Search

An annular die is used to extrude cylindrical starch foams which are then sliced to yield foam sheets suitable for cushioning protection and insulation of shipping containers. Although starch foams, as a possible replacement of petroleum-based foams, have been prepared in the past, their sensitivity to humidity remained a problem. Extensive research in the last few years has been focused on resolving the collapse of the foam at high humidity, improve the cushioning protection, and develop an economical foaming process. However, these issues are still problematic and need to be resolved before such biobased foams can gain entry into the marketplace. In this study, a BoxBehnken statistical design of experiment was used to optimize the properties of foams extruded with various additives. It was found that the density, cell structure, and the rate of water penetration of these foams were affected by the feed rates (e.g., foam composition) of the water, talc, and poly(hydroxy ether) (PHE). The use of PHE was found to be extremely effective to minimize the water sensitivity and it significantly increased the water penetration time of the foam sheets. These starch foams efficiently absorb impacts and recover its physical shape quickly to provide multiple cushion protection for moderately delicate products. POLYM. ENG. SCI., 53:857-867, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Advances in petroleum-based polymers have contributed numerous benefits to the chemical industry and currently most polymers are derived from nonrenewable resources. However, continuous depletion of crude oil resources presents [...]

Polycaprolactone (PCL) was blended in a twin-screw extruder with chemically modified thermoplastic starch (CMPS) to provide biobased and biodegradable resin composition. Reaching starch with maleic anhydride (MA) in the presence of a plasticizer and a free radical initiator provided the CMPS. The starch modification improved interfacial adhesion and processabitiy in blending with other thermoplastic polyesters. The rheological, mechanical, thermal, and morphological properties of the blends were examined. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) studies revealed that the PCL/CMPS blends are thermodynamically immiscible. However, they formed compatible blends due to the reaction of the carboxyl groups on starch backbone with hydroxyl groups of the PCL chain ends. The tensile strength and elongation decreased with increasing CMPS content, whereas the modulus increased. Dynamic viscoelastic measurements showed that the flow behavior of PCL was that of Newtonian fluid within the tested frequencies, whereas the CMPS exhibited strong shear thinning characteristics. The flow behavior of the blends varied with the CMPS content. The complex viscosity, storage, and loss moduli of the blends containing more than 40% of CMPS were higher than those of pure CMPS and PCL. In addition, the properties of CMPS to those of chemically unmodified thermoplastic starch (TPS) were compared. POLYM. ENG. SCI., 48:2126-2133, 2008. [C] 2008 Society of Plastics Engineers, INTRODUCTION Interest in biobased and biodegradable polymers is increasing, due to concerns about managing carbon emissions in a sustainable manner, and the environmental requirements for the safe and effective disposal [...]

This article concerns the utilization of maleated thermoplastic starch (MTPS) in the reactive extrusion melt-blending with poly(butylene adipate-co-terephthalate) (PBAT) in blown film applications. First, MTPS was prepared from cornstarch with glycerol (plasticizer) and maleic anhydride (MA; esterification agent). MTPS was then melt-blended with PBAT in a subsequent downstream extrusion operation. The effects of both polyester and MA contents were studied on the physicochemical parameters of melt-blends. For high polyester fractions (>60 wt%), PBAT-g-MTPS graft copolymers were obtained through transesterification reactions. They were promoted by the MA-derived acidic moieties grafted onto the starch backbone as shown by selective Soxhlet extraction experiments and FTIR analyses. At lower polyester content, no significant reaction occurred more likely due to an inversion in the phase morphology between both components. Tensile properties of PBAT-g-MTPS graft copolymer containing 70 wt% polyester were much higher as the TPS/PBAT melt-blend modified with MA. This can be explained by a finer morphology of the dispersed phase in the continuous PBAT matrix, and an increased interfacial area for the grafting reaction as attested by morphological studies. POLYM. ENG. SCI., 48:1747-1754, 2008. © 2008 Society of Plastics Engineers, INTRODUCTION Plastic packaging is now subjected to strong pressure from environmental and disposal regulations in the design of single-use disposable packaging (1), (2). Obviously, there is a need for the [...]

Cylindrical starch foam shapes were produced on a small scale (~11-12 kg/hr) Werner Pfleiderer ZSK-30 twin-screw extrusion (TSE) process using water, which functions as a plasticizer as well as a blowing agent. The properties of the starch foams depend on the type of starch used (hydroxypropylated high amylose corn starch, 70% amylose), the amount of water and additives (poly(hydroxyamino ether)) (PHAE) used, and extrusion conditions such as temperature and the screw configuration. PHAE offers the adhesion and durability of epoxy resins with the flexibility and processibility of thermoplastic resins. PHAE was successful in imparting mechanical strength and toughness, cell integrity, weather and water resistance to the foam structure. The purpose of this work was to study the effects of the extrusion (melt) temperature, amount of water added and the screw configuration on the density of starch foams. The water externally added was varied from 3% to 12%, while the PHAE content was varied from 3% to 15% of the starch used (on a wet basis). The foaming was carried out at melt temperatures in the range from 85 to 145[degrees]C. A match of material properties with process engineering conditions was achieved to facilitate the control of expansion to a structure with valuable commercial properties. The effects of processing conditions on the foaming process were studied using a Werner Pfleiderer ZSK-30 twin screw extruder. The optimum temperature, blowing agent content, and PHAE content were determined. The density of the cylindrical foam extrudates obtained was 22-25 kg/[m.sup.3]. The screw configuration, temperature and pressure profiles, and additives affected the morphology, expansion ratio (ER), resilience, and compressibility of the product. These results were then employed on an industrial scale (410-420 kg/hr) twin-screw food extruder, a Wenger-80, to manufacture foam sheets. The density of the foam sheets was 27-30 kg/[m.sup.3]. The cushioning and insulation properties were studied and are reported. POLYM. ENG. SCI., 46: 438-451, 2006. [c] 2006 Society of Plastics Engineers, INTRODUCTION Foam plastic packaging is experiencing growing pressure from existing and proposed environmental and disposal regulations, and from market based sustainability initiatives. It presents a major disposal problem for companies [...]

