HDPE Blend for Cold-Crack Resistant Pallets
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Solution Overview
Problem
Conventional wooden pallets are prone to damage, contamination, and environmental hazards, while plastic pallets tend to crack in cold temperatures and are more expensive, making them economically problematic.
Innovation Solution
A polymer composition comprising two high density polyethylenes of markedly different Melt Flow Rates (MFR) is used to create a durable plastic pallet with enhanced crack resistance and load capability, addressing the limitations of both wooden and traditional plastic pallets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plastic pallets are made from conventional HDPE, then they are durable and resistant to weathering, wet rot, chemicals and corrosion, but they have a tendency to crack in cold temperatures
Solution Approach 1:
The patent applies composite materials by blending two different HDPE polymers with distinct molecular weight characteristics. The first HDPE has a molecular weight between 50,000-200,000 g/mol providing durability and environmental resistance, while the second HDPE has a molecular weight between 200,000-500,000 g/mol providing crack resistance in cold temperatures. This composite polymer system combines the beneficial properties of both components to create a pallet material that maintains reliability while improving strength in cold conditions.
Solution Approach 2:
The patent employs parameter changes by controlling the molecular weight distribution of the HDPE components. Specifically, the patent specifies narrow molecular weight distributions (Mw/Mn ratio between 1.5-3.0) for both polymer components, and controls the blend ratio to achieve an overall MFR of 0.5-5.0 g/10min. These parameter optimizations enable the material to maintain both durability and cold-temperature crack resistance.
2Duration of action of stationary object
If plastic pallets are used instead of wooden pallets, then they offer longer service life span and better product protection, but they are more expensive making them economically problematic
Solution Approach 1:
The patent optimizes manufacturing parameters by controlling the overall MFR of the polymer blend between 0.5-5.0 g/10min and the Mw/Mn ratio between 1.5-3.0. These parameter optimizations enable efficient injection molding with reduced cycle times and lower energy consumption, thereby reducing manufacturing costs while maintaining the long service life span benefits of plastic pallets.
3Adaptability or versatility
If conventional polymer blends are used in pallet manufacture, then various design requirements can be met, but the crack resistance and load capability are insufficient
Solution Approach 1:
The patent creates a specialized composite material system using two HDPE polymers with specifically controlled molecular weights and narrow molecular weight distributions. This composite provides superior crack resistance and load capability compared to conventional polymer blends, while still allowing design flexibility through the controlled MFR range of 0.5-5.0 g/10min that accommodates various pallet designs and manufacturing methods.
Data Source
Figure 1
AI summary
A polymer composition comprising a blend of two or more high density polyethylenes: (A) a first high density polyethylene having a density of at least 940 kg/m3 and an MFR2 of 0.25 g/10min or less; and (B)a second high density polyethylene having a density of at least 940 kg/m3 and an MFR2 of 1.0 g/10min to 20 g/10min; wherein said polymer composition has an MFR2 of 0.25 to 15 g/10min and wherein the components (A) and (B) combined form at least 91 wt% of said polymer composition.