Influence of resin molecular weight on bonding interface, water resistance, and mechanical properties of bamboo scrimber composite

The major hurdle in melt-processing of ultra-high molecular weight polyethylene (UHMWPE) nanocomposite lies on the high melt viscosity of the UHMWPE, which may contribute to poor dispersion and distribution of the nanofiller. In this study, UHMWPE/cellulose nanofiber (UHMWPE/CNF) bionanocomposites were prepared by two different blending methods: (i) melt blending at 150 °C in a triple screw kneading extruder, and (ii) non-melt blending by ethanol mixing at room temperature. Results showed that melt-processing of UHMWPE without CNF (MB-UHMWPE/0) exhibited an increment in yield strength and Young’s modulus by 15% and 25%, respectively, compared to the Neat-UHMWPE. Tensile strength was however reduced by almost half. Ethanol mixed sample without CNF (EM-UHMWPE/0) on the other hand showed slight decrement in all mechanical properties tested. At 0.5% CNF inclusion, the mechanical properties of melt-blended bionanocomposites (MB-UHMWPE/0.5) were improved as compared to Neat-UHMWPE. It was also found that the yield strength, elongation at break, Young’s modulus, toughness and crystallinity of MB-UHMWPE/0.5 were higher by 28%, 61%, 47%, 45% and 11%, respectively, as compared to the ethanol mixing sample (EM-UHMWPE/0.5). Despite the reduction in tensile strength of MB-UHMWPE/0.5, the value i.e., 28.4 ± 1.0 MPa surpassed the minimum requirement of standard specification for fabricated UHMWPE in surgical implant application. Overall, melt-blending processing is more suitable for the preparation of UHMWPE/CNF bionanocomposites as exhibited by their characteristics presented herein. A better mechanical interlocking between UHMWPE and CNF at high temperature mixing with kneading was evident through FE-SEM observation, explains the higher mechanical properties of MB-UHMWPE/0.5 as compared to EM-UHMWPE/0.5.

Download Full-text

Improving Rheological and Mechanical Properties of Various Virgin and Recycled Polypropylenes by Blending with Long-Chain Branched Polypropylene

Polymers ◽

10.3390/polym13071137 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1137

Author(s):

Sascha Stanic ◽

Thomas Koch ◽

Klaus Schmid ◽

Simone Knaus ◽

Vasiliki-Maria Archodoulaki

Keyword(s):

Mechanical Properties ◽

Molecular Weight ◽

Tensile Test ◽

Reactive Extrusion ◽

Original Material ◽

Melt Flow Rate ◽

Single Screw Extruder ◽

Pp Blends ◽

The Impact ◽

Long Chain

Blends of two long-chain branched polypropylenes (LCB-PP) and five linear polypropylenes (L-PP) were prepared in a single screw extruder at 240 °C. The two LCB-PPs were self-created via reactive extrusion at 180 °C by using dimyristyl peroxydicarbonate (PODIC C126) and dilauroyl peroxide (LP) as peroxides. For blending two virgin and three recycled PPs like coffee caps, yoghurt cups and buckets with different melt flow rate (MFR) values were used. The influence of using blends was assessed by investigating the rheological (dynamic and extensional rheology) and mechanical properties (tensile test and impact tensile test). The dynamic rheology indicated that the molecular weight as well as the molecular weight distribution could be increased or broadened. Also the melt strength behavior could be improved by using the two peroxide modified LCB-PP blends on the basis of PODIC C126 or PEROXAN LP (dilauroyl peroxide). In addition, the mechanical properties were consistently enhanced or at least kept constant compared to the original material. In particular, the impact tensile strength but also the elongation at break could be increased considerably. This study showed that the blending of LCB-PP can increase the investigated properties and represents a promising option, especially when using recycled PP, which demonstrates a real “up-cycling” process.

Download Full-text

Chitosan-Based Adhesive: Optimization of Tensile Shear Strength in Dry and Wet Conditions

Polysaccharides ◽

10.3390/polysaccharides2010008 ◽

2021 ◽

Vol 2 (1) ◽

pp. 110-120

Author(s):

Maisa Abdelmoula ◽

Hajer Ben Hlima ◽

Frédéric Michalet ◽

Gérard Bourduche ◽

Jean-Yves Chavant ◽

...