Three-arm poly (ζ-caprolactone, reactive extruded) (REX-PCL) polymer was continuously produced using a twin-screw extruder with aluminum tri-sec butoxide (ATSB) initiator in residence times of less than five minutes. Monomer conversions in excess of 95% were achieved, and high molecular weight PCL was produced. The number average molecular weight of each arm of REX-PCL ranged from 30,000 to 200,000 g/mol. A screw configuration comprising entirely of conveying elements was most effective in the extrusion polymerization process. The REX-PCL polymer was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and intrinsic viscosity measurements. POLYM. ENG. SCI., 46:235-240, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION Poly (ζ-caprolactone) (PCL) and similar polyesters such as polylactides (PLA), poly hydroxyl butyrate (PHB), and poly hydroxy (butyrate-co-valerate) (PHBV) are biodegradable, and attention to their use in disposable short [...]

Bulk polymerization of ζ-caprolactone (CL), 1,4-dioxan-2-one (PDX), and mixtures of PDX and CL was carried out by initiation with Al([O.sup.sec]Bu)[.sub.3] in a co-rotating twin-screw extruder through a fast single-step process. Both homopolymerizations and copolymerization of PDX and CL proceed very rapidly and reach almost complete (co)monomer(s) conversion as soon as 8 mol% of CL are added in the feed. Even though poly(1,4-dioxan-2-one) (PPDX) is known to thermally degrade mainly through unzipping depolymerization promoted from the hydroxyl end-groups and yielding PDX monomer, it turns out that the thermal stability of PPDX chains is substantially improved by the copolymerization of PDX with limited amounts of CL. Interestingly, DSC analysis of the so-obtained P(PDX-co-CL) copolymers has demonstrated that a CL molar fraction as high as 11 mol% does not prevent the crystallization of the resulting copolymer, which retains a melting temperature close to 95°C. This last observation has been explained by the formation of a blocky-like copolymer structure, in which short PPDX and PCL sequences are randomly distributed. POLYM. ENG. SCI., 45:622-629, 2005. © 2005 Society of Plastics Engineers, INTRODUCTION The recent environmental regulations and growing societal concerns have triggered renewed efforts in the plastic industry to develop new products and processes compatible with our environment. In this respect, [...]

A new high-molecular-weight three-arm poly([epsilon]-caprolactone) (PCL) polymer was synthesized in bulk (in the absence of any solvent) by using aluminum tri-sec butoxide as a tri-functional initiator. The ring-opening polymerization of [epsilon]-caprolactone occurs via a coordination-insertion mechanism that links three growing polyester chains to the Al central atom via metal alkoxide bonds. The global kinetics of the bulk polymerization was determined, and a kinetic model based on monomer-polymer equilibrium was developed to predict the fractional extent of monomer conversion. Monomer conversions in excess of 95% to form high-molecular-weight PCL were achieved. Polym. Eng. Sci. 44:1491-1497, 2004. [c] 2004 Society of Plastics Engineers., INTRODUCTION In recent years there has been mounting interest in the use of 'environmentally friendly' polymer materials that are biodegradable, recyclable, or derived from annually renewable resources. The rationale for [...]

Polycaprolactone (PCL) has been blended with thermoplastic starch (TPS), prepared from regular corn starch and glycerol, in a twin-screw extruder. The rheological, mechanical, thermal and morphological properties of the blends were examined. Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) studies revealed that PCL/TPS blends are thermodynamically immiscible. However, they form compatible blends as a result of the hydrogen bonding interaction between the ester carbonyl of PCL and the -OH groups on starch. Biodegradability of the blends increased with increasing TPS content. Dynamic viscoelastic measurements concluded that blends containing above 60-wt% TPS had higher storage and loss moduli than those of pure TPS and PCL. In addition, these blends had higher complex viscosities. Polym. Eng. Sci. 44: 1429-1438. 2004. [c] 2004 Society of Plastics Engineers., INTRODUCTION Interest in biodegradable polymer blends and composites is increasing because of environmental requirements for safe and effective disposal of polymers (like plastics) after use. Since Griffin (1) prepared starchfilled [...]

Biofibers, natural lignocellulosics, have an outstanding potential as a reinforcement in thermoplastics. This study deals with the preparation of lignocellulosic composites by reactive extrusion processing in which good interfacial adhesion is generated by a combination of fiber modification and matrix modification methods. PP matrix was modified by reacting with maleic anhydride and subsequently bonded to the surface of the modified lignocellulosic component, in-situ. The fiber surface was modified by reacting it with a silane in a simple and quick aqueous reaction system, similar to that employed for glass fibers. The modified fibers are then extruded with the modified polymer matrix to form the compatibilized composite. The various reactions between the lignocellulosic fiber/filler and modified polymer chains, is expected to improve the interfacial adhesion significantly as opposed to simple mixing of the two components, since new covalent bonds between the fiber surface and matrix are created in the former case. These composite blends were then injection molded for mechanical characterization. Typical mechanical tests on strength, toughness and Izod impact energy were performed and the results are reported. These findings are discussed in view of the improved adhesion resulting from reactions and enhanced polar interactions at phase boundaries., INTRODUCTION Government regulations and a growing environmental awareness throughout the world have triggered a paradigm shift towards designing materials compatible with the environment. The use of bio-fibers, derived from annually [...]