extrusion rate of polymers from a cylindrical tube or slit (a "die") is in practice limited by the appearance of "melt fracture" instabilities which give rise to unwanted distortions or even fracture of the extrudate. We present the results of a weakly nonlinear analysis which gives evidence for an intrinsic generic route to melt fracture via a weakly nonlinear subcritical instability of viscoelastic Poiseuille flow. This instability and the onset of associated melt fracture phenomena appear at a well-defined ratio of the elastic stresses to viscous stresses of the polymer solution.     

Alkylpyrazines from hymenoptera: Isolation,identification and synthesis of 5-methyl-3- n-propyl-2-(1-butenyl)pyrazine from Aphaenogaster ants (formicidae)

Mandibular glands of Aphaenogaster rudis workers contain 5 - methyl - 3-n - propyl - 2 -(1 -butenyl)pyrazine, a new natural product. This pyrazine and several of its isomers have been synthesized from the corresponding 2,3-, 2,5- or 2,6-dimethylpyrazines. Marked differences in the mass spectra of these multialkylated pyrazines are discussed. In addition, dimethylalkylpyrazines are reported from a variety of aculeate wasps.     

Migration Study of Polypropylene (PP) Oil Blends in Food Simulants

Migration study in aqueous and olive oil food simulants was carried out on PP and its blend with oil mixture. It was found that after 10 days at 44 °C PP with oil content up to 0.83% had overall migration into olive oil less than 10 mg/dm². However, under high temperature migration test (at 110–138 C for 4 hours), the overall migration into olive oil was large for both the virgin PP and all its blends. The overall migration in water, 10% ethanol, and 3% acetic acid was smaller than those in olive oil under both migration test conditions. DSC and density measurement showed that addition of oil in PP led to smaller spherulite size and increased degree of crystallinity in the pure PP part. Small decrease in tensile strength in the oil blends was also observed but there was no significant change in tensile strength after migration test.     

Lower bounds on volumes of hyperbolic Haken 3-manifolds

We prove a volume inequality for 3-manifolds having metrics ``bent' along a surface and satisfying certain curvature conditions. The result makes use of Perelman's work on the Ricci flow and geometrization of closed 3-manifolds. Corollaries include a new proof of a conjecture of Bonahon about volumes of convex cores of Kleinian groups, improved volume estimates for certain Haken hyperbolic 3-manifolds, and a lower bound on the minimal volume of orientable hyperbolic 3-manifolds. An appendix compares estimates of volumes of hyperbolic 3-manifolds drilled along a closed embedded geodesic with experimental data.