Gregory D. Smith

Fusion bonding of maleic anhydride grafted polypropylene to polyamide 6 via in situ block copolymer formation at the interface

Reference LTC-ARTICLE-1996-001doi:10.1016/0032-3861(96)80839-1View record in Web of Science URL: http://www.sciencedirect.com/science/journal/00323861 Record created on 2006-06-26, modified on 2016-08-08

A Comparison of Two Resin Flow Models for Laminate Processing

Two well-established resin flow models for laminate processing by autoclave/vacuum degassing are compared. These are the sequential compaction and the squeezed sponge models, both based on viscous flow through porous media. A detailed examination of these models in this investigation shows that, contrary to what is com monly assumed, the fibre bed carries some of the applied pressure in the sequential com paction model. Equations for the implicit fibre bed compaction behaviour are derived, and using these equations, it is shown that the sequential compaction model is essentially a special case of the squeezed sponge model. The fibre bed pressure/compaction curve and the fibre bed permeability are identified as the two key relevant material properties. For one special case of these material properties, the squeezed sponge model predicts a se quential compaction sequence, with a roughly linear resin pressure profile, as assumed by the sequential compaction model. Using the fibre bed compaction and permeability as the primary parameters in the squeezed sponge flow model it is shown that a range of laminate compaction behaviour, from sequential to uniform compaction, can be obtained. It is also shown that the permeability controls the compaction time and the fibre bed behaviour con trols the shape of the laminate compaction response.

Non-isothermal fusion bonding of polypropylene

The fusion bonding of neat polypropylene (PP) has been investigated under non-isothermal conditions with different initial adherend temperatures, and the results compared with results from bonds prepared under isothermal conditions with identical adherend temperatures. The mode I critical strain energy release rate of the bonds, Gc, was measured using a double cantilever beam geometry with a constant crack opening displacement. The effect of the adherend temperature and the hold time are summarized in time-temperature and fracture energy-temperature maps, a methodology that is easily applicable to other systems. Of immediate practical interest is the observation that for estimated interface temperatures just above the melting point, non-isothermal bonding gave bonds with Gc approaching that of the bulk resin after much shorter times than isothermal bonding.

Fusion bonding of maleic anhydride grafted polypropylene-polyamide 6 blends to polyamide 6

Keywords: Fusion bonding ; blends ; semi-crystalline polymers Reference LTC-ARTICLE-1998-003doi:10.1016/S0032-3861(98)00092-5View record in Web of Science URL: http://www.sciencedirect.com/science/journal/00323861 Record created on 2006-06-26, modified on 2016-08-08

Natural fiber reinforced polyester composites: A literature review:

Many composite products are made of thermosetting polymers reinforced with synthetic fibers. Despite the high mechanical properties associated with these fibers they are heavy and expensive compared with natural fibers. The use of natural plant fibres, combinations of natural and synthetic fibers, and wood furnish as reinforcement in polyester matrix for making low cost engineering materials has generated much interest recently. Natural fibers with good specific stiffness and strength, low density, low embodied energy, and good biodegradability have an advantage over synthetic fibers. Despite these benefits they have poor compatibility with the matrix due to their hydrophilic nature. This paper reviews the literature on the effects of chemical treatments on fiber–matrix interfacial adhesion and the wettability of natural fibers by polyester. The efficiency of incorporating glass fiber into the natural fiber for the purpose of reducing water uptake and increasing the stiffness of composite is also discussed.

Evaluating the suitability of hybrid poplar clones for the manufacture of oriented strand boards

Abstract Clonal trees from five different plantation-grown, industrially relevant hybrid poplar genotypes of the same age, grown on a common site in British Columbia, Canada, were tested for their performance in strand production and properties of oriented strand board (OSB). The results were compared against a benchmark mill-run OSB furnish derived from native aspen (Populus tremuloides). Variation in solid wood density among the hybrid poplar clones was shown to influence the compaction ratio and densification of the OSB, which in turn led to variation in board strength properties. After accounting for specimen density using co-variate statistical models, it was apparent that there were significant effects of genotype on bonding strength and thickness swell. Lower density wood from the fastest growing P. deltoides×P. trichocarpa (DTAC 7) clone resulted in better mat compaction and higher bond strength, whereas higher density wood from a P. trichocarpa×P. deltoides (TD 50-184) clone resulted in lower compaction and bonding strength. Flexural strength (rupture and elastic moduli) and nail pull through were not as significantly affected by either board density or genotype when adjusted for density. The study clearly demonstrates that fast grown, large diameter wood of lower initial wood density from hybrid poplar is highly suited for OSB production.