Keyword(s):

Molecular Weight ◽

Shear Strength ◽

Bond Strength ◽

Water Resistance ◽

Tensile Shear Strength ◽

Tensile Shear ◽

Spread Rate ◽

Assembly Time ◽

Deacetylation Degree ◽

Dry And Wet Conditions

Commercial adhesives present a high bond strength and water resistance, but they are considered non-healthier products. Chitosan can be considered as an interesting biosourced and biodegradable alternative, despite its low water resistance. Here, its wood bonding implementation and its tensile shear strength in dry and wet conditions were investigated depending on its structural characteristics. Firstly, the spread rate, open assembly time, drying pressure, drying temperature, and drying time have been determined for two chitosans of European pine double lap specimens. An adhesive solution spread rate of 1000 g·m−2, an open assembly time of 10 min, and a pressure temperature of 55 °C for 105 min led to a bond strength of 2.82 MPa. Secondly, a comparison between a high molecular weight/low deacetylation degree chitosan and a lower molecular weight/higher deacetylation degree chitosan was conducted. Tests were conducted with beech simple lap specimens in accordance with the implementation conditions and the conditioning treatments in wet and dry environments required for thermoplastic wood adhesive standards used in non-structural applications (EN 204 and EN 205). The results clearly revealed the dependence of adhesive properties and water resistance on the structural features of chitosans (molecular weight and deacetylation degree), explaining the heterogeneity of results published notably in this field.

Download Full-text

Enhanced mechanical properties, water resistance, thermal stability, and biodegradation of the starch-sisal fibre composites with various fillers

Materials & Design ◽

10.1016/j.matdes.2020.109373 ◽

2021 ◽

Vol 198 ◽

pp. 109373

Author(s):

Maocheng Ji ◽

Fangyi Li ◽

Jianyong Li ◽

Jianfeng Li ◽

Chuanwei Zhang ◽

...

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Water Resistance ◽

Sisal Fibre ◽

Fibre Composites

Download Full-text

The Effect of Stereocomplex Polylactide Particles on the Stereocomplexation of High Molecular Weight Polylactide Blends

Polymers ◽

10.3390/polym13122018 ◽

2021 ◽

Vol 13 (12) ◽

pp. 2018

Author(s):

Muhammad Samsuri ◽

Ihsan Iswaldi ◽

Purba Purnama

Keyword(s):

Mechanical Properties ◽

Molecular Weight ◽

High Molecular Weight ◽

Nucleating Agent ◽

Solution Casting ◽

Casting Method ◽

Crystalline Fraction ◽

Crystalline Structures ◽

Solution Casting Method

Stereocomplexation is one of several approaches for improving polylactide (PLA) properties. The high molecular weight of poly L-lactide (PLLA) and poly D-lactide (PDLA) homopolymers are a constraint during the formation of stereocomplex PLAs (s-PLAs). The presence of s-PLA particles in PLA PLLA/PDLA blends can initiate the formation of s-PLA crystalline structures. We used the solution casting method to study the utilization of s-PLA materials from high molecular weight PLLA/PDLA blends for increasing s-PLA formation. The s-PLA particles initiated the formation of high molecular weight PLLA/PDLA blends, obtaining 49.13% s-PLA and 44.34% of the total crystalline fraction. In addition, the mechanical properties were enhanced through s-PLA crystalline formation and the increasing of total crystallinity of the PLLA/PDLA blends. The s-PLA particles supported initiation for s-PLA formation and acted as a nucleating agent for PLA homopolymers. These unique characteristics of s-PLA particles show potential to overcome the molecular weight limitation for stereocomplexation of PLLA/PDLA blends.

Download Full-text

Cationic Copolymerization of Isobutylene with 4-Vinylbenzenecyclobutylene: Characteristics and Mechanisms

Polymers ◽

10.3390/polym12010201 ◽

2020 ◽

Vol 12 (1) ◽

pp. 201 ◽

Cited By ~ 1

Author(s):

Zhifei Chen ◽

Shuxin Li ◽

Yuwei Shang ◽

Shan Huang ◽

Kangda Wu ◽

...

Keyword(s):

Mechanical Properties ◽

Molecular Weight ◽

Cationic Polymerization ◽

Transfer Reaction ◽

Chain Transfer ◽

Solid Phase ◽

Random Copolymer ◽

Glass Transition Temperatures ◽

Cationic Copolymerization ◽

Chain Transfer Reaction

A random copolymer of isobutylene (IB) and 4-vinylbenzenecyclobutylene (4-VBCB) was synthesized by cationic polymerization at −80 °C using 2-chloro-2,4,4-trimethylpentane (TMPCl) as initiator. The laws of copolymerization were investigated by changing the feed quantities of 4-VBCB. The molecular weight of the copolymer decreased, and its molecular weight distribution (MWD) increased with increasing 4-VBCB content. We proposed a possible copolymerization mechanism behind the increase in the chain transfer reaction to 4-VBCB with increasing of feed quantities of 4-VBCB. The thermal properties of the copolymers were studied by solid-phase heating and crosslinking. After crosslinking, the decomposition and glass transition temperatures (Tg) of the copolymer increased, the network structure that formed did not break when reheated, and the mechanical properties remarkably improved.

Download Full-text