Characterizing hydro-thermal compression behavior of aspen wood strands.

Abstract Wood-based composites, such as oriented strand board, are typically manufactured by consolidating mats of resinated wood elements under heat and pressure. During this process, the temperature and moisture content distributions within the mat greatly affect the properties of end products. To improve the fundamental understanding of mat consolidation during hot-pressing, a model is established to investigate the transverse compression behavior of aspen wood strands for a variety of combinations of temperatures (20–200°C) and moisture contents (0–15%). A regression approach is used to obtain the modulus-temperature-moisture relationship. In addition, elevated temperatures and moistures are found to influence the strain function of wood strands, which was previously assumed to be independent of these factors.

A generalized mat consolidation model for wood composites

Abstract A generalized model for the prediction of mat pressure-density relationship of wood-based composites was developed. Based on the compression models for fiber assembly, this model treats the composite mat structure as a system of bending units, thus making element bending the dominant mechanism during early stage of mat consolidation. The consolidation behavior of fiber, strand, and particle mats were experimentally investigated. Satisfactory agreement was found between the model predictions and experimental results. Combined with the compression model, the entire strand mat consolidation can be predicted based on the properties of the wood constituents.

Comparison of the flexural behavior of natural and thermo-hydro-mechanically densified Moso bamboo

The flexural properties in the longitudinal direction for natural and thermo-hydro-mechanically densified Moso bamboo (Phyllostachys pubescens Mazel) culm wall material are measured. The modulus of elasticity (MOE) and modulus of rupture (MOR) increase with densification, but at the same density, the natural material is stiffer and stronger than the densified material. This observation is primarily attributed to bamboo’s heterogeneous structure and the role of the parenchyma in densification. The MOE and MOR of both the natural and densified bamboo appear linearly related to density. Simple models are developed to predict the flexural properties of natural bamboo. The structure of the densified bamboo is modelled, assuming no densification of bamboo fibers, and the flexural properties of densified bamboo are then predicted using this structure and the same cell wall properties of that of the natural material modelling. The results are then compared with those for two analogous structural bamboo products: Moso bamboo glulam and scrimber.

Characterizing macro-voids of uncompressed mats and finished particleboard panels using response surface methodology and X-ray CT

Abstract Macro-voids in the core of uncompressed particle mats and pressed particleboard manufactured from novel particleboard furnishes were characterized using a response surface method with mixture design and X-ray CT technology. Industrial particles were screened into core-fine, medium, and coarse size classes and their dimensions were measured. Wooden blocks measuring 10 times the mean dimensions of these particles were cut and used as surrogates for the industrial particles. Novel particle mixtures were prepared by mixing together various proportions from each particle size class. The mixtures were packed to simulate particleboard mat formation and a pre-pressed particle mat. Panels were then fabricated from the industrial furnish mixtures. The void fraction of the packed particles and the finished panels were measured and correlated with the IB strength and edge screw withdrawal resistance. Results indicated that densely packed hammer-milled industrial particles had a maximum void fraction of 63.2%. The void fraction of a randomly packed, dense particle mat was described using a full cubic model. In both particle mats without resin and the pressed panels, increasing the core-fine content decreased void volume, whereas increasing coarse particle fraction increased void volume in the mat only. The macro-void ratio in the pressed panels increased exponentially with void fraction for the randomly packed, loose particle mats. Particle mixtures that resulted in boards with the smallest void fraction were not necessarily the strongest boards; low density particleboard panels made from the novel 100% coarse mixture were found to have the highest mechanical properties